KAERI, Daejon
Proton therapy has features of minimal effect on tumor surrounding healthy tissue and huge damage on tumor volumes specifically. Due to these characteristics of proton therapy the number of patients with receiving proton therapy is increasing every year. Proton therapy is useful for tumor treatment but still not know mechanism of proton beam that how to kill the tumor cells. In korea, a lot of current research progressed at the cellular level by using a proton accelerator, the animal experiments was not held virtually because of the absence of the device. In this study, we installed a animal experiment device for proton beam irradiation in MC-50 cyclotron LEPT (Low Energy Proton Therapy) beam line. Bouls and collimator, we easily made to be installed and we used PMMA sheet in order to reduce the energy. In addition, we used ridge filter type modulator for making SOBP and depth-dose measurement system for a proton beam dosimetry.
Manchester University, Manchester
UMAN, Manchester
University of Huddersfield, Huddersfield
Thorium fueled Accelerator Driven Subcritical Reactors have been proposed as a more comprehensive alternative to conventional nuclear reactors for both energy production and for burning radioactive waste. Several new classes have been added by the authors to the GEANT4 simulation code, extension which allows the state-of-the-art code to be used for the first time for nuclear reactor criticality calculations. In this paper we investigate the impact of the subcriticality and injected proton beam energy on the ADSR performance for novel ADSR configurations involving multiple accelerator drivers and associated neutron spallation targets within the reactor core.
Muons, Inc, Batavia
Positrons produced by electrons impinging on a target cover a broad momentum range. By bending the positrons 180° in a dipole magnetic field the momenta are dispersed according to their momenta along the exit plane of the magnet. A wedge-shaped absorber placed at the exit plane can reduce the momenta accordingly to produce a quasi-monochromatic beam of positrons. Simulation results are presented for 2 to 10 MeV/c quasi-mono-chromatic positrons produced by 75 MeV electrons on a tungsten target.
GSI, Darmstadt
IPCP, Chernogolovka, Moscow region
Universidad de Castilla-La Mancha, Ciudad Real
Rostock University, Rostock
Intense particle beams lead to volumetric heating of solid targets that generates large samples of High Energy Density (HED) matter. Such samples are very suitable to study the thermophysical properties of this important state of matter that spans over numerous fields of basic and applied physics. Facility for Antiprotons and Ion Research (FAIR) at Darmstadt, will generate very powerful bunched beams of the heaviest particles (uranium) that will deposit unprecedented high levels of specific power in the target. Extensive theoretical work has been carried out over the past decade to design HED physics experiments at the FAIR. So far, four different experimental schemes have been proposed. These include, HIHEX (Heavy Ion Heating and Expansion, which is suitable to study equation-of-state properties of HED matter), LAPLAS (Laboratory Planetary Science, which is suitable to generate physical conditions that exist in the interiors of the giant planets), Study of the growth of the Richtmyer-Meshkov instability and finally , the ion beam driven Ramp Compression which is suitable to study material properties like shear modulus and yield strength, under dynamic conditions.
KEK, Ibaraki
FAIS, Akatsuka, Tsukuba, Ibaraki
A new type of rotating anticathode X-ray generator has been developed, in which the electron beam irradiates the inner surface of a U-shaped Cu anticathode. A high-flux electron beam is focused on the inner surface of the anticathode by optimizing the geometry of the bending magnet. In order to minimize the sizes of the X-ray source, the electron beam is focused in a short distance by the combined function magnets. A shape on the surface of the bending magnet was determined by simulation. The beam trajectories and bending magnet were optimized by the General Particle Tracer(GPT) and Opera-3D code simulation. The result of simulation clearly shows that the bending magnet gap surface angle parameters are important to the beam focused in a short distance. FWHM sizes of the beam from the simulation were obtained to be 0.45mm(horizontal) and 0.05mm(vertical) of which the anticathode with a beam voltage and current were 120kV and 75mA, respectively. The effective brilliance to be about 500kW/mm2 simulated predict that with the supposition of a two-dimensional Gaussian distribution. In this paper, the optimization of the focusing magnet and the results of the prototype test are reported.
TUB, Beijing
For the miniaturization of low energy linear accelerators, X-band pulsed magnetron with stable performance of 1.5 MW peak power is needed to be developed. This paper presents the 3D particle-in-cell (PIC) of an X-band coaxial magnetron. A time evolved electron flow exhibits N/2 spokes in the simulations, which confirms the generation of pi-mode. Computer modeling indicates the mode competition in the startup process according to the spectra. By changing the DC voltage, we got the voltage-current characteristics of this magnetron, and comparison with the experiment was also been presented.
KAERI, Daejon
We made an experiment apparatus for the investigation of nano particle synthesis by proton inducing. It is composed of water tank, thin sample case with large area, ultrasonic oscillator, beam entrance window, monitoring camera, etc. Pt nano particles were fabricated. Nano particle characteristics are influenced by the condition of the solution, such as concentrations of H2PtCl6, CP and IPA. The experiment apparatus was designed that Pt nano particles were fabricated fore conditions. For a proton induced synthesis, some parameters, such as beam energy, beam current, flux, total dose, dose rate, etc. are also known as important process variables. To identify the effects of these irradiation parameters, we investigated the properties of nano particles according to the changes of these parameters. The energy was changed in the range of 10 ~ 40 MeV, beam current 1 uA. It could be examined by using an experiment apparatus developed for this purpose.
KAERI, Daejon
Uniform irradiation is very important for many kinds of experiments of proton beam utilization. In general, scanning magnet have been used for the uniform irradiation of high energy proton beam in the type of wobbler scanning, raster scanning, spiral scanning, etc. In the case of using magnets, it is not easy and needs high cost to install and operate because the magnet size and power become bigger with increase of beam energy accordingly. In this paper, we proposed simpler method and apparatus for uniform irradiation using 2D motional stage. It is composed of two motion systems for X- and Y- direction motion and goniostage. The maximum area is 20cm x 20cm and the incident angle can be controlled from +15 to -15 degree. Maximum sample weight have to be less than 5kg. In this paper, preliminary results for simple wobbler scanning is shown when the proton energy and beam current are about 40MeV and 1~10 nA respectively. The uniform scanning area was checked by using GAF film, MD-55 or HD-810. The stage can be used for the beam alignment and beam profile measurement at any position of beam line.
University of Huddersfield, Huddersfield
Manchester University, Manchester
STFC/RAL, Chilton, Didcot, Oxon
GEANT4 provides an extensive set of alternative hadronic models. Simulations of the ISIS muon production using three such models applicable in the energy range of interest are presented in this paper and compared with the experimental data.
University of Huddersfield, Huddersfield
Manchester University, Manchester
STFC/RAL, Chilton, Didcot, Oxon
ISIS is the world's most successful pulsed spallation neutron source that provides beams of neutrons and muons that enable scientists to study the properties of the matter at the atomic level. Restrictions are imposed on the muon target regarding thickness as this will affect the proton transmission to the second neutron target. However, it could be possible to improve the muon production by optimizing the target geometry. Currently the muon target is a 7 mm thick graphite plate oriented at 45 degrees with respect to the proton beam. A set of slabs placed at variable distance is proposed instead of the 7 mm thick graphite target. The performance of the set of slabs is examined in this paper.
University of Huddersfield, Huddersfield
Manchester University, Manchester
The European Spallation Source (ESS) is one of Europe's biggest and most prestigious science projects to design and construct the next generation facility for research with neutrons. ESS will be the world's most powerful spallation source and it will provide a unique tool for research into the atomic structure and dynamics of matter. We investigate the effects of the dimensions of the ESS spallation target on the total neutron yield integrated over the neutron energy and emission angle. We also investigate different material choices for the ESS target.
University of Huddersfield, Huddersfield
Manchester University, Manchester
STFC/RAL, Chilton, Didcot, Oxon
Simulations studies have been carried out to examine the impact of the energy of the proton driver on muon production. The muon flux is calculated as a function of proton energy over a wide range, which covers the energies at the existing muon and neutron facilities worldwide. The muon and higher energy pion yields are normalised per beam current and accelerator power. The case of a higher energy of the proton driver at the ISIS muon facility is also examined.
KEK, Ibaraki
Injection into the J-PARC main ring is implemented by 4 kickers and 2 pulsed septa at 3 GeV in a long straight section. To accommodate the injection beam of 54 pmm.mrad, both septa have large physical acceptance of 81 pmm.mrad. However, large aperture leads to large end fringe field interfereing the circulating beam and causing beam loss, which has been observed even at low beam intensity during the beam commissioning. To provide users a proton beam with high beam power, the injection beam intensity will increase greatly in future, which creates difficulties for the present injection system. To accommodate these high intensity beams with low beam loss, the injection system needs to be upgraded. Taking account the strong space charge effects, even larger physical is needed to reduce the localized beam loss, which creates severer end fringe leakage field. This paper will discuss the problems encountered in operating the present septa, and give an optimized design for the new septa.
NSRRC, Hsinchu
A magnet array of superconducting undulator SU15, with 130 poles and length 0.98 m, was constructed, and the field measurement and training are also performed at National Synchrotron Radiation Research Center (NSRRC). The NbTi wires were excited to 1.36 T @ 497 A after 28 times quench. A cryogenic Hall probe (length 2500 mm) was used to characterize the distribution of the magnetic field of magnet arrays in the 5.6-mm magnetic gap. The measurement region of the cryogenic Hall probe is greater than 1200 mm in the vertical dewar. The length shrinkage or expansion of the Hall probe depends on the thermal variation at both ends of the Hall probe. The length of the Hall probe will be evaluated in the field measurement region. The reproducibility of the measurement system was verified in the same experiment. A field shimming method involving a trim iron piece was used to correct for deviations of the magnetic field. This paper discusses the measurement accuracy in the cryogenic Hall probe system and presents results of the field shimming.
TEMF, TU Darmstadt, Darmstadt
For the computation of the electromagnetic fields in large accelerator components, such as the superconducting dipole magnets to be installed in the heavy-ion synchrotron SIS100 at GSI, Darmstadt in context of the FAIR project, very large numerical models are required. By using parallelization techniques in combination with higher-order finite element approaches, full 3D solutions for the complicated geometry can be obtained in reasonable computational time. This is important, in particular, if repeated simulations need to be performed as in case of the determination of the sensitivity of the results to parametric changes, e.g. due to manufacturing tolerances. For that purpose, a parallelized 3D simulation tool is developed and applied to the prototype of the SIS100 dipole magnet. The results for the field quality during transient operation considering eddy currents in the conductive parts of the assembly are reported.
KEK, Ibaraki
To supply the electrical power for the superconducting correctors in the interaction region of the proposed SuperKEKB, a kind of vapor cooled current leads is designed, which consists of 8 brass leads and can transport currents to 4 correctors simultaneously. The design current of the leads is about 50 A. The thermal and electrical behaviors have studied by the finite elements method and the cryogenic experiment is also planed to validate the performance. In this paper the design will be presented and the finite element model will be compared with the experimental data.
INFN/LNF, Frascati (Roma)
INFN-Roma, Roma
A neutron source, based on photo-neutron production, has been designed and is under construction to upgrade the electron/positron/photon DAΦNE Beam Test Facility (BTF). We present the feasibility study, the solution chosen and the optimization done in order to maximize the neutron/photon yield as well as the comparison between different simulation codes (FLUKA/GEANT4/MCNPX). The first experimental test is foreseen in March 2010.
Danfysik A/S, Jyllinge
Danfysik A/S has developed a novel approach in constructing a low voltage, very high current and highly stable magnet power supply using parallel SCR converter stages. The design is well suited for driving superconducting magnets in a two quadrant operation. A ±10V 18kA power supply has been built to EPFL Lausanne with four parallel converters showing excellent performances and a very low installation time. One of the major difficulties in paralleling SCR converters is the current sharing between the individual converters, which becomes even harder at low voltages. The novel design, which will be presented here, assures current sharing within a few percent in the whole working area. The power supply has been developed having the following highlights in mind: High accuracy and stability (50ppm.), Good current sharing between parallel coupled converters without band width degradation, Very high current, One or two quadrant operation and Computer controlled. This paper describes the power converter topology ensuring the excellent current sharing.
UNIDO, Dortmund
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
We consider the formation of machine background induced by proton losses in the long straight section of the LHCb experiment at LHC. Both sources showering from the tertiary collimators located in the LHCb insertion region as well as local beam-gas interaction are taken into account. We present the procedure for, and results of, numerical studies of such background for various conditions. The expected impact on the experiment and signal characteristics are also discussed.
CERN, Geneva
The layout of the interaction region for the LHC upgrade project is based on a number of new magnets that will provide the required strengths to focus the colliding beams as well as to separate them after the collision. As in the nominal LHC, a triplet of quadrupole magnets is foreseen for the upgrade optics and in addition a separator dipole to limit the parasitic bunch crossings of the two counter rotating bunch trains. Due to the smaller beta function at the IP however, the requirements for the free aperture of these IR magnets are more demanding and the effect of the higher order multipoles is more severe than under the nominal LHC conditions. Using the tracking simulations to study these effects, target values for the multipole coefficients of the new magnets have been defined as well as a multipole correction scheme that will be used to compensate those field errors which cannot be avoided due to design and construction tolerances. Based on these considerations the required field quality of the new LHC low beta magnets is discussed and the resulting dynamic aperture for different multipole correction scheme is presented.
CERN, Geneva
The transfer lines from the SPS to the LHC, TI2 and TI8, with a total length of almost 6km are the longest ones in the world. For that reason even small systematic optics errors are not negligible because they add up and result in an injection mismatch in the LHC. Next to other lattice measurement methods Kick-response measurements were the most important sources of information during the early phases of beam commissioning of these transfer lines and the LHC ring. This measurement technique was used to verify orbit-corrector and BPM gains as well as to sort out optics errors. Furthermore fits to off-momentum kick response turned out to be an appropriate method to establish a model for systematic errors of the transfer line magnets. This paper shortly describes the tools and methods developed for the analysis of the taken data and presents the most important results of the analysis.
CERN, Geneva
SLAC, Menlo Park, California
Fermilab, Batavia
Unbunched beam is a potentially serious issue in the LHC as it may quench the superconducting magnets during a beam abort. Unbunched particles, either not captured by the RF system at injection or leaking out of the RF bucket, will be removed by using the existing damper kickers to excite resonantly the particles in the abort gap. Following beam simulations, a strategy for cleaning the abort gap at different energies was proposed. The plans for the commissioning of the beam abort gap cleaning are described, and the first results from the beam commissioning are presented.
CERN, Geneva
EPFL, Lausanne
The control of the high intensity beams of the CERN Large Hadron Collider (LHC) is particular challenging and requires a precise knowledge of the critical beam and machine parameters. In recent years efforts were devoted to the design of a software infrastructure aimed at mimicking the behavior of the LHC. An online model of the machine, based on the accelerator design tool MADX, has been developed to support the commissioning and the operation of the LHC. This model is integrated into the JAVA-based LHC software framework and provides the full computing power of MADX, including the best knowledge of the machine aperture and magnetic models. The MADX implementation is server-based and provides various facilities for optics computation to other application clients. In this paper, we present the status of the MADX online application and illustrate how it has been used during the LHC commissioning. Possible future implementations are also discussed.
Fermilab, Batavia
Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations.
Heidelberg University, Heidelberg
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
CERN, Geneva
The LHC BRAN luminosity detector monitors the high luminosity interaction regions (Atlas and CMS). This chamber, which is an Argon gas ionization detector measures the forward neutral particles from collisions the interaction region. To predict and improve the understanding of the detector's performance, we produced a detailed model of the detector and its surroundings in FLUKA. In this paper, we present the model and results of our simulations including the detector's estimated response to interactions for beam energies of 3.5, 5.0, and 7.0 TeV.
LBNL, Berkeley, California
CERN, Geneva
BNL, Upton, Long Island, New York
The Luminosity Monitor for the LHC is ready for operation during the planned 2009-2010 run. The device designed for the high luminosity regions is a gas ionization chamber, that is designed with the ability to resolve bunch by bunch luminosity as well as survive extreme levels of radiation. The devices are installed at the zero degree collision angle in the TAN absorbers ±140m from the IP and monitor showers produced by high energy neutrons from the IP. They are used in real time as a collider operations tool for optimizing the luminosity at ATLAS and CMS. A photo-multiplier based system is used at low luminosities and also available. We will present early test results, noise and background studies and correlation between the gas ionization and the PMT. Comparison with ongoing modeling efforts will be included.
JINR, Dubna, Moscow Region
In order to decrease the energy of an ion accelerated in a cyclotron on value of some MeV/eau it is possible to run an ion beam through a thin metal foil (degrader). One can calculate the final ion energy, angular and energy stragglings, which the beam attains in the degrader, for example, by means of code LISE++. The formulae for calculation of the beam second order moments after degrader were obtained. The formulae for calculation of final beam momentum spread, new values of rms beam emittances, Twiss parameters and the dispersion functions were also obtained. The new ion beam parameters allow one to calculate the beam transportation along the beam line after degrader.
IAP, Frankfurt am Main
TU Darmstadt, Darmstadt
GSI, Darmstadt
StrahlSim is a unique code for the simulation of charge exchange driven beam loss and dynamic vacuum effects in heavy ion synchrotrons. Dynamic vacuum effects are one of the most challenging problems for accelerators using intermediate charge state, high intensity heavy ion beams (e.g. AGS Booster, LEIR, SIS18). StrahlSim can be used as a design tool for synchrotrons, e.g. for the estimation of pumping power needed to stabilize the dynamic vacuum. Recently, StrahlSim has been extended to simulate time dependent longitudinal pressure profiles. The new code calculates a self-consistent static pressure distribution along the accelerator and simulates local pressure rises caused by dynamic and systematic beam losses. StrahlSim determines the loss distribution of charge exchanged beam ions and respects the beam energy dependence of the charge exchange cross sections. The beam loss calculated by means of the new time dependent longitudinal pressure profiles has been benchmarked with measured data from the latest SIS18 machine experiments.
PSI, Villigen
A new current monitor (MHC5) based on a re-entrant cavity tuned at the 2nd RF harmonic (101.26 MHz) has been in operation since April 2009 at PSI. It monitors the current of the high intensity 590 MeV proton beam at 8 m downstream of the graphite meson production target (TgE). The scattered particles and their secondaries from TgE introduce a heavy thermal load approximately of 230 W on MHC5 at 2 mA beam intensity, which is carried away by active water cooling. The inhomogeneous temperature profile in MHC5 results in thermomechanical deformations which leads to a change in its HF electromagnetic characteristics. Indeed, an anomalous RF drifts were observed during initial operations, which had to be compensated for, to obtain correct beam current monitoring. In this paper, the physics of the observed RF drift is analyzed by using advanced multiphysics simulation technologies.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The ISIS Facility at the Rutherford Appleton Laboratory in the UK produces intense neutron and muon beams for condensed matter research. The accelerator facility consists of a 70 MeV H- linac and a 50 Hz proton synchrotron accelerating up to 3.75x1013 protons per pulse from 70 to 800 MeV, delivering a mean beam power of 0.24 MW. Present upgrade studies are investigating how replacement of the existing linac and increased injection energy could increase beam power in the existing ISIS ring. Such an upgrade would replace one of the oldest sections of the ISIS machine, and with reduced space charge and optimised injection, may allow substantially increased intensity in the ring, perhaps towards the 0.5 MW regime. A critical aspect of such an upgrade would be the new higher energy injection straight. This paper summarises beam dynamics and hardware requirements for 180MeV H- charge exchange injection into ISIS including; optimisation of the injection magnets; requirements for beam dumps and results of stripping foil simulations with estimates of stripping efficiency and foil heating.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. A novel design method, integrating the CAD and electromagnetic design of the RFQ with beam dynamics simulations, is being used to optimise the design of the RFQ. Basic RFQ parameters are produced with the RFQSIM code. A full CAD model of the RFQ vane tips is produced in Autodesk Inventor, based upon these parameters. This model is then imported into a field mapping code to produce a simulation of the electrostatic field around the vane tips. This field map is then used to model the beam dynamics within the RFQ using General Particle Tracer (GPT). Previous studies have been carried out using field mapping in CST EM Studio. A more advanced technique using Comsol Multiphysics and Matlab, that more tightly integrates the CAD modelling, field mapping and beam dynamics simulations, is described. Results using this new method are presented and compared to the previous optimisation process using field maps from CST.
University of Warwick, Coventry
Fundación Tekniker, Elbr (Guipuzkoa)
Bilbao, Faculty of Science and Technology, Bilbao
Fundación TEKNIKER, Eibar (Gipuzkoa)
STFC/RAL, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Elytt Energy, Madrid
Imperial College of Science and Technology, Department of Physics, London
The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory is intended to demonstrate the early stages of acceleration (0-3 MeV) and beam chopping required for high power proton accelerators, including proton drivers for pulsed neutron spallation sources and neutrino factories. A Low Energy Beam Transport (LEBT), consisting of three solenoids and four drift sections, is used to transport the H- beam from the ion source to the FETS Radio Frequency Quadrupole. We present the status of the installation and commissioning of the LEBT, and compare particle dynamics simulations with preliminary measurements of the H- beam transport through the LEBT.
CEA, Gif-sur-Yvette
BNL, Upton, Long Island, New York
To preserve proton polarization through acceleration, it is important to have a correct model of the process. It has been known that with the insertion of the two helical partial Siberian snakes in the Alternating Gradient Synchrotron (AGS), the MAD model of AGS can not deal with a field map with offset orbit. The stepwise ray-tracing code Zgoubi provides a tool to represent the real electro-magnetic fields in the modeling of the optics and spin dynamics for the AGS. Numerical experiments of resonance crossing, including spin dynamics in presence of the snakes and Q-jump, have been performed in AGS lattice models, using Zgoubi. This contribution reports on various results so obtained.
CERN, Geneva
Fermilab, Batavia
Two events, occurring in 2008 during commissioning of the LHC circuits, lead to fundamental changes to the scope of circuit protection. The discovery of aperture-symmetric quenches and the accidental rupture at 9kA of an interconnecting busbar resulted in an emergency program for development and implementation of new protection facilities. The new scheme comprises a distributed busbar supervision system with early warning capabilities based on high-precision splice resistance measurements and system interlocks for rapid de-excitation of the circuit in case of a sudden splice resistance increase. The developed symmetric quench detectors are digital systems with radiation-resistant FPGA logic controllers, having magnet heater firing capabilities. This program successfully allowed a safe re-powering of the collider. The concept of the new electronics boards and the powering modules will be described. More than 14'600 extra cables and 6'000 new detector and control cards were added to the existing QPS system. A first evaluation of the system performance as well as a number of interesting discoveries made during the commissioning will be presented.
CEA, Gif-sur-Yvette
The RF design of a RFQ should satisfied several conditions, namely: voltage profile required by beam dynamics, a tunable structure, RF stability and reasonable sensitivity to possible perturbations induced by power operation. Voltage profile may be obtained either by a dedicated profiling of 2D cross-section and/or slug tuner adjustment. Tunability is directly related to spatial distribution of tuners. RF stability requires sufficient separation between accelerating quadrupole mode and (i) adjacent quadrupole modes, or (ii) adjacent dipole modes. Quadrupole modes separation is directly related to RFQ length, and can be increased if necessary via segmentation; position of dipole modes spectrum w.r.t. quadrupole spectrum may be adjusted using rod stabilizers inserted at RFQ ends and on either side of coupling circuits. We present a thorough comparison of these two options for a 6-meter long structure at 352 MHz, and show they both lead to a tunable structure. The design includes 3D electromagnetic simulation and application of transmission line to tuning. The sensitivity of both designs to perturbations is also evaluated.
CEA, Gif-sur-Yvette
CERN, Geneva
In the Linac 4 and the SPL, a 3 MeV RFQ is required to accelerate the H- beam from the ion source to the DTL input energy. While the 6-meter long IPHI RFQ was initially chosen for this application, a CERN study* suggested that a dedicated, shorter 3-meter RFQ might present several advantages. The 2D cross-section is optimized for lower power dissipation, while featuring simple geometrical shape suitable for easy machining. RF stability is evaluated using a 4-wire transmission model and 3D simulations, taking electrode modulation into account. The resulting RFQ is intrinsically stable and do not require rod stabilizers. End circuits are tuned with dedicated rods. RF power is fed via a ridged waveguide and a slot iris. Vacuum port assemblies are positioned prior to brazing to minimize RF perturbation. The 32 tuning slugs form a set of stable sampling, able to tune 9 modes. Tuner parameters are derived from bead-pull accuracy specification and fabrication tolerances. Signals delivered by pickup loops inserted in 16 of these tuners will be used to reconstruct the voltage profile under operation. Thermo-mechanical simulations are used to design temperature control specifications.
IAP, Frankfurt am Main
Abstract A short RFQ prototype was built for tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-Simulations with CST Microwave Studio and measurements were done. Conditioning of the facility with 20 kW/m and simulations of thermal effects with ALGOR are on focus now. First results and the status of the project will be presented.
IAP, Frankfurt am Main
GSI, Darmstadt
At the Institute for Applied Physics a superconducting CH-Cavity (Crossbar H-Mode) has been developed. It is the first multi-cell drift tube cavity for the low and medium energy range of proton and ion linacs. A 19 cell, β = 0.1 prototype cavity has been fabricated and tested successfully with a voltage of 5.6 MV corresponding to gradients of 7 MV/m. The construction of a new superconducting 325 MHz 7-gap CH-cavity has started. This cavity has an optimized geometry with respect to tuning possibilities, high power RF coupling, minimized end cell lengths and options for surface preparation. Static tuning is carried out by small niobium cylinders on the girders. Dynamic tuning is performed by a slow bellow tuner driven by a step motor and a fast bellow tuner driven by a piezo. Additional thermal and mechanical simulations have been performed. It is planned to test the cavity with a 10 mA, 11.4 AMeV (β = 0.158) beam delivered by the Unilac at GSI. Another cavity (f = 217 MHz, β = 0.059) is currently under development for the cw Heavy Ion Linac at GSI. It is the first of nine sc CH-Cavities planned for this project covering an energy range from 1.4 to 7.3 AMeV.
IAP, Frankfurt am Main
The goal of the Frankfurt Funneling Experiment is to multiply beam currents by merging two low energy ion beams. In an ideal case this would be done without any emittance growth. Our setup consists of two ion sources, a Two-Beam-RFQ accelerator and a multi cell deflector which bends the beams to one common beam axis. The end section of the RFQ electrodes are designed to achieve a 3d focus at the crossing point of the two beam axis. New simulations with the RFQSIM-Code for a matching system with extended electrodes will be presented.
IAP, Frankfurt am Main
Buncher-cavities re-accelerate, bunch or re-bunch particle beams. A special form of these buncher-rf-cavities is a spiral-structure. Two different spiral resonators were simulated and build for the new EBIS LINAC at Brookhaven National Laboratory. These buncher-cavities have a remarkably large aperture of 100 mm. To optimize the cavities to the BNL-frequency of 100 MHz, simulations have been carried out. The impact of changing the gap width, drifttube-, and spiral arm-length on the design of the spiral cavities, has been analyzed. Results of simulations and measurement will be presented.
IAP, Frankfurt am Main
EUROTRANS is a EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator-Driven System. Frankfurt University is responsible for the development of the 352MHz injector which mainly consists of a 3MeV RFQ and a 3-17MeV CH-DTL. Based on the beam dynamics design, the CH-cavities were designed with the concern to optimize the RF properties. In the cavity design, the tube-gap configurations were modified, so the beam dynamics has been adjusted to fit the new effective gap voltage profiles accordingly. A comparison of the beam dynamics results before and after the RF optimization is presented.
Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova
INFN/LNL, Legnaro (PD)
GREPHE/LAPLACE, Toulouse
The thermonuclear fusion experiment ITER, requires 33 MW of auxiliary heating power from two Neutral Beam Injectors (NBI), each of them providing 40 A of negative deuterium ions. The EU activities oriented to the realisation of the electrostatic accelerator comprise the construction in Padova of SPIDER, a facility devoted to the optimisation of the beam source. SPIDER parameters are: 100 keV acceleration, 40/60 A (deuterium/hydrogen) current. For the optimised SPIDER accelerator the present contribution provides a characterisation of secondary particles, which include electrons produced by impact of ions on grid surfaces, stripped from negative ions inside the accelerator, and produced by ionisation of the background gas, and the corresponding positive ions. Currents and heat deposited on the various grids and spatial distribution by secondaries will be described. It is found that most of the heat loads on the accelerator grids is due to electrons; moreover the features of secondaries exiting the accelerator and back-streaming towards the source will be presented. The results will be compared with old investigations concerning the NBI 1 MeV accelerator.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05MeV to 3MeV toward the following DTL. As the trip rates of the practically using RFQ increased in autumn 2008, we started the preparation of a new RFQ as a backup machine. The beam dynamics design of the new RFQ is the same as the current cavity, however, the engineering and RF designs are changed. The processes of the vane machining and the surface treatments have been carefully considered to reduce the discharge problem. The vacuum brazing technique has been chosen for vane integration. In this report, the detailed design will be described with the progress of the fabrication of the new RFQ.
RLNR, Tokyo
A new type Linac, HSC (hybrid single cavity) linac for cancer therapy, which configuration combines RFQ (Radio Frequency Quadrupole) accelerating structure and DT (Drift Tube) accelerating structure is being finished designs and simulations now. This HSC linac design had adopted advanced power-efficiency-conformation, IH (Interdigital H) structure, which acceleration efficiency is extremely high in the low-middle energy region, and had also adopted most advanced computer simulation technology to evaluate cavity electromagnetic distribution. The study purposes of this HSC linac focus to design of injector linac for synchrotron of cancer radiotherapy facilities. Here, this HSC linac has an amazing space effect because of compact size by coupled complex acceleration electrode and integrated the peripheral device which is made operation easy to handle.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Imperial College of Science and Technology, Department of Physics, London
The front end test stand (FETS) [1] being constructed at the Rutherford Appleton Laboratory is entering the next stage of commissioning, with the three-solenoid magnetic low energy beam transport (LEBT) now installed and undergoing commissioning. The next major component to be manufactured is the 3 MeV, 324 MHz, four metre radio frequency quadrupole (RFQ). The mechanical design is almost complete so a comprehensive finite element model of the entire RFQ has been made in ANSYS to ensure the electromagnetic, thermal and structural properties are sound. An analysis of the cooling strategy and expected resonant frequency shift due to thermal expansion are presented.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The Medium Energy Beam Transport (MEBT) line for the Front End Test Stand (FETS) at RAL will transport a 60 mA, 2ms, 50 pps H- beam at 3 MeV. It uses a number of quadrupoles, re-bunching cavities and a fast-slow chopping system. In this paper we present the underlying MEBT design philosophy, beam dynamics simulations and implementation details.
Imperial College of Science and Technology, Department of Physics, London
JAI, Egham, Surrey
The PAMELA (Particle Accelerator for MEdicaL Applications) project aims to design an ns-FFAG accelerator for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. Our integrated RFQ design process* has been developed further using Comsol Multiphysics for electric field modelling. The design parameters for the RFQ are automatically converted to a CAD model using Autodesk Inventor, and the electric field map for this model is simulated in Comsol. Particles can then be tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Possible designs for the PAMELA RFQ, including super-conducting and normal-conducting solutions, will be presented and discussed, together with results of the field map simulations and particle tracking for these designs.
* M J Easton et al., RFQ Design Optimisation for PAMELA Injector, PAC09, Vancouver, Canada, April 2009, FR5REP066.
LANL, Los Alamos, New Mexico
We are developing high-efficiency normal-conducting RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. Such IH-PMQ accelerating structures following a short RFQ can be used in the front end of ion linacs or in stand-alone applications, e.g. a compact deuteron-beam accelerator up to the energy of several MeV. Results of combined 3-D modeling for a full IH-PMQ accelerator tank ' electromagnetic computations, beam-dynamics simulations with high currents, and thermal-stress analysis ' are presented. The accelerating field profile in the tank is tuned to provide the best beam propagation using coupled iterations of electromagnetic and beam-dynamics modeling. A cold model of the IH-PMQ tank is being manufactured.
GSI, Darmstadt
Nagaoka University of Technology, Nagaoka, Niigata
FZJ, Jülich
JINR, Dubna, Moscow Region
The stochastic cooling is employed to reduce the momentum spread of accelerated 2 GeV proton beam at COSY. In addition the barrier voltages are successfully used to compensate the mean energy loss of the beam due to the thick internal target such as pellet target. To analyze the experimental results at COSY, we have developed the particle tracking code which simulate the particle behavior under the influences of stochastic cooling force, Schottky diffusion, thermal diffusion and IBS effects. The synchrotron motion due to the RF fields are included with 4th order symplectic way. The simulation results are well in agreement with the observed cooling process for the case of barrier voltage as well as RF field of harmonic number=1. In the present paper, the systematic analysis of the experimental results with use of the developed tracking codes are described. In addition the process of short bunch formation at the heavy ion collider at NICA project is investigated with use of the stochastic cooling. In that case the strong IBS effects are main limiting factor of making and keeping the short bunch as well as the space charge effects. Details of the simulation study will be presented.
FZJ, Jülich
GSI, Darmstadt
Numerical studies of longitudinal filter and time-of-flight (TOF) cooling suggest that the strong mean energy loss due to an internal Pellet target in the High Energy Storage Ring (HESR) at the FAIR facility can be compensated by cooling and operation of a barrier bucket (BB) cavity. In this contribution detailed experiments at COSY to compensate the mean energy loss are presented. The internal Pellet target was similar to that being used by the PANDA experiment at the HESR. A BB cavity was operated and either TOF or filter stochastic momentum cooling was applied to cool a proton beam. Experimental comparisons between the filter and TOF cooling method are discussed. Measurements to determine the mean energy loss which is used in the simulation codes are outlined. The experiments proved that the mean energy loss can be compensated with a BB cavity. Results are compared with numerical tracking simulations which include the synchrotron motion in a barrier bucket as well as in an h = 1 cavity and stochastic momentum cooling. A detailed discussion of the tracking simulation code will be outlined in a separate contribution to this conference.
National Technical University of Athens, Zografou
A compact ring with an internal target for the production of Li-8 or B-8 as neutrino or antineutrino emitters has been proposed*, to enhance the flux of radioactive isotopes for a beta-beam facility. The circulating beam is expected to survive for thousands of turns and, according to this scheme, the ionization cooling provided by the target itself and a suitable RF system will be enough to keep the beam transverse and longitudinal emittances under control. The ionization cooling potential for a preliminary ring design is here investigated by means of tracking simulations and analytical considerations, keeping in mind that a correct modeling of the beam-target interactions is fundamental for these studies. Technological issues for such a ring and possible show-stoppers are also briefly discussed.
* C.Rubbia et al, NIM-A 2006..
Nagaoka University of Technology, Nagaoka, Niigata
FZJ, Jülich
GSI, Darmstadt
A small momentum spread of proton beam has to be realized and kept in a storage ring during an experiment with a dense internal target such as a pellet target. A stochastic cooling alone does not compensate the mean energy loss by the internal target. Barrier bucket operation will cooperate effectively the energy loss. In addition, the further small momentum spread can be realized with use of an electron cooling. In the present study, the simulation results on the simultaneous use of stochastic cooling and electron cooling at COSY are presented.
Fermilab, Batavia
JLAB, Newport News, Virginia
Muons, Inc, Batavia
Fast muon beam six dimensional (6D) phase space cooling is essential for muon colliders. The Helical Cooling Channel (HCC) uses hydrogen-pressurized RF cavities imbedded in a magnet system with solenoid, helical dipole, and helical quadrupole components that provide the continuous dispersion needed for emittance exchange and effective 6d beam cooling. A series of HCC segments, each with sequentially smaller aperture, higher magnetic field, and higher RF frequency to match the beam size as it is cooled, has been optimized by numerical simulation to achieve a factor of 105 emittance reduction in a 300 m long channel with only a 40% loss of beam. Conceptual designs of the hardware required for this HCC system and the status of the RF studies and HTS helical solenoid magnet prototypes are described.
HIP, University of Helsinki
Comenius University in Bratislava, Faculty of Mathematics Physics and Informatics, Bratislava
Helsinki University, Department of Physics, University of Helsinki
The Super-FRS is a superconducting fragment separator that will be built as part of the FAIR facility. For the slow-extraction part of the beam diagnostics system a total of 32 detectors are needed for beam monitoring and for tracking and characterization of the produced ions. Since GEM-TPC detectors can perform over wide dynamic range without disturbing the beam, they are suitable for this kind of in-beam detection. We have studied the performance of a prototype GEM-TPC. The current status of the prototype detector and the measurement results are shown.
U. Erlangen-Nurnberg LHFT, Erlangen
Siemens Med, Erlangen
The usability of conventional BPM topologies in compact linear accelerators used for medical and industrial applications is very limited due to tight space restrictions in such systems. To overcome these limitations, a different approach is introduced which is based on integrating the pickups into low-field regions of the accelerating structure and evaluating higher beam harmonics. Applications based on this approach will require RF frontends in frequency ranges beyond those covered by BPM dedicated hardware which is currently commercially available. Therefore, a demonstrator setup is presented which is capable of investigating suitable RF frontends for the proposed method. The demonstrator uses capacitive pickups of the button type for displacement sensing and allows for control of the beam position with the help of feedback steering coils which are typically used for compact linacs. Representative sensitivity measurement results based on the evaluation of the 2nd S-Band beam harmonic are also presented in this paper.
DESY, Hamburg
IKP, Mainz
Luminescent screens are widely used for particle beam diagnostics, especially in transverse profile measurements at hadron machines and low energy electron machines where the intensity of optical transition radiation (OTR) is rather low. The experience from modern linac based light sources showed that OTR diagnostics might fail even for high energetic electron beams because of coherence effects in the OTR emission process. An alternative way to overcome this limitation is to use luminescent screens, especially inorganic scintillators. However, there is only little information about scintillator properties for applications with high energetic electrons. Therefore a test experiment has been performed at the 855 MeV beam of the Mainz Microtron MAMI (University of Mainz, Germany) in order to study the spatial resolution. The results of this experiment will be presented and discussed in view of scintillator material properties and observation geometry.
DESY, Hamburg
Università di Roma I La Sapienza, Roma
The control and stabilization of RF systems for accelerators has a considerable importance. In case of high-gain free-electron lasers (FEL) with magnetic bunch compressors, the RF phases determine the attainable bunch peak current, which is a relevant parameter for driving the FEL process. In order to measure the bunch peak current in a simple and fast but indirect way, both bunch compressors at FLASH are equipped with compression monitors (BCM) based on pyroelectrical detectors and diffraction radiators (CDR). They provide substantial information to tune the bunch compression and are used for beam-based feedback to stabilize RF phases. This monitor system becomes more important and more challenging after the installation of a third-harmonic RF system for longitudinal phase space linearization in front of the first bunch compressor. In this paper, we describe the hardware upgrade of the bunch compression monitor and show the expected performance by simulations of the CDR source and the radiation transport optics. Particle tracking simulations are used for generation of the simulated BCM-signal for various compression schemes. Comparison with experimental data will be presented.
ELETTRA, Basovizza
DEEI, Trieste
FERMI@Elettra is a soft X-ray fourth generation light source under construction at the ELETTRA laboratory. To characterize the beam phase space by means of measurements of the bunch length and of the transverse slice emittance two deflecting cavities will be positioned at two points in the linac. One will be placed at 250 MeV (low energy), after the first bunch compressor (BC1); the second at 1.2 GeV (high energy), just before the FEL process starts. The Low-Energy RF Deflector consists in a 5 cells, standing wave, normal conducting, RF copper cavity. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. In this paper we discuss and report on results of electromagnetic, thermal, and structural analysis.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
Energy Recovery Linac (ERL) as synchrotron light source is planned to construct in KEK. Before the construction of full-set of ERL, compact ERL to study the accelerator technologies will be constructed. For the injector, a high voltage photoemission gun with DC operation and measurement systems for the low emittance beam will be developed. In order to observe bunch length and longitudinal beam profile, we have designed a single-cell deflecting cavity with 2.6 GHz dipole mode. We describe the optimization of the cavity, mechanical design and the measurements results with simulation.
RIKEN/SPring-8, Hyogo
The x-ray FEL facility at SPring-8 produces a very short-bunch beam by using bunch compressors (BC) consisting of magnetic chicanes. Since the bunch compression ratio is strongly depends on the beam energy and the energy chirp, we need to monitor the energy from the beam position at the dispersive part of the BC with a 0.1% resolution. However, a beam profile at the dispersive part is horizontally flat and wide, maximally 50 mm, due to the large energy chirp of the beam. Therefore, we designed a multi-stripline beam position monitor. This monitor has a flat rectangular duct with a 70 mm width and a 10 mm height. Six stripline electrodes at individual intervals of 10 mm are equipped on each of the top and the bottom surface. Due to the small height of the monitor, each electrode is sensitive to the electron position within 10 mm in the horizontal. Therefore, the monitor provides a rough charge profile and the beam position which is calculated from the gravity center of the signals. We prepared a prototype of the monitor and tested it at the SCSS test accelerator. We confirmed that the position sensitivity was better than 0.1 mm, which corresponds to 0.1 % energy resolution.
KEK, Ibaraki
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
UH, Honolulu, HI
An x-ray beam size monitor based on coded aperture imaging* has been developed at CesrTA, for the purpose of making bunch-by-bunch, turn-by-turn measurements of low emittance beams. Using low-emittance beam (~44 pm, or 16 microns at the x-ray source point) we have been able to make detailed comparisons between the measured mask response and that predicted by theory, validating our simulations of the mask response. In turn, we demonstrate the ability to measure both integrated and single-bunch turn-by-turn beam sizes and positions for monitoring the progress of the low-emittance tuning of the machine, and for electron-cloud instability-related beam dynamics studies.
* J.W. Flanagan et al., EPAC08, 1029 (2008).
TUB, Beijing
The coherent Smith-Purcell radiation (CSPR) has been demonstrated as an efficient technique for measuring the longitudinal profile of beam bunches. To measure the ultrashort beam bunches, the simulations for the measurements using CSPR are anlyzed with tools of three dimensional particle-in-cell simulations and Kramer-Kronig reconstruction. Different parameters such as rms length of beam bunch and profiles of grating are studied. Furthermore, the measurement device based on a Martin-Puplett Interferometer is introduced, in which noises and attenuation can be reduced.
RAS/INR, Moscow
Bunch shape monitors with low energy secondary electrons transverse modulation have found a use for measurements of longitudinal distribution of charge in bunches for ion linear accelerators. Temporal bunch structure is coherently transformed into the spatial distribution through transverse rf scanning. The fields of the analyzed beam can influence the trajectories of the secondary electrons thus resulting in a distortion of the transformation and hence to a deterioration of measurement accuracy revealed in worsening of a phase resolution and in appearance of an error of phase reading. The first error component aggravates observation of the bunch fine structure. The second one distorts the measured shape of the bunch as a whole. Two models have been used for the effect analysis. In the first model a target potential of the bunch shape monitor is supposed to be undistorted by the analyzed beam space charge. In the second model a target potential is completely defined by the potential of the analyzed beam bunch. The applicability of the two models is discussed. The results of simulations for typical beam parameters are presented for the latest bunch shape monitor elaborations.
IFIC, Valencia
SLAC, Menlo Park, California
In this paper we describe the design, installation and first calibration tests of a Multi Optical Transition Radiation (OTR) monitor system in the beam diagnostic section of the Extraction (EXT) line of ATF2, close to the multi wire scanner system. This system will be a valuable tool for measuring beam sizes and emittances from the ATF Damping Ring (DR). With an optical resolution of about 2 um an original OTR design demonstrated the ability to measure a 5.5um beam size in one beam pulse and to take many fast measurements. This gives the OTR the ability to measure the beam emittance with high statistics, giving a low error and a good understanding of emittance jitter. Furthermore the near by wire scanners will be a definitive test of the OTR as a beam emittance diagnostic device. The muti-OTR system design proposed here is based on the existing OTR1X, located after the septums at the entrance of the EXT line.
CERN, Geneva
LINAC4 is the first step in the upgrade of the injector chain for the LHC and will accelerate H- ions to 160 MeV. The ion source has initially been installed in a laboratory setup where its commissioning started at the end of 2009. A slit-grid system is used to monitor the transverse emittance at the exit of the source. Measurement results have been compared to analytical and numerical predictions of the system performance, addressing the system resolution, accuracy and sensitivity. This information has been used to improve the design of a new slit-grid system required for commissioning the linac at higher energies.
EPFL, Lausanne
CERN, Geneva
To improve the quality of the CLIC Test Facility 3 drive beam, it has been proposed that a photo injector replaces the actual thermionic gun. This would produce a lower emittance beam and minimize beam losses in the injector since the RF bunching and sub‐harmonic bunching systems would not be needed anymore. Such a photo injector, named PHIN, is currently being developed at CERN. One of the difficulties is to provide a high intensity beam (3.5A) with a stable (0.1%) beam energy over 1.5us as well as a relative energy spread less than 1%. A 90° spectrometer line featuring a segmented dump and an Optical Transition Radiation screen has been constructed and commissioned in order to study the time evolution of the beam energy along the pulse duration. In the following paper, we present the design as well as the results from the previous two PHIN runs.
CERN, Geneva
University of Oslo, Oslo
The CLIC study is based on the so‐called two‐beam acceleration concept and one of the main goals of the CLIC Test Facility 3 is to demonstrate the efficiency of the CLIC RF power production scheme. As part of this facility a Test Beam Line (TBL), presently under commissioning, is a small scale version of a CLIC decelerator. To perform as expected the beam line must show efficient and stable RF power production over 16 consecutive decelerating structures. As the high intensity electron beam is decelerated its energy spread grows by up to 60%. A novel segmented beam dump for time resolved energy measurements has been designed to match the requirements of the TBL. As a complement, a diffusive OTR screen is also installed in the same spectrometer line. The combination of these two devices will provide both a high spatial resolution measurement of both the energy and energy spread and a measurement with a few nanoseconds time response. This paper describes the design of the new segmented dump and presents the results from the first commissioning of the TBL spectrometer line.
JAI, Egham, Surrey
CERN, Geneva
Royal Holloway, University of London, Surrey
A setup for the investigation of Coherent Diffraction Radiation (CDR) from a conducting screen as a tool for non-invasive longitudinal electron beam profile diagnostics has been designed and installed in the Combiner Ring Measurement (CRM) line of the CLIC Test Facility (CTF3, CERN). In this report the status of the monitor development and results on the interferometric measurements of CDR spectra are presented. The CDR signal correlation with an RF pickup and a streak camera is reported. The future plans for the system improvements are also discussed.
The University of Liverpool, Liverpool
MPI-K, Heidelberg
Cockcroft Institute, Warrington, Cheshire
Supersonic gas-jets have attracted much interest as experimental targets in several fields of science since they combine low internal temperatures with high directionality. Axisymmetric jets have found widespread application, triggering a wealth of studies on their properties, while only a limited number of detailed studies have been done on planar jets. In this paper, the design of a beam profile monitor based on a planar supersonic gas-jet for use in the Ultra-low energy Storage Ring (USR) at the Facility for Antiproton and Ion Research (FAIR) in Germany is described. Optimization of the monitor requires investigation into different characteristic jet parameters. For that purpose extensive simulation work with the Gas Dynamics Tool (GDT) was done. The results of these studies are presented together with a description of a novel nozzle-skimmer configuration and an experimental test stand to benchmark the numerical results.
JAI, Oxford
We report on the possible utilisation of Smith-Purcell radiation to measure the longitudinal profile of 50-femtoseconds electron bunches. This length is typical for the bunches currently produced by Laser Wakefield Acceleration and is at the limit of what is achievable by alternative techniques, such as Electro-Optic sampling.
JAI, Oxford
Although the pepper-pot method has been used for decades at low energy to measure the transverse emittance of particles sources, it has only been extended to high energy very recently. We report on some of the recent measurements done at high energy (several hundred MeVs) and discuss the practical consideration of such measurements. We show demonstrate that an extended pepper-pot does not significantly affect the phase space of the beam and thus provides a valid transverse emittance measurement.
Fermilab, Batavia
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
INFN-Ferrara, Ferrara
PNPI, Gatchina, Leningrad District
BNL, Upton, Long Island, New York
The T980 crystal collimation experiment is underway at the Tevatron to study various crystal types and parameters and evaluate if this technique would increase TeV beam-halo collimation efficiency at high-energy hadron colliders such as the Tevatron and the LHC. The setup has been substantially enhanced during the Summer 2009 shutdown by installing a new O-shaped crystal in the horizontal goniometer, adding a vertical goniometer with two alternating crystals (O-shaped and multi-strip) and additional beam diagnostics. First measurements with the new system are quite encouraging, with channeled and volume-reflected beams observed on the secondary collimators as predicted. Investigation of crystal collimation efficiencies with crystals in volume reflection and channeling modes are described in comparison with an amorphous primary collimator. Results on the system performance are presented for the end-of-store studies and for entire collider stores. Planning is underway for dedicated studies during a Tevatron post-collider physics running period.
ANL, Argonne
Peta-scalable software packages for beam dynamic simulations are being developed and used at the Argonne Leadership Computing Facility. The standard Particle-In-Cell (PIC) method and direct Vlasov solvers in 4 dimensions have been developed and benchmarked with respect to each other. Both of them have been successfully run on 32 thousands processors on BG/P at Argonne National Laboratory. Challenges and prospects of developing Vlasov solvers in higher dimensions will be discussed. Several scalable Poisson solvers have been developed and incorporated with these software packages. Domain decomposition method has been used for the parallelization. In the future developments, these algorithms will be applied to hundreds of thousands processors for peta-scale computing. These software packages have been applied for the design of accelerators, and some large scale simulations will be shown and discussed.
UFPel, Pelotas
UDESC, Joinville
IF-UFRGS, Porto Alegre
Although undesired in many applications, the intrinsic spurious spatial inhomogeneity that permeates real systems is the forerunner instability which leads high-intensity charged particle beams to its equilibrium. In general, this equilibrium is reached in a particular way, by the development of a tenuous particle population around the original beam, conventionally known as the halo. In this way, the purpose of this work is to analyze the influence of the magnitude of initial inhomogeneity over the dynamics and over the equilibrium characteristics of initially quasi-homogeneous mismatched beams. For that, all beam constituent particles, which are initially disposed in an equidistant form, suffer a progressive perturbation through random noise with a variable amplitude. Dynamical and equilibrium quantities are quantified as functions of the noise amplitude, which indirectly is a consistent measure of the initial beam inhomogeneity. The results have been obtained by the means of full self-consistent N-particle beam numerical simulations and seem to be an important complement to the investigations already carried out in prior works.
UFPel, Pelotas
IF-UFRGS, Porto Alegre
Beams of charged particles usually reach their stationary state by the development of a halo. Halo formation in charged beams is in fact a macroscopic transcription of microscopic instabilities acting inside the beam and upon its constituent particles. In previous works, investigations have been carried out to understand the role of the initial envelope mismatch and of magnitude of inhomogeneity in the beam route to the equilibrium. Although in that works the action of the mentioned instabilities has been studied individually, it is clear that in real implemented beams both act together. In this sense, the main purpose of this work is to generalize previous models, considering now concomitantly the effects of the envelope mismatch and of the inhomogeneity. As a final product of the investigation, a particle-core model for beam constituent particles is presented. The agreement with full self-consistent N-particle beam numerical simulations is satisfactory and the results provided by the model seem to be more compatible with that would be expected experimentally.
MEPhI, Moscow
The undulator linear accelerator using electrostatic undulator (UNDULAC-E) is suggested as an initial part of high intensity ion linac*. In UNDULAC ion beam accelerating and focusing are realized by of the combined field of two non-synchronous harmonics. Indeed, the main factor limiting beam intensity in ion accelerator is a space charge force. There exist, at least, two ways to increase ion beam intensity: to enlarge the beam cross section and to use the space charge neutralization. The ribbon ion beam dynamics in UNDULAC-E was discussed in**. Accelerating force value in UNDULAC is proportional to squared particle charge and oppositely charged ions with the identical charge-to-mass ratio can be accelerated simultaneously within the same bunch and the beam space charge neutralization can be realized. These methods will be studied analytically and verified by numerical simulation for UNDULAC-RF in this paper.
*E.S. Masunov, Sov. Phys. ' Tech. Phys., 1990, v. 35 (8), pp. 962-965. **Masunov, S.M. Polozov. NIM A, 558 (2006), pp. 184-187.
MEPhI, Moscow
The beam loading effect is one of main problems limiting the beam current. Usually this effect takes into account only in high energy electron linacs. Due to low energy electron and, especially, ion linacs nowadays current increasing the beam loading effect should be considered here. Self consistent beam dynamics simulation methods with Coulomb field and beam loading effect are discussed. The simulation results are in good agreement with experiment which have been carried out on NRNU MEPhI electron linac.
CIEMAT, Madrid
CEA, Gif-sur-Yvette
The design of the future IFMIF accelerators will be validated with the 9 MeV, 125 mA deuteron accelerator IFMIF-EVEDA. For this validation phase, a High Energy Beam Transport line (HEBT) is designed to drive the beam toward a beam dump with the required expansion, under the hands-on maintenance constraint. It consists of eight quadrupoles and one dipole. Given the very high space charge regime and the very high power (1.1 MW), any small deviation from the nominal conditions could seriously compromise the HEBT objective. That is why possible misalignments and rotations of those magnets as well as power supply errors have been thoroughly studied. The error budget is fairly distributed among the tolerances for the different components, and effects of those errors on loss distribution and beam profile at the beam dump entrance carefully analysed.
NSC/KIPT, Kharkov
The electron injector for a storage ring is one of numerous applications of the rf linacs of intensive short-pulsed beams with duration about 100 ns, current about 1 A and energy of particles in a few ten MeB. Since acceleration of intensive short-pulsed beams takes place in transient mode, then the energy spread is determined by both intro- and multi- bunch spread. Getting the energy spread less than 1% is the actual problem. In this work we simulate numerically unsteady self-consistent dynamics of charged particles in an rf linac that consist of a low-voltage (25 keV) thermionic gun, a compact evanescent wave buncher, a traveling wave accelerating structure. For transient beam loading compensation a method of delay of a beam relatively rf pulse are applied. The simulation takes into account influence on the beam dynamic of such factors as: initial energy and phase spread; sliding of particles in relation to a wave in the initial part of accelerating section; temporal dependence of phase and energy of bunches at the enter of section; space charge field.
NSC/KIPT, Kharkov
At present work the results of numeral simulation of electron dynamics in an unhomogeneous disk-loaded waveguide which is used in the S-band linac are presented. Two approaches taking into account the self-fields of beam radiation are considered: the first method estimative based on the power diffusion equation; the second one based on of self-consistent equations of field excitation and particles motion. The self-consistent approach showed the presence of substantial phase slipping of particles in the homogeneous part of the rf structure, conditioned by the reactive beam loading.
GSI, Darmstadt
IPCP, Chernogolovka, Moscow region
Universidad de Castilla-La Mancha, Ciudad Real
CERN, Geneva
Safety of the personnel and the equipment is an issue of great concern when operating with mighty particle beams like the ones generated by the LHC. Any uncontrolled release of even a very small fraction of the beam energy could cause considerable damage to the equipment. A worst case scenario is in which the entire beam is lost at a single point. Over the past years, we have carried out extensive numerical simulations to assess the consequences of an accident of this magnitude. We have simulated the thermodynamic and the hydrodynamic response of cylindrical targets made of solid copper and solid graphite, respectively, that are facially irradiated with one LHC beam. Our simulations show that the 7 TeV/c LHC protons will penetrate up to about 35 m in solid copper and about 10 m in solid graphite during the 89 μs beam duration time. In both cases, the target is severely damaged and a substantial part of the target is converted into High Energy Density Matter state.
CERN, Geneva
Mission critical systems at the European Organisation for Nuclear Research (CERN) make extensive use of Programmable Logic Devices (PLDs) such as Field Programmable Gate Arrays (FPGAs) to implement their safety critical functions. The dependability of these safety critical functions is difficult to determine using traditional techniques. A robust approach is needed if PLD technology is to be accepted in mission critical systems. This paper discusses techniques which are being developed and employed by CERN to give confidence in the use of PLDs in mission critical systems, the Safe Machine Parameter system development is used as an example.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
The use of a beam stop to absorb full or partial beam at various points along a particle accelerator is commonplace. The design of accelerator components such as magnets, linacs and beam instruments tends to be a fairly focused and collective effort within the particle accelerator community with well established performance and reliability criteria. Beam stop design by contrast has been relatively isolated and unconstrained historically with much more general goals. This combination of conditions has lead to a variety of facility implementations with virtually no standardization and minimal concensus on approach to development within the particle accelerator community. At the Spallation Neutron Source (SNS), for example, there are four high power beam stops in use, three of which have significantly different design solutions. This paper describes the design of a new off-momentum beam stop for the SNS. Content will be balanced between hardware description, analyses performed and the methodology used during the development effort. Particular attention will be paid to the approach of the design process with respect to future efforts to meet beam stop performance metrics.
IPM, Tehran
CERN, Geneva
The pulse compressor is located after the klystron to increase the power peak by storing the energy at the beginning and releasing it near the end of klystron output pulse. In the CTF3 [1] pulse compressors a doubling of the peak power is achieved according to our needs and the machine parameters. The magnitude of peak power, pulse length and flatness can be controlled by using a phase modulator for the input signal of klystrons. A C++ code is written to simulate the pulse compressor behaviour according to the klystron output pulse power. By manually changing the related parameters in the code for the best match, the quality factor and the filling time of pulse compressor cavities can be determined. This code also calculates and sends the suitable phase to the phase modulator according to the klystron output pulse power and the desired pulse length and peak power.
ESS Bilbao, Bilbao
Bilbao, Faculty of Science and Technology, Bilbao
ESS-Bilbao, Zamudio
University of the Basque Country, Faculty of Science and Technology, Bilbao
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Design, implementation and some practical results of the pulsed digital LLRF system (amplitude, phase and tuning loops) of the RFQ for the ISIS front end test stand are presented. The design is based on a fast analog front-end for RF-baseband conversion and a model-based Virtex-4 FPGA unit for signal processing and PI regulation. Complexity of the LLRF timing is significantly reduced and the LLRF requirements are fulfilled by utilizing the RF-baseband conversion method compared to the conventional RF-IF approach. Validity of the control loops is ensured practically by hardware-in-the-loop co-simulation of the system in MATLAB-Simulink using an aluminium mock-up cavity. It was shown through extensive tests that the LLRF system meets all the requirements including amplitude and phase stability, dynamic range, noise level and additionally provides a full amplitude and phase control range and a phase margin larger than 90 degrees for loop stability.
SLAC, Menlo Park, California
ANL, Argonne
DESY, Hamburg
The FLASH L-band (1.3 GHz) superconducting accelerator facility at DESY has a Low Level RF (LLRF) system that is similar to that envisioned for ILC. This system has extensive monitoring capability and was used to gather performance data relevant to ILC. Recently, waveform data were recorded with both beam on and off for three, 8-cavity cryomodules to evaluate the input RF and cavity gradient stability and study the RF overhead required to achieve constant gradient during the 800μs pulses. In this paper, we present the recent experimental results and discuss the pulse-to-pulse input RF and cavity gradient stability for both beams on and off cases. In addition, a model of the gradient variation observed in the beam off case will be described.
SLAC, Menlo Park, California
CERN, Geneva
Radio Frequency (RF) accelerating system noise and non-idealities can have detrimental impact on the LHC performance through longitudinal motion and longitudinal emittance growth. A theoretical formalism has been developed to relate the beam and RF loop dynamics with the bunch length growth [1]. Measurements were conducted at LHC to validate the formalism, determine the performance limiting RF components, and provide the foundation for beam diffusion estimates for higher energies and intensities. A brief summary of these results is presented in this work.
[1] T. Mastorides et. al., "RF system models for the LHC with Application to
Longitudinal Dynamics", prepared for submission to Physical Review ST-AB.
INFN-Ferrara, Ferrara
UNIFE, Ferrara
IHEP Protvino, Protvino, Moscow Region
We present an analytical model to calculate the physical quantities of interest experienced by relativistic particles in their motion aligned with periodic complex atomic structures. Classical physics equations and the expansion of periodic functions as a Fourier series have been used for the calculation. This method allows calculating the contribution from all the planes and axes inside the crystal, in contrast to other simulation codes for which the motion is evaluated only on nearest neighbors atomic strings. Based on the calculation technique we have developed the "ECHARM" program, which allows calculating one- and two- dimensional averaged physical quantities of interest. The calculation holds for the main axes of any orthorhombic and tetragonal structures and for any orientation in the cubic structure. To underline the capability of the program, complex structures such as zeolites have been worked out. Based on the "ECHARM" code, simulation of the relativistic particle motion within complex structures has been developed. With this code it is possible to simulate the motion in bent crystal to study planar and axial channeling volume reflection.
USTC/PMPI, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Collinear load is a substitute for waveguide load to miniaturize irradiation accelerators and make the system compact. The key technology is to design coaxial cavities coated inside with attenuating materials which will terminate the remnant power, meanwhile the operation frequency of 2856 MHz retains. For lossy materials such as Kanthal (25%Cr-5%Al-Fe) alloy, CST is used to simulate the effect of the coating on the load cavity properties like the operation frequency and attenuation. The frequency shifts caused by the coatings would be compensated by the strategy of cavity dimensions adjustment. Simulations revealed the compensation rules of the cavity inner radius b. Meanwhile the relationship between the attenuation and the coating area was also resolved. Based on a specified power allocation, a 15 kW collinear load consisting of six cavities at 2π/3 mode was designed with one-way attenuation of -18.8 dB. Two sets of prototype cavities have been manufactured and the experiment results are presented, compared with the CST simulations.
USTC/PMPI, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Microwave-absorbing material is an essential part of LINAC collinear load. It is coated on the inner walls of several trailing accelerating cavities to transform the remnant microwave power into heat. Fe-85%Si-9.6%Al-5.4% alloy, which reveals low outgassing rate and high attenuation, is selected for collinear load R&D. To measure the permittivity and permeability of FeSiAl at 2856 MHz, the coaxial transmission-reflection method is adopted. The system is firstly examined by testing the hollow coaxial fixture and comparing the results with the electromagnetic parameters of the air. Measurements of two PTFE rings show that the air gaps between the fixture and samples influence the test results seriously. CST is utilized to simulate the effects on the FeSiAl measure-ments. Eventually a scheme of molding the samples of FeSiAl powder mixed with paraffin to form a wax mold is proposed and the permittivity and permeability of FeSiAl are derived from the electromagnetic parameters equivalent formulas of mixed medium.
CEA, Gif-sur-Yvette
LPSC, Grenoble Cedex
Lattice design tools are being developed, and related beam and spin dynamics simulations are being performed, in the framework of the international collaboration regarding the super-B project. The present contribution reports on this work.
University of Pisa and INFN, Pisa
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
SuperB is an international project for an asymmetric 2 rings collider at the B mesons cm energy to be built in the Rome area in Italy. The two rings will have very small beam sizes at the Interaction Point and very small emittances, similar to the Linear Collider Damping Rings ones. In particular, the ultra low vertical emittances, 7 pm in the LER and 4 pm in the HER, need a careful study of the misalignment errors effects on the machine performances. Studies on the closed orbit, vertical dispersion and coupling corrections have been carried out in order to specify the maximum allowed errors and to provide a procedure for emittance tuning. A new tool which combines MADX and Matlab routines has been developed, allowing for both corrections and tuning. Results of these studies are presented.
KEK, Ibaraki
Optics parameters at the interaction point, beta, x-y coupling, dispersion and their chromatic aberrations, seriously affect the beam-beam performance as is shown in experiments and simulations. The control of the optics parameters is essential to maintain the high luminosity in KEKB. They drift day by day, or before and after the beam abort. They were often monitored at intervals of the operation with taking the study time. They are recently measured during the physics run using a pilot bunch without collision. We show the measured the optics parameters and their variations and discuss the relation to the luminosity.
KEK, Ibaraki
Super B factories are designed with very low emittance and very low beta function at the interaction point. The two beams collide with a large crossing angle, thus the overlap area of the beams is limited at a small part of their length. Simulation of the beam-beam effects is hard because of the longitudinal slice of the beam is the order of 100. We discuss two methods for the simulation. One is a simplified method, which is mixture of the particle in cell and Gaussian approximation. The other is fully strong-strong simulation using the particle in cell. The shifted Green function is used to calculate the beam-beam force for less overlap of the beam distribution. Luminosity and its degradation due to IP optics errors in Super B factories are discussed.
KEK, Ibaraki
Single bunch instability caused by electron cloud can depend on emittance, because the electron oscillation period in positron bunch is large. The single bunch instability should appear as a head-tail motion with synchro-beta frequency. We discuss the single bunch instability in low emittance rings, CesrTA, Super B factories and ILC damping ring with focusing the threshold and synchro-beta oscillation.
KEK, Ibaraki
Using a weak-strong beam-beam code, in which the symplectic maps for the linear coupling and chromatic aberrations were implemented, the luminosity degradation caused by the linear and chromatic X-Y couplings at the interaction point (IP) were evaluated for the SuperKEKB project under design. The linear and chromatic X-Y couplings were estimated through modeling the machine errors using random seeds, based on a baseline design of the SuperKEKB rings. It was found that the linear and chromatic X-Y couplings can potentially degrade the luminosity performance.
KEK, Ibaraki
SLAC, Menlo Park, California
Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.
KEK, Ibaraki
University of Tokyo, Tokyo
Tohoku University, Graduate School of Science, Sendai
SuperKEKB is the upgrade plan of the current B-factory experiment with the KEKB accelerator at KEK. Its luminosity is designed to be 8x1035 /cm2/s (40 times higher than KEKB) and the integrated luminosity is expected to be 50 ab-1. In SuperKEKB, it is important to evaluate the beam induced BG and design the interaction region (IR) to assure the stable detector operation. To estimate the beam induced BG, we construct the beam-line simulation based on the GEANT4 simulation. In this paper, we report the BG evaluation and the IR design for SuperKEKB.
SLAC, Menlo Park, California
We discuss the feasibility of an application of an implicit finite-difference approximation to calculate the fields of a bunch moving with no restriction inside the vacuum chamber.
MPI-P, München
IHEP Beijing, Beijing
Simulations of frictional cooling for a muon collider front end scheme show that it is a viable technique for quickly producing colliding beams. The Frictional Cooling Demonstration experiment at the Max Planck Institute for Physics, Munich, aims to demonstrate the working principle of frictional cooling on protons using a 10-cm-long cooling cell. The experiment is nearing the final data taking stages. The status of the experiment is presented along with recent data. Simulation of the experiment setup is also presented.
MPI-P, München
IHEP Beijing, Beijing
Muon colliders would open new frontiers of investigation in high energy particle physics, allowing precision measurements to be made at the TeV energy frontier. One of the greatest challenges to constructing a muon collider is the cooling of a beam of muons on a timescale comparable to the lifetime of the muon. Frictional cooling holds promise for use in a muon collider scheme. By balancing energy loss to a gas with energy gain from an electric field, a beam of muons is brought to an equilibrium energy in 100s of nanoseconds. A frictional cooling scheme for producing high-luminosity beams for a muon collider is presented.
BNL, Upton, Long Island, New York
The proposed electron ion collider, eRHIC, requires large average polarized electron current of 50mA, which is more than 20 times higher than the present experiment results of single polarization source, such as GaAs. To achieve the current requirement of eRHIC, we have designed the multi-cathode DC electron gun for injection. 24 GaAs cathodes will be prepared and emit electrons at the arranged pattern. Despite of ultra-high vacuum and precise timing, multi-cathode DC electron gun has high demand on the electric field symmetry, magnetic field shielding, and arcing prevention. In the paper, we present the 3D simulation results of the latest model for the multi-cathode DC electron gun. The results will give guidance to the actual design in the future.
CERN, Geneva
DESY, Hamburg
The Super Proton Synchrotron (SPS) at CERN with a peak energy of 450GeV is at the top of the LHC preaccelerator-complex. Apart from the LHC, SPS is with Tevatron the accelerator with the largest stored beam energy of up to 2.5MJ. The SPS has a known vulnerability to fast equipment failures that led to an uncontrolled loss of a high intensity beam in 2008, which resulted in major damage of a main dipole. The beam loss was caused by a fast tune decrease towards an integer resonance. Simulations and distinct experimental studies provide clear understanding of the beam dynamics at different SPS tune resonances. Diverging closed orbit oscillations, dispersion explosion and increased beta-beating are the driving effects that lead to a complete beam loss in as little as 3 turns (70μs). Dedicated experiments of fast failures of the main power converters reveal that the current interlock systems are much too slow for an adequate machine protection. To counteract the vulnerability of the SPS, current research focuses on a new fast position interlock system which is planned to become operational in 2010.
GSI, Darmstadt
CERN, Geneva
The presence of an electron cloud in an accelerator generates a number of interesting phenomena. In addition to electron-driven beam instabilities, the electron "pinch" occurring during a beam-bunch passage gives rise to a highly nonlinear force experienced by individual beam particles. A simple 1-dimensional model for the effect of the electron pinch on the beam reveals a surprisingly rich dynamics. We present the model and discuss simulation results.
BNL, Upton, Long Island, New York
The luminosity of a ring-ring electron-ion collider is limited by the beam-beam effect on the electrons. Simulation studies have shown that for short ion bunches this limit can be significantly increased by head-on beam-beam compensation via an electron lens. However, due to the large beam-beam parameter experienced by the electrons, together with an ion bunch length comparable to the beta-function at the IP, electrons perform a sizeable fraction of a betatron oscillation period inside both the long ion bunches and the electron lens. Recent results of our simulation studies of this effect will be presented.
KEK, Ibaraki
Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its scheme from 'high current' option to 'nano-beam' scheme. In the latter the current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. The emittance of the injected beam should be low and, since the Tousheck lifetime is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. For the electron beam a low-emittance high-intensity RF gun is adopted. For the positron beam a damping ring has been proposed. The design of the damping ring has been performed for the high-current option*. In this paper an updated design for the nano-beam scheme is presented.
* Nucl. Instr. Meth. A 556 (2006) 13-19
BINP SB RAS, Novosibirsk
A new beam extraction scheme from a synchrotron is put forward. The main difference from other schemes of extraction is the use of a magnetic shields instead of a septum. Magnetic shields are located in the central dipole magnets of a pulsed chicane. The magnetic shield is a multi-layer copper-iron tube. Numerical simulations and experimental results for the magnetic shield are presented. A good accordance between them has shown. The advantages of the new scheme are easy technical implementation and compactness. The area of application is extraction from a synchrotron. The proposed scheme will be used in a new synchrotron radiation source in Novosibirsk.
EBG MedAustron, Wr. Neustadt
CERN, Geneva
The LHC beam dump system has to safely dispose all beams in a wide energy range of 450 GeV to 7 TeV. A 3 μs abort gap in the beam structure for the switch-on of the extraction kicker field ideally allows a loss free extraction under normal operating conditions. However, a low number of asynchronous beam aborts is to be expected from reliability calculations and from the first year's operational experience with the beam dump kickers. For such cases, MAD-X simulations including all optics and alignment errors have been performed to determine loss patterns around the LHC as a function of the position of the main protection elements in interaction region six. Special attention was paid to the beam load on the tungsten collimators which protect the triplets in the LHC experimental insertions, and the tracking results compared with semi-analytical numerical estimates. The simulations are also compared to the results of beam commissioning of these protection devices.
CERN, Geneva
The tilt mismatch between the LHC and its transfer lines arises from the use of combined horizontal and vertical bends. The mismatch gives rise to several subtle optical effects, including a coupling at injection into the LHC which depends on the phase of the oscillation amplitude at the injection point. This coupling was observed for the first time in 2008, and in 2009 dedicated measurements were made. The results are described and compared with the expectations, and the operational implications detailed.
CERN, Geneva
We report on first observations and detailed simulations of beam gas rates in the LHC. For the simulations, a comprehensive tool has been set up to simulate in a few hours the expected beam gas losses when pressure maps, collimator settings, and/or beam optics changes. The simulation includes both elastic and inelastic scattering, with subsequent multiturn tracking of proton residues. This provides amongst others a more realistic collimator loss distributions from elastic interactions than what was previously available.
CERN, Geneva
Background and loss rates vary when beams are brought into collisions in the LHC and when the beam separation is varied during luminosity scans. We report on the first observations in the early LHC operation. The observed effects are analyzed and compared with models and simulation.
INFN-Roma, Roma
CERN, Geneva
JINR, Dubna, Moscow Region
We present a detailed analysis of the beam loss data collected at the SPS during the 2009 machine developments devoted to test crystal collimation. Scintillator counters and Gas electron multiplier detectors were installed in special points to detect the effect of inelastic interaction of protons with the crystals in various orientation with respect to the beam. Clear correlations of the counting rates with the crystal positions and orientation were detected during the data-taking and were crucial to put the crystal in optimal channeling position. For one of the crystal the pattern of losses showed evidence of several planar and axial channeling conditions.
SLAC, Menlo Park, California
The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite secondary collimators with 30 high Z Phase II collimators. This paper reports on BPM and impedance considerations and measurements of the integrated BPMs in the prototype rotatable collimator to be installed in the Super Proton Synchrotron (SPS) at CERN. The BPMs are necessary to align the jaws with the beam. Without careful design the beam impedance can result in unacceptable heating of the chamber wall or beam instabilities. The impedance measurements involve utilizing both a single displaced wire and two wires excited in opposite phase to disentangle the driving and detuning transverse impedances. Trapped mode resonances and longitudinal impedance are to also be measured and compared with simulations. These measurements, when completed, will demonstrate the device is fully operational and has the impedance characteristics and BPM performance acceptable for installation in the SPS.
RRCAT, Indore (M.P.)
BARC, Mumbai
Four and eight cell Plane Wave Transformer (PWT) linac structures have been developed as part of the injector development for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) at RRCAT. In this paper, we discuss the tuning of resonant frequency and waveguide-cavity coupling coefficient for these structures, and compare results obtained from cold tests with those predicted by RF simulations. We also compare energy gain and RF properties of these structures, determined from transient and steady state behavior of the structure during recent high power tests, with those predicted by cold tests.
ISIR, Osaka
KEK, Ibaraki
HU/AdSM, Higashi-Hiroshima
We conduct research on Free Electron Laser (FEL) in the infrared region and pulse radiolysis for radiation chemistry using the 40 MeV, 1.3 GHz L-band linac of Osaka University. At present, the L-band linac is equipped with a thermionic electron gun. It can accelerate a high-intensity single-bunch beam with charge up to 91 nC but the normalized emittance is large. In order to advance the research, we have begun development of a photocathode RF gun for the L-band electron linac in collaboration with KEK and Hiroshima University. We start the basic design of the RF gun cavity for the L-band linac at ISIR, Osaka University, based on the 1.5 cells, which is a normal conducting photocathode RF gun. A material of the cathode should be Cs2Te, which has the high quantum efficiency of a few percents, to produce a beam with high charge up to 30 nC/bunch. We improve the cooling system of the cavity for high duty operation to suppress the thermal deformation due to the heat load of input rf power. The simulation study has been also performed for the L-band linac at ISIR with a high charge electron beam. In this conference, we describe the details of the L-band photocathode RF gun development.
Tohoku University, School of Scinece, Sendai
Tohoku University, Research Center for Electron Photon Science, Sendai
A test accelerator for the coherent terahertz source (t-ACTS) has been under development at Laboratory of Nuclear Science, Tohoku University*. Intense coherent terahertz radiation will be generated by the very short electron bunch less than 100 fs using a thermionic RF gun (ITC RF-gun). ITC RF-gun is designed to have two cells uncoupled with each other, so that it can be operated at various combinations of different rf-power level and phase difference so as to optimize the longitudinal phase space distribution of the electron beam for bunch compression**. The gun employs single-crystal LaB6 cathode with small diameter of 1.8 mm to obtain a very small initial emittance with sufficiently high current density. The RF gun has been already manufactured and the measurement of RF characteristics is now in progress. We will present the results of low-power measurement and also discuss the effect of the cathode misalignment on the beam parameters such as transverse emittance and longitudinal phase space distribution.
* H. Hama et al., New J. Phys. 8 (2006) 292.
** H. Hama et al., Nucl. Instr. and Meth., A 528, (2004) 371.
TUB, Beijing
In this paper, we present the preliminary structure design and optimization of a C-band photocathode RF gun for a compact electron diffraction facility. It will work at 5.712GHz. A dual coupler and elliptical iris between half-cell and full-cell are adopt in this gun for lower emittance and larger mode separation. A detailed 3D simulation of the C-band RF gun with coupler is performed. This paper likewise presents the beam dynamics parameters and analysis of this gun.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The injector for the UK's New Light Source project is required to deliver low emittance 200 pC electron bunches at a repetition rate of up to 1 MHz. Initial design of a photoinjector based around a 1' cell L-band superconducting RF gun able to meet these requirements is presented, including beam dynamic simulations of the injector up to the end of the first linac module.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The injector for the UK's New Light Source project is required to deliver low emittance 200 pC electron bunches at a repetition rate of up to 1 MHz. A possible solution to these requirements is an injector based around a normal conducting VHF RF gun. The injector design and results of beam dynamics simulations are presented for cases with and without an independent buncher cavity.
UCLA, Los Angeles, California
INFN/LNF, Frascati (Roma)
Rome University La Sapienza, Roma
A unique SW/TW hybrid photoinjector are being developed under the collaboration of UCLA, LNF/INFN, and University of Rome. It can produce 240-fs (rms) bunch with 500 pC at 21 MeV. The bunch distribution has a strong spike (54 fs FWHM) and the peak current is over 2kA. As the bunch form factor at 1 THz is 0.43, it can produce coherent radiation at 1 THz. We are considering three types of way to generate it; coherent Cherenkov radiation (CCR), superradiant FEL, and coherent transition/edge radiation (CTR/CER). CCR used hollow dielectric with the outer surface metallic-coated. OOPIC simulation showed 21 MW of the peak power (5 mJ) at 1 THz. For FEL and CTR/CER simulation, QUINDI, which was written at UCLA to solve the Lienard-Wiechert potential, was used to calculate the radiation properties. In the contrast to CCR, their spectra were broad and their pulse lengths were short. They will be useful for fast pumping.
SLAC, Menlo Park, California
SLAC is studying the feasibility of using an X-band RF photocathode gun to produce low emittance bunches for applications such as an MeV gamma source (in collaboration with LLNL) and an injector for a compact FEL. Systematic beam dynamics study are being done for a 5.5 cell X-band gun followed by several 53 cm long high-gradient X-band accelerator structures. A fully 3D program, ImpactT*, is used to track particles taking into account space charge forces, short-range longitudinal and transverse wakefields and the 3D rf fields in the structures, including the quadrupole component of the couplers. The effect of misalignments of the various elements (drive-laser, gun, solenoid and accelerator structures) are being evaluated. This paper presents these results and estimates of the expected bunch emittance versus bunch charge and cathode gradient.
*Ji Qiang, LBNL-62326, January 25, 2007.
Rome University La Sapienza, Roma
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
LBNL, Berkeley, California
Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.
USTC/NSRL, Hefei, Anhui
In order to obtain more straight sections for insertion devices and higher brilliance synchrotron radiation, an upgrade project of Hefei Light source (HLS) is undergoing. A new injection system has been designed to improve injection efficiency and keep the machine running stably. Four kickers will be used to generate a local injection bump. Effects of injection system to injecting beam and stored beam have been simulated considering errors. Finally, ELEGANT code was used to simulate the injection process with new designed bump system. The simulation results show that the injection efficiency would be higher than 99% and perturbation on stored beam would be small enough, which are benefit to full energy injection and top-up operation of HLS in the future.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The proposed UK New Light Source project will need beam dump to absorb a bunch charge of 200 pC with the repetition rates starting from 1 KHz initially up to 1 MHz in the upgrade. We are exploring an option of a solid dump with a graphite core to absorb the beam power up to 450 kW for the upgrade option as this is the most challenging design. Since the beam dump design will also affect the building layout the choice of its design should be made at an early stage. Based on the feasibility studies of a solid dump, a decision not to go for more complex water dump can be taken. The post linac collimation section should protect the undulators from irradiation due to beam halo particles. This paper shows results and conclusions from simulations of the impact of the NLS beam on different solid beam dump solutions and the effect of the beam halo on the collimators.
CEA, Bruyeres le Chatel
GETINGE - La Calhene, Villebon sur Yvette
The original linac consists of an electron gun (45 kV, 6 A peak, 4 μs pulses @ 210 Hz) and 8 accelerating cells coupled with coupling cells in π/2 mode @ 3 GHz to provide for a 1 mA and 5 MeV beam. A loss of control of electron emission was experimentally observed due to anomalous heating of the cathode. We simulate the linac operation with the 2D1/2 MAGIC® electromagnetic PIC code to understand and suppress these phenomena. We show that electrons are accelerated back from the accelerating structure to the cathode. Their power is responsible for the unwanted cathode heating and emission control loss. To overcome these phenomena, a new design is proposed. A buncher cavity and a solenoid are inserted to improve the coupling between the electron beam and the accelerating cells.
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Precise and fast 3D space-charge calculations for bunches of charged particles are still of growing importance in recent accelerator designs. Whereas an adaptive discretization of a bunch is often required for efficient space charge calculations in practice, such a technique is not implemented in many computer codes. For instance, the FFT Poisson solver that is often applied allows only an equidistant mesh. An adaptive discretization following the particle density distribution is implemented in the GPT tracking code (General Particle Tracer, Pulsar Physics) together with a multigrid Poisson solver. The disadvantage of this approach is that jumps in the distribution of particles are not taken into account and the hierarchical construction of meshes in multigrid can not be used. In this paper we present an approach to an adaptive discretization which is based on the multigrid technique. The goal is that the error estimator needed for the adaptive distribution of mesh lines can be calculated directly from the multigrid procedure. The algorithm will be investigated for several particle distributions and compared to that adaptive discretization method implemented in GPT.
Sokendai, Ibaraki
KEK, Ibaraki
Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.
* K. Kanazawa et al., PAC05, 1054.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).
Muroran Institute of Technology, Department of Electrical and Electronic Engineering, Muroran
TEMF, TU Darmstadt, Darmstadt
A Time Domain Boundary Element Method (TDBEM) has advantages of grid dispersion free property, treatment of electron bunch with curved trajectory, etc. in wake field analysis. On the other hand, the TDBEM has also serious problems of heavy calculation cost and large required memory which are main reasons why the TDBEM can not be widely used yet. For the large memory problem, moving window scheme was introduced into the TDBEM and it was shown that the TDBEM can be applied to very long accelerator structures*. This paper presents a new formulation of the TDBEM, an initial value problem formulation. To use the initial value problem formulation of the TDBEM, a new type of moving window scheme, which can be applied to curved trajectory or electron motion with smaller velocity than the speed of light, will be introduced.
* K.Fujita, H.Kawaguchi, R.Hampel, W.F.O.Muller, T.Weiland, S.Tomioka,"Time Domain Boundary Element Analysis of Wake Fields in Long Accelerator Structures,"IEEE Trans. Nucl. Sci.,55[5](2008),pp.2584-2591.
MEPhI, Moscow
This paper introduces "Hellweg 2D" code, a special tool for electron dynamics simulation in waveguide accelerating structure. The underlying theory of this software is based on the numerical solutions of differential equations of particle motion. The effects considered in this code include beam loading, space charge forces, external focusing magnetic field. "Hellweg 2D" is capable to deal with multisectional accelerators. Along with a manual input of electrodynamical parameters of the cells, for disk-loaded structures they can be calculated automatically with a help of experimental data tables. In order to obtain the maximum capture in the buncher section, the optimizer of phase velocity and electric field strength functions is developed. The comparison of U-1-M buncher beam dynamics simulations via "Hellweg 2D" and experimental data is provided.
PSI-LRF, Villigen, PSI
PSI, Villigen
ETH, Zurich
The X-ray Free Electron Laser (SwissFEL) under development at the Paul Scherrer Institut (PSI) will employ a special type of a deflecting cavity, LOLA*, for beam diagnostics. Since this cavity's design breaks the symmetry, a complete 3-dimensional eigenmodal analysis is indispensable. The 3-dimensional eigenmodal solver femaxx employs the finite element method and has been developed in a collaboration between PSI and the Swiss Federal Institute of Technology Zurich (ETH). The femaxx code uses the graphical frontend program heronion for the application of boundary conditions, including symmetry, and generates a tetrahedral mesh. We use femaxx to analyze the existing LOLA cavity design**, compute electromagnetic eigenmodes with their corresponding eigenfrequencies, and associated performance figures. Since these are large computational problems femaxx has been optimized for distributed memory parallel compute clusters. For the further usage in the beam dynamics code OPAL we sample the eigenmodal fields on a 3-dimensional Cartesian grid.
* A. Falone, et al: RF deflector for bunch length measurement at low energy at PSI. Proceedings of PAC2009.
** P. Arbenz et al., Parallel Computing, 32: 157-165 (2006).
Cockcroft Institute, Lancaster University, Lancaster
Tech-X, Boulder, Colorado
The design of RF cavities is a multivariate multi-objective problem. Manual optimisation is poorly suited to this class of investigation, and the use of numerical methods results in a non-differentiable problem. Thus the only reliable optimisation algorithms employ heuristic methods. Using an evolutionary algorithm guided by Pareto ranking methods, a crab cavity design can be optimised for transverse voltage (VT) while maintaining acceptable surface fields and the correct operating frequency. Evolutionary algorithms are an example of a parallel meta-heuristic search technique inspired by natural evolution. They allow complex, epistatic (non-linear) and multimodal (multiple optima and/or sub-optima) optimization problems to be efficiently explored. Using the concept of domination the solutions can be ordered into Pareto fronts. The first of which contains a set of cavity designs for which no one objective (e.g. the transverse voltage) can be improved without decrementing other objectives.
UMAN, Manchester
Cockcroft Institute, Warrington, Cheshire
MERLIN is a highly abstracted particle tracking code written in C++ that provides many unique features, and is simple to extend and modify. We have investigated the addition of high order wakefields to this tracking code and their effects on bunches, particularly with regard to collimation systems for both hadron and lepton accelerators. Updates have also been made to increase the code base compatibility with current compilers, and speed enhancements have been made to the code via the addition of multi-threading to allow cluster operation on the grid. In addition, this allows for simulations with large numbers of particles to take place. Instructions for downloading the new code base are given.
Royal Holloway, University of London, Surrey
Serpentine is a Python library, written for the purpose of simulating charged particle accelerators. It has been written to allow for the simulation of both rings and single-shot machines in a light-weight way (i.e. without requiring significant computational resources for typical calculations, such as the determination of transfer matrices, or matching of Twiss parameters), and has been structured to be highly modular (i.e. allowing extension of the simulations to include effects not already included in the base installation). Through the use of the Universal Accelerator Parser (UAP), Serpentine has no need for a new lattice representation, and allows access to any lattice format understood by UAP. The operation of this code on several complex accelerator designs is demonstrated.
ANL, Argonne
NekCEM is a high-performance parallel code for simulating wakefields based on high-order discretizations*,**. We will present performance of NekCEM code at large count of processors. A newly developed communication kernel for NekCEM enables simulations on 10K-100K processors. We will demonstrate scalablity analysis for P>10K, depending on the number of grid points per processor for wakepotential simulations with a 9-cell TESLA cavity.
* Spectral element discontinuous Galerkin (SEDG) simulations with a moving window, Proc. PAC09
** SEDG simulations for bunched beam in accelerating structures, Proc. PAC07
Muons, Inc, Batavia
Illinois Institute of Technology, Chicago, Illinois
There are dozens of programs for designing and modeling accelerator systems, most of which have their own language for describing the system. This means a designer must spend considerable time learning the languages of different programs and converting system descriptions among them. This paper describes a project to develop a new language for accelerator modeling, together with a portable suite of programs to implement it. These programs will assist the user while editing, visualizing, developing, simulating, and sharing models of accelerator components and systems. This suite is based on a Graphical User Interface (GUI) that will permit users to assemble their system graphically and then display it and check its sanity visually, even while using modeling programs that have no graphical or visualization capabilities. Incorporating the concept of libraries as a primary component of the language will encourage collaboration among geographically diverse teams. The requirements for developing this language and its tools will be based on generality, flexibility, extensibility, portability, usability, and sharability.
Muons, Inc, Batavia
Illinois Institute of Technology, Chicago, Illinois
The G4beamline program* is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit**, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available at: http://g4beamline.muonsinc.com
* http://g4beamline.muonsinc.com
** http://geant4.cern.ch
LBNL, Berkeley, California
Numerical simulation of some systems containing charged particles with highly relativistic directed motion can be speeded up dramatically by choice of the proper Lorentz-boosted frame*. Orders of magnitude speedup has been demonstrated for simulations from first principles of laser-plasma accelerator, free electron laser, and particle beams interacting with electron clouds. We summarize the technique and the most recent examples. We then address the application of the Lorentz-boosted frame approach to coherent synchrotron radiation (CSR), which can be strongly present in bunch compressor chicanes. CSR is particularly relevant to the next generation of x-ray light sources and difficult to simulate in the lab frame because of the large ratio of scale lengths. It can increase both the incoherent and coherent longitudinal energy spread, effects that often lead to an increase in transverse emittance. We use the WARP code** to simulate CSR emission around dipole simple bends. We present some scaling arguments for the possible computational speed up factor in the boosted frame and initial 3D simulation results for some standard CSR test cases.
* J.-L. Vay, Phys. Rev. Lett. 98 (2007) 130405
** D.P. Grote, A. Friedman, J.-L. Vay, and I. Haber, AIP Conf. Proc. 749 (2005), 55.
Tech-X, Boulder, Colorado
Imagine a virtual cylinder passing through an rf cavity. Given field data on the surface of this cylinder, one can compute accurate high-order transfer maps for particles traversing the cavity*. This technique is robust against errors or noise present in the surface data; moreover, it is not limited to accelerating modes. We describe this technique and present recent work that uses VORPAL** field data as a starting point for modeling crab cavities. In addition, we present realistic models, including fringes, for several standing-wave modes. These models, which include a simple accelerating mode and a TM-110 (crab) mode, are useful for the accurate computation of transfer maps as well as for constructing model fields that can be used for testing and comparing a variety of rf cavity codes.
* D.T. Abell, Phys. Rev. ST Accel. Beams 9, 052001, (2006).
** C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004).
Tech-X, Boulder, Colorado
Data organization of simulations outputs differs from application to application. This makes development of uniform visualization and analysis tools difficult and impedes comparison of simulation results. VizSchema is an effort to standardize metadata of HDF5 format so that the subsets of data needed to visualize physics can be identified and interpreted by visualization tools. Based on this standard, we developed a powerful VisIt-based visualization tool. It allows a uniform approach for 3D visualization of large data of various kinds (fields, particles, meshes) from the COMPASS suite for SRF cavities and laser-plasma acceleration. In addition, we developed a specialized graphical interface to streamline visualization of VORPAL outputs and submit remote VORPAL runs. In this paper we will describe our approach and show some visualizations results.
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
There are many simulation codes for accelerator modeling. Each one has some strength but not all. Collaboration is formed for the effort of providing a platform to host multiple modeling tools. In order to achieve such a platform, a set of common physics data structure has to be set. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype will be presented.
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
High level applications often suffer from poor performance and reliability due to lengthy initialization, heavy computation and rapid graphical update. Service oriented architecture (SOA) is trying to separate the initialization and computation from applications to distributed service providers. Heavy computation such as beam tracking will be done periodically on a dedicated server and data will be available to client applications at all time. Industrial standard service architecture can help to improve the reliability and maintainability of the service providers. Robustness will also be improved by reducing the complexity of individual client applications.
SLAC, Menlo Park, California
The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. One of the primary goals of the CesrTA program are to investigate the interaction of the electron cloud with low emittance positron beam, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies. This paper report the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using 3D code CLOUDLAND. The transverse distribution of electron cloud in a wiggler magnet is similar to a dipole magnet except in the zero vertical field regions where the electrons have complicated trajectories and therefore a longer lifetime. Fortunately, these electrons are dominantly direct-photo-electrons and can be easily reduced by properly arranging photon absorbers. Simulations show that the electron cloud in a quadrupole magnet can be trapped for long time due to the mirror field effect.
SLAC, Menlo Park, California
SLAC is proposing a rotatable collimator design for the LHC phase II collimation upgrade. This design has 20 facet faces on each cylindrical jaw surface and the two jaws, which will move in and out during operation, are rotatable in order to introduce a clean surface in case of a beam hitting a jaw in operation. When the beam crosses the collimator, it will excite broadband and narrowband modes that can contribute to the beam energy loss and power dissipation on the vacuum chamber wall and jaw surface. In this paper, the parallel eigensolver code Omega3P is used to search for all the trapped modes in the SLAC collimator design. The power dissipation generated by the beam in different vacuum chamber designs with different jaw end geometries is simulated. It is found that the longitudinal trapped modes in the circular vacuum chamber design with larger separation of the two jaws may cause excessive heating. Adding ferrite tiles on the vacuum chamber wall can strongly damp these trapped modes. The short-range wakefields will also be calculated to determine the broadband beam heating and transverse kick on the beam. We will present and discuss the simulation results.
ORNL, Oak Ridge, Tennessee
At an age of twelve years, the collective beam dynamics particle tracking code, ORBIT, is considered mature. Even so, we continue to enhance ORBIT's capabilities. Two such enhancements are reported here. The first enhancement allows for the use of time dependent waveforms for the strengths of all magnetic elements, a capability that previously was limited to kickers and to RF cavities. This capability should prove very useful for applications to synchrotrons, in which tunes are often manipulated during acceleration. The second enhancement provides an internal calculation of the lattice functions. Previously, these had to be read from an external file, but given the capability of dynamically programming the lattice magnet strengths, it is extremely useful to be able to calculate the lattice functions on demand. Examples illustrating these new ORBIT capabilities will be presented.
Euclid TechLabs, LLC, Solon, Ohio
LETI, Saint-Petersburg
ANL, Argonne
Beam breakup (BBU) effects resulting from parasitic wakefields are a serious limitation to the performance of dielectric structure based accelerators. We report here on numerical studies and experimental investigations of BBU and its mitigation. An experimental program is underway at the Argonne Wakefield Accelerator facility that will focus on BBU measurements in dielectric wakefield devices. We examine the use of external FODO channels for control of the beam in the presence of strong transverse wakefields. We present calculations based on a particle-Green's function beam dynamics code (BBU-3000) that we are developing. We will report on new features of the code including the ability to treat space charge. The BBU code is being incorporated into a software framework that will significantly increase its utility (Beam Dynamics Simulation Platform). The platform is based on the very flexible Boinc software environment developed originally at Berkeley for the SETI@home project. The package can handle both task farming on a heterogeneous cluster of networked computers and computing on a local grid. User access to the platform is through a web browser.
CASA, newport news
JLAB, Newport News, Virginia
One key limiting factor to a collider luminosity is bean-beam interactions which usually can cause serious emittance growth of colliding beams and fast reduction of luminosity. Such nonlinear collective beam effect can be a very serious design challenge when the machine parameters are pushed into a new regime. In this paper, we present simulation studies of the beam-beam effect for a medium energy ring-ring electron-ion collider based on CEBAF.
CASA, newport news
JLAB, Newport News, Virginia
We present early stage of a new code for self-consistent, 2D simulations of beam dynamics affected by CSR. The code is of the particle-in-cell variety: the beam bunch is sampled by macroparticles, which are deposited on the grid; the corresponding forces on the grid are then computed using retarded potentials according to causality, and interpolated so as to advance the particles in time. The retarded potentials are evaluated by integrating over the 2D path history of the bunch, with the charge and current density at the retarded time obtained from interpolation of the particle distributions recorded at discrete timesteps. The code is benchmarked against analytical results obtained for a rigid-line bunch. We also outline the features and applications which are currently being developed.
TEMF, TU Darmstadt, Darmstadt
GSI, Darmstadt
For the future operation as an injector for the FAIR project the SIS18 synchrotron has to deliver intense and high quality ion bunches with high repetition rate. One requirement is that the initial momentum spread of the injected coasting beam should not exceed the limit set by the SIS18 rf bucket area. Also the Schottky spectrum should be used to routinely measure the momentum spread and revolution frequency directly after injection. During the transverse multi-turn injection the SIS18 is filled withμbunches from the UNILAC linac at 36 MHz. For low beam intensities theμbunches debunch within a few turns and form a coasting beam with a Gaussian-like momentum spread distribution. With increasing intensity we observe persistent current fluctuations and an accompanying pseudo-Schottky spectrum. We will explain that the multi-stream instability of theμbunch filaments is responsible for the turbulent current spectrum that can be observed a few 100 turns after injection. The current spectrum observed in the SIS18 and the results from a longitudinal simulation code will compared to an analytical model of the multi-stream instability induced by the space charge impedance.
TEMF, TU Darmstadt, Darmstadt
GSI, Darmstadt
Electron clouds generated by residual gas ionization pose a potential threat to the stability of the circulating heavy ion beams in the existing SIS-18 synchrotron and in the projected SIS-100. The electrons can potentially accumulate in the space charge potential of the long bunches. As an extreme case we study the accumulation of electrons in a coasting beam under conditions relevant in the SIS-18. Previous studies of electron clouds in coasting beams used Particle-In-Cell (PIC) codes to describe the generation of the cloud and the interaction with the ion beam. PIC beams exhibit much larger fluctuation amplitudes than real beams. The fluctuations heat the electrons. Therefore the obtained neutralization degree is strongly reduced, relative to a real beam. In our simulation model we add a Langevin term to the electron equation of motion in order to account for the heating process. The effect of natural beam fluctuations on the neutralization degree is studied. The modification of the beam response function as well as the stability limits in the presence of the electrons is discussed. Finally we will also address the electron accumulation in long bunches.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
The Longitudinal emittance in J-PARC RCS should be controlled to accelerate a high intensity proton beam with minimal beam loss. In order to study and minimize the beam loss during acceleration, the optimized way to add the 2nd higher harmonic rf has been calculated by a particle tracking code. Furthermore, the bunch shape at RCS extraction should be controlled and optimized for the MR injection. For this purpose, the optimum RCS acceleration pattern has been calculated. We describe the simulation results and the comparison with the beam test.
TUB, Beijing
Tsinghua University, Beijing
HU/AdSM, Higashi-Hiroshima
LBNL, Berkeley, California
JAEA/TARRI, Gunma-ken
During the beam crystallization process, the main heating source is Intra-beam scattering (IBS), in which the Coulomb collisions among particles lead to a growth in the 6D phase space volume of the beam. The results of molecular dynamics (MD) simulation have shown an increase of heating rate as the temperature is increased from absolute zero, but then a peak in the heating rate, and subsequent decrease with ever increasing temperature*. This phenomenon has been carefully studied by Y. Yuri, H. Okamoto, and H. Sugimoto**. On the other hand, in the traditional IBS theory valid at high temperatures, heating rate is monotonically increasing as the temperature becomes lower***. In this paper we attempt to understand the "matching" at low temperatures between the MD results and traditional IBS theory, by including many body effects in the traditional IBS theory. In particular the Debye shielding is included. We shall present how the traditional theory is modified by shielding, and show how this effect improves the "matching" with the results from MD.
* J. Wei, H. Okamoto, and A. Sessler, Phys. Rev. Lett. 80, 2606
** Y.Yuri, H. Okamoto, and H. Sugimoto, J. Phys. Soc. Jpn. 78, 124501
***A. Piwinski, Lect. Notes Phys. 296, 297 (1988)
CERN, Geneva
PSI, Villigen
The performance of the CERN PS Booster (PSB) synchrotron is believed to be limited mainly by direct space charge effects at low energy. The main motivation to construct Linac4 is to raise the PSB injection energy to mitigate direct space charge effects. At present, simulation of the injection and the ow energy part of the cycle aim at defining Investigations on the influence of parameters of the injected beam on the performance of the PSB are described.
MPI-K, Heidelberg
GSI, Darmstadt
JINR, Dubna, Moscow Region
Cockcroft Institute, Warrington, Cheshire
Electrostatic storage rings have proven to be invaluable tools for atomic and molecular physics. Due to the mass independence of the electrostatic rigidity, these machines are able to store a wide range of different particles, from light ions to heavy singly charged bio-molecules. However, earlier measurements showed strong space charge limitations; probably linked to non-linear fields that cannot be completely avoided in such machines. The nature of these effects is not fully understood. In this contribution, we present the results from simulating an electrostatic storage ring under consideration of non-linear fields as well as space charge effects using the computer code SCALA.
Fermilab, Batavia
CIPS, Boulder, Colorado
Tech-X, Boulder, Colorado
Precision simulations of the electron cloud at the Fermilab Main Injector have been studied using the plasma simulation code VORPAL. Fully 3D and self consistent solutions that includes Yee-type E.M. field maps generated by the cloud and the proton bunches have been obtained, as well detailed distributions of the 6D phase space occupied by the electrons. We plan to include such maps in the ongoing simulation of the space charge effects in the Main Injector. Simulations of the response of retarded field analyzers and microwave transmission experiments are ongoing.
LBNL, Berkeley, California
CERN, Geneva
A replacement for the PS storage ring is being considered, in the context of the future LHC accelerator complex upgrade, that would likely place the new machine (the PS2) in a regime where the electron-cloud (EC) effect might be an operational limitation. We report here our present understanding of the ECE build-up based on simulations. We focus our attention on the bending magnets and the field-free regions, and consider both proposed bunch spacings of 25 and 50 ns. The primary model parameters exercised are the peak secondary emission yield (SEY) δmax, and the electron-wall impact energy at which SEY peaks, Emax. By choosing reasonable values for such quantities, and exploring variations around them, we estimate the range for the EC density ne to be expected in nominal operation. We present most of our results as a function of bunch intensity Nb, and we provide a tentative explanation for a curious non-monotonic behavior of ne as a function of Nb. We explore the sensitivity of ne to other variables such as the beam pipe radius in the field-free regions.
LBNL, Berkeley, California
The propagation of TE waves is sensitive to the presence of an electron cloud primarily through phase shifts generated by the altered dielectric function, but can also lead to polarization changes and other effects, especially in the presence of magnetic fields. These effects are studied theoretically and also through simulations using WARP-POSINST. Full electromagnetic simulations are performed for CesrTA parameters, and used as a benchmark for simplified phase shift estimates that are also implemented in WARP/POSINST. Nonlinear effects such as electron heating are also examined.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
Fermilab, Batavia
CERN, Geneva
SLAC, Menlo Park, California
A new proton synchrotron, the PS2, is under design study to replace the the current proton synchrotron at CERN for the LHC upgrade. Nonlinear space charge effects could cause significant beam emittance growth and particle losses and limit the performance of the PS2. In this paper, we report on studies of the potential space-charge effects at the PS2 using three-dimensional self-consistent macroparticle tracking codes, IMPACT, MaryLie/IMPACT, and Synergia. We will present initial benchmark results among these codes. Effects of space-charge on the emittance growth, especially due to synchrotron coupling, and the aperture sizes will also be discussed.
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
Retarding field analyzers (RFAs) provide an effective measure of the local electron cloud density and energy distribution. Proper interpretation of RFA data can yield information about the behavior of the cloud, as well as the surface properties of the instrumented vacuum chamber. However, due to the complex interaction of the cloud with the RFA, particularly in regions of high magnetic field, understanding these measurements can be nontrivial. This paper will examine different methods for interpreting RFA data via cloud simulation programs. Possible techniques include postprocessing the output of a simulation code to predict the RFA response, and incorporating an RFA model into the program itself.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
CalPoly, San Luis Obispo, CA
SLAC, Menlo Park, California
The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent tune shifts for a variety of electron and positron beam energies, bunch current levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters such as the synchrotron radiation flux, its interaction with the vacuum chamber wall, the beam emittance and lattice optics, as well as to those of the various contributions to the electron secondary yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modelling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.
GSI, Darmstadt
ITEP, Moscow
Octupole magnets can be used as a passive cure against transverse collective instabilities. The octupole field creates a betatron frequency spread due to amplitude-dependent tune shift and thus enhances Landau damping. The drawback is the reduction of the dynamic aperture (DA). Ultimately, a balance between collective damping and DA must be found. Here we analyse the transverse coherent instability thresholds in SIS100 with octupoles and nonlinear space-charge taken into account. As the major impedance sources at low frequencies, the resistive wall and the kickers are considered. A coasting beam is assumed, which results in a conservative stability estimation. On the other hand, we simulate the DA of the SIS100 lattice using the MADX code, with systematic multipole errors, random multipole errors, and closed-orbit errors taken into account.
MPI-P, München
SINAP, Shanghai
SSRF, Shanghai
Fast ion instability has been observed in the early commissioning and operation of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. In this paper, a weak-strong code is used to simulate the fast ion instability in SSRF storage ring. Various fill patterns and gas pressures are investigated. The results show that the mini-train fill patterns are very effective to suppress the growth of the fast ion instability. By employing a fast feedback system, it is possible to damp the growth of beam oscillation amplitude below the beam size.
ELETTRA, Basovizza
Step-out transition is one of the most frequent component, commonly used on the new generation light source facilities where very short and dense electron bunches are considered. The numerical calculation of the short-range wake at this type of transition requires a spatial mesh size equal to a fraction of bunch length. This calculation becomes for a very short bunch, e.g. σ = 25μm, very time consuming due to the large number of mesh points required. On the other hand, the available analytical models that calculate the transverse wake field are applicable only on a narrow range of bunch lengths. We developed an ABCI-based analytical model that can calculate accurately the kick factor. The advantage of this model is quick, accurate and covers wide range of rms bunch lengths (up to σ = 1000μm). The model also covers a wide range of beam pipe ratio b/a.
INFN/LNF, Frascati (Roma)
U. Sannio, Benevento
The bunch-to-bunch evolution of the electron cloud density can be modeled using a cubic map. The map approach has been proved reliable for RHIC* and LHC**. The coefficients that parameterize the map may be obtained by fitting from time consuming numerical simulations. In this communication we derive a simple approximate formula for the quadratic coefficient, which determines the saturation of the cloud due to space charge, in the electron cloud density map, under the assumptions of round chambers and free-field motion of the elctrons in the cloud. Results are compared with simulations for a wide range of parameters governing the evolution of the elctron cloud.
* U.Iriso, S.Peggs, Phys. Rev.STAB 8, 024403, 2005.
** T.Demma, S.Petracca, G.Rumolo, F.Ruggiero, F.Zimmermann, Phys. Rev.STAB 10, 114401, 2007.
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
Some collective effects have been studied for the SuperB* high luminosity collider. Estimates of the effect of Intra Beam Scattering on the emittance and energy spread growths have been carried up for both the High Energy (HER, positrons) and the Low Energy (LER, electrons) rings. Electron cloud build up simulations for HER were performed with the ECLOUD code, developed at CERN**, to predict the cloud formation in the arcs, taking into account possible remediation techniques such as clearing electrodes. The new code CMAD, developed at SLAC***, has been used to study the effect of this electron cloud on the beam and assess the thresholds above which the electron cloud instability would set in.
* M. E. Biagini, proceedings of PAC'09.
** F. Zimmermann, CERN, LHC-Project-Report-95, 1997.
*** M. Pivi, proceedings of PAC'09.
KEK, Ibaraki
The near beam electron cloud density in a magnetic field was estimated with a simple electron current detector at KEKB LER. The estimation is based on the assumption that high energy electrons which hit a chamber wall come directly from the region around the beam after the interaction with a circulating bunch. The first successful application of this idea for a drift space was reported at PAC05 by the authors. In a solenoid field of 50 G, the near beam cloud density is reduced by about four orders of magnitude compared to the no field case. In a quadruple magnet, the density around the beam is by two orders of magnitude lower than the density in a typical drift space, as most simulations show.
CERN, Geneva
The effects of direct space charge forces on the Transverse Mode Coupling Instability (TMCI) are studied using numerical techniques. We have implemented a third order symplectic integrator for the equation of motion, taking into account non linear space charge forces coming from a Gaussian shaped bunch. We performed numerical simulation for the Super Proton Synchrotron (SPS) bunch at 26 GeV of kinetic energy, using either resistive wall or broad band transverse wake fields. In both cases the result of applying direct space charge, leads to an intensity threshold increase by almost 20% before the TMCI appears. Far above the TMCI intensity threshold, the growth rate is almost 10% higher if no space charge forces are applied.
CERN, Geneva
Amorphous carbon coatings with low secondary electron yield have been applied to the liners in the electron cloud monitors and to vacuum chambers of three dipole magnets in the SPS. The electron cloud is completely suppressed for LHC type beams in these monitors even after 3 months air venting and no performance deterioration is observed after more than one year of SPS operation. Upon variation of the magnetic field in the monitors the electron cloud current maintains its intensity down to weak fields of some 40 Gauss, where fast conditioning is observed. This is in agreement with dark traces observed on the RF shields between dipoles. The dynamic pressure rise has been used to monitor the behavior of the magnets. It is found to be about the same for coated and uncoated magnets, apart from a weak improvement in the carbon coated ones under conditions of intense electron cloud. Inspection of the coated magnet is foreseen in order to detect potential differences with respect to the coated monitors. Measurements of the stray fields outside the dipoles show that they are sufficiently strong to induce electron cloud in these regions.
EPFL, Lausanne
CERN, Geneva
Transition crossing in the CERN PS is critical for the stability of high intensity beams, even with the use of a second order gamma jump scheme. The intense single bunch beam used for the neutron Time-of-Flight facility (n-ToF) needs a controlled longitudinal emittance blowup at flat bottom to prevent a fast single-bunch vertical instability from developing near transition. This instability is believed to be of Transverse Mode Coupling (TMCI) type. A series of measurements taken throughout 2008 and 2009 aim at using this TMCI observed on the ToF beam at transition, as a tool for estimating the transverse global impedance of the PS. For this purpose, we compare the measurement results with the predictions of the HEADTAIL code and find the matching parameters. This procedure also allows a better understanding of the different mechanisms involved and can suggest how to improve the gamma jump scheme for a possible intensity upgrade of the n-ToF beam.
CERN, Geneva
EPFL, Lausanne
The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of an intensity upgrade of the LHC. In this paper, CST Particle Studio time domain electromagnetic simulations are performed to obtain the longitudinal and transverse impedances/wake potentials of simplified models of ferrite loaded kickers. The simulation results have been successfully compared with some existing analytical expressions. In the transverse plane, the dipolar and quadrupolar contributions to the wake potentials have been estimated from the results of these simulations. For some cases, simulations have also been benchmarked against measurements on PS kickers. It turns out that the large simulated quadrupolar contributions of these kickers could explain both the negative total (dipolar+quadrupolar) horizontal impedance observed in bench measurements and the positive horizontal tune shift measured with the SPS beam.
EPFL, Lausanne
PSI, Villigen
CERN, Geneva
Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present work focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Our simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. The two cases of 3TeV and 500GeV have been examined in this paper.
EPFL, Lausanne
CERN, Geneva
The SPS kickers are major contributors to the SPS transverse beam coupling impedance. The current "flat chamber" impedance model for a kicker is obtained by applying form factors to the theoretical impedance of an axisymmetric ferrite beam pipe. This model was believed to be acceptable for the vertical dipolar impedance, as two-wire measurements on SPS kickers revealed a satisfactory agreement. However, one-wire measurements on PS kickers suggested that this model underestimates the kickers' transverse quadrupolar (detuning) impedance. The longitudinal and transverse dipolar impedances of another kicker model that accounts for the metallic plates on each side of the ferrite were derived in the past by H. Tsutsui. The same formalism is used in this paper to derive the quadrupolar impedance. These formulae were then successfully benchmarked to electromagnetic simulations. Finally, simulating the interaction of an SPS bunch with the improved kickers' model results in a positive horizontal tune shift, which is very close to the tune shift measured with the SPS beam.
EPFL, Lausanne
CERN, Geneva
INFN/LNF, Frascati (Roma)
Honorary CERN Staff Member, Grand-Saconnex
The beam coupling impedance of the CERN SPS is expected to be one of the limitations to an intensity upgrade of the LHC complex. In order to be able to reduce the SPS impedance, its main contributors need to be identified. An impedance model for the SPS has been gathered from theoretical calculations, electromagnetic simulations and bench measurements of single SPS elements. The current model accounts for the longitudinal and transverse impedance of the kickers, the horizontal and vertical electrostatic beam position monitors, the RF cavities and the 6.7 km beam pipe. In order to assess the validity of this model, macroparticle simulations of a bunch interacting with this updated SPS impedance model are compared to measurements performed with the SPS beam.
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is a new third generation synchrotron storage ring which will be built at the present site of the NSRRC. The paper summarizes results of the impedance studies of the storage ring vacuum components for the TPS project. The main goal of this work was to support the design of the vacuum chamber and, at the same time, to get a detailed model of the machine impedance, which can be used later for detail studies of collective effects. Wake potentials and impedances for each component of the storage ring have been simulated with a 3D electromagnetic code GdfidL. Numerically obtained data have been compared to analytical results for simplified geometries of the vacuum chamber components.
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is a new third generation synchrotron storage ring which will be built at the present site of the NSRRC. Collective effects in the TPS storage ring have been simulated with tracking code ELEGANT. Quasi-Green's function for the entire ring and coherent synchrotron radiation (CSR) have been taken into account in the simulations. Thresholds of the longitudinal microwave instability and the CSR induced instability have been estimated. Time-dependent sawtooth oscillations of the bunch length at high bunch currents have been analyzed and compared to the bunch length oscillations observed at the SLC damping ring.
Diamond, Oxfordshire
JAI, Oxford
SOLEIL, Gif-sur-Yvette
Within the common programme on the analysis of collective instabilities at Diamond and SOLEIL, the numerical codes mbtrack and sbtrack have been extended to include a full description of the nonlinearities in the storage rings by means of the nonlinear one-turn map. We present the details of the map implementation and the recent results on the analysis of the effects of the nonlinear terms of the map on the characteristics of the collective instabilities at the two machines.
Fermilab, Batavia
BNL, Upton, Long Island, New York
In order to avoid the effects of long-range beam-beam interactions which produce beam blow-up and deteriorate beam life time, a compensation scheme with current carrying wires has been proposed. Two long-range beam-beam compensators were installed in RHIC rings in 2006. The effects of the compensators have been experimentally investigated. An indication was observed that the compensators are beneficial to beam life time in measurements performed in RHIC during 2009. In this paper, we report the effects of wire compensator on beam loss and emittance for proton-proton beams at collision energy.
Fermilab, Batavia
Increasing the luminosity requires higher beam intensity and often focusing the beam to smaller sizes at the interaction points. The effects of head-on interactions become even more significant. The head-on interaction introduces a tune spread due to a difference of tune shifts between small and large amplitude particles. A low energy electron beam so called electron lens is expected to improve intensity lifetime and luminosity of the colliding beams by reducing the betatron tune shift and spread. In this paper we discuss the results of beam simulations with the electron lens in RHIC.
Fermilab, Batavia
We investigate the dynamics of longitudinally flat bunches created with a second harmonic cavity in a high energy collider. We study Landau damping in a second harmonic cavity with analytical and numerical methods. The latter include particle tracking and evolution of the phase space density. The results are interpreted in the context of possible application to the LHC.
Fermilab, Batavia
Electron lenses are proposed as a way to mitigate head-on beam-beam effects for the LHC upgrade. An extensive effort was put together within the US LARP in order to develop numerical simulations of beam-beam effects in the presence of electron lenses. In this report the results of beam-beam simulations for RHIC and LHC are presented. The effect of electron lenses is demonstrated and sensitivity of beam-beam compensation to imperfections is discussed.
LBNL, Berkeley, California
CERN, Geneva
One of the options under consideration for a future upgrade of the LHC injector complex includes the replacement of PS with PS2 (a longer circumference and higher energy ring). Efforts are currently underway to design the new machine and characterize the beam dynamics. Electron cloud effects represent a potentially serious limitation to the achievement of the upgrade goals. We report on ongoing numerical studies aiming at estimating the e-cloud density threshold for the occurrence of single bunch instabilities or significant degradation of the beam emittance. We present selected results obtained in the more familiar quasi-static approximation and/or in the Lorentz-boosted frame.
Northern Illinois University, DeKalb, Illinois
Tech-X, Boulder, Colorado
Terahertz (THz) radiation has generated much recent interest due to its ability to penetrate deep into many organic materials without the damage associated with ionizing radiations. The generation of copious amounts of narrow-band THz radiation using a Smith-Purcell FEL operating as a backward wave oscillator is being pursued by several groups. In this paper we present start-to-end simulations of a Smith-Purcell FEL operating in the superradiant regime. Our concept incorporates a double grating configuration to efficiently bunch the electron beam, followed by a single grating to produce Smith-Purcell radiation. We demonstrate the capabilities and performances of the device, including initial beam properties (emittance and energy spread), with the help of numerical simulations using the conformal finite-difference time-domain electromagnetic solver VORPAL.
SLAC, Menlo Park, California
In accelerator design, there is often a need to evaluate the threshold to the (longitudinal) microwave instability for a bunched beam in a storage ring. Several computational tools are available that allow us, once given a wakefield, to numerically find the threshold current and to simulate the development of the instability. In this work, we present the results of computer simulations with codes recently developed at the SLAC National Accelerator Laboratory. Our simulations include the cases of the resonator broadband impedance, the resistive wall impedance and the coherent synchrotron radiation impedance. We compare the accuracy of the threshold prediction and discuss the capabilities and limitations of the codes.
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
Collimators and other similar accelerator structures usually include small-angle tapering to lower the wakefields generated by the beam. While the low-frequency impedance is well described by Yokoya's formula (for axisymmetric geometry), much less is known about the behavior of the impedance in the high frequency limit. In this paper we develop an analytical approach to the high-frequency regime for round collimators and tapers. Our analytical results are compared with computer simulations using the code ECHO.
SUT, Noda-shi, Chiba
KEK, Ibaraki
New terahertz(THz) generator using the non-relativistic electron beam was developed based on the beam optics and the RF deflector. The conventional THz generators using the electron beam are almost based on the relativistic beam to utilize the lorentz factor as FELs or the strong magnet to make high electron density like gyrotrons or BWOs. Thus it causes that the total equipment becomes large. New THz generator uses the non-relativistic electron beam. And it consists of the beam optics which makes the sliced beam by using a anode slit to focus at second slit as the THz radiation plane. In this configuration, the RF deflector works to move for the transverse direction matched with the phase velocity of the radiated electromagnetic field. The moving sliced beam separates into a number of bunches through the second slit and the bunches makes the THz coherent radiation in zero time interval. In this new THz generator, no strong magnet is required and the large diameter beam can be utilized to generate the high power THz electromagnetic wave. In this paper, the design of new THz generator and its experimental results are reported.
CANDLE, Yerevan
DESY, Hamburg
The options for an extremely low bunch charge regime (20 pC) of the European XFEL project are studied. The parameter study (saturation length and power) is performed for a wide range of the beam normalized emittance, bunch length and energy spread. The study is based both on analytical scaling of the SASE FEL performance and numerical simulations.
CBS, Mumbai
BARC, Mumbai
The stability of free-electron laser (FEL) resonators differs from that of resonators of conventional lasers, because of the nature of the FEL interaction. Therefore the stability diagram is modified, and near-concentric configurations are preferred to near-confocal. We study the stability of FEL resonators (especially for g1 =/ g2) using simulations, as well as using a simple thin-lens model, and show that the near-concentric configuration is indeed preferable, while the confocal configuration becomes unstable. Also, since FELs can be widely tuned in wavelength, we investigate the stability of the resonator as a function of the wavelength.
JAEA/Kansai, Kyoto
Kyoto Univeristy, Kyoto
Interactions of x-ray free electron laser (XFEL) light with a single cluster target are numerically investigated. The irradiation of XFEL light onto material leads to the ionization of the target by photo-ionization and generation of high energy electrons. This results in the further ionization via Auger effect, collisional ionization, and field ionization. The ionization rate or time scale of each process depends on the condition of XFEL (intensity, duration, photon energy) and target size. In order to understand the ionization dynamics, we used a three-dimensional Particle-in-Cell code which includes the plasma dynamics as well as relevant atomic processes such as photo-ionization, the Auger effect, collisional ionization/relaxation, and field ionization. It is found that as the XFEL intensity increases to as high as roughly 1021 photons/pulse/mm2, the field ionization, which is the dominant ionization process over the other atomic processes, leads to rapid target ionization. The target damage due to the irradiation by XFEL light is numerically evaluated, which gives an estimation of the XFEL intensity so as to suppress the target damage within a tolerable range for imaging.
* T. Nakamura, et al., Phys. Rev. A, vol. 80, 053202 (2009)
TUB, Beijing
Smith-Purcell radiation (SPR) is emitted when an electron passes near the surface of a periodic metallic grating. The radiation wavelength λ observed at the angle θ measured from a direction of surface grating is determined by λ=D/|n|(1/β cosθ), Where D is the grating period, βc is the electron velocity, c is the speed of light, and the integer n is the spectral order. This radiation mechanism is widely applicated to THz radiation source, for which can be developed into tunable and compact one. In this paper, the radiation characteristics of terahertz (THz) SPR generated from the ultrashort electron beam are analyzed with the three-dimensional particle-in-cell simulation. For obtaining the intense THz radiation, the grating parameters and that of ultrashort electron beam are optimum. The radiation power and energy are obtained by the PIC simulation. The band width of train bunches is compared with that of single bunch. The formation factors including the longitudinal and transverse are calculated. Through this study, we observe that the radiation power is enhanced and the band width can be adjusted.
TUB, Beijing
Tsinghua University Thomson X-ray source ( TTX ) has been proposed at Tsinghua University. With the nominal electron beam parameters ( beam energy of 50MeV, slice energy spread of 5keV, peak current of 600A, rms normalized emittance of 2 mm mrad ) of the TTX linac , the design of Free Electron Laser ( FEL ) by the Echo-Enabled Harmonic Generation ( EEHG ) scheme is presented in this paper. High harmonics of the seeding laser is generated by the EEHG scheme. Parameters of the undulators and seeding lasers are optimized. Simulation results using the GENESIS code are also presented in this paper.
PAL, Pohang, Kyungbuk
POSTECH, Pohang, Kyungbuk
Due the field asymmetry in RF gun due the holes in full cell cavity, the emittance of electron beam can be increased. To generate the low emittance electron beam for XFEL, the elimination of the each field components is very important. The RF field can be decomposed as dipole and quadrupole components. The effect on the emittance increase of each component is studied in this presentation by numerical method. The 3D field map is constructed by MATLAB code as input of PARMELA code with each component distribution of the RF field. In this paper the emittance increase of electron beam by the each component of the RF field will be presented.
NSC/KIPT, Kharkov
Simulation results of subpicosecond bunch formation due to phase motion of electrons in traveling wave are presented. It has been shown that at satisfying phase conditions of electron injection that are necessary for velocity bunching, relative phase velocity of the total wave excited both by RF generator and particles becomes different from unit increasing bunch compression. Simulation of transportation of obtained 8.5 MeV bunches through undulator with a period of 90.6 mm and estimation of bunch form-factor at 446 harmonic of bunch repetition rate of 2797.15 MHz also was carried out. The data obtained allow to expect coherent radiation from undulator at wave-length of 240 um.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
SLAC, Menlo Park, California
USTRAT/SUPA, Glasgow
Optimisation studies of an HHG-seeded harmonic cascade FEL design for the UK's proposed New Light Source (NLS) facility are presented. Three separate FELs are planned to meet the requirements for continuous coverage of the photon energy range 50-1000 eV with variable polarisation, 20 fs pulse widths and good temporal coherence. The design uses an HHG seed source tuneable from 50-100 eV to provide direct FEL seeding in this range, and one or two stage harmonic cascades to reach the higher photon energies. Studies have been carried out to optimise a harmonic cascade FEL operating at 1 keV; topics investigated include modulator configuration, seed power level and effects of the HHG seed structure. FEL simulations using realistic electron beam distributions are presented and tolerance to increased emittance has been considered.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
USTRAT/SUPA, Glasgow
Cockcroft Institute, Warrington, Cheshire
A scheme for the generation of attosecond pulse trains in FEL amplifiers was recently proposed*. The method uses repeated equal temporal delays between the electron bunch and co-propagating radiation to generate a modal structure in the radiation field. The modes may be phase-locked via an energy modulation in the electron beam. As a consequence of the radiation /electron delays, the relative radiation /electron slippage during the interaction is increased and leads to a longer cooperation length with the effect of improving the temporal coherence. In this paper we present simulations demonstrating this effect. In particular, we show that the average spacing between the temporal spikes in a SASE FEL is increased in proportion to the increase in the cooperation length. It may therefore be possible to operate a SASE FEL in single-spike mode with longer, higher charge, electron bunches than previously thought possible.
* Physical Review Letters 100, (203901) 2008.
USTRAT/SUPA, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Pulsar Physics, Eindhoven
Recent progress in developing laser-plasma accelerators is raising the possibility of a compact coherent radiation source that could be housed in a medium sized university department. Furthermore, since the duration of electron bunches from laser-plasma wakefield accelerators is determined by the relativistic plasma wavelength, radiation sources based on these accelerators can produce pulses with femtosecond durations. Beam properties from laser-plasma accelerators have been traditionally thought of as not being of sufficient quality to produce amplification. Our work shows that this is not the case. Here we present a study of the beam characteristics of a laser-plasma accelerator and the compact ALPHA-X (Advanced Laser Plasma High-energy Accelerators towards X-rays) FEL. We discuss the implementation of a focussing system consisting of a triplet of permanent magnet quadrupoles and a triplet of electromagnetic quadrupoles*. We will present a study of the influence of beam transport on FEL action in the undulator, paying particular attention to bunch dispersion in the undulator. This is an important step for developing a compact synchrotron source or a SASE free-electron laser.
*The design of these devices has been carried out using the GPT code, which considers space charge effects and allows a realistic estimate of electron beam properties along the beam line.
SLAC, Menlo Park, California
Simulations of ion migration in the LCLS RF gun and injector A. Brachmann On behalf of the LCLS commissioning team The motivation for this work was the observed surface contamination of the first LCLS RF gun copper cathode. We will present the results of simulations in regards to ion migration in the LCLS gun. Ions of residual gases will be created by interaction of molecular gas species with the UV drive laser beam and by the electron beam itself. The larger part of those ionized molecules remain in the vicinity of creation, are transported towards beam line walls or away from the cathode. However a significant fraction gains enough kinetic energy to be focused by RF and magnetic fields, reaching the cathode and producing an undesirable increase of the cathode's surface work function. Although this fraction is small, during long term operation, this effect becomes a significant factor limiting the source performance.
SLAC, Menlo Park, California
LBNL, Berkeley, California
EPFL, Lausanne
ECHO-7 is a proof-of-principle echo-enabled harmonic generation* FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which is the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.
* G. Stupakov, PRL, 102, 074801 (2009); D. Xiang and G. Stupakov, PRST-AB, 12, 030702 (2009).
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
KEK, Ibaraki
In ERL-based light sources, higher accuracy is expected to be required for RF control and timing, because the ERL beam has much shorter bunch length (less than 100 fs at minimum) compared with that of the existing SR sources. We studied effects of RF amplitude and phase variation of main superconducting cavities and effects of timing jitter of beam injection from an injector, using a simulation code 'elegant'. In this paper, we present the simulation results and discuss tolerances for the RF amplitude and phase and the injection timing.
KEK, Ibaraki
Kyungpook National University, Daegu
KNU, Deagu
Start-to-end (S2E) simulation from electron gun to beam dump is required to estimate light source performance and beam loss, which are essential parts in synchrotron light source based on Energy Recovery Linacs (ERL). Since the beam energy is widely varied from eV to GeV order in the ERL, the S2E simulation have to include many effects, e.g., space charge (SC) effect, coherent synchrotron radiation (CSR), cathode model, wake function, ions and beam break up. In order to carry out the S2E simulation, the preparation of it using General Particle Tracer (GPT), which is a particle tracking code including SC routine, has been started for compact ERL (cERL) beamline. The cERL is a test accelerator to establish accelerator technologies for GeV-class synchrotron light source based on ERL, and consists of an injector with photo cathode DC gun, a merger section, SRF cavities for acceleration and energy recovery, return loops, and a beam dump. In this presentation, the result of the S2E simulation from gun to the middle of return loop with SC and CSR effects, and the results of bench marking for each part in cERL, e.g. injector, merger, SRF cavities and return loop section, are shown.
CLASSE, Ithaca, New York
Coherent Synchrotron Radiation (CSR) can be a detrimental effect on particle bunches with high charge and short bunch lengths. CSR can contribute to an increase in emittance and energy spread, and can limit the process of bunch compression. It is especially important in Energy Recovery Linacs (ERLs), because any relative energy spread induced at high energy is magnified after deceleration, and any energy lost by the particles is energy that cannot be recovered. Here we present CSR simulation results using the particle tracking code BMAD for the main operation modes in the proposed Cornell ERL, including an additional bunch compression mode. These simulations consider the effect of CSR shielding, as well as CSR propagation between bends.
CLASSE, Ithaca, New York
The current status of the lattice and layout for the proposed Cornell Energy Recovery Linac lightsource is presented. This design is centered about a new hard X-ray user facility to be located on Cornell's campus, and is adapted to the local topography in order to incorporate the existing CESR tunnel and Wilson Laboratory. Nonlinear charged-particle optics for this new machine have been designed and analyzed. The lattice is populated with various components for the appropriate accelerator physics requirements for orbit, bunch length, and emittance growth control, including a vacuum system compatible with rest-gas-scattering limits, a collimation system for halo from effects like Touschek scattering, and correction coils and BPMs for sub-micron beam stabilization. We also show calculations for an additional bunch compression mode, which compresses 19~pC bunches at a 1.3~GHz repetition rate to 25~fs.
KEK, Ibaraki
KEKB is an e-/e+ collider for the study of B physics and is also used for machine studies for future machines. The peak luminosity of KEKB, which is the world-highest value, has been still increasing. This report summarizes recent progress at KEKB.
Tohoku University, Graduate School of Science, Sendai
KEK, Ibaraki
Tohoku University, School of Scinece, Sendai
We have studied a beam orbit tilt monitor for stabilizing the beam orbit in ATF2. Once we can measure a beam orbit tilt with high precision at one point, we can relate this data with the beam position profile at the focal point. A tilt monitor is composed of a single rectangular sensor cavity and a waveguide to extract the signal. In the sensor cavity, there is the most basic resonant mode called monopole mode. This monopole mode is perpendicular to the nominal beam axis, and excited by the beam tilt. We extract this monopole mode. As the result, the amplitude of the extracted signal is proportional to the tilt angle. The tilt monitor is almost indepnedent with beam postion, so we can get the tilt date independently. According to our simulation, the sensitivity is estimated about 35nrad in the vertical direction. The prototype was completed and installed in the test area on the ATF2 beamline. The first beam test will be performed in December 2009. We will report this result and future update plan.
GSI, Darmstadt
CERN, Geneva
The measurement of synchrotron nonlinear components is an essential step for devising an effective compensation scheme for improving machine performances. A validation test of a recently proposed method called nonlinear tune response matrix (NTRM) for measuring circular accelerator nonlinear components is undergoing in a CERN-GSI joint effort. The test consists in the attempt of reconstructing few controlled octupolar components in the SPS synchrotron. In this proceeding we report on the SPS benchmarking experiment and discuss the performances the NTRM method applied to this measurements.
LBNL, Berkeley, California
SLAC, Menlo Park, California
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven transverse instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability. We will present our latest simulation results, contrast them with actual measurements and discuss the implications for the design of the actual feedback system.
KIT, Karlsruhe
The Karlsruhe Institute of Technology (KIT) proposes to build a new light source called TBONE (THz Beam Optics for New Experiments), which aims at a spectral range from 0.1 to 150 THz with a peak power of several MW and a pulse length of only 5 fs. In order to achieve this, a beam transport system with minimal losses and a high bunch compression is required. In this paper we present first beam dynamic simulations of the superconducting linac as well as the bunch compressor and give a short status report of the TBONE project.
IPM, Tehran
Shahrood University of Technology, Shahrood
NSTRI, Tehran
The effects of utilizing a third harmonic RF cavity in the lengthening mode have been investigated on quality of the electron beam and the emitted photons in the deflecting RF structures for TPS. For the obtained optimum synchronous and relative harmonic phases and harmonic voltage of 0.7 MV, the equilibrium horizontal and vertical emittances blow up as much as 13% and 97%, respectively. In addition, the intensity of the emitted X-ray pulses with 0.54 ps FWHM reduces by 30%.
IPM, Tehran
The effect of surface roughness on the secondary electron emission from a sandblasted surface is investigated using a Monte-Carlo method. Sandblasted surfaces can significantly reduce the secondary emission yield and have a large sensitivity to the percentage of surface roughness.
ELETTRA, Basovizza
Elettra established top-up operations taking advantage of its new full energy injector. The safety simulations and personnel safety conditions, the radiation measurements, the implementation and the operations of the whole system are presented and discussed.
SSRF, Shanghai
SINAP, Shanghai
To investigate the higher order mode(HOM) damping in the higher harmonic cavity for Shanghai Synchrotron Radiation Facility(SSRF) when using HOM absorbers,simulations have been done for changing the position and the length as well as the thickness of ferrite of HOM damper. The best values under which the Q value of HOMs can be greatly lowered and the impedance of harmonic cavity will be trapped in the impedance threshold have been found.
CLASSE, Ithaca, New York
BNL, Upton, Long Island, New York
Commissioning of the high brightness photoinjector for the Energy Recovery Linac at Cornell University continues. To aid in this process we have developed a 'Virtual Accelerator' application, which provides the beam physicist with an online high-level physics description of the machine. This application combines a linear optics model called Numerical Transfer Matrix (NTMAT), developed at Cornell, and EPICS-DDS, a middle-layer software based on the Experimental Physics and Industrial Control System (EPICS) toolkit and the Data Distribution Service (DDS) data-centric publish/subscribe model. We present the initial results of implementing this new software tool and its deployment in the Cornell ERL injector control room.
BNL, Upton, Long Island, New York
SLAC, Menlo Park, California
ANL, Argonne
A modular environment for beam commissioning and operation is under development, which is based on the client/server model. The service oriented architecture consists of a server for each supported service. At NSLS-II, a so-called "virtual accelerator" has been developed, which wraps simulator engines such as Tracy and Elegant onto an EPICS system. However, with the current solution, access to data is not flexible. We are designing a new online simulator server using structured data to provide a flexible method for accessing the simulation data. This paper describes recent results of the simulator server development.
BNL, Upton, Long Island, New York
ANL, Argonne
A fundamental infrastructure of software framework for beam commissioning for NSLS-II storage ring is in development. It adopts client/server model, and consists of various servers for data communication and management. Based on this structure, some physics applications are developed to satisfy the requirements of day-1 beam commissioning. This paper describes our status of infrastructure development and its applications.
JAI, Oxford
IFIC, Valencia
The commissioning of the ATF2 final focus test beam line facility is currently progressing towards the achievement of its first goal: to demonstrate a transverse beam size of about 40 nm at the focal point. In parallel, studies and R&D activities have already started towards the second goal of ATF2, which is the demonstration of nanometer level beam orbit stabilization. These two goals are important to achieve the luminosity required at future linear colliders. Beam-based intra-train feedback systems will play a crucial role in the stabilization of multi-bunch trains at such facilities. In this paper we present the design and simulation results of beam-based intra-train feedback systems at the ATF2: one system located in the extraction line at the entrance to the final focus, and another at the interaction point. The requirements and limitations of these systems are also discussed.
NSRRC, Hsinchu
As the latest generation light source, TPS (Taiwan Photon Source) has stringent requirements to perform submicron beam stability with low emittance. The slow and fast correctors of integrated orbit feedback system have been designed for TPS project, therefore some feedback system designed based on them an operation experiences from TLS. This report will present performance simulation and the initial design of system infrastructure for large scale calculation and wide bandwidth communication. To perform this requirement, FPGA-based platform will be implemented to achieve low latency and fast computation. Some studies of integrated feedback loop, communication structure, devices control such as BPM electronics and corrector power supplies are also described.
JAI, Oxford
The design luminosity of the future linear colliders requires transverse beam size at the nanometre level at the interaction point (IP), as well as stabilisation of the beams at the sub-nanometre level. Different imperfections, for example ground motion, can generate relative vertical offsets of the two colliding beams at the IP which significantly degrade the luminosity. In principle, a beam-based intra-train feedback system in the interaction region can correct the relative beam-beam offset and steer the beams back into collision. In addition, this feedback system might considerably help to relax the required tight stability tolerances of the final doublet magnets. For CLIC, with bunch separations of 0.5 ns and train length of 156 ns intra-train feedback corrections are specially challenging. In this paper we describe the design and simulation of an intra-train feedback system for CLIC. Results of luminosity performance simulation are presented and discussed.
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
CERN, Geneva
The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. We present recent MD data from the SPS, details of the instrument technique and spectral analysis methods which help reveal complex vertical motion that develops within a subset of the injected bunch trains. The beam motion is detected via wide-band exponential taper striplines and delta-σ hybrids. The raw sum and difference data is sampled at 50 GHz with 1.8 GHz bandwidth. Sliding window FFT techniques and RMS motion techniques show the development of large vertical tune shifts on portions of the bunch of nearly 0.025 from the base tune of 0.185. Results are presented via spectrograms and rms bunch slice trajectories to illustrate development of the unstable beam and time scale of development along the injected bunch train. The study shows that the growing unstable motion occupies a very broad frequency band of 1.2 GHz. These measurements are compared to numerical simulation results, and the system parameter implications for an Ecloud feedback system are outlined.
BNL, Upton, Long Island, New York
CERN, Geneva
The SPS exponential coupler stripline are used to study single bunch instabilities. An accurate description of the response of the pickup is required to obtain high resolution measurements of the bunch vertical motion along the longitudinal axis. In this study we present the results of the comparison between dedicated beam experiments and electromagnetic simulations of a geometrical model of the stripline.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
A fiber-based beam loss monitors (BLM) is under development for the undulator section of the SPring-8 X-FEL: the system is based on the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber. Various parameters come into account in the final performance of the system, such as the impact angle and energy of the lost electrons, the fiber position (angular and radial) with respect to the point of impact, fiber characteristics (numerical aperture, index, diameter), etc. Thorough numerical studies have been carried out to investigate the performances of the system. Comparison with the experimental results obtained at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL are also given.
CERN, Geneva
Poznań University of Technology, Poznań
The LHC beam loss measurement system is mainly used to trigger the beam abort in case a magnet coil quench level is approached. The predicted heat deposition in the superconducting coils of the magnets have been determined by particle shower simulation codes, while the liquid helium cooling capacity of the system has been both simulated and measured. The results have been combined to determine the abort thresholds. Measurements of the energy depositions of lost protons from the initial beams in the LHC are used to determine the accuracy of the beam abort threshold settings. The simulation predictions are reviewed and compared with the measurement results.
CERN, Geneva
Particle losses in the LHC arcs are mainly expected in the interconnection region between a dipole and quadrupole magnet. The maximal beam size, the maximal orbit excursion and aperture changes cause the enhancement of losses at this location. Extensive Geant4 simulations have been performed to characterise this particular region to establish beam abort settings for the beam loss monitors in these areas. Data from first LHC beam loss measurements have been used to check and determine the most likely proton impact locations. This input has been used to optimise the simulations used for the definition of thresholds settings. The accuracy of these settings is investigated by comparing the simulations with actual loss measurements.
CERN, Geneva
SLAC, Menlo Park, California
The LHC beam dump system relies on extraction kickers that need 3 microseconds to rise up to their nominal field. As a consequence, particles crossing the kickers during this rise time will not be dumped properly. The proton population during this time should remain below quench and damage limits at all times. A specific monitor has been designed to measure the particle population in this gap. It is based on the detection of Synchrotron radiation using a gated photomultiplier. Since the quench and damage limits change with the beam energy, the acceptable population in the abort gap and the settings of the monitor must be adapted accordingly. This paper presents the design of the monitor, the calibration procedure and the detector performance with beam.
BARC, Mumbai
BARC is involved in the development of superconducting cavities for Accelerator Driven Sub-critical System (ADSS). The performance of superconducting RF structure can be greatly affected due to multipacting. Hence 2D and 3D multipaction simulation studies have been carried out for a medium velocity (β=0.49) elliptical Niobium cavity operating at 1050 MHz. An in-house code has been developed which uses finite element method based software to calculate electromagnetic field of the structure. Leap frog method algorithm has been used to solve Lorenz force equation for trajectory tracking of electrons which are launched inside from different initial positions. Electron trajectories are tracked until they hit the surface. An interpolation function is used to calculate SEY at different impact energies. By repeating the process at different field level for different primary electrons multipacting field levels are identified. The study revealed that the cavity structure is not multipacting prone up to 17 MV/m average accelerating field. Two point first order multipacting is observed at the equatorial region of the cavity when the accelerating field is between 18 MV/m and 28 MV/m.
KEK, Ibaraki
The limitation of the accelerating gradient is one of the current major issues in the development of 1.3 GHz superconducting RF accelerator structures. While some of single-cell cavities and a few of 9-cell structures have occasionally seen accelerating gradients over 50 MV/m and 40 MV/m respectively, the reproducibility of high gradient performance is still poor. Field emission and thermal breakdown due to surface imperfections are supposed to limit the gradient. Magnetic field enhancement at small surface defects can give rise to thermal breakdown through local heating ending up with low gradients. Simulations with idealized primitive models are totally unrealistic since real existing defects have complicated and irregular shapes. Profilometry-based realistic high-fidelity modelling of field enhancement will be presented.
KEK, Ibaraki
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
We started to develop an input power coupler for a 1.3GHz ERL superconducting cavity for ERL main linac. Required input power is about 20kW for the cavity acceleration field of 20MV/m and the beam current of 100mA in energy recovery operation. The input coupler is designed based on the STF-BL input coupler, especially choke-mode type ceramic window was applied. After that some modifications are applied for the CW 20kW power operation. We fabricated input coupler components such as ceramic windows and bellows and carried out the high-power test of the components by using a 30kW IOT power source and a test stand constructed.
KEK, Ibaraki
JAEA/ERL, Ibaraki
ISSP/SRL, Chiba
The coaxial-type input couplers are frequently used for accelerators, since it can successfully propagate high power of RF. Thus we have been developing the coaxial-type input coupler for ERL main linac, operated at 1.3 GHz. When performing high power test of its component, however, we suffered from the heat load due to unexpected loss. A resonance just around 1.3 GHz was found from the low-level measurement. In order to investigate the cause of that resonance, precise calculation was done with MW-studio and HFSS codes. Both codes showed one of dipole modes exists at around 1.3 GHz, near coaxial ceramic window. Details of the mode were further investigated. It showed that the resonant frequency of it depends on, for example, the thickness of the ceramic, the permittivity of the ceramic, and the sizes of inner and outer conductors. In this report, we summarize the experimental observations and the some results from the calculations.
Peking University, School of Physics, Beijing
PKU/IHIP, Beijing
This paper introduce a possible solution to improve the efficiency of the very low beta SC accelerating structure, via extending the gaps number of 4-gap interdigital QWR by doubling its stems number. The new cavity is a 8-gap QWR, which is comprised of two parallel TEM resonant lines operating in opposing phase from each other. It maintains the 4-gap QWR's good EM parameters and enables the use of demountable flange. The more important advantage is the potential improvement of efficiency. According to a preliminary estimation of longitudinal dynamics, the 8-gap QWR could stably accelerate heavy ion at the velocities 0.01<v/c<0.05.
PKU/IHIP, Beijing
Peking University, School of Physics, Beijing
Spoke cavities have been developed and have apparent advantages for high current proton accelerator based on superconductivity at low and medium energy region. As the research and the technical reserve, Peking University has started the R&D program of single spoke cavity (SSC). The work is proposed to do beam load experiment on the HI-13 Tandem at CIAE. The maximum kinetic energy of proton beam is 26MeV, and the frequency of the chopper for superconducting is 150MHz. It leads us to the choice of a 450MHz and β=0.2 single spoke cavity. In this paper, the RF design, mechanical study, fabrication arts, tolerance analysis, and room temperature RF test is presented.
Imperial College of Science and Technology, London
Imperial College of Science and Technology, Department of Physics, London
Cockcroft Institute, Lancaster University, Lancaster
The ever-growing demand for higher beam energies has dramatically increased the risk of RF breakdown, limiting the maximum achievable accelerating gradient. Field emission is the most frequently encountered RF breakdown where it occurs at regions of locally enhanced electric field. Electrons accelerated across the cavity as they tunnel through the surface in the presence of microscopic defects. Upon Impact, most of the kinetic energy is converted into heat and stress. This can inflict irreversible damage to the surface, creating additional field emission sites. This work aims to investigate, through simulation, the physics involved during both emission and impact of electrons. A newly developed 3D field model of an 805 MHz cavity is generated by COMSOL Multiphysics. Electron tracking is performed using a Matlab based code, calculating the relevant parameters needed by employing fourth Order Runge Kutta integration. By studying such behaviours in 3D, it is possible to identify how the cavity surface can alter the local RF field and lead to breakdown and subsequent damages. The ultimate aim is to introduce new surface standards to ensure better cavity performance.
UMAN, Manchester
DESY, Hamburg
Fermilab, Batavia
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
We analyse the higher order modes in the 3.9GHz bunch shaping cavities recently installed in the XFEL/FLASH facility at DESY. We report on recent experimental results on the frequency spectrum, both beam and probe based. These are compared to those predicted by finite element computer codes, globalised scattering matrix calculations and a two-band circuit model. This study is focused on the dipole component of the multiband expansion of the wakefield.
UMAN, Manchester
We present an optimized geometry for a 1.3 GHz superconducting cavity in which the surface electromagnetic fields have been minimized and the bandwidth of the fundamental mode has been maximized. We refer to this design as the New Low Surface Field (NLSF) cavity*. Earlier work* focused the fundamental mode properties. Here we study higher order modes (HOMs), means of damping them, and short range wakefields. A two-band circuit model is employed in order to facilitate rapid characteristic of the HOMs in the cavity.
* N. Juntong and R.M. Jones, High-Gradient SRF Cavity with Minimized Surface E.M. Fields and Superior Bandwidth for The ILC, SRF2009, THPPO024, 2009.
CERN, Geneva
Fermilab, Batavia
Royal Holloway, University of London, Surrey
Over the last months the general layout of the CLIC main beam RTML has stabilized and most important lattices are existing. This allowed us to perform detailed studies of tolerances on magnetic stray fields and on magnet misalignment. Additionally, beam lines could be improved in terms of performance and flexibility. We discuss the overall layout as will be described in the CLIC conceptual design report, highlight the improvements which have been made and show results of tolerance studies.
Royal Holloway, University of London, Surrey
BNL, Upton, Long Island, New York
The Superconducting Proton Linac (SPL) is part of the proposed upgrade of the LHC injection chain, intended to significantly improve the characteristics of the beam circulating in the collider. SPL will rely on two classes of superconducting cavities; beta=0.65 and beta=1; each containing 5-cells resonant at 704 MHz. Presented here are the results of some initial simulations of the beta=1 design, performed at the NERSC supercomputing facility with the highly-parallelised ACE3P codes released by the Advanced Computations Department at SLAC National Accelerator Laboratory. The HOM spectrum in the baseline design has been calculated, and dangerous modes identified by their high R/Q value. In addition, perturbations due to the location of the various couplers, and the structure of the beampipes have been investigated, and are presented here.
CLASSE, Ithaca, New York
The high magnetic and electric radio-frequency fields in superconducting microwave cavities cause heating of the inner cavity surface and generate Lorentz-forces, which deform the shape of the cavity and thereby result in a shift of the fundamental mode frequency. 3-dimensional numerical codes can create complex coupled simulations of the electromagnetic fields excited in a cavity, of heat dissipation and heat transfer, as well as of mechanical effects. In this paper we summarize our simulation results using the engineering simulation package ANSYS.
ODU, Norfolk, Virginia
Using high-pressure RF cavities for muon colliders would provide higher accelerating gradients, that is crucial for fast acceleration of short-living muons .This approach requires a good evaluation for mechanisms of muon - low-Z gas interaction, including such effects as multiple scattering and space charge effects. Most present simulation tools (GEANT4, G4MICE) for muon beams are based on single particle tracking, where collective effects are not taken into account. We use a modified molecular dynamic simulation technique to study effects of both multiple scattering and space charge screening by the gas on scattering, energy loss, and propagation of muons during both ionization cooling and acceleration.
BNL, Upton, Long Island, New York
The damper of 56 MHz cavity is designed to extract all modes to the resistance load outside, including the fundamental mode. Therefore a high-pass filter is required to reflect the fundamental mode back into the cavity. A preliminary design of the filter was previously done. In this paper, we optimize all elements to eliminate the poor filter performance above 1 GHz. The circuit diagram is extracted from microwave lumped elements that reproduce the frequency spectrum of the finalized filter. We also show mode damping results with dampers and filters in the desired configuration, determining the final performance of the cavity.
BNL, Upton, Long Island, New York
A 56 MHz cavity was designed for a luminosity upgrade of the Relativistic Heavy Ion Collider (RHIC), including requirements for Higher Order Mode (HOM) damping. A preliminary design of the HOM damper was previously done without optimization. In this paper, we describe our optimization of the damper's performance, and modifications made to its original design. We also show the cavity damper efects with different geometries. Magnetic field enhancement at the ports is reduced to a value less than the highest field in the cavity to eliminate electrical breakdown. All HOMs up to 1 GHz are simulated with their frequencies, mode configurations, R/Qs and shunt impedances, and all modes are well-damped with the optimized design and configuration.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
At BESSY II photon energies above 2keV can be produced only with bending magnets, a permanent magnet wiggler, superconducting (SC) wavelength shifters and a SC-wiggler. The wiggler brilliance suffers from the depth of field effect and the bending magnets and wavelength shifters produce the X-rays only with a single pole. Experiments such as HIgh Kinetic Energy photoelectron spectroscopy (HIKE) or microspectroscopy on nanostructured materials demand a high brilliance and flux as it is provided by a small period cryogenic undulator. This paper discusses the requirements for the operation of small gap cryogenic devices at BESSY II. A scheme with two adjacent, vertical low beta sections inside of one of the long straight sections is suggested. The straight is divided into two parts by a quadrupole triple in the center. An optic with an increased, vertical beta tune by 0.5 is presently studied. The optics outside of the low beta section and the horizontal tune are kept unchanged.
KIT, Karlsruhe
Karlsruhe Institute of Technology (KIT), Karlsruhe
CERN, Geneva
In the superconductive undulator SCU14, installed at ANKA, time dependent drifts in the magnetic fields were observed*. Simulations with the software OPERA 3D showed, that the cause of these drifts might be leak and eddy currents in the iron body of the undulator caused by the time-varying currents and fields during current ramps, which slowly decay by ohmic losses. This assumption was crosschecked by measurements at different mockup bodies. This contribution discusses the results of the simulations and measurements and the consequential strategies for avoiding this effect.
* S. Ehlers et. al. "Magnetic field transients in superconductive undulators", in Proceedings of the Particle Accelerator Conference, Vancouver, 2009, to be published.
Karlsruhe Institute of Technology (KIT), Karlsruhe
BNG, Würzburg
A 1.5 m long superconducting undulator with a period length of 15 mm is planned to be installed in ANKA middle 2010 to be the light source of the new beamline NANO for high resolution X-ray diffraction. The key specifications of the system are an undulator parameter K higher than 2 (for a magnetic gap of 5mm) and a phase error smaller than 3.5 degrees. In order to characterize the magnetic field properties of the superconducting coils local field measurements have been performed by moving a set of Hall probes on a sledge in a liquid helium bath: the results are reported.
Karlsruhe Institute of Technology (KIT), Karlsruhe
BNG, Würzburg
One of the advantages of superconducting insertion devices (IDs) with respect to permanent magnet IDs is the possibility to enlarge the spectral range by changing the period length by reversing the direction of the current in a part of the windings. In this contribution we report the first experimental test of this principle demonstrated on a 70mm NbTi mock-up coil with period tripling, allowing to switch between a 15mm period length undulator and a 45mm wiggler.
KEK, Ibaraki
We have been developing a rapid-polarization-switching source at the B15-16 straight section in the PF 2.5GeV ring. The source consists of tandem two APPLE-II type elliptically polarizing undulators (EPU), namely U#16-1 and U#16-2, and a fast kicker system. These two undulators are designed to obtain the soft x-ray at the energy region from 200eV to 1keV with various polarization states. We have constructed U#16-1 and installed in the PF ring in March 2008. The operation of U#16-1 for the user experiments has been started successfully since April 2008. The construction of the second undulator U#16-2 is underway. U#16-2 will be installed in the PF ring at this summer. We report the result of the magnetic field adjustment of the U#16-2.
NSRRC, Hsinchu
Shimming magnetic field error on each pole in the Elliptically Polarized Undulator (EPU) is a time-consuming work and highly based on experience without scientific systematic methods. Therefore, an auto-field shimming program is developed to save time on pole shimming process. The program is including two major steps to analyze where the poles is defective or imperfect. Step one is to clarify the magnetic pole quality. If its quality is far away to user-defined standards, we change the pole instead of processing to balance them relatively for uniform magnetic field. The magnetic pole quality is based on deltaB/Bavg and deltaI/Iavg(half period of integral) percentage. The second step is to build the effective field and once integral model of pole and permanent magnet calculation. If we shim the defective pole by moving vertically and transversely, it would surge intrinsic change of the deltaB/Bavg and deltaI/Iavg at defective and surrounded poles. Auto-field shimming algorithm would assist us to plan shimming strategies to deal with magnetic poles.
NSRRC, Hsinchu
We design and implement a power convert to supply dc power bus for the MCOR30 correction supply. The dc power supply's characteristics were variable frequency at heavy and medium/light load. These characteristics matched with the correction supply working requirement. The dc power bus has a relaxation oscillator generating a symmetrical triangular waveform, which MOSFET's switching is locked to. The frequency of this waveform is related to a current that will be modulated by feedback circuitry. As a result, the tank circuit driven by half-bridge will be stimulated at a frequency dictated by the feedback loop to keep the output voltage regulated, thus exploiting its frequency-dependent transfer characteristics. The high performance characteristics of the resonant dc power bus are illustrated in this paper.
NSRRC, Hsinchu
This paper presents an implementation of a precision corrector magnet power converter using the digitally controlled pulse width modulation method. The output current precision of this ±10A/±50V corrector magnet power converter is within ±10ppm. The digital control circuit of the power converter is implemented with using a high speed ADS8382 18-bits analog-to-digital converter and a TMS320F28335 digital signal processor. The converter uses a full bridge configuration, the switching frequency of power MOSFET is 40 kHz and the control resolution is 17-bits. Using a DCCT as the current feedback component the output current ripple of this converter could be lower than 5 ppm that is beyond the requirement of TLS corrector power converter and suitable to be used in TPS.
CIEMAT, Madrid
CERN, Geneva
The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues of the CLIC scheme. The extracted drive beam from the combiner ring (CR), a pulse of 35 A magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX). A Tail Clipper (TC) kicker is required, in the CR to CLEX transfer line, to allow the duration of the beam pulse to be adjusted: the unwanted bunches are kicked into a collimator. The TC must have a fast field rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss. Striplines are used for the TC: to establish the required fields, the applied pulse wave front must fully propagate along the striplines. To reduce the wave front propagation time, the overall length of the stripline assembly is sub-divided into 4 sections. The TC has been designed with the aid of detailed numerical modelling: the stripline cross-section and coaxial-to-stripline transitions were carefully optimized using a 3D code. The results of simulations and the measured behaviour of the striplines are presented; in addition measured current pulses are shown.
CERN, Geneva
Proton and ion beams will be injected into LHC at 450 GeV by two kicker magnet systems, producing magnetic field pulses of up to 7.8 μs flat top duration with rise and fall times of not more than 900 ns and 3 μs, respectively. Both systems are composed of four traveling wave kicker magnets, powered by pulse forming networks. One of the stringent design requirements of these systems is a field flat top and post pulse ripple of less than ±0.5 %. A carefully matched high bandwidth system is required to obtain the stringent pulse response. Screen conductors are placed in the aperture of the kicker magnet to provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against Wake fields: these conductors affect the field pulse response. Recent injection tests provided the opportunity to directly measure the shape of the kick field pulse with high accuracy using a pilot beam. This paper details the measurements and compares the results with predictions and laboratory measurements.
CERN, Geneva
University of Applied Sciences Karlsruhe, Karlsruhe
In many particle accelerators considerable amounts of RF power reaching the megawatt level are converted into heat in dummy loads. After an overview of RF power in the range 200 MHz to 1 GHz dissipated at CERN we discuss several developments that had come up in the past using vacuum tube technology for RF-DC conversion. Amongst those the developments the cyclotron wave converter CWC appears most suitable. With the availability of powerful Schottky diodes the solid state converter aspect has to be addressed as well. One of the biggest problems of Schottky diode based structures is the junction capacity. GaAs and GaN Schottky diodes show a significant reduction of this junction capacity as compared to silicon. Small rectenna type converter units which had been already developed for microwave powered helicopters can be used in waveguides or with coaxial power dividers.
CERN, Geneva
The vertical beam dump system of the CERN Super Proton Synchrotron (SPS) uses two matched magnets with an impedance of 2 Ω and combined kick strength of 1.152 Tm at 60 kV supply voltage. For historical reasons the two magnets are powered from three 3 Ω pulse forming networks (PFN) through three thyratron-ignitron switches. Recently flashovers were observed at the entry of one of the magnets, which lead, because of the electrical coupling between the kickers, to a simultaneous breakdown of the pulse in both magnets. To improve the reliability an upgrade of the system was started. In a first step the radii of surfaces at the entry of the weak magnet were increased, and the PFN voltage was reduced by 4 %; the kick strength could be preserved by reducing the magnet termination resistance by 10 %. The PFNs were protected against negative voltage reflections and their last cells were optimised. In a second step the two magnets will be electrically separated and powered individually by new 2 Ω PFNs with semiconductor switches.
LLNL, Livermore, California
Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from the triple junction. These electrons strike the insulator surface and produce secondary electrons, which also strike the insulator surface to create more secondary electrons and lead to avalanche. Magnetic field from the external sources, the high-current electron beam, the conduction current in the transmission line or the displacement current in the insulator can deflect primary and secondary electrons' trajectories either toward to or away from the insulator surface, and hence affect the performance of the high-voltage vacuum insulator. The displacement current effects are particularly interesting for short pulse applications. This paper presents the displacement current effects with various short applied voltage pulses on performance of high-gradient insulators. Optimal HGI configurations will also be discussed.
KEK, Ibaraki
IHEP Beijing, Beijing
For preserving low emittance beam in the ILC (International Linear Collider) main linacs, Dispersion Matching Steering (DMS) is planed to be used as a main correction method. The linacs are following the earth's curvature and the designed vertical dispersion in the linacs should not be zero. For this reason, the orbit difference due to beam energy difference will have to be measured accurately and tolerance of scale error of beam position monitors (BPM) can be tight. Here, the tolerance of the scale error are estimated by tracking simulations. Choice of optics design for relaxing the tolerance is also discussed.
Sokendai, Ibaraki
KEK, Ibaraki
We have designed Demountable Damped Cavity (DDC) for ILC main linac. DDC has two design concepts. One is the coaxial waveguide for HOM damping, which can strongly couple HOM's. Accelerating mode is reflected by a choke filter. The axial symmetry can reduce the beam kick effect. The other concept is demountable structure which can make easy cleaning of end group in order to suppress the Q-slope problem at a high field. In this paper we will report the RF design and measurement results in model cavity.
CERN, Geneva
The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the position of the beam. The beam position will be sensitive to external dynamic magnetic fields (stray fields) in the nanotesla regime. The impact of these fields on the CLIC main beam has been studied by performing simulations on the lattices and tolerances have been determined. Several mitigation techniques will be discussed.
CERN, Geneva
One crucial development for CLIC is an adjustable high-power rf device which controls the output power level of individual Power Extraction and Transfer Structures (PETS) even while fed with a constant drive beam current. The CLIC two-beam rf system is designed to have a low, approximately 10-7, breakdown rate during normal operation and breakdowns will occur in both accelerating structures and the PETS themselves. In order to recover from the breakdowns and reestablish stable operation, it is necessary to have the capability to switch off a single PETS/accelerating structure unit and then gradually ramp generated power up again. The baseline strategy and implementation of such a variable high-power mechanism is described.
Fermilab, Batavia
In the paper the results are presented for calculation of the transverse wake and RF kick from the power and HOM couplers of the ILC acceleration structure. The RF kick was calculated stand-alone by HFSS, CST MWS and COMSOL codes while the wake kick was calculated by GdfidL. The calculation precision and convergence for both cases are discussed and compared to the results obtained independently by other group.
Osaka University, Osaka
The COMET is an experiment to search for the process of muon to electron conversion in a muonic atom, and is in its design phase to be carried out at J-PARC in near future. The experiment uses a long superconducting solenoid channels from a pion production target to a detector system. In order, to study the solenoid channel the g4beamline is used for the magnetic field calculation and beam tracking. This paper reports the status of the simulation studies.
IHEP Beijing, Beijing
MPI-P, München
MPI für Physics, Muenchen
Low energy muon beams are useful for a wide range of physics experiments. High quality muon beams are also required for muon colliders and neutrino factories. The frictional cooling method holds promise for delivering slow muon beams with narrow energy spreads. With this technology, we consider the production of a cold muon beam from a surface muon source, such as that at the Paul Scherrer Institute. A cooling scheme based on frictional cooling is outlined. Simulation results show that the efficiency of slow muon production can be raised to 1%, which is significantly higher than current schemes.
Imperial College of Science and Technology, Department of Physics, London
Fermilab, Batavia
The COherent Muon to Electron Transition (COMET) experiment aims to measure muon to electron conversion with an unprecedented sensitivity of less than 1 in 10 million billion. The COMET experiment was given stage 1 approval by the J-PARC Program Advisory Committee in July 2009 and work is currently underway towards preparing a technical design report for the whole experiment. The need for this sensitivity places several stringent requirements on the beamline, such as, a pulsed proton beam with an extinction level between pulses of 9 orders of magnitude; a 5T superconducting solenoid operating near a high radiation environment; precise momentum selection of a large emittance muon beam and momentum selection and collimation of a large emittance electron beam. This paper will present the current status of the various components of the COMET beamline.
Imperial College of Science and Technology, Department of Physics, London
BNL, Upton, Long Island, New York
JLAB, Newport News, Virginia
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The IDS study showed that a Neutrino Factory seems to be the most promising candidate for the next phase of high precision neutrino oscillation experiments. A part of the increased precision is due to the fact that in a Neutrino Factory the decay of muons produces a neutrino beam with narrow energy distribution and divergence. The effect of beam loading on the energy distribution of the muon beam in the Neutrino Factory has been investigated numerically. The simulations have been performed using the baseline accelerator design including cavities for different number of bunch trains and bunch train timing. A detailed analysis of the beam energy distribution expected is given together with a discussion of the energy spread produced by the gutter acceleration in the FFAG and the implications for the neutrino oscillation experiments will be presented.
Fermilab, Batavia
BNL, Upton, Long Island, New York
IIT, Chicago, Illinois
LBNL, Berkeley, California
An accelerator complex that can produce ultra-intense beams of muons presents many opportunities to explore new physics. A facility of this type is unique in that, in a relatively straightforward way, it can present a physics program that can be staged and thus move forward incrementally, addressing exciting new physics at each step. At the request of the US Department of Energy's Office of High Energy Physics, the Neutrino Factory and Muon Collider Collaboration and the Fermilab Muon Collider Task Force have recently submitted a proposal to create a Muon Accelerator Program that will have, as a primary goal, to deliver a Design Feasibility Study for an energy-frontier Muon Collider after a 7 year R&D program. This paper presents a description of a Muon Collider facility with a brief physics motivation, gives an overview of the proposal with respect to its organization and timeline and then discusses in some detail its major technical components.
Fermilab, Batavia
CERN, Geneva
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Muons, Inc, Batavia
We discuss the design of the muon capture front end of a neutrino factory and present studies of variations of its components. In the front end, a proton bunch on a target creates secondary pions that drift into a capture transport channel, decaying into muons. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. The cooling section uses absorber material (reducing the 3-D muon momenta) alternating with rf cavities (restoring longitudinal momentum) within strong focusing magnetic fields. The design is affected by limitations on accelerating gradients within magnetic fields. The effects of gradient limitations are explored, and mitigation strategies are presented. Variations of the ionization cooling and acceleration scenarios and extensions toward use in a muon collider are discussed.
Muons, Inc, Batavia
Fermilab, Batavia
Intense muon beams have many potential applications, including neutrino factories and muon colliders. However, muons are produced as tertiary beams, resulting in diffuse phase space distributions. To make useful beams, the muons must be rapidly cooled before they decay. An idea conceived recently for the collection and cooling of muon beams, namely, the use of a Quasi-Isochronous Helical Channel (QIHC) to facilitate capture of muons into RF buckets, has been developed further. The resulting distribution could be cooled quickly and coalesced into a single bunch to optimize the luminosity of a muon collider. After a brief elaboration of the QIHC concept, some recent developments are described.
LANL, Los Alamos, New Mexico
We propose a high-gradient linear accelerator for accelerating low-energy muons and pions in a strong solenoidal magnetic field. The acceleration starts immediately after collection of pions from a target by solenoidal magnets and brings muons to a kinetic energy of about 200 MeV over a distance of the order of 10 m. At this energy, both an ionization cooling of the muon beam and its further acceleration in a superconducting linac become feasible. The project presents unique challenges ' a very large energy spread in a highly divergent beam, as well as pion and muon decays ' requiring large longitudinal and transverse acceptances. One potential solution incorporates a normal-conducting linac consisting of independently fed 0-mode RF cavities with wide apertures closed by thin metal windows or grids. The guiding magnetic field is provided by external superconducting solenoids. The cavity choice, overall linac design considerations, and simulation results of muon acceleration are presented. While the primary applications of such a linac are for homeland defense and industry, it can provide muon fluxes high enough to be of interest for physics experiments.
LANL, Los Alamos, New Mexico
Many groups are working on muon accelerators for future neutrino factory and muon colliders. One of the applications of muon accelerator is muon radiography which is a promising method to investigate large objects taking advantage of the long penetration lengths of muons. We propose a compact muon accelerator that has a large energy and a phase acceptance to capture relatively low energy pion/muon of 10 - 100 MeV and accelerates them to 200 MeV without any beam cooling. Like an RFQ, mixed buncher/acceleration mode provides phase bunching during the acceleration. Our current design uses 805 MHz zero-mode normal-conducting cavities with 35 MV/m peak field*. The normal conducting cavities are surrounded by superconducting coils that produce 5 T focusing field. We ran Monte Carlo simulations to optimize linac parameters such as frequency and acceleration gradient. Muon energy loss and scattering effects at the cavity windows are studied, too. The simulation showed that about 10 % of the pion/muon injected into the linac can be accelerated to 200 MeV. Further acceleration is possible with superconducting linac.
* S. Kurennoy et al., IPAC 2010.
UCLA, Los Angeles, California
RadiaBeam, Marina del Rey
One of the challenges of the proposed muon collider is the beam size at the interaction region. The current target for the beta function (beta-star) is 10mm for the 1.5TeV scenario with a beam emittance of 25mm-mrad. In this paper, we describe the design and development of a final focusing scheme that attempts to reach these parameters. The final focus scheme is based on the use of permanent magnet quadrupoles (PMQ) in a triplet configuration. Initial simulations show that the PMQs reach gradients as high as ~990T/m using Praseodymium based magnets in a Halbach style arrangement. Possible methods for tuning the PMQs at the interaction region, via temperature control and high-resolution movers, are also described.
UCR, Riverside, California
A significant reduction in the six-dimensional emittance of the initial beam is required in any proposed Muon Collider scheme. Two lattices based on the original RFOFO ring design representing different stages of cooling are considered. One is the so-called open cavity lattice addressing the problem of the 201.25 MHz RF cavities running in a magnetic field, the other one is the 805 MHz RF lattice that is used for smaller emittances. The details of the acceptance analysis and tracking studies of both channels are presented and compared to the independent ICOOL implementation.
UCR, Riverside, California
Fermilab, Batavia
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
In the Muon Ionization Cooling Experiment (MICE), muons are cooled by ionization cooling. Muons are passed through material, reducing the total momentum of the beam. This results in a decrease in transverse emittance and a slight increase in longitudinal emittance, but overall reduction of 6D beam emittance. In emittance exchange, a dispersive beam is passed through wedge-shaped absorbers. Muons with higher energy pass through more material, resulting in a reduction in longitudinal and transverse emittance. Emittance exchange is a vital technology for a Muon Collider and may be of use for a Neutrino Factory. Two ways to demonstrate emittance exchange in the straight solenoidal lattice of MICE are discussed. One is to let a muon beam pass through a wedge shaped absorber; the input beam distribution must be carefully selected to accommodate chromatic aberrations in the solenoid lattice. Another approach is to use the input beam for MICE without beam selection. In this case no polynomial weighting is involved; however, a more sophisticated shape of the absorber is required to reduce longitudinal emittance.
National Technical University of Athens, Zografou
CERN, Geneva
Due to the high bunch density, the output emittances of the CLIC Damping Rings (DR) are strongly dominated by the effect of Intrabeam Scattering (IBS). In an attempt to optimize the ring design and using classical IBS formalisms and approximations, the scaling of the extracted emittances and IBS growth rates is being studied, with respect to several ring parameters including energy, bunch charge, optics and wiggler characteristics. Results from the simulations using a multi-particle tracking code are also presented.
CERN, Geneva
The CLIC 3 TeV nominal design requires very low emittance of the electron and positron beams to be reached in the damping rings. Due to low energy and to relatively high bunch charge and ultra-low emittance, Intra-Beam Scattering (IBS) effect is very strong and an accurate calculation is needed to check if the required emittance is effectively reached. For this reason it is being developed at CERN a new Software for IBS and Radiation Effects (SIRE), which simulates the evolution of the beam particle distribution in the damping rings, taking into account radiation damping, IBS and quantum excitation. In this paper we present the results of our simulations performed with SIRE on the current lattice of the CLIC damping rings.
SLAC, Menlo Park, California
LBNL, Berkeley, California
CLASSE, Ithaca, New York
INFN/LNF, Frascati (Roma)
ANL, Argonne
Cockcroft Institute, Warrington, Cheshire
KEK, Ibaraki
CERN, Geneva
As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The neutrino factory requires a source of pions within a momentum window determined by the ‘muon front end' accelerator structure downstream. The technique of finding which parts of a large target block are net absorbers or emitters of particles may be adapted with this momentum window in mind. Therefore, analysis of a hadronic production simulation run using MARS15 can provide a candidate target shape in a single pass. However, changing the shape of the material also affects the absorption/emission balance, so this paper investigates iterative schemes to find a self-consistent optimal, or near-optimal, target geometry.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
Beryllium is being considered as an option material for the CLIC energy collimators in the Beam Delivery System. Its high electrical and thermal conductivity together with a large radiation length compared to other metals makes Beryllium an optimal candidate for a long tapered design collimator that will not generate high wakefields, which might degrade the orbit stability and dilute the beam emittance, and in case of the beam impacting the collimator temperature rises will not be sufficient enough to melt the metal. This paper shows results and conclusions from simulations of the impact of a CLIC bunch train hitting the collimator.
Euclid TechLabs, LLC, Solon, Ohio
LETI, Saint-Petersburg
CERN, Geneva
In this presentation, dielectric collimator concepts for the linear collider will be described. Cylindrical and planar dielectric collimator designs for CLIC and ILC parameters will be presented, and results of simulations to minimize the beam impedance will be discussed. The prototype collimator system is planned to be fabricated and experimentally tested at Facilities for Accelerator Science and Experimental Test Beams (FACET) at SLAC.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
USC, Los Angeles, California
Given the recent success of >GV/m dielectric wakefield accelerator (DWA) breakdown experiments at SLAC, and follow-on coherent Cerenkov radiation production at the UCLA Neptune, a UCLA-USC-SLAC collaboration is now implementing a new set of experiments that explore various DWA scenarios. These experiments are motivated by the opportunities presented by the approval of FACET facility at SLAC, as well as unique pulse-train wakefield drivers at BNL. The SLAC experiments permit further exploration of the multi-GeV/m envelope in DWAs, and will entail investigations of novel materials (e.g. CVD diamond) and geometries (Bragg cylindrical structures, slab-symmetric DWAs), and have an over-riding goal of demonstrating >GeV acceleration in ~33 cm DWA tubes. In the nearer term before FACET's commissioning, we are planning measurements at the BNL ATF, in which we drive ~50-200 MV/m fields with single pulses or pulse trains. These experiments are of high relevance to enhancing linear collider DWA designs, as they will demonstrate potential for high efficiency operatio with pulse trains.
HU/AdSM, Higashi-Hiroshima
Hiroshima University, Faculty of Science, Higashi-Hirosima
An ion plasma confined in a compact trap system is Coulomb crystallized near the absolute zero temperature. The emittance of the crystallized ion plasma is close to the ultimate limit, far below those of any regular ion beams. This implies that, if we can somehow accelerate a crystal without serious heating, an ion beam of extremely low emittance becomes available*. Such ultra-low emittance beams, even if the current is low, can be used for diverse purposes including precise single ion implantation to various materials and for systematic studies of radiation damage effects on semiconductors and bio-molecules. We performed proof-of-principle experiments on the extraction of Coulomb crystals from a linear Paul trap system developed at Hiroshima University. A string crystal of 40Ca+ ions is produced with the Doppler laser cooling technique and then extracted by switching DC potentials on the trap electrodes. We demonstrate that it is possible to transport the ultra-low temperature ion chain keeping its ordered configuration.
* M. Kano et al., J. Phys. Soc. Jpn. 73, No.3, 760 (2004).
INFN/LNF, Frascati (Roma)
To achieve luminosities significantly higher than in existing machines, future storage-ring based colliders will need to operate in novel parameter regimes combining ultra-low emittance, large Piwinski angle and high bunch charge; implementation of techniques such as a "crab waist" will add further challenges. Understanding the beam-beam interaction in these situations will be essential for the design of future very high luminosity colliders. Recent developments in modeling tools for studying beam-beam effects, capable of investigating the relevant regimes, will be discussed and examples, including tests with crab waist collisions in DAΦNE, will be presented.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
In the frame of the SPARC-X project, the energy of the Photo-Injector SPARC, in operation at INFN-LNF, will be upgraded from 180 to 250 MeV by replacing a low gradient S-band traveling wave accelerating section with two C-band units, designed and developed at LNF. The new system will consist of a 50 MW klystron, supplied by a pulsed modulator, to feed the high gradient C-band structures through a RF pulse compressor. This paper deals with the design of the full system, the C-band R&D activity and study of the related beam dynamics.
Rome University La Sapienza, Roma
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
INFN/LNF, Frascati (Roma)
The quest for high brightness beams is a crucial key for the SPARX-FEL Project. In this paper, we present the design (including RF modeling, cooling, thermal and stress analyses as well as frequency detuning) of a single feed S-Band RF Gun capable of running near 500 Hz. An alternative design with dual feed has already been designed. Also, experimental results from the RF characterization of the prototype, including field measurements, are presented. The RF design follows the guidelines of the LCLS Gun, but the approach diverges significantly as far as the management of the cooling and mechanical stress is concerned. Finally, we examine the new proprietary approach of RadiaBeam Technologies for fabricating copper structures with intricate internal cooling geometries that may enable very high repetition rate.
* C.Limborg et al., "RF Design of the LCLS Gun".
** P. Frigola et al., "Development of solid freeform fabrication (SFF) for the production of RF Photoinjectors".
KEK, Ibaraki
JAEA/J-PARC, Tokai-mura
The RF cavity using Magnetic Alloy (MA) cores has been developed for achieving the high field gradient in J-PARC. For reducing the beam loading effects, the Q-value of the RF cavities in the Main Ring (MR) is controlled by using the cut-core configuration. In order to check the effect of HOMs between the cut-core gap, a simulation method of MA cores was studied and electromagnetic fields of excitation modes have been calculated by HFSS. We present the detail of the simulation method of MA cores and the HOM analysis of the cavity with the cut-cores.
Toshiba, Yokohama
JASRI/SPring-8, Hyogo-ken
TOSHIBA is manufacturing the L-band acceleration system for the SPring-8 Joint Project for XFEL. We have developed a new type duct-shaped SiC dummy load for its power distribution system. The load terminates a WR650 waveguide and can absorb the maximum mean power of 10kW. In order to reduce VSWR less than 1.1 in the frequency range of 1.428GHz, we shaped the SiC absorber into a 35cm long tapered cylinder and mounted matching stubs in the waveguide near the inlet of the load. The SiC absorber was fit into a cylindrical copper with efficient water-cooling channels. The design and manufacture and the low-power tests of our original dummy load are described in this paper.
TUB, Beijing
CAEP/IFP, Mainyang, Sichuan
Mini-LIA was a miniature linear induction accelerator designed and manufactured by China Academy of Engineering Physics and Tsinghua University. To investigate the higher order mode (HOM) of Mini-LIA cavity, especially the frequency and quality factor Q of the TM110 and TM120 in it, both numerical simulation and experiments were performed. Several models of the cavity were established and calculated by using E module of MAFIA code. Network analyzer was applied to measure the frequency and Q in cavity. Both the simulation results and the experiment results are presented in this paper. The results of the experiments were coincident with the calculated results. Finally, The HOM characteristic of Mini-LIA cavity with metglass core in it was explored, and some interesting results was obtained.
USTC/PMPI, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Collinear load, consisted of several coaxial cavities, is a substitute for traditional waveguide-type load to absorb the remnant power of the LINAC and makes the accelerating structure compact and small-size. The power loss on the cavities of collinear load brings thermal deformation which affects their resonant frequency deeply. In this paper, a new approach of 3D reconstruction of the thermal deformed cavities is utilized to evaluate the accurate influence on frequency change caused by non-uniform deformation and water cooling strategies of collinear absorbing load are studied. Then the thermal behavior of a six-cavity collinear load, which is coated with Kanthal alloy and FeSiAl alloy and used on a 2856MHz, 2π/3 mode respectively, is researched. The results show that the collinear load with Kanthal alloy can only absorb up to 10kW, while with FeSiAl alloy it can dissipate 15kW when the water flow controlled within 3.0kg/s for energy saving.
* Tian Z. etc., "Finite Element Analysis of RF Cavity", Parietti L. etc., "Thermal/Structural Analysis and Frequency Shift", Anthony, etc. "A NURBS-based Technique for Subject-specific Construction".
HUST, Wuhan
The design study of a 10MeV compact cyclotron CYCHU-10 has been developed at Huazhong University of Science and Technology (HUST). We developed the basic shapes and dimensions and carried out the simulations for the CYCHU-10 cavities with 3D numerical calculation softwares in this paper. The distributions of electromagnetic field are illustrated by means of the electromagnetic and structural analysis, and the wooden model test is preformed as well. In addition, this paper gives mechanical tolerance effects which deformed due to the limit of mechanical working of cavities under practical conditions. This work helps to evaluate the performances of capacitive frequency trimmer design.
MEPhI, Moscow
Nano, Moscow
New possibilities of the polarization plane stabilization in the traveling hybrid TM11 wave deflectors are considered in this paper. These possibilities are realized in two new structures: DLW with two peripheral recesses in cells and DLW with oval aperture. In terms of electro-dynamic parameters, thermal regimes and manufacturing technology these structures as well as a classical structure with two stabilizing holes show some advantages and some disadvantages. The advantages of the new structures are good RF mode separation and effective cooling. The specifics of such structures tuning are also described.
MEPhI, Moscow
Nowadays the DC potential using was proposed for ion beam focusing in linear accelerators. It was proposed to use the DC potential for combined beam focusing (electrostatic focusing and focusing by using of higher RF field spatial harmonics) in bunching section of linac *. These accelerators use an IH-type resonator. So-called linear undulator accelerator (UNDULAC) was proposed for ribbon ion beam bunching and acceleration **. One of possible scheme of UNDULAC can be realized using an electrostatic undulator in E-type resonator. In this report the different types of the electrostatic potential inputting into resonator will discussed.
* P.А. Demchenko at al., Problems of Atomic Science and Technology, 2008, 5 (50), pp. 28-32.
** E.S. Masunov at al., Radiation Physics and Chemistry, 2001, v. 61, рр. 491-493.
Fermilab, Batavia
Muons, Inc, Batavia
Alternative RF cavity fabrication techniques for accelerator applications at low frequencies are needed to improve manufacturability, reliability and cost. RF cavities below 800 MHz are large, take a lot of transverse space, increase the cost of installation, are difficult to manufacture, require significant lead times, and are expensive. Novel RF cavities partially loaded with a ceramic for accelerator applications will allow smaller diameter cavities to be designed and built. The manufacturing techniques for partially loaded cavities will be explored. A new 200MHz cavity will be built for the Fermilab Proton Source to improve the longitudinal emittance and energy stability of the linac beam at injection to the Booster. A cavity designed for 400 MHz with a ceramic cylinder will be tested at low power at cryogenic temperatures to test the change in Qo due to the alumina ceramic. Techniques will be explored to determine if it is feasible to change the cavity frequency by replacing an annular ceramic insert without adversely effecting high power cavity performance.
IUCF, Bloomington, Indiana
In this report, we present our design of a fast extraction kicker for ALPHA. Due to the fast rise time and high voltage requirement, we choose the traveling wave kicker. Both 2D Posisson and 3D Microwave Studio simulation are carried out. Uniformity of electric field, energy transmission through the stripline structure and time response of the kicker are studied carefully. A prototype kicker will be built and tested soon.
LLNL, Livermore, California
SLAC, Menlo Park, California
In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz mono-energetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedingly high quality to produce narrow-bandwidth gamma-rays. Modeling efforts will be presented, along with plans for a multi-bunch test stand at LLNL. The test stand will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The photoinjector will be a high gradient standing wave structure, featuring a dual feed racetrack coupler. The accelerator will increase the electron energy so that the emittance can be measured using quadrupole scanning techniques. Multi-bunch diagnostics will be developed so that the beam quality can be measured and compared with theory. Design will be presented with modeling simulations, and layout plans.
RadiaBeam, Marina del Rey
JLAB, Newport News, Virginia
NCSU, Raleigh, North Carolina
University of Texas El Paso, W.M. Keck Center for 3D Innovation, El Paso, Texas
University of Texas at El Paso, El Paso, Texas
A key issue for high average power, normal conducting radio frequency (NCRF), photoinjectors is efficient structure cooling. To that end, RadiaBeam has been developing the use of Solid Freeform Fabrication (SFF) for the production of NCRF photoinjectors. In this paper we describe the preliminary design of a high gradient, very high duty cycle, photoinjector combining the cooling efficiency only possible through the use of SFF, and the RF efficiency of a re-entrant gun design. Simulations of the RF and thermal-stress performance will be presented, as well as material testing of SFF components.
RadiaBeam, Marina del Rey
SLAC, Menlo Park, California
UCLA, Los Angeles, California
There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The commonly used S-band SLAC-type structure has an operating gradient of only about 20 MV/m; while much higher operating gradients (up to 70 MV/m) have been recently achieved in X-band, as a consequence of the substantial efforts by the Next Linear Collider (NLC) collaboration to push the performance envelope of RF structures towards higher accelerating gradients. Currently however, high power X-band RF sources are not readily available for industrial applications. Therefore, RadiaBeam Technologies is developing a short, standing wave S-band structure which uses frequency scaled NLC design concepts to achieve up to a 50 MV/m operating gradient at 2856 MHz. The design and prototype commissioning plans are presented.
CUT, Krakow
The array of corrector magnets in the LHC is powered by means of a superconducting line attached to the main magnets. The subcooling time of the line has to be minimized in order not to delay the operation of the collider. The corresponding cable-in-conduit problem is formulated in the framework of two-fluid model and the Gorter-Mellink law of heat transport in superfluid helium. A model of λ front propagation along the narrow channel containing superconductors and liquid helium is presented. The one-dimensional model* adopts plane wave equations to describe λ front propagation. This approach to normal-to-superfluid phase transition in liquid helium allows to calculate the time of subcooling and the temperature profile on either side of the travelling front in long channels containing superconducting bus-bars. The model has been verified by comparing the analytical solutions with the experimental results obtained in the LHC String 2 experiment. The process of the LHC Dispersion Suppressors subcooling has been optimized by using the presented model. Based on the results, a novel concept of copper heat exchanger for LHC DS operating in superfluid helium is introduced.
* M. Sitko, B. Skoczeń, Modelling HeI-HeII phase transformation in long channels containing superconductors, Int. Journal of Heat and Mass Transfer, Vol. 52, Issues 1-2,pp. 9-16, 2009.
IAP, Frankfurt am Main
The beam transport experiments in toroidal magnets were first described in EPAC08 within the framework of a proposed low energy ion storage ring at Frankfurt University. The experiments with two room temperature 30 degree toroids are needed to design the accumulator ring with closed magnetic fields up to 6~8T. The test setup aims on building an injection system with two beam lines. The primary beam line for the experiments was installed and successfully commissioned in 2009. A special probe for ion beam detection was installed. This modular technique allows online diagnostics of the ion beam along the beam path. In this paper we present new results on beam transport experiments and discuss transport and transverse beam injection properties of that system.
INFN/LNF, Frascati (Roma)
CNAO Foundation, Milan
CERN, Geneva
University of Pavia, Pavia
The National Centre for Oncological Hadrontherapy (CNAO) is the first Italian centre for the treatment of patients affected by tumours with proton and carbon ions beams. Its status and commissioning results are presented in this conference in several papers. The synchrotron beam extraction is based on the use of a betatron core. The possibility of using the RF-knockout method as alternative system is being investigated, trying to optimise the performances with the already present hardware and minimum upgrades. A multiparticle tracking program has been written to simulate the beam dynamics during the extraction of the synchrotron, and to optimise the parameters of the radio frequency system. Two types of signals have been studied in order to obtain a constant spill with the minimum ripple: a carrier wave with a frequency and amplitude modulation, and a noise at a given range of frequencies modulated in amplitude. The results of the optimisation and the parameters of the proposed system are presented.
NIRS, Chiba-shi
The betatron tune fluctuation due to the current ripple of power supplies brings the beam spill ripple through the stable area variation in resonant slow extraction. The effect becomes dominant especially in the case of the low beam rate extraction. The RF-knockout slow extraction method is insensitive to the tune ripple compared to the ordinary one because it uses the diffusion with the transverse RF field. However, the ripple effect appears even in the beam spill extracted by it. The amount of the separatrix fluctuation due to the tune ripple depends on the difference between the bare and the resonant tune, and the sextupole magnetic strength. We measured the correlation between the beam spill and the tune ripple which was the artificially generated with low and high frequency components of 67 Hz and 1167 Hz near those of the real current ripple. We confirmed the reduction of the beam spill ripple by setting the tune away from the resonance while keeping the separatrix area. The comparison between the experimental results, the analytical calculation and the simulation will be reported.
KEK, Ibaraki
RIKEN Nishina Center, Wako
JAEA, Ibaraki-ken
The measurement of 12C(alpha,gamma) reaction is planned at TRIAC(Tokai Radioactive Ion Accelerator Complex). An intense pulsed alpha beam with the width of less 10ns and the interval between 250ns and 500ns is required for this experiment. Because the Split Coaxial RFQ (SCRFQ), which is one of the TRIAC accelerators, has a radio frequency of 26MHz, the bunch interval becomes 38.5ns. In order to make the bunch interval of 250ns or more, the pre-buncher with a frequency of 2-4MHz, is considered to be installed upstream of the SCRFQ. It is designed as the pre-buncher has two gaps with non-Pi mode. In order to make the bunching beam profile like a pseudo sawtooth-wave, the RF voltage synthesized three harmonic frequencies is applied to these gaps. Consequently, the pre-buncher has a compact size and no leakage electric field outside gaps, and can keep the RF voltage low. Recently, the beam test of this pre-buncher with a case of 2MHz-RF and SCRFQ was performed by using 16O4+ and 12C3+ beams. The clear bunch structure with a interval of 500ns was obtained by the SSD set downstream of the SCRFQ. The results of the beam test are almost consistent with those of the beam simulation code.
KEK/JAEA, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The beam commissioning of J-PARC/MR has been started from May 2008 and is in progress*. One key purpose of MR commissioning is the 30 GeV beam fast extraction to Neutrino beam line, which reflect the overall commissioning result. In the MR, the third straight section is assigned for the fast extraction. 5 kickers and 8 septa were installed there, which can give beam a bipolar kick to inside or outside of MR. Inside kick means beam to Neutrino Oscillation Experiment, while outside kick means beam dumped to abort line. However before commissioning, the measured magnetic field distribution of each septa shows non-linear profile along the horizontal direction. In order to find the influence, a simulation with these measured field has been performed. Depends on this study and some OPI (Operation Interface) made by code SAD for orbit modification online, fast extraction of 30 GeV beam to Neutrino line has been achieved on April 23rd 2009. Beam orbit have been tuned to less than 0.5 mm and 0.1 mrad in both horizontal and vertical at the beginning of Neutrino line, which is also the end of MR fast extraction. And so far, 100 kW continual operation to neutrino line have been achieved, too.
* T. Koseki, "Challenges and Solutions for J-PARC Commissioning and Early Operation", in these proceedings
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
The beam loss caused by the nuclear scattering together with the multiple Coulomb scattering at the stripping foil is one of the key issue in RCS (Rapid Cycling Synchrotron) of the J-PARC (Japan Proton Accelerator Research Accelerator). In order to have a very realistic understanding, a systematic study with both experiment and simulation has been carried out recently. A total of seven targets with different thickness were used and the measured beam losses were found to be good in agreement with that in the simulation. A detail and realistic understanding from such a study will be very useful not only to optimize the foil system including the thickness and size at present with the injection beam energy of 181 MeV but also for the near future upgrade with 400 MeV and in addition can be a good example for similar existing and proposing projects.
KEK, Ibaraki
Mitsubishi Electric Corp., Communication Systems Center, Amagasaki City, Hyogo
The L-band inductive output tube (IOT) without trolly was developed to operate under higher applied voltage. The operation frequency of conventional IOTs is tuned using its trolly. This mechanism is based on the lower frequency IOT. However it causes less insulation voltage of the ceramics since the electric insulation oil is not available for its trolly and the length of the insulation ceramics is limited because it is a part of the resonant cavity. In case of IOTs, it is important to increase the applied voltage for higher output power since the grid gap is very narrow and its area cannot be increased to keep the gain. Thus we developed an IOT which has a longer insulating ceramic and the input cavity is filled with vacuum to use the electric insulation oil. Further the dielectric waveguide can solve to feed the input microwave to the cathode grid without trolly. These new features of the IOT is very effective for the fixed frequency application such as the accelerator, for example the energy recovery linac. The design and the experimental results will be presented in this report.
Lancaster University, Lancaster
Cockcroft Institute, Lancaster University, Lancaster
2D Photonic crystals (PC) with defects can act as standing-wave resonators, which offer benefit of high mode selectivity for building novel RF sources. We introduce our work on designing two-cavity single-beam and multi-beam klystrons using triangular lattice metallic PCs. We present the cold test results of the stub-coupled single-beam structure, which show that at resonance a very low reflection can be obtained, and the waves are well confined. We also present bead-pull measurement results of field strengths in the defect, using modified perturbation equation for small unit dielectric cylinder, which are in very good agreement to numerical results. A 6-beam klystron cavity is designed as a 6-coupled-defect structure with a central stub, which only couples to the in-phase mode at the lowest frequency. Finally, we present a feasibility discussion of using this multi-defect PC structure to construct an integrated klystron-accelerator cavity, along with numerical results showing a peak acceleration field of 22MV/m can be achieved.
SLAC, Menlo Park, California
A 12 GHz 50MW X-band klystron is under development at the SLAC National Accelerator Laboratory Klystron Department. The klystron will be fabricated to support programs currently underway at three European Labs; CERN, PSI, and INFN Trieste. The choice of frequency selection was due to the CLIC RF frequency changing from 30 GHz to the European X-band frequency of 11.9942 GHz in 2008. Since the Klystron Department currently builds 50MW klystrons at 11.424 GHz known collectively as the XL4 klystrons, it was deemed cost-effective to utilize many XL4 components by leaving the gun, electron beam transport, solenoid magnet and collector unchanged. To realize the rf parameters required, the rf cavities and rf output hardware were necessarily altered. Some improvements to the rf design have been made to reduce operating gradients and increase reliability. Changes in the multi-cell output structure, waveguide components, and the window will be discussed along with testing of the devices. Five klystrons known as XL5 klystrons are scheduled for production over the next two years.
SLAC, Menlo Park, California
The SLAC National Accelerator Laboratory Klystron Department is developing a 10 MW, 5 Hz, 1.6 ms, 1.3 GHz plug-compatible Sheet-Beam Klystron as a less expensive and more compact alternative to the ILC baseline Multiple-Beam Klystron. Earlier this year a beam tester was constructed and began test. Device fabrication issues have complicated the analysis of the data collected from an intercepting cup for making beam quality measurements of the 130 A, 40-to-1 aspect ratio beam. Since the goal of the beam tester is to confirm 3d beam simulations it was necessary to rebuild the device in order to mitigate unwanted effects due to imperfect focusing construction. Measurements are underway to verify the results of this latest incarnation. Measurement will then be made of the beam after transporting through a drift tube and magnetic focusing system. In the klystron design, a TE oscillation was discovered during long simulation runs of the entire device which has since prompted two design changes to eliminate the beam disruption. The general theory of operation, the design choices made, and results of testing of these various devices will be discussed.
DESY, Hamburg
Building an accelerator facility brings together civil construction and mechanical engineering, two trades with very different working cultures, practices and tool sets: While construction sites are traditionally paper-based and 2D oriented, the accelerator and its infrastructure are completely modeled in 3D. At the European XFEL, methods and tools known from plant construction were introduced to civil construction to enable efficient collaboration of all trades. Integrated 3D models encompass design models of all technical subsystems. An electronic "XFEL room book" captures requirements and manages assignments of space, infrastructure and equipments in the buildings. The DESY Engineering Data Management System (EDMS) manages and links the information with additional documentation. Electronic workflows coordinate e.g. reviews and change management. 3D models, room book and documentation databases together constitute the so-called "Building Information Model" (BIM). The BIM addresses the entire building lifecycle and is a basis for later facility operation. The poster describes information management procedures, tools and experience in the civil construction of the European XFEL.
NSRRC, Hsinchu
NTUT, Taipei
The stability of air temperature in the storage ring tunnel is one of the most critical factors. Therefore, a series of air conditioning system upgrade studies and projects have been conducted at the Taiwan Light Source (TLS). The global air temperature variation related to time in the storage ring tunnel has been controlled within ±0.1 degree C for years. This study is aimed at more precise temperature control. Some temperature control schemes are applied on this study. We also performed computational fluid dynamics (CFD) to simulate the flow field and the spatial temperature distribution in the storage ring tunnel.
NSRRC, Hsinchu
Previously, the Taiwan Light Source (TLS) has proven that the temperature stability of de-ionized cooling water is one of the most critical factors of electron beam stability. A series of efforts were devoted to these studies and promoted the temperature stability of the de-ionized cooling water system within ±0.1°C. Further, a high precision temperature control ±0.01°C has been conducted to meet the more critical stability requirement. Using flow mixing mechanism and specified control philosophy can minimize temperature variation effectively. The paper declares the mechanism through simulation and verifies the practical influences. The significant improvement of temperature stability between cooling devices and de-ionized water are also presented.
Lucknow University, Lucknow
BARC, Mumbai
CBS, Mumbai
Nonlinear, high-amplitude plasma waves are excited in the wake of an intense laser pulse propagating in a cold plasma, providing acceleration gradients up to GeV/m. Linear analytic analyses have shown that the wakefield amplitude is optimal for a certain ratio of the pulse length and plasma wavelength*,**. Here we present results of simulation studies to optimize the nonlinear wakefield amplitudes. Variation in the laser pulse length is considered for maximizing amplitudes of wakefields generated by half-sine and Gaussian pulse profiles. Further, the advantages of using a transversely inhomogeneous plasma for the generation of the nonlinear wakefields are studied and compared with the homogeneous case.
* E. Esarey, P. Sprengle, J. Krall and A. Ting, IEEE Trans. Palsma Sci. 24, 252 (1996)
** L. M. Gorbunov and V. I. Kirsanov, Zh. Eksp. Teor. Fiz. 93, 509 (1987), Sov. Phys. JETP, 46, 290 (1988).
BARC, Mumbai
Lucknow University, Lucknow
CBS, Mumbai
We study electron acceleration by two laser pulses co-propagating one behind the other in a homogeneous plasma. We show, using one-dimensional simulations, that the wake amplitude can be amplified or diminished depending on the time delay between the two lasers, in agreement with linear analytic theory. We extend the study to the bubble regime using two-dimensional simulations. We find that the one-dimensional optimization holds in two dimensions also. Trapping and acceleration of quasi-monoenergetic electrons (up to around 300 MeV) is found in the bucket behind the second laser, even for low intensities, where there is no trapping with a single laser. Thus, this scheme could be very useful for achieving a desired accelerated energy with less intense lasers, or, equivalently, increasing the accelerated energy for a given laser intensity.
* G. Raj, A. K. Upadhyay, R. K. Mishra and P. Jha, Phys. Rev. ST Accel. and Beams 11, 071301 (2008).
KERI, Changwon
Using the nonlinear interaction between the high power laser and the plasma, we can generate strong acceleration field, called the laser wake field acceleration. The plasma density is very crucial to generate high energy electron. In this work, we studied the effect of the plasma density structure on the accelerated electron energy. We used 20 TW, 40 fs laser system to generate the plasma wakefield. A gas jet was used as a target. The plasma density was controlled by the back pressure of the gas nozzle and measured by the interferometer. The accelerated electron energy was measured using the electron energy spectrometer with 0.5 T magnet. The bunch charge was measured integrated charge transformer (ICT). When the plasma density is uniform, 2×1019 cm-3 we can generate 200 MeV electron beam with bunch charge 33 pC. The electron beam divergence was less than 5 degree. If there exists the downward density tramp, the electron energy is only 50 MeV. The PIC simulation also indicates that if there is density ramp structure, the electron is not accelerated well. In this presentation, the overall experimental and simulation results are presented.
Tech-X, Boulder, Colorado
Stanford University, Stanford, California
SLAC, Menlo Park, California
Photonic crystal waveguides are promising candidates for laser-driven accelerator structures because of their ability to confine a speed-of-light mode in an all-dielectric structure. Because of the difference between the group velocity of the waveguide mode and the particle bunch velocity, fields must be coupled into the accelerating waveguide at frequent intervals. Therefore efficient, compact couplers are critical to overall accelerator efficiency. We present designs and simulations of high-efficiency coupling to the accelerating mode in a three-dimensional photonic crystal waveguide from a waveguide adjoining it at 90 degrees. We discuss details of the computation, including an optimization routine to modify the geometric parameters of the coupler for maximum efficiency, the resulting transmission, and estimates of the fabrication tolerance for these devices. We include some background on the accelerator structure and photonic crystal-based optical acceleration in general.
ISIR, Osaka
Femtosecond electron beam pulse radiolysis which has time resolution of 250 fs was achieved by a Photocathode RF gun LINAC in the ISIR, Osaka University. And geminate ion recombination (charged pair dynamics) in n-dodecane was studied. Kinetics of the Radical cation of n-dodecane was measured. As a result, the existence of the excited-radical cation, and generation of the radical cation via relaxation from the excited-radical cation were suggested. Those new results were obtained in the field of the radiation chemistry by the photocathode RF gun.
Cockcroft Institute, Warrington, Cheshire
Lancaster University, Lancaster
LLNL, Livermore, California
Imperial College of Science and Technology, Department of Physics, London
The University of Liverpool, Liverpool
The efficiency of future positron sources for the next generation of high-energy particle colliders (e.g. ILC, CLIC, LHeC) can be improved if the positron-production target is immersed in the magnetic field of adjacent capture optics. If the target is also rotating due to heat deposition considerations then eddy currents may be induced and lead to additional heating and stresses. In this paper we present data from a rotating target wheel prototype for the baseline ILC positron source. The wheel has been operated at revolution rates up to 1800rpm in fields of the order of 1 Tesla. Comparisons are made between torque data obtained from a transducer on the target drive shaft and the results of finite-element simulations. Rotordynamics issues are presented and future experiments on other aspects of the positron source target station are considered.
LLNL, Livermore, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The positron source at a future TeV scale electron linear collider will need to generate positrons at a rate two orders of magnitude larger than have been previously achieved. We report on a design of a 3.5 Tesla pulsed flux concentrator magnet which uses liquid nitrogen cooling of the flux concentrator plates to reduce the electrical resistance leading to reduced energy deposition and the ability to generate the required 1 ms pulse duration. This magnet can double the collection efficiency of positrons emitted from the target.
GSI, Darmstadt
CERN, Geneva
In the complex of the accelerators of the FAIR project the RESR storage ring is mainly designed as an accumulator ring for antiprotons. The continuous accumulation of pre-cooled batches with a cycle time of 10 s from the collector ring is essential to achieve the goal of a production rate of 10 million antiprotons per second. The accumulation in the RESR uses a stochastic cooling system which operates in longitudinal phase space, similar as previous antiproton accumulator rings at CERN and FNAL. The ingredients of the accumulation system, the ring lattice functions, the electrode design and the electrical circuits have been studied in detailed simulations. A system has been found which safely provides the required performance and offers the option of upgrades, if higher accumulation rate is required in future. Maximum intensities of 100 billion cooled antiprotons are planned which are expected to stay below the instability threshold.
INFN-Bari, Bari
BINP SB RAS, Novosibirsk
The charge breeding technique is used for Radioactive Ion Beam (RIB) production in the Isotope Separation On Line (ISOL) method in order of optimizing the re-acceleration of the radioactive element ions produced by a primary beam in a thick target. That technique is realized by using a device capable of increase the radioactive ion charge state from +1 to a desired value +n. In some experiments a continuous RIB of a certain energy could be required. The EBIS based charge breeding device cannot reach a real CW operation because the high charge state ions produced are extracted by the same part where the 1+ ions are injected, that is, from the electron collector. In this way, the ions extraction system, placed in the electron beam collector, can be left only to extract the n+ ions, and then the CW operation, at least in principle, could be reached. In this paper, a charge breeding test experiment based on a EBIS which has an e-gun with hollow cathode will be described. Furthermore, the status report of the experiment that is under way at the INFN Laboratori Nazionali di Legnaro (LNL) will be presented.
INFN/LNL, Legnaro (PD)
Universita' degli Studi di Milano e INFN, Milano
In a Malmberg'Penning trap like ELTRAP an electron beam can be stored or propagated in a space charge dominated condition, due to the low acceleration voltage used; in particular we can test the longitudinal expansion of the electron bunch with several diagnostics, including Thomson scattering. Pulsed electron beams produced by an external photocathode source in the 1'10 keV energy range and with 4 ns length have been measured also by two electrostatic diagnostic systems. A proper software is needed to compensate for the capacitance of the pickup electrodes. Rf can be applied to the sectored electrode to produce a plasma source or to excite or to detect rotational modes; in particular the use of a new 8 sector electrode will allow up to m=3 modes.
JINR, Dubna, Moscow Region
The radioactive ion isotopes 11C6+, 10C6+ and others are produced at interaction of primary carbon ion beam with target. These isotopes can be applied for Positron Emission Tomography. The projectile-fragmentation method is used for the production of radioactive isotopes. The intensity of radioactive ion beam is defined by the target optimal thickness, material and by available longitudinal and transverse acceptances of transportation channel. An increase of target thickness permits to improve production rate of radioactive ion beams, however it increase the energy and angle spreads of secondary ions and finally it gives a reduction of number of useful radioactive ions which can be transported to the PET camera. The GEANT 4 simulations related to formation of 11C6+ secondary ion beams at interaction with different targets are discussed.
ESS Bilbao, Bilbao
Fundación TEKNIKER, Eibar (Gipuzkoa)
Bilbao, Faculty of Science and Technology, Bilbao
University of the Basque Country, Faculty of Science and Technology, Bilbao
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ESS-Bilbao, Zamudio
Imperial College of Science and Technology, Department of Physics, London
Elytt Energy, Madrid
The rationale behind the Bilbao Accelerator Ion Source Test Stand (ITUR) project is to perform a comparison between different kinds of hydrogen ion sources using the same beam diagnostics setup. In particular, a direct comparison will be made in terms of the emittance characteristics of Penning-type sources such as those currently being used in ISIS (UK) and those of microwave type such as CEA-Saclay and INFN. The aim here pursued is to build an Ion Source Test Stand where virtually any type of source can be tested and, thus, compared to the results of other sources under the same gauge. It would then be possible to establish a common ground for effectively comparing different ion sources. The work here presented reports on the first simulations for the H-/H+ extraction system, as well the devices that conform the diagnostic vessel: Faraday Cup, Pepperpot and Retarding Potential Analyzer (RPA), among others.
ESS Bilbao, Bilbao
Bilbao, Faculty of Science and Technology, Bilbao
University of the Basque Country, Faculty of Science and Technology, Bilbao
ESS-Bilbao, Zamudio
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The main objective of the Bilbao Front End Test Stand (ETORFETS) is to set up a facility to demonstrate experimentally the design ideas for the future ESS LINAC that are being proposed in discussion forums by the technical scientific community. ETORFETS is focused on the first stage of the linear accelerator, namely, that of the Radio-Frequency Quadrupole (RFQ) and its pre and post beam transport systems. The RFQ bunches, focuses transverse and longitudinally, and accelerates charged particles in the low-energy range (up to ~ 3 MeV), thus becoming one of the main components of the accelerating structure. The first RFQ simulations, performed in Superfish and GPT software packages, will be presented in this work.
GSI, Darmstadt
TU Darmstadt, Darmstadt
INFIM, Bucharest
Within the frame of the EuCARD program, the GSI Darmstadt is performing accelerator R&D in workpackage 8: ColMat. The effort is focused on materials important for building the FAIR accelerator facility at GSI and the LHC upgrade at CERN. Accelerator components and especially protection devices have to be operated in high dose environments. The radiation hazard occurs either by the primary proton and ion beams or the secondary radiation. Detailed numerical simulations have been carried out to study the damage caused to solid targets by the full impact of the LHC beam as well as the SPS beam. Tungsten, copper and graphite targets have been studied. Experimental an theoretical studies on radiation damage on materials used for the LHC upgrade and the FAIR accelerators are performed at the present GSI experimental facilities. Technical decisions based on these results will have an impact on the FAIR component specifications. A cryogenic ion-catcher prototype will be constructed and tested. The ion-catcher is essential for reaching highest heavy ion beam intensities in SIS100. The prototype will be set-up at GSI to perform measurements with heavy ion beams of synchrotron SIS18.
CERN, Geneva
Linac4 is the new H- linear accelerator under construction at CERN aiming to double the brightness of the beam injected to the CERN PS Booster (PSB) for delivering proton beams to experiments or further CERN accelerators, down to the LHC. The injection system in the PSB is based on the H- charge exchange where the 160 MeV H- beam is converted into an H+ beam by stripping the electrons with a carbon foil. A beam dump located inside a pulsed magnet for the injection bump will intercept the unstripped ions (H0 and H-) and measure the collected charge to detect the relative efficiency and degradation of the stripping foil. The challenge of the dump design is to meet the requirements of a beam dump providing a current measurement and at the same time minimizing the perturbation of the magnetic field of the surrounding pulsed magnet. This paper describes all phases of the dump design and the main issues related to its integration in the line.
CERN, Geneva
The Phase I Luminosity Upgrade of LHC (SLHC) will be based on a new Nb-Ti inner triplet for the high luminosity region ATLAS and CMS. The new proposed layout aims at pushing beta* down to 30 cm replacing the current LHC inner triplet, with longer ones operating at lower gradient (123 T/m) and therefore offering enough aperture for the beam to reduce beta* to its prescribed value. As a consequence of this new longer interaction region, the number of parasitic encounters will increase from 15 to 21 before the separation dipole D1, with an impact on the dynamic aperture of the machine. In this paper the effect of the beam-beam interaction is evaluated for the SLHC layout and optics, at injection and in collision, evaluating the possible impact of a few additional parasitic collisions inside and beyond the D1 separation dipole till the two beams do no longer occupy the same vacuum chamber. Whenever needed, a comparison with the nominal LHC will be given. Then a possible backup collision optics will be discussed for the SLHC, offering a much wider crossing angle at an intermediate beta* of 40 cm in order to reach a target dynamic aperture of 7.5 σ.
CERN, Geneva
JINR, Dubna, Moscow Region
A number of tests were performed by the UA9 Collaboration* in the North area of the SPS in view of investigating crystal-particles interactions for future application in hadron colliders. The rate of nuclear reactions was measured with 400 GeV proton beams directed into a silicon bent crystal. In this way the background induced by the crystal itself either in amorphous or in channeling orientation was revealed. The results provide fundamental information to put in perspective the use of silicon crystals to assist halo collimation in hadron colliders, whilst minimizing the induced loss. Crystals made of Germanium were also investigated in view of the expected increase of the collimation efficiency respect to silicon. Finally, crystals were tested in axial orientation and with incoming particles of negative charge. The collected results are presented in details.
* http://greybook.cern.ch/programmes/experiments/UA9.html
PSI, Villigen
A simulation based optimization of a collimator system at the 590 MeV PSI proton accelerator is presented, for the ongoing beam power upgrade from the current 1.2 MW [2 mA] towards 1.8 MW [3 mA]. The collimators are located downstream of the 4 cm thick graphite meson production target. These are designed to shape the optimal beam profile for low-loss beam transport to the neutron spallation source SINQ. The optimized collimators are predicted to withstand the beam intensity up to 3 mA, without sacrificing intended functionalities. The collimator system is under the heavy thermal load generated by a proton beam power deposition approximately of 240 kW at 3 mA, and it needs an active water cooling system. Advanced multiphysics simulations are performed for a set of geometric and material parameters, for the thermomechanical optimization of the collimator system. In particular, a FORTRAN subroutine is integrated into CFD-ACE+, for calculating local beam stopping power in the collimator system. Selected results are then compared with those of full MCNPX simulations.
STFC/RAL, Chilton, Didcot, Oxon
University of Warwick, Coventry
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Sheffield University, Sheffield
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The UK programme of high power target developments for a Neutrino Factory is centred on the study of high-Z materials (tungsten, tantalum). A description of lifetime shock tests on candidate materials is given as part of the research into a solid target solution. A fast high current pulse is applied to a thin wire of the sample material and the lifetime measured from the number of pulses before failure. These measurements are made at temperatures up to ~2000 K. The stress on the wire is calculated using the LS-DYNA code and compared to the stress expected in the real Neutrino Factory target. It has been found that tantalum is too weak to sustain prolonged stress at these temperatures but a tungsten wire has reached over 26 million pulses (equivalent to more than ten years of operation at the Neutrino Factory). An account is given of the optimisation of secondary pion production from the target and the issues related to mounting the target in the muon capture solenoid and target station are discussed.
Sheffield University, Sheffield
University of Warwick, Coventry
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Recently reported results on the tungsten lifetime/fatigue tests under conditions expected in the Neutrino Factory target have strengthened the case of solid target option for a Neutrino Factory. This paper gives description of the detailed measurements of the tungsten properties at high temperature and high stress. We have performed extensive set of measurements of the surface displacement and velocity of the tungsten wires that were stressed by passing a fast, high current pulse through a thin sample. Radial and longitudinal oscillations of the wire were measured by a Laser Doppler Vibrometer. The wire was operated at temperatures of 300-2500 K by adjusting the pulse repetition rate. In doing so we have tried to simulate the conditions (high stress and temperature) expected at the Neutrino Factory. Most important result of this study is an experimental confirmation that strength of tungsten remains high at high temperature and high stress. The experimental results have been found to agree very well with LS-DYNA modelling results.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
A study of a pion production and capture system for a 4MW target station for a neutrino factory or muon collider is presented. Using the MARS code, we simulate the pion production produced by the interaction of a free liquid mercury jet with an intense proton beam. We study the variation of meson production with the direction of the proton beam relative to the target. We also examine the influence on the meson production by the focusing of the proton beam. The energy deposition in the capture system is determined and the shielding required in order to avoid radiation damage is discussed.
PKU/IHIP, Beijing
As part of the updated DC-SC injector, a 3.5cell cavity has been fabricated at Peking University, which includes two Coaxial High Order Mode (HOM) couplers. The effect of the HOM couplers has been studied by numerical simulation and measurement. The results are highly uniform and show that the two couplers do effectively damp the HOMs.
CERN, Geneva
Royal Holloway, University of London, Surrey
We report on a study of muon backgrounds in CLIC. For this we combined halo and tail generation using HTGEN with detailed tracking by BDSIM of impacting halo particles and resulting secondaries from the collimation spoilers to the detector.
Fermilab, Batavia
Northern Illinois University, DeKalb, Illinois
We report our experimental demonstration of longitudinal phase space modulation using transverse-to-longitudinal emittance exchange technique. The experiment is carried out at the A0 photoinjector at Fermi National Accelerator Lab. A vertical multi-slit plate is inserted into the beamline prior to the emittance exchange, thus introducing beam horizontal profile modulation. After the emittance exchange, the longitudinal phase space coordinates (energy and time structures) of the beam are modulated accordingly. This is a clear demonstration of the transverse-to-longitudinal phase space exchange. In this paper, we present our experimental results on the measurement of energy and time profile of the electron beam, as well as numerical simulations of the experiment.
Fermilab, Batavia
Northern Illinois University, DeKalb, Illinois
Fermilab is currently constructing a superconducting RF (SRF) test linear accelerator at the New Muon Lab (NML). Besides testing SRF accelerating modules for ILC and Project-X, NML will also eventually support a variety of advanced accelerator R&D experiments. The NML incorporates a 40 MeV photoinjector capable of providing electron bunches with variable parameters. The photoinjector is based on the 1+1/2 cell DESY-type gun followed by two superconducting cavities. It also includes a magnetic bunch compressor, a round-to-flat beam transformer and a low-energy experimental area for beam physics experiments and beam diagnostics R&D. In this paper, we explore, via beam dynamics simulations, the performance of the photoinjector for different operating scenarios.
CEA, Gif-sur-Yvette
Brunel University, Middlesex
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
JAI, Oxford
The Electron Model for Many Applications FFAG (EMMA) has been the object of extensive beam dynamics simulations during its design and construction phases, using the ray-tracing code Zgoubi, which has been retained as the on-line simulation engine. On the other hand EMMA commissioning requires further advanced beam dynamics studies as well as on-line and off-line simulations. This contribution reports on some aspects of the studies so performed during the last months using Zgoubi.
USTC/NSRL, Hefei, Anhui
Fixed-Field Alternating Gradient (FFAG) accelerator accelerates in smaller costs heavy-ion with higher beam current than conventional circular accelerator, which could be more useful for the study of radioactive material. In this paper, the periodic focusing structure model of a Helium ion FFAG with a few MeV energy, which is contributed to study the impact of Helium embitterment on fusion reactor envelope material is proposed. A large-aperture magnet for Helium ion FFAG synchrotron is designed by using a 3D magnetic field simulation code OPERA-3D. The linear and nonlinear beam dynamics is studied through tracking the particle in the magnetic field generated by OPERA-3D.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
Cockcroft Institute, Warrington, Cheshire
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The first results from commissioning EMMA - the Electron Model of Many Applications- are summarised in this paper. EMMA is a 10 to 20 MeV electron ring designed to test our understanding of beam dynamics in a relativistic linear non-scaling fixed field alternating gradient accelerator (FFAG). EMMA will be the world's first non-scaling FFAG and the paper will outline the characteristics of the beam injected in to the accelerator as well as summarising the results of the extensive EMMA systems commissioning. The paper will report on the results of simulations of this commissioning and on the progress made with beam commissioning.
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA (Electron Model with Many Applications) is the first proof-of-principle non-scaling FFAG accelerator and is presently under construction at Daresbury Laboratory in the UK. To probe different parts of the bunch phase space during the acceleration from 10 to 20 MeV (which requires rapid resonance crossing), electron bunches are needed with sufficiently small emittance. To understand the phase space painting into the 3000 mm-mrad EMMA acceptance, we have modelled ALICE (Accelerators and Lasers in Combined Experiments) - which acts as an injector for EMMA - using GPT and compared the estimated emittances with measurements made with a variety of screen-based methods. Although the emittances are not yet as small as desired, we obtain reasonable agreement between simulation and measurement.
Cockcroft Institute, Warrington, Cheshire
We present a simulation study on the reconstruction of the phase space distribution of a beam in the EMMA injection line. The initial step has been to use a Gaussian beam to calculate the phase space distribution and the horizontal and vertical beam projections which would be expected at a screen. The projections obtained from a range of optical configurations are provided as input for reconstructing the phase space distribution using a standard tomography method. The result from the reconstruction can be compared with the known phase space distribution. By taking into account the limited range of quadrupole strengths available, we can determine how practical limitations may affect the reconstruction.
*"EMMA: THE WORLD'S FIRST NON-SCALING FFAG," R. Edgecock, D. Kelliher, S. Machida, STFC/RAL, Didcot, UK et al. in Proceedings of EPAC08, Genoa, Italy
HHUD, Dusseldorf
National University of Defense Technology, Changsha, Hunan
By using multi-dimensional particle-in-cell simulations, we investigate the stability of proton beam acceleration in a two-specie ultra-thin foil. In this two-specie regime, the lighter protons are initially separated from the heavier carbon ions due to their higher charge-to-mass ratio Z/m. The laser pulse is well-defined so that it doesn't penetrate the carbon ion layer. The Rayleigh-Taylor-like (RT) instability seeded at the very early stage then only degrades the acceleration of the carbon ions which act as a "cushion" for the lighter protons. Due to the absence of proton-RT instability, the produced high quality mono-energetic proton beams can be well collimated even after the laser-foil interaction concludes.
INFN/LNF, Frascati (Roma)
After a short description of the Frequency Multiplication Scheme of the CLIC drive beam we present the impact of beam loading in the RF deflectors. First order scaling laws for the beam loading have been obtained to compare the effects in CLIC with those in the Test Facility CTF3. A dedicated tracking code has been written to study the multi-bunch multi-turn beam dynamics and the results are presented. Possible solutions to mitigate the beam loading effects such as the use of multiple RF deflectors are shown.
INFN-Ferrara, Ferrara
IHEP Protvino, Protvino, Moscow Region
UNIFE, Ferrara
Università dell'Insubria & INFN Milano Bicocca, Como
INFN/LNL, Legnaro (PD)
PNPI, Gatchina, Leningrad District
JINR, Dubna, Moscow Region
INFN MIB, MILANO
CERN, Geneva
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
INFN-Trieste, Trieste
INFM-CNR, Istituto Nazionale di Fisica della Materia - Consiglio Nazionale delle Ricerche, Brescia
New results in coherent interaction of negatively-charged particles with bent crystals showed unprecedentedly and significantly high efficiency to manipulate such beams, in the same way as for positively charged particles. Key feature under experimental attainment was the usage of high-quality suitably thin silicon crystals. We experimentally tested crystals Vs. 150 GeV negative pions at external lines of CERN SPS. We observed planar channeling at full deflection angle 30% high single-pass efficiency and large acceptance (about 20μrad). Moreover in the axial case, we reached more than 90% deflection efficiency and larger acceptance (about 60μrad). We also observed volume reflection in a bent crystal, at more than 70% single-pass efficiency with such a wide acceptance as the bending angle. At last, volume reflection by several planes in a single bent crystal was successfully tested with very high efficiency (about 80%). In summary both channeling and volume reflection modes appear to be useful technique for the manipulation of negatively charged beams, e.g. for collimation in the new generation of high intensity accelerators.
The UA9 collaboration
Center for Optical Research and Education, Utsunomiya University, Utsunomiya
Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang
National University of Defense Technology, Graduate School, Changsha
Shanghai Jiao Tong University, Shanghai
National University of Defense Technology, Changsha, Hunan
Ruhr-Universität Bochum, Bochum
National University of Defense Technology, Parallel and Distributed Processing, Changsha
Energetic protons of tens MeV or more produced by intense lasers have been observed in recent experiments and numerical simulations. Meanwhile, significant efforts have been made to improve the proton beam quality *,**,***. For most applications, it is important to improve the quality of the proton beam both during the production and during the propagation. Some schemes are proposed to improve the quality of the proton beam both during the production form the laser plasma interaction and during the propagation. The physics is investigated by 2D3V and 3D particle-in-cell codes PLASIM and PLASIM3D. In this paper, we propose to use an umbrella-like target to accelerate, and collimate protons. It is found that high intensity collimated MeV-proton beams can be produced ****. We also propose a scheme to generate quasi-monoenergetic proton beam from the interactions of an ultra-intense laser pulse and a thin tailored hole target. Particle simulation shows that a monoenergetic proton beam is generated from the hole. The propagation of a proton beam both in vacuum and in a plasma is also studied. Compared with the propagation in vacuum, the proton beam quality can be improved obviously.
* T. Toncian, et al. Science 312, 410(2006).
** B. M. Hegelich, et al. Nature 439, 441(2006).
*** H. Schwoerer, et al. Nature 439, 445(2006).
**** Y. Y. Ma et al., Phys Plasmas 16, 34502(2009).
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
High frequency, high power rf sources are needed for many applications in particle accelerators, communications, radar, etc. We have developed a 26GHz high power rf source based on the extraction of wakefields from a relativistic electron beam. The extractor is designed to couple out rf power generated from a high charge electron bunch train traversing a dielectric loaded waveguide. The first high beam experiment has been performed at Argonne Wakefield Accelerator facility. The experimental results successfully demonstrate the 15ns 26GHz rf pulse generated from the wakefield extractor with a bunch train of 16 bunches. Meanwhile, ~ 30MW short rf pulse has been achieved with a bunch train of 4 bunches. Beam Breakup has prevented charge transport through the power extractor beyond 10nC. We are doing simulations and developing methods to alleviate the BBU effect.
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
Ceramics Ltd., St. Petersburg
Dielectric-Loaded Accelerating (DLA) structures are generally lack of approaches to tune frequency after the fabrication. A tunable DLA structure has been developed by using an extra nonlinear ferroelectric layer. Dielectric constant of the applied ferroelectric material is sensitive to temperature and DC voltage. Bench test shows the +14MHz/°C, and 6MHz frequency tuning range for a 25kV/cm of DC bias field. A beam test is planned at Argonne Wakefield Accelerator facility before the IPAC conference. Detailed results will be reported.
Euclid TechLabs, LLC, Solon, Ohio
LETI, Saint-Petersburg
Fermilab, Batavia
Materials possessing variations in the permittivity as a function of the electric field exhibit a variety of phenomena for electromagnetic wave propagation such as frequency multiplication, wave steepening and shock formation, solitary waves, and mode mixing. New low loss nonlinear microwave ferroelectric materials present interesting and potentially useful applications for both advanced and conventional particle accelerators. Accelerating structures (either wakefield-based or driven by an external rf source) loaded with a nonlinear dielectric may exhibit significant field enhancements. In this paper we will explore the large signal permittivity of these new materials and applications of nonlinear dielectric devices to high gradient acceleration, rf sources, and beam manipulation. We describe planned measurements using a planar nonlinear transmission line to characterize in detail the electric field dependence of the permittivity of these materials. We will present a concept for a nonlinear transmission line that can be used to generate short, high intensity rf pulses to drive fast rf kickers.
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
Current advanced accelerator modeling applications require a more sophisticated treatment of dielectric and paramagnetic media properties than simply assuming a constant permittivity or permeability. So far active media have been described by a linear, frequency-dependent, single-frequency, scalar dielectric function. We have been developing algorithms to model the high frequency response of dispersive, active, and nonlinear media. The work described also has applications for modeling of other electromagnetic problems involving realistic dielectric and magnetic media. Results to be reported include treatment of multiple Lorentz resonances based on auxiliary differential equation, Fourier, and hybrid approaches. We will also report on recent measurements of paramagnetic active microwave materials using EPR spectroscopy. Comparison of the results to numerical simulations will be presented.
IN2P3-LAPP, Annecy-le-Vieux
IHEP Beijing, Beijing
KEK, Ibaraki
SLAC, Menlo Park, California
At the first stage of the ATF2 beam tuning, vertical beam size is usually bigger than 3um at the IP. Beam waist measurements using wire scanners and a laser wire are usually performed to check the initial matching of the beam through to the IP. These measurements are described in this paper for the optics currently used (βx=4cm and βy=1mm). Software implemented in the control room to automate these measurements with integrated analysis is also described. Measurements showed that beta functions and emittances were within errors of measurements when no rematching and coupling corrections were done. However, it was observed that the waist in the horizontal (X) and vertical (Y) plane was abnormally shifted and simulations were performed to try to understand these shifts. They also showed that multiknobs are needed in the current optics to correct simultaneously αx, αy and the horizontal dispersion (Dx). Such multiknobs were found and their linearity and orthogonality were successfully checked using MAD optics code. The software for these multiknobs was implemented in the control room and waist scan measurements using the αy knob were successfully performed.
TU Darmstadt, Darmstadt
The Superconducting Linear Accelerator S-DALINAC at the University of Darmstadt/ Germany is a recirculating Linac with two recirculations. Currently acceleration in the Linac is done on crest of the acceleration field using the maximum of the field in every turn. The recirculation of the beam is done isochronous without any longitudinal dispersion. In this recirculation scheme the energy spread of the resulting beam is determined by the stability of the used RF system. In this work we will present a new non-isochronous recirculation scheme, which uses longitudinal dispersion in the recirculations and an acceleration on edge of the accelerating field as it is done in microtrons. We will present beam dynamic calculations which show the usability of this system even in a Linac with only two recirculations and first measurements of longitudinal dispersion using RF monitors.
IAP, Frankfurt am Main
The stellarator-type storage ring for multi- Ampere proton and ion beams with energies in the range of 100 AkeV to 1AMeV was designed. The main idea for beam confinement with high transversal momentum acceptance was presented in EPAC06 and EPAC08. Stable beam transport in opposite directions is possible through the same aperture with two crossing points along the structure. Elsewhere the beams are separated by the RxB drift motion in curved sections. The space charge compensation through the trapped or circulated electrons will be discussed. This ring is typically suited for experiments in plasma physics and nuclear astrophysics. Here we present the complete simulations for optimization of ring geometry, a stable beam confinement and developments in beam injection.
University of Delhi, Delhi
Fermilab, Batavia
It is well known that insertion of a coupler into a RF cavity breaks the rotational symmetry of the cavity, resulting in an asymmetric field. This asymmetric field results in a transverse RF Kick. This RF kick transversely offsets the bunch from the nominal axis & it depends on the longitudinal position of the particle in the bunch. Also, insertion of coupler generates short range transverse wake field which is independent from the transverse offset of the particle. These effects cause emittance dilution and it is thus important to study their behavior & possible correction mechanisms. These coupler effects, i.e. coupler's RF kick & coupler's wake field are implemented in a beam dynamics program, Lucretia. Simulations are performed for main linac & bunch compressor of International Linear Collider (ILC) like lattices. Results are compared with Placet results & a good agreement has been achieved.
KEK, Ibaraki
IHEP Beijing, Beijing
A perturbation method based on Lie technique, originated by J. Irwin and C.-x. Wang, was extended to calculate the linear maps for the fringe field of a quadrupole. In our method, the fringe field shape is not necessarily anti-symmetric with respect to the hard-edge position. The linear maps were explicitly expressed as functions of fringe field integrals. Thus they can be used to assess the influence of the quadrupole fringe fields in beam dynamics.
Tohoku University, School of Scinece, Sendai
We have studied production of the very short-bunch electron beam to generate intense coherent THz radiation*. The bunch length of 100 fs is required to produce CSR around 1 THz. The beam from the thermionic RF-gun is introduced into the bunch compression system consist of an alpha magnet and a linac. The alpha magnet is often used as a bunch compressor for electron energy of several MeV. However, for our system, the alpha magnet plays a role of the longitudinal phase space rotator and energy filter. The bunch compression is done in the linac employing velocity bunching. The beam is injected on near the zero-cross phase of the RF field in the linac, and then the beam phase slip toward the crest. The longitudinal phase space and beam phase with respect to RF field at the entrance of the linac are optimized so that the bunch length would be minimum. In current analysis using numerical simulation based on the GPT code**, an rms bunch length of 30 fs has been obtained for a bunch charge of 20 pC. We will discuss the bunch compression scheme and the beam dynamics in the system. Prospect of the coherent radiation from the beam will be also reported.
* H. Hama et al, Proc. Ultrashort Electron & Photon Beam Techniques and Applications, Xian, China (2009)
** General Particle Tracer (GPT), URL: http://www.pulsar.nl/gpt
IHEP Beijing, Beijing
KEK, Ibaraki
IN2P3-LAPP, Annecy-le-Vieux
The ATF2 project is the final focus system prototype for ILC and CLIC linear collider projects, with a purpose to reach a 37nm vertical beam size at the interaction point. During initial commissioning, we started with larger than nominal β-functions at the IP, to reduce the effects from higher-order optical aberrations and thereby simplify the optical corrections needed. We report on simulation studies at two different IP locations developed based on waist scan, dispersion, coupling and β function multiknobs correction in the large β optics of ATF2, in the presence of two kinds of magnet inaccuracies (quadrupole gradient and roll errors) to generate all possible linear optics distortions at the IP. A vertical beam size which is very close to the nominal beam size is obtained based on the simulation study.
Kyungpook National University, Daegu
Proton Engineering Frontier Project (PEFP) Linac has a plan of the addition of 1 GeV RCS ring. The lattice of the rapid cycling synchrotron is affected by a non-linear beam dynamics. In this study, we investigated about non-linear dynamics due to sextupoles in PEFP RCS. Notably, we investigated about 3rd integer resonance due to sextupoles. To slowly and continuously extract the proton beam, we utilize the 3rd integer resonance. For the reason, we investigated non linear beam dynamics due to 3rd integer resonance and slow extraction system by using of MAD8.
BINP SB RAS, Novosibirsk
Fermilab, Batavia
One of the possible ways to increase luminosity of hadron colliders is the compensation of beam-beam tune-spread with an electron lens (EL). At the same time, EL as an additional nonlinear element in the lattice can increase strength of nonlinear resonances so that its overall effect on the beam lifetime will be negative. Time-consuming numerical simulations are often used to study the effects of the EL. In this report we present a simplified model, which uses analytical formulae derived for certain electron beam profiles. Based on these equations the idealized shapes of the compressed tune spread can be rapidly calculated. Obtained footprints were benchmarked against several reference numerical simulations for the Tevatron in order to evaluate the selected configurations. One of the tested criteria was the so-called "folding" of the compensated footprint, which occurs when particles with different betatron amplitudes have the same tune shift. Also studied were the effects of imperfections, including misalignment of the electron and proton beams, and mismatch of their shapes.
CERN, Geneva
BNL, Upton, Long Island, New York
After the incident in the LHC in 2008, few skew quadrupoles were damaged and subsequently removed from the tunnel. This could limit the correction of local coupling in the LHC. In order to increase the flexibility in the coupling correction it has been proposed to use of vertical orbit bumps at the sextupoles is studied. Moreover a simultaneous coupling and vertical dispersion can be implemented. Various studies are presented addressing the optimal approach for the correction of the vertical dispersion and the sum and difference coupling resonances.
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is the second synchrotron light source in Taiwan which is currently under construction at the NSRRC existing site. With a 3 GeV beam energy, low emittance, 24-DB structure in the storage ring, the TPS can generate higher brilliance and more abundant X-ray sources. TPS is in complementary to the overbooked 1.5 GeV Taiwan Light Source (TLS). The MATLAB-based accelerator physics application programs planned for the TPS commissioning and operation is a high-level software collection including the MML, AT, LOCO, etc., developed at ALS and SLAC. In this report, the testing results by employing this package to the Taiwan Light Source (TLS) are given and the simulations of the TPS virtual machine are also demonstrated.
Brunel University, Middlesex
The University of Liverpool, Liverpool
The Non Scaling Fixed Field Alternating Gradient (NS-FFAG) EMMA accelerator has a purely linear lattice and thus allows important tune variation. The crossing of resonances during acceleration is a key characteristic of the beam dynamics. An accurate measurement of the tune is therefore mandatory. However commonly used measurement techniques requires the beam to perform an important number of turns in the machine. Simulations have shown that fast decoherence of the beam requires the study of another measurement technique. The model independent analysis (MIA) has been investigated. The singular value decomposition (SVD) of a matrix composed of simulated BPMs reading of various bunches trajectories gives a description of the optics function at each Beam Position Monitor. Including misalignment errors and electronic noise, an accurate value of the tune has been derived from statistical treatment repeating this process few hundreds of time.
yoel.giboudot@stfc.ac.uk
Fermilab, Batavia
Phase space manipulation techniques within two degrees of freedom are foreseen to enhance the performances of next generation accelerators such as high-energy physics colliders and accelerator based light sources. At the Fermilab A0 photoinjector, a proof-of-principle experiment to demonstrate the exchange of the transverse and longitudinal emittances is ongoing. The emittance exchange beamline consists of a 3.9 GHz normal conducting deflecting mode cavity flanked by two doglegs. Electron bunches with charges of 250 pC and energy of 14.3 MeV are routinely sent through the exchanger. In this paper, we report our latest results on the demonstration of emittance exchange obtained with significantly improved beam diagnostics. We also compare our experimental results with a simple numerical model.
SLAC, Menlo Park, California
Turn-by-turn beam position monitor (BPM) data from multiple BPMs are fitted with a tracking code to calibrate magnet strengths in similar manner as the well known LOCO code. Simulation shows that this method can be a quick and efficient way for optics calibration. The method is applicable to both linacs and ring accelerators. We also show experimental measurement of the transfer matrix with turn by turn BPM data.
ORNL, Oak Ridge, Tennessee
A Medium Energy Beam Transport line (MEBT) is employed in the SNS linac to match the beam from an RFQ to a DTL and to perform other functions. The MEBT lattice consists of fourteen electromagnetic quadrupoles. The quads have very small aspect ratios (steel length over aperture diameter), and they are densely packed in the lattice. Significant fringe fields and magnetic interference cause difficulties in beam matching. We have performed 3D simulations of the magnets, computed their optical properties, and compared their performance with what predicted by simple hard edge models. This paper reports our findings and possible solutions to the problem.
CERN, Geneva
INFN/LNF, Frascati (Roma)
The wigglers of the DAΦNE main rings have been one of the main sources of the non-linearities in the collider. A method to minimize the odd integrated multipoles around the beam trajectory (the even ones tend to vanish due to the periodicity of the device) is described. It consists in displacing the magnetic axis of each pole towards the position of the beam in such a way that the integrated odd multipoles are minimized in each half period of the wiggler. After a study, including multipolar and tracking analysis, has performed to determine the best position of the axes, the wigglers in the DAΦNE main rings have been modified accordingly. To validate this approach magnetic measurements and tests with beam by means of closed orbit bumps have been performed.
HU/AdSM, Higashi-Hiroshima
LLNL, Livermore, California
Resonant instabilities of ion plasmas confined in a linear Paul trap are studied using the particle-in-cell code WARP. Transverse two-dimensional model is employed to save computing time and perform systematic investigations. Both applied and self-field forces are calculated with a boundary condition assuming a quadrupole electrode structure. A large number of simulations were carried out with rms matched plasmas to clarify characteristics of the instability caused by linear and nonlinear coherent resonances. Stop band distributions produced by the simulation runs are consistent with theoretical prediction. These results are also compared to experimental results obtained from Hiroshima University Paul trap that is developed to study beam dynamics. It is shown that the stop band distributions of both numerical and experimental results are good agreement each other. We confirmed from these results that coherent resonances are excited when one of the coherent tunes is close to a half integer.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Nonlinear space charge interaction in high intensity proton rings causes beam loss, which limits the performance. Simulations based on particle in cell method has been performed for JPARC-Rapid Cycle Synchrotron and Main Ring. Beam loss estimation during acceleration and resonances analysis are discussed with various simulations using dynamic and frozen models.
KEK, Ibaraki
Synchro-beta resonances enhance beam sizes dynamically. For accelerators aimed for high luminosity, the effect can be more serious since a difference between vertical emittance and longitudinal emittance tends to be larger. Therefore, it is necessary to estimate a tune spread of the synchro-beta resonances properly. Synchro-beta effect is caused by chromatic aberrations, which characterize how optics parameters, including tune, Twiss parameter, X-Y coupling parameter, and other parameters, depend on the momentum deviation. The chromatic aberrations are actually defined by coefficients of an optics parameter in is expansion in terms of momentum deviation. The synchro-beta resonances caused by chromatic aberrations are discussed in this conference. We use 6-dimensional symplectic map which is obtained from measured optics parameters in order to simulate beam motion precisely*.
* Y. Seimiya and K. Ohmi, TH6PFP020, Particle Accelerator Conference PAC09, 4-8 May 2009, Vancouver, Canada.
Tohoku University, School of Scinece, Sendai
NTHU, Hsinchu
In compact linac system, alpha magnet seems to be a useful device to manipulate the longitudinal phase space. Particularly combined use with thermionic RF gun has been regarded as a convenient system for bunch compression. The alpha magnet simply acts to rotate the longitudinal phase space of the beam, besides energy selection by an aperture in it. However, by using the alpha magnet, if we like to produce high brilliant electron beam with considerable charge, space charge force has to be carefully taken into account to evaluate the beam property for not only the longitudinal but also the transverse. Since the both transverse motions and the longitudinal one are coupled with each other in the alpha magnet, it is mostly impossible to evaluate the space charge effect analytically. Meanwhile, because energies of the electrons from the thermionic RF gun are ranging from zero to the maximum, a conventional way to count Coulomb force in the rest frame may be not satisfactorily valid in numerical simulations. We will discuss space charge dominated phase spaces derived from 3-D tracking simulations* for the alpha magnet. *GPT (General Particle Tracer) and an FDTD code developed ourselves.
PAL, Pohang, Kyungbuk
A superconducting RF cavity is used in the storage ring of the Pohang Light Source (PLS) upgrade project (PLS-II) at Pohang Accelerator Laboratory (PAL) for increasing the electron beam current and energy from 2.5GeV/200mA to 3.0GeV/400mA. In order to meet the requirement of lower beam emittance and higher photon energies, as well as more straight sections for insertion devices, the vacuum chambers in the storage ring need to be reconstructed. To control the spurious harmonic resonances' effect to beam position monitors (BPMs) in the PLS and PLS-II storage ring vacuum chamber, the TE mode distribution in vacuum chambers has been analyzed by both numerical simulation and experiment. Based on this analysis, the proper method to control the strength of TE mode at the position of BPMs is suggested.
BINP SB RAS, Novosibirsk
We applied Frequency Map Analysis (FMA) - a method that is widely used to explore dynamics of Hamiltonian systems - to beam-beam effects study. The method turned out to be rather informative and illustrative in case of a novel Crab Waist collision approach, when "crab" focusing of colliding beams results in significant suppression of betatron coupling resonances. Application of FMA provides visible information about all the working resonances, their widths and locations in the planes of betatron tunes and betatron amplitudes, so the process of resonances suppression due to the beams crabbing is clearly seen.
CERN, Geneva
UMAN, Manchester
The first phase of the HIE-ISOLDE project at CERN consists of a superconducting (SC) linac upgrade in order to increase the energy of post-accelerated radioactive ion beams from 2.8 MeV/u to over 10 MeV/u (for A/q = 4.5). In preparation for the upgrade, we present beam dynamics studies of the booster section of the normal conducting (NC) REX-ISOLDE linac, focused on the longitudinal development of the beam in the 101.28 MHz IH cavity, employing a Combined Zero Degree Structure* (KONUS), pulsing at a high gradient of over 3 MV/m. The evolution of the transverse emittance in the superconducting linac depends critically on the injected phase space distribution of particles from the existing linac and, with a better understanding of the longitudinal beam dynamics upstream, the performance of the upgrade can be optimised. Data taken during the commissioning phase of the REX-ISOLDE linac is analysed to understand the properties of the beam in the booster and combined with beam dynamics simulations which include the realistic fields of the IH structure, determined from both simulation and perturbation measurement. The matching of the NC and SC machines is also discussed.
*Ratzinger, U., "The IH-structure and its capability to accelerate high current beams," Particle Accelerator Conference, 1991.
CERN, Geneva
A scaling law for the time-dependence of the dynamic aperture, i.e., the region of phase space where stable motion occurs, was proposed in previous papers, about ten years ago. The use of fundamental theorems of the theory of dynamical systems allowed showing that the dynamic aperture has a logarithmic dependence on time. In this paper this result, proven by mean of numerical simulations, is used as a basis for deriving a scaling law for the intensity evolution in a storage ring. The proposed scaling law is also tested against experimental data showing a remarkable agreement.
CERN, Geneva
During the design phase of the CERN Large Hadron Collider the dynamic aperture, i.e., the domain in phase space where stable motion occurs, was used as figure-of-merit to specify the field quality of the various classes of superconducting magnets. The programme of magnetic measurements performed within the framework of the magnets' acceptance process has produced a large amount of information available, which can be used to estimate the value of the dynamic aperture for the actual machine. In this paper the results of massive numerical simulations based on the measured field quality, both for injection and top energy configurations, are presented and discussed in detail.
CERN, Geneva
ESRF, Grenoble
Recently, a novel multi-turn injection technique was proposed. It is based on beam merging via resonance crossing. The various beamlets are successively injected and merged back by crossing a stable resonance generated by non-linear magnetic fields. Space charge is usually a crucial effect at injection in a circular machine and it could have an adverse impact on the phase space topology required for merging the various beamlets. Numerical simulations were performed to assess the stability of the merging process as a function of injected beam charge. The results are presented and discussed in this paper.
CERN, Geneva
MPI-K, Heidelberg
Cockcroft Institute, Warrington, Cheshire
Higher Order Modes (HOMs) can severely limit the operation of superconducting cavities in a linac with high beam current, high duty factor and complex pulse structure. The full HOM spectrum has to be analyzed in order to identify potentially dangerous modes already during the design phase and to define their damping requirements. For this purpose a dedicated beam simulation code focused on beam-HOM interaction was developed, taking into account important effects like the HOM frequency spread, beam input jitter, different chopping patterns, as well as klystron and alignment errors. Here this code is used to investigate in detail the HOM properties of the cavities foreseen in the Superconducting Proton Linac (SPL) at CERN and their potential to drive beam instabilities. A special focus is set to HOM excitation by chopped pulses with high repetition rate and on the influence of HOMs on recirculating electron beams in the high-energy part of the SPL. Finally, the HOM characteristics of similar linac designs are presented and compared to the SPL.
BNL, Upton, Long Island, New York
CERN, Geneva
The adiabaticity of the AC dipole might be compromised by noise or unwanted frequency components in its signal. An effort has been put to characterize and optimize the signal quality of the LHC AC dipoles. The measured signal is used in realistic simulations in order to evaluate its impact on beam dynamics and to ultimately establish safe margins for the operation of the LHC AC dipoles.
PSI, Villigen
The filling pattern can have a big impact in the effective bunch lengthening of a passive 3rd harmonic system and as a consequence in the Touschek component of the beam lifetime. Using a longitudinal dynamics tracking code, in which the effects of the accelerating system and the 3rd harmonic system are taken into account, we can calculate the synchronous phase drift caused by the transient beam-loading and thus the effective bunch increase for several different filling patterns. In this paper we present a comparison between simulation and measurements for the SLS.
ANL, Argonne
APS has started a program of upgrading old BPM electronics to new FPGA-based devices. We present here the use of such BPMs for online measurement of betatron tunes during topup operation. In topup injection, the stored beam is kicked and experiences betatron oscillations that can be used for online monitoring of the betatron tunes. Also, due to kicker waveform time dependence, different bunches experience kicks of different amplitude. By collecting data from different bunches one can also monitor tune shift with amplitude. In the case of APS, the matter is complicated by the very fast decoherence of oscillations. We describe methods used to derive tunes and present results of online monitoring.
BNL, Upton, Long Island, New York
An electron lens was proposed to compensate the head-on beam-beam effect for polarized proton operations in the Relativistic Heady Ion Collider (RHIC). With head-on beam-beam compensation, we plan to reduce the beam-beam tune footprint and increase the beam-beam parameter to increase the luminosity. Here we carry out 6-D weak-strong beam-beam simulations to study the stability of proton particles and the proton beam lifetime in the presence of head-on beam-beam compensation. The effects and tolerances of the errors and noises in the compensation are also calculated.