CERN, Geneva
The LHC hardware and beam commissioning and initial operation will be reviewed both in terms of beam and hardware performance. The implemented machine protection measures and their impact on LHC operation will be presented.
CERN, Geneva
University of Malta, Faculty of Engineering, Msida
The relation between field and current in each family of the Large Hadron Collider magnets is modeled with a set of empirical equations (FiDeL) whose free parameters are fitted on magnetic measurements. They take into account of residual magnetization, persistent currents, hysteresis, saturation, decay and snapback during initial part of the ramp. Here we give a first summary of the reconstruction of the magnetic field properties based on the beam observables (orbit, tune, coupling, chromaticity) and a comparison with the expectations based on the large set of magnetic measurements carried out during the 5-years-long production. The most critical issues for the machine performance in terms of knowledge of the relation magnetic field vs current are pinned out.
SNU, Seoul
NCC, Korea, Kyonggi
Chung-Ang University, Seoul
Accelerator mass spectrometry (AMS) using a cyclotron has been studied because the system can be more compact and economical compared to the widespread commercial Tandem AMS. However, the previous efforts to build such a system showed that it has weakness in stability and transmission efficiency. To increase transmission efficiency it is important for the injection system to match not only the transverse phase space of a beam but also the longitudinal phase space with cyclotron acceptance. We plan to adopt a sawtooth RF buncher to increase transmission efficiency in the acceleration region of the cyclotron and a radial injection beam line. A goal in designing the injection line is to minimize the number of beam line elements to keep the system compact. The design of the injection system was carried out using the codes such as TRANSPORT and TRACE-3D. A prototype of the injection system is being constructed, and some results will be presented.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
ODU, Norfolk, Virginia
Parametric-resonance Ionization Cooling (PIC) is envisioned as the final 6D cooling stage of a high-luminosity muon collider. Implementing PIC imposes stringent constraints on the cooling channel's magnetic optics design. This paper presents a linear optics solution compatible with PIC. Our solution consists of a superposition of two opposite-helicity equal-period and equal-strength helical dipole harmonics and a straight normal quadrupole. We demonstrate that such a system can be adjusted to meet all of the PIC linear optics requirements while retaining large acceptance.
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.
IUCF, Bloomington, Indiana
IUCMB, Bloomington, Indiana
We are building a low energy electron storage ring that has many desirable properties, such as varying momentum compaction factor, damping partition numbers, favorable betatron tunes for multiturn accumulations, and excellent dynamic aperture. This storage ring can be used for debunching rf linac beams in one turn, for compression of linac pulses, and more importantly for a compact photon source based on inverse Compton scattering of laser beams.
DESY, Hamburg
Printed circuit boards offer a simple method for the design of hysteresis free, compact air coil magnets. The emphasis for the steering magnets developed for the FLASH injector is placed on a high integrated field strength for a short magnetic length to cope with space limitations in the injector beam line. The possibility to combine a pair of orthogonal steerers at the same longitudinal position has been realized by two layers of printed circuit boards. Design principles and magnetic measurements will be discussed.
CNAO Foundation, Milan
CERN, Geneva
LPSC, Grenoble
INFN/LNF, Frascati (Roma)
CNAO is a synchrotron accelerator presently under commissioning in Pavia. The aim of this accelerator is to treat tumors with hadrons and to perform advanced clinical and radiobiological research. The CNAO will start treating patients with protons (60-250 MeV range) and carbon ions (120-400 MeV/u range) in three treatment rooms with four beam lines. Future upgrade with gantries is foreseen. This paper describes the design, magnetic measurements and sorting criterion used for the sixteen synchrotron main dipoles and twenty-four quadrupoles. The magnetic measurements results are compared with magnetic simulation.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
HSRC, Higashi-Hiroshima
The HiSOR-II is a storage ring planned as a successive machine of HiSOR, a present ring at Hiroshima Synchrotron Radiation Center. This accelerator has the circumference equal to or less than 50 m, and it has the emittance about 14 nm-rad and aims at the beam energy of 700 MeV. In the HiSOR-II project, we decided to adopt electromagnets with combined function. This type magnet has an advantage for constructing a small storage ring by reducing the total number of magnet, though it has a difficulty for the independent tuning of multipole field components. In addition, we decided to share a single return yoke between a bending magnet and adjacent quadrupole magnets. In this paper, we discuss about a possible magnetic interference between a bending magnet and a quadrupole magnet. Calculation is made with magnetic field simulation cord RADIA to analyze interference effect and examine the possibility of adoption to HiSOR-II storage ring. Also, we perform the tracking simulation of the beam with the mapping data of a magnetic field provided by this three-dimensional magnetic field analysis. By the simulation, the dynamic aperture is determined.
NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo
A multi-element octupole-base corrector magnet is designed and fabricated. The new corrector magnet will be installed in the electron storage ring NewSUBARU in place of vertical steering (skew dipole) magnets. It has coil windings to produce skew quadrupole, skew sextupole, normal octupole, and the skew dipole field. The skew dipole element is used to achieve vertical steering. The skew quadrupole and the skew sextupole elements are for the resonance correction. The normal octupole element is used to control the higher order dispersion function and the higher order momentum compaction factor. In this design the main coil is wound around the return yoke instead of the pole. We expect improvement of the beam lifetime and injection efficiency during normal operation as well as improved isochronism during extreme quasi-isochronous operation. In designing the magnet, careful consideration is given to field interference caused by a neighboring magnet, set close to the corrector magnet of comparable yoke and bore diameter dimensions. The magnetic field with field interference is calculated using OPERA-3D.
KEK, Ibaraki
The KEKB is a high luminosity accelerator which achieved the highest luminosity record of 2.1x1034. It requires the precise and stable beam control to keep its high luminosity continually. Slight change of the magnetic field may easily deteriorate the performance of the collisions of the very small and thin beams. The field measurement accuracy better than 10-4 has been already achieved. The resolution of the measurement has reached to a few 10-5. But it is known by the beam studies that the field change less than 10-4 may cause deterioration of the luminosity. The requirement on the stability of magnetic field will be stricter for future nano beam colliders. We have studied the effects of the following conditions on the magnetic field by using some KEKB magnets: changes of the magnetic field due to air or cooling water temperature, changes due to initialization conditions, field coupling between the adjacent magnets, effect of excitation of the adjacent magnet and behavior of the magnetic field under polarity change have been measured. These studies are not only useful for the existing KEKB but also important for future nano beam accelerators.
PAL, Pohang, Kyungbuk
Pohang Light Source (PLS) is planning a major upgrade of the storage ring to meet the more demanding requirement from the synchrotron light users. The main features of the major upgrade are (1) increasing the electron beam energy from 2.5 GeV to 3.0 GeV for more higher energy X-ray photons, (2) decreasing the electron beam emittance from 1.89 nm to 5.8 nm to increase the photon brilliances, and (3) increasing the number of straight sections to install the insertion devices from 10 to 20 to meet the demand for insertion devices. in the upgraded PLS (PLS-II), there will be 24 combined function dipole magnets, 96 quadrupole magnets, and 144 sextupole magnets with some auxiliary magnets for electron beam injection. In this report, the physical design features, mechanical aspects of the magnet design are described.
CERN, Geneva
U. Sannio, Benevento
One of the main requirements for the operation of the Large Hadron Collider at CERN is the correction of the dynamic multipole errors produced in the main magnets*. In particular, integrated sextupole errors in the main dipoles must be kept well below 0.1 units to ensure acceptable chromaticity. The feed-forward control of the LHC is based on the Field Description for the LHC (FiDel), a semi-empirical mathematical model capable of forecasting the magnet's behaviour in order to generate suitable corrector current waveforms. Measurement campaigns were recently undertaken to validate the model making use of a novel fast rotating-coil magnetic measurement system (FAME)**, able to detect superconductor decay and snapback transients with unprecedented accuracy and temporal resolution. In this paper we discuss the test setup and the results obtained both on the test bench and in the actual operation of the accelerator.
* P. Xydi et al, "A Demonstration Experiment For The Forecast Of Magnetic Field … ", EPAC 2008
** N. R. Brooks et al, "Estimation Of Mechanical Vibration Of …", IEEE TAS 2008
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is a new third generation synchrotron storage ring with energy 3 GeV, which consists of 24 double-bend cells and its circumference is 518.4 m. Various accelerator lattice magnets which consist of 48 bending magnets, 240 quadrupoles and 168 multifunction sextupole magnets. All magnets pole profiles, edge shim and magnet end chamfer were designed in TOSCA and RADIA magnetic computation code. In order to verify the magnetic field quality of computation code, prototype magnets have been manufactured in this year. Two measurement systems, hall probe and rotating coils, were used for magnetic field mapping. This paper presents magnetic field mapping results of prototype magnets and compared with original magnetic circuit designs.
CEA, Gif-sur-Yvette
S3 (Super Separator Spectrometer) [1] is a future device designed for experiments with the very high intensity heavy ion stable beams of SPIRAL2. It will be set-up at the exit of the linear accelerator LINAG at GANIL (Caen, France). It will include a target resistant to very high intensities, a first stage momentum achromat for primary beam suppression, a second stage mass spectrometer and a dedicated detection system. This mass spectrometer includes a set of four large aperture quadrupole triplets with embedded multipolar corrections. These magnets are a combination of three multipoles which could be realized with superconductor wound in flat racetrack coils. To enable the primary beam extraction one triplet has to be opened on one side, which requires a careful design of such a multipolar magnet. This paper describes the opened multipole geometry. It is adapted to large apertures as demonstrated by Opera 3d© magnetic simulations [2], including harmonic analysis and integral field homogeneity.
GSI, Darmstadt
The FAIR SIS100 accelerator at GSI Darmstadt will be equipped with fast ramped superconducting magnets. The high current Uranium beam modes with intermediate charge states, require ultra low vacuum pressures that can be achieved in long term operation only by cold beam pipes acting as a cryopump with stable temperatures well below 12 K for all operating cycles. The straightforward layout for reliable cooling usually conflicts with an efficient design for fast ramped superconducting accelerator magnets, strongly affected by AC loss generation, field distortion and mechanical stability problems. A full functional vacuum chamber design for SIS 100 has to take into account all these conflicting boundary conditions and trade off between mechanical stability, acceptable field distortions, AC loss minimisation and achievable temperatures. We discuss the cooling conditions for the dipoles and for the beam pipe including first test results. The analysis of the principal design aspects for the vacuum chamber with respect to the magnets operation parameters and an integral design approach are given. We present a technological feasible solution for model testing and full scale manufacturing.
GSI, Darmstadt
IKP, Mainz
BNL, Upton, Long Island, New York
The Electron Nucleon Collider, proposed as an extension to the High Energy Storage Ring (HESR), is currently investigated and a first layout of the Interaction Region (IR) proposed. The limited size of the machine, the low beam energy and the Lorentz force vector pointing in the same direction for both beams make the IR design demanding. In this paper we present the parameters of the IR magnets, show the boundary conditions given by the beam dynamics and the experiments. We present first 2D designs for the electron and proton triplet magnets along with the separating dipole next to the collision point. Different methods to shield the beam in the spectrometer dipoles are investigated and presented.
GSI, Darmstadt
JINR, Dubna, Moscow Region
TEMF, TU Darmstadt, Darmstadt
Superconducting magnets are planned to be installed at the SIS100 accelerator ring for FAIR. The error compensation multipole corrector and the steerer are built as nested magnets to save longitudinal space in the ring, the chromaticity sextupole is a superferric magnet. We present the dynamic field quality of the SIS100 dipole and the vacuum chamber deterioration next to the 2D and 3D field quality of the multipole corrector and of the chromaticity corrector. The quality of the injection field of the SIS100 dipole is mainly dominated by eddy currents as soon as the field ramp starts. We show its AC losses concerning the hydraulic limits for cooling the magnet with forced two phase helium flow and conclude on the maximum chromaticity correction which is feasible for the foreseen magnet design. The results are discussed in respect of recent beam dynamic calculations on the ramp.
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
Kyoto University, Kyoto
University of Tokyo, Tokyo
A superconducting magnet system for the J-PARC neutrino beam line was completed at the end of 2008. The system consists of 14 doublet cryostats; each contains 2 combined function magnets (SCFM). The SCFM uses two single layer left/right asymmetric coils that produce a dipole field of 2.6 T and quadrupole of 19 T/m. By 2008, the world first SCFM had been developed and tested successfully at KEK. The mass-production was started in 2005, and completed by summer 2008. The system installation and commissioning took place from Feb. 2008 to Mar. 2009. The beam operation was started in April 2009 and the first neutrino beam was generated on April 23rd. Since then beam operation and commissioning to increase beam intensity has been performed to achieve the near term milestone of 100 kW beam operation. The paper briefly summarizes the history of SCFM development and the system construction as an introduction to a discussion on beam operation experience of the SCFM system.
JINR, Dubna, Moscow Region
NICA (Nuclotron-based Ion Collider fAcility) is the new accelerator complex currently under construction at JINR. The facility is aimed to provide collider experiments with heavy ions up to uranium (gold at the beginning stage) with a centre of mass energy up to 11 GeV/u and an average luminosity up to 1027 cm-2 s-1. The collisions of polarized deuterons and protons are foreseen also. The accelerator complex includes two injector linacs, a superconducting booster synchrotron, a 6 GeV/u superconducting synchrotron (existing Nuclotron) and a collider consisting of two storage rings. Different modifications of superferric magnets based on a hollow composite NbTi cable operating at 4.5 K is proposed to be used for the NICA booster and collider rings. The twin-aperture collider dipole consists of two vertically assembled cold masses placed inside a common thermal shield and a common cryostat. The dipole good field aperture is fixed to 60 mm. The 2 T option, which design is very similar to the Nuclotron's one, was fixed as basis for the collider of 350 m long. R&D work on a curved 4 T Cosine(θ)-dipoles based on a hollow Nuclotron-type cable is proposed to be continued.
CERN, Geneva
Force transducers based on strain and capacitive gauges have been developed and used for monitoring the coil pre-stress during assembly and excitation of magnet models. This paper will summarize and compare the new techniques of mechanical measurements use at CERN for the New Inner Triplet Project. Furthermore the paper will give a comparison of the gauge performances (Creep effects, temperature effects, etc.) and will present the performances of the new data acquisition system developed at CERN to measure simultaneously the strain gauges, the capacitive gauges and other external parameters for the magnet.
CERN, Geneva
Fermilab, Batavia
At each interconnection between LHC main magnets, a low-resistance solder joint must be made between superconducting cables to provide a continuous current path through the superconductor, and between the surrounding copper stabilizer to provide a current path in case the cable quenches. About 10,000 such joints exist in the LHC. An extensive campaign has been undertaken to characterize and map the resistances of both types of joints. All of the superconducting cable splices were measured using the enhanced protection system of the LHC superconducting circuits. No high-resistance superconductor splices were found above 3 nano-Ohms. Non-invasive measurements of the stabilizer joints were made at 300K in 5 of the 8 sectors, and at 80K in 3 sectors. More precise local measurements were made on suspect interconnects that were opened up, and poor joints were repaired. However, it is likely that additional imperfect stabilizer joints still exist in the LHC. A statistical analysis is used to place bounds on the remaining worst-case resistances. This sets limits on the maximum operating energy of the LHC, prior to a more extensive intervention.
CERN, Geneva
On 19th September 2008 the Large Hadron Collider (LHC) experienced a serious incident, caused by a bad electrical joint, which stopped beam operation just a few days after its beginning. During the following 14 months the damage was repaired, additional protection systems were installed and the measures to avoid a similar incident were taken (i.e. new layer of the Magnet Quench Protection System [nQPS], more efficient He release valves). As a consequence, a large number of powering tests had to be repeated or carried out for the first time. The re-commissioning of the already existing systems as well as the commissioning of the new ones has been carefully studied, then performed taking into account the history of each of the eight LHC sectors (warm-up, left at floating temperature,'). Moreover, a campaign of measurements of the bus-bar splice resistances has been carried out with the nQPS in order to spot out non conformities, thus assessing the risk of the LHC operation for the initial energy level. This paper discusses how the guidelines for the LHC 2009 re-commissioning were defined, providing a general principle to be used for the future re-commissioning.
Fermilab, Batavia
Linear accelerators based on a superconducting technology need various superconducting magnets installed inside SCRF Cryomodules. At front end of Linear Accelerators installed relatively weak iron-dominated magnets. The focusing quadrupoles have integrated gradients in the range of 1 T - 4 T, and apertures 35 mm - 90 mm. At Fermilab were designed superconducting dipole correctors, and quadrupoles for various projects. In the paper presented these magnet designs, and test results of fabricated dipole corrector. There are also briefly discussed: magnetic and mechanical designs, quench protection, cooling, fabrication, and assembly inside cryomodule.
Fermilab, Batavia
Helical Solenoids (HS) were proposed for a muon beam ionization cooling. There are substantial up to 30 MeV/m energy losses during passing the muon beam through an absorber. The main issue of such system is the energy recovery. A conventional RF cavity has diameter which is too large to be placed inside HS. In the paper presented results of dielectric filled RF cavity design. The proposed cavity has helical configuration. Presented Helical Cooling Channel module design which includes: high pressure vessel, RF cavity, and superconducting HS. Discussed parameters of this module sub-systems and shown results of muon beam tracking in combined magnetic and electric 3D fields.
Fermilab, Batavia
Conceptual designs of superconducting magnets (dipoles and quadrupoles) for a muon collider with a 1.5 TeV c.o.m. energy and an average luminosity of 1034 cm-2s-1 are presented. All magnets are based on the Nb3Sn superconductor and designed to provide an adequate operation field/field gradient in the aperture with the critical current margin required for reliable machine operation. In contrary to proton machines, the dipole magnets should have open midplanes, and, for some of them, the required good field quality region needs to have a vertical aspect ratio of 2:1 that imposes additional challenges for the magnet design. Magnet cross-sections were optimized to achieve the best possible field quality in the magnet aperture occupied with beams. The magnets and corresponding protective measures are designed to handle about 0.5 kW/m of dynamic heat loads from the muon beam decays. Magnet parameters are reported and compared with the requirements.
Fermilab, Batavia
Muons, Inc, Batavia
The Helical Cooling Channel (HCC) is a technique proposed for six-dimensional (6D) cooling of muon beams. The HCC for muon collider and some other applications is usually divided into several sections each with progressively stronger fields, smaller aperture, and shorter helix period to achieve the optimal muon cooling rate. Novel magnet design concepts based on simple coils arranged in a helical solenoid configuration have been developed to provide HCC magnet systems with the desired parameters. The level of magnetic field in the HCC high-field sections suggests using a hybrid coil structure with High Temperature Superconductors (HTS) in the innermost coil layers and Nb3Sn superconductor in the outer coil layers. The development of the concepts and engineering designs of hybrid helical solenoids based on advanced superconductor technologies, with special emphasis on the use of HTS for high fields at low temperature is the key step towards a practical HCC. This paper describes the conceptual designs and parameters of a short HTS model of a hybrid helical solenoid, and discusses the structural materials choices, fabrication techniques, and first test results.
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.
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.
INFN/LNL, Legnaro (PD)
Torino University, ., Torino
INFN-Torino, Torino
In order to validate the tuning and stabilization procedures established for the IFMIF RFQ, a campaign of low power tests on an aluminum real-scale RFQ built on purpose has been carried out. Such campaign consisted of the determination of mode spectra, the measurements of the electric field distribution with bead pulling technique, and the implementation of the tuning procedure. The main outcomes and results obtained are reported in the article.
INFN/LNL, Legnaro (PD)
An important issue for high intensity RFQs (tenth of mA beam current and more) is the necessity of keeping the beam losses as low as possible, in order to allow reliable and safe maintenance of the machine. Typically, beam dynamics outcomes driven by these constraints result both in a RFQ length that is considerably higher than the wavelength and in an intra-vane voltage admitted variation with respect to the design value that must not exceed a few percent. Therefore an analytical tool is needed in order to foresee the effect of geometric perturbations on the voltage profile, in order to give an indication on the permitted ranges of geometrical errors in the RFQ construction. In this article a five conductors transmission line equivalent circuit for the four-vane RFQ is presented and the effects of geometrical perturbations on the voltage profile are analyzed in some particular cases. The case study is the IFMIF RFQ (125 mA deuteron current, 9.8 m length, 175 MHz frequency), whose features are particularly suitable for this kind of analysis.
IHEP Beijing, Beijing
The accelerator of China Spallation Neutron Source (CSNS) consists of a low energy linac and a Rapid Cycling Synchrotron (RCS). The opimization of beam dynamics design for RCS and two beam transport line are introduced, and the details design and some simulation results are presented.
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.
GSI, Darmstadt
The engineering design, including the specifications for the accelerator components of the FAIR synchrotron SIS100 has been summarized in the Technical Design Report. The final stage of technical planning shall approach production readiness for the major technical systems in 2010. Significant progress has been achieved in the design of the cryomagnetic system with its main dipole and quadrupole modules, enabling the production of the first pre-series dipole magnet. Slight modifications of the lattice have been implemented to equalize most of the cryostat interconnections, leading to a simplified design and installation effort, and a reduced variety of components and spar parts. The new parallel tunnel allows optimal short interconnections between the supply units and power converters and the accelerator components. The status of the engineering design of SIS100 will be reported.
HIT, Heidelberg
While ramping the magnets in a synchrotron the magnetic fields deviate from their set values. Especially the field errors in dipole and quadrupole magnets result in different problems during operation. At the Heidelberg Ion Therapy Center HIT a measuring system with extremely high precision has been developed. It can measure in real time integral magnetic fields with a precision of better than 5*10-5 in a reproducible way. A feed-back control system for the magnetic fields is being installed and will be operational in May 2010. This control loop lets the magnets reach the nominal field much faster and thus shortens the dead time in a synchrotron cycle. The cycle can be reduced by 30% and more patients can be treated.
JINR, Dubna, Moscow Region
JINR/LHE, Moscow
The main goal of the Nuclotron booster construction are following: accumulation up to 4·10+9 Au32+ ions; acceleration of the ions up to energy of 600 MeV/u that is sufficient for stripping of the ions to the bare nucleus state; simplification of the requirements to the vacuum conditions in the Nuclotron; forming of the required beam emittance at the energy of 100 MeV/u with electron cooling system. The features of this booster, the requirement to the main synchrotron systems and their parameters are presented.
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.
TUB, Beijing
TechSource, Santa Fe, New Mexico
NUCTECH, Beijing
The design progress of the Radio Frequency Quadrupole (RFQ) accelerator for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University is presented in this paper. The RFQ will accelerate protons from 50 keV to 3 MeV, with the RF frequency of 325 MHz. The objective is to obtain the optimum structure of the RFQ accelerator with high transmission rate and tolerable total length. The beam dynamics are studied by the simulation of the proton beam in the RFQ accelerator with the code of PARMTEQM. The output proton beam from the RFQ is well matched into the DTL without Medium-Energy-Beam-Transport (MEBT) between the RFQ and DTL.
* K.R. Crandall et al., RFQ Design Codes, LA-UR-96-1836.
IKP, Mainz
During the last three years at the 1.5 GeV Harmonic Double Sided Microtron (HDSM)* of MAMI a lot of improvements concerning the longitudinal operation of the accelerator were tested and installed. To monitor the rf power dissipated in the accelerating sections, their cooling water flow and its temperature rise are now continuously logged. Phase calibration measurements of the linacs and the rf-monitors revealed nonlinearities of the high precision step-motor driven waveguide phase shifters. They were recalibrated to deliver precise absolute values. Thereby it is now possible to measure not only the first turn's phase very exactly, but also determine the linac's rf-amplitude within an error of less than 5%, using the well known longitudinal dispersion of the bending system. These results are compared to the thermal load measurements. For parity violating experiments the beam energy has to be stabilised to some ppm. A dedicated system measuring the time-of-flight through a bending magnet is now used in routine operation and controls the output energy via the proper linac phases.
* K.-H. Kaiser et al., NIM A 593 (2008) 159 - 170, doi:10.1016/j.nima.2008.05.018
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
J-PARC, KEK & JAEA, Ibaraki-ken
The J-PARC RCS is an M-Watt class rapid cycling synchrotron and it has delivered an intensive beam to the neutron target and the MR. In order to overcome large space charge effect, its physical aperture is designed to be more than 250mm in diameter. Even though its chamber size is very large, the BPM system gives precise data to determine beam optics parameters of the ring. For this purpose, only relative positions and resolutions are important. However, for much higher intensity, the absolute beam position and accurate COD correction are indispensable. We have carefully installed the BPM and measured the position with respect to the quadrupole magnet (QM) nearby. But it is also necessary to estimate its absolute position by using beam. If each QM could be controlled independently, the simple beam based alignment technique can be utilized, but it is not the case for RCS. There are seven families of QM, and only each family can be controlled at one time. We developed a new technique by expanding the simple method for the case of multiple QM focusing changed simultaneously, and applied to the J-PARC RCS. The paper describes this method and discussed about experimental results.
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.
JAI, Egham, Surrey
Royal Holloway, University of London, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
Kyungpook National University, Daegu
UCL, London
KNU, Deagu
Fermilab, Batavia
PLS, Pohang
The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance.
Fermilab, Batavia
UMiss, University, Mississippi
There are conflicting requirements on the value of the momentum compaction factor during energy ramp in a synchrotron: at low energies it should be positive and sufficiently large to make the slippage factor small so that it is possible to work closer to the RF voltage crest and ensure sufficient RF bucket area, whereas at higher energies it should be small or negative to avoid transition crossing. In the present report we propose a lattice with variable momentum compaction factor and consider the possibility of using it in a high repetition rate proton driver for muon collider and neutrino factory.
Fermilab, Batavia
CERN, Geneva
A common-mode free cavity BPM is currently under development at Fermilab within the ILC-CLIC collaboration. This monitor will be operated in a CLIC Main Linac multi-bunch regime, and needs to provide both, high spatial and time resolution. We present the design concept, numerical analysis, investigation on tolerances and error effects, as well as simulations on the signal response applying a multi-bunch stimulus.
BNL, Upton, Long Island, New York
CEA, Gif-sur-Yvette
Commissioning of spin flipper in the RHIC (Relativistic Heavy Ion Collider) Blue ring during the 2009 RHIC polarized proton run showed significant global vertical coherent betatron oscillations induced by a two AC dipole plus four DC dipole configuration. These global orbital coherent oscillations affected collision rates and Yellow beam polarization when beams were in collision. The measured depolarizing strength of of the two AC dipoles at a phase difference of 180 degrees at injection with a different spin tune also confirmed that a single isolated spin resonance can not be induced in the presence of this global vertical coherent betatron oscillation. Hence, a new design was proposed to eliminate the coherent orbital oscillation outside the spin flipper with three additional AC dipoles. This paper presents the new design and supporting numerical simulations. In the RHIC 2010 Au run, only one AC dipole was inserted between the two original AC dipoles; and the measured closure of this AC dipole bump is also presented.
This work is under the auspices of the US Department of Energy
CERN, Geneva
PSI, Villigen
BNL, Upton, Long Island, New York
Optics stability during all phases of operation is crucial for the LHC. The optical properties of the machine have been optimized based on a detailed magnetic model of the SC magnets and on their sorting. Tools and procedures have been developed for rapid checks of beta beating, dispersion, and linear coupling, as well as for prompt optics correction. Initial optics errors, correction performance and optics stability from the first LHC run will be reported, and compared with expectations. Possible implications for the collimation cleaning efficiency and LHC machine protection will be discussed.
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.
Fermilab, Batavia
University of Delhi, Delhi
Results of analysis are presented for the longitudinal and transverse effects of High-Order Mode (HOM) excitation in the acceleration RF system of the CW proton linac of the Project X facility. Necessity of HOM dampers in the SC cavities of the linac is discussed.
NIRS, Chiba-shi
AEC, Chiba
Toshiba Medical Systems Corporation, Tochigi
In the routine operation of HIMAC synchrotron, a pulse system of field change with 0.2 Gauss in the monitor dipole magnet (B-clock) is used to generate pattern data in the acceleration system. To eliminate error pulse due to noise in analogue field signal, a clock system locked to a 1.2kHz clock for a power supplies was developed, which can be used to generate pattern data of an acceleration system with maximum frequency of 192kHz. This 1.2kHz clock is synchronized to a power line frequency of 50Hz that will fluctuate about 0.1%, so the clock of 192kHz must also follow this frequency fluctuation. To demonstrate the performance of new clock system, we have tested beam acceleration, and compared with the conventional B-clock system. Acceleration efficiencies were checked with changing these clock rates in the both systems. With these tests, we have found that the relatively low clock rate in the newly developed system is enough to get good acceleration performance. In this paper the clock system, and their beam tests will be presented.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK/JAEA, Ibaraki-Ken
KEK, Ibaraki
The wide-band RF cavities in the J-PARC RCS are operated in the dual-harmonic operation, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation large amplitude second harmonic signals for the bunch shape manipulation are generated without extra cavities. The phase control of the second harmonic RF is a key for the bunch shape manipulation. The fundamental RF signal is controlled by the phase feedback loop to damp the dipole oscillation. The second harmonic is locked to the phase of the vector-sum phase of the fundamental RF signals. We present the system detail and the performance in the beam operation of the RCS.
CERN, Geneva
EPFL, Lausanne
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg
Electron cloud is a limitation to increasing the beam current in the CERN SPS in the frame of an intensity upgrade of the LHC complex. Coating the vacuum chamber with a thin amorphous carbon layer is expected to reduce the electron cloud build-up. Three SPS straight sections have been coated to study the performance of this carbon coating. The microwave transmission method is one possible way to monitor electron cloud and hence to test the effect of the coating. In this paper the evolution of the experimental setup for measurements of the electron cloud using LHC type beams with different bunch spacing will be described. Due to the low revolution frequency of about 43 kHz serious electromagnetic compatibility problems and intermodulation have been found. These effects and their mitigation are described. Finally we present the measurement results illustrating the possible reduction due to the carbon coating.
INFN/LNF, Frascati (Roma)
Metallic clearing electrodes have been designed to absorb the photo-electrons in the DAΦNE positron ring. They have been inserted in the wigglers and dipoles vacuum chambers and have been connected to external high voltage generators. In the paper we present the design of the devices and the results of the electromagnetic simulations related to both the transfer and longitudinal beam coupling impedances. We also present the results of the RF measurements and the first results with the DAΦNE circulating positron beam.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
The Super-B asymmetric e+e- collider is designed for 1036 cm-2sec-1 luminosity and beam energies of 6.7 and 4.18 GeV for e+ and e-, respectively. The machine will have the High and Low Energy Rings (HER and LER), and one Interaction Point (IP) with 60 mrad crossing angle. The INFN-LNF at Frascati is one of the proposed sites, and a lattice for short 1.3 km rings fitting to this site has been designed. The two rings are radially separated by 2 m except near the IP and in the dogleg on the opposite side of the rings. The injection sections and RF cavities are included. The lattice is optimized for a low emittance required for the desired high luminosity. Final Focus chromaticity correction is optimized for large transverse and energy acceptance. The "crab waist" sextupoles are included for suppression of betatron resonances induced at the IP collisions with large Piwinski angle. The LER spin rotator sections provide longitudinal polarization for the electron beam at IP. The lattice is flexible for tuning the design parameters and compatible with reusing the PEP-II magnets, RF cavities and other components. Design criteria and details on the lattice implementation are presented.
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.
Fermilab, Batavia
JINR, Dubna, Moscow Region
Design of a muon collider interaction region (IR) presents a number of challenges arising from low beta* < 1 cm, correspondingly large beta-function values and beam sizes at IR magnets, as well as the necessity to protect superconducting magnets and collider detectors from muon decay products. As a consequence, the designs of the IR optics, magnets and machine-detector interface are strongly interlaced and iterative. A consistent solution for the 1.5 TeV c.o.m. muon collider IR is presented. It can provide an average luminosity of 1034/cm2/s with an adequate protection of magnet and detector components.
SLAC, Menlo Park, California
Cockcroft Institute, Warrington, Cheshire
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
The availability of longitudinally polarized electrons is an important aspect of the design of the proposed SuperB project at LNF Frascati. Spin rotators are an integral part of the design of the Interaction Region (IR). We have chosen a solenoid-dipole design; at the 4.18 GeV nominal energy this is more compact that a design purely based on dipole magnets. Integration with the local chromaticity correction of the ultra-low beta* IR has been achieved. The spin rotators are symmetric about the Interaction Point, this design saves a significant amount of length as the dipoles become a part of the overall 360 deg. bend. The layout leaves limited opportunity to setup the optics for minimum depolarization; this is acceptable since beam life time in SuperB at high luminosity is only about 5 min and up-to 90% polarized electrons will be injected continuously. In this way an average beam polarization of about 70% is maintained. Simulations and analytic estimates with the DESY code SLICKTRACK and other codes indicate such operation is feasible from a spin-dynamics point of view. The paper will discuss the overall spin-rotator design as well as the spin dynamics in the ring.
CERN, Geneva
N.U, Nigde
UMAN, Manchester
Cockcroft Institute, Warrington, Cheshire
Ankara University, Faculty of Sciences, Tandogan/Ankara
The University of Liverpool, Liverpool
UU, Bursa
DESY Zeuthen, Zeuthen
BNL, Upton, Long Island, New York
University of Pisa and INFN, Pisa
INFN-Bologna, Bologna
DESY, Hamburg
SLAC, Menlo Park, California
In a linac-ring electron-proton collider based on the LHC ("LR-LHeC"), the final focusing quadrupoles for the electron beam can be installed far from the collision point, as far away as the proton final triplet (e.g. 23 m) if not further, thanks to the small electron-beam emittance. The inner free space could either be fully donated to the particle-physics detector, or accommodate "slim" dipole magnets providing head-on collisions of electron and proton bunches. We present example layouts for either scenario considering electron beam energies of 60 and 140 GeV, and we discuss the optics for both proton and electron beams, the implied minimum beam-pipe dimensions, possible design parameters of the innermost proton and electron magnets, the corresponding detector acceptance, the synchrotron radiation power and its possible shielding or deflection, constraints from long-range beam-beam interactions as well as from the LHC proton-proton collision points and from the rest of the LHC ring, the passage of the second proton beam, and the minimum beta* for the colliding protons.
BNL, Upton, Long Island, New York
In this paper we present the design and prototype measurement of small gap (5mm to 10 mm aperture) dipole and quadrupole for the future high energy ERL (Energy Recovery Linac). The small gap magnets have the potential of largely reducing the cost of the future electron-ion collider project, eRHIC, which requires a 10GeV to 30 GeV ERL with up to 6 energy recovery passes (3.8 km each pass). We also studied the sensitivity of the energy recovery pass and the alignment error in this small magnets structure and countermeasure methods.
BNL, Upton, Long Island, New York
IKP, Mainz
FZJ, Jülich
To facilitate studies of collisions between polarized electron and protons at √{s} = 14 GeV constructing an electron-nucleon collider at the FAIR facility has been proposed. This machine would collide the stored 15 GeV polarized proton beam in the HESR with a polarized 3.3 GeV electron beam circulating in an additional storage ring. We describe the interaction region design of this facility, which utilizes the PANDA detector.
IHEP Beijing, Beijing
Optics correction is an important issue at BEPCII. Due to the errors in all kinds of components of a storage ring, the real optics of a storage ring is different from the design one. This paper introduces some developments of optics calibration at BEPCII storage ring. We use the method that fit the measured response matrix to the model response matrix to get the fudge factor of the quadrupole field and the sextupole field. On the other hand, in considering fringing fields of quadrupole magnet and interaction of quadrupole magnet iron core and sextupole magnet iron core, the model is calibrated.
KEK, Ibaraki
The carbon stripping foil is the key element for the high-intensity proton accelerator. At KEK, the foil test system using the 650keV H- Cockcroft-Walton accelerator is in operation, which can simulate the energy depositions to the foil with the same amount in the J-PARC. In order to quantatively observe the foil degradations (such as foil thinning, pin-hole production) during irradiation, online energy and particle analyzing system is under construction. This report outlines the design detail of the analyzing system including the detectors.
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.
CERN, Geneva
TRIUMF, Vancouver
In 2008, the SPS-to-LHC transfer line operation allowed for the first time to perform beam measurements in the last part of the lines and into the LHC. Beam parameters were measured and compared with expectation. Discrepancies were observed in the dispersion matching into the LHC, and also in the vertical phase advance along the line. In 2009, extensive theoretical and simulation work was performed in order to understand the possible sources of these discrepancies. This allowed establishing an updated model of the beam line, taking into account the importance of the full magnetic model, the limited dipole corrector strengths and the precise alignment of beam elements. During 2009, beam time was allocated in order to perform further measurements, checking and refining the optical model of the transfer line and LHC injection region and validating the different assumptions. Results of the 2009 optics measurements and comparison with the beam specification and model are presented.
SLAC, Menlo Park, California
CERN, Geneva
KIT, Karlsruhe
A current issue with the LHC collimation system is single-diffractive, off-energy protons from the primary collimators that pass completely through the secondary collimation system and are absorbed immediately downbeam in the cold magnets of the dispersion suppression section. Simulations suggest that the high impact rate could result in quenching of these magnets. We have studied replacing the 60 cm primary graphite collimators, which remove halo mainly by inelastic strong interactions, with 5.25 mm tungsten, which remove halo mainly by multiple coulomb scattering and thereby reduce the rate of single-diffractive interactions which cause losses in the dispersion suppressor.
POSTECH, Pohang, Kyungbuk
PAL, Pohang, Kyungbuk
A Brookhaven National Laboratory (BNL) type S-band photocathode RF gun is used at Pohang Accelerator Laboratory (PAL) to produce femtosecond tera hertz (fs-THz) radiation. In order to upgrade the fs-THz Facility at PAL, we need to develop the performance of the RF gun. The requirements for new RF gun are following: 1 nC beam charge, 60 Hz repetition frequency and 1 mm mrad normalized rms transverse emittance. A dual feed photocathode RF gun is designed satisfy these requirements. Two additional pumping ports are used to remove the field asymmetry. A large radius and short length of the iris increases the mode separation. The coupling scheme is changed to make the fabrication simpler. The RF gun structure had been modeled using 3D field solver to provide the desired RF parameters and to obtain the field profile. In this paper the new RF gun design and the cold test results will be presented.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Cockcroft Institute, Warrington, Cheshire
JAI, Oxford
Diamond, Oxfordshire
We present progress in the design of the recirculating linac option for the UK New Light Source. Improvements in all accelerator sections have been made such that the output meets the required specifications to drive the seeded NLS FELs. Full start-to-end simulations and tolerance studies are presented together with a comparison to the baseline, single pass linac design.
LBNL, Berkeley, California
For quadrupole or sextupole magnets, the field at the center is zero and will not disturb the stored beam, while the field away from the center increases in magnitude, giving a larger kick to the particles off axis. By pulsing such multipole magnets it is possible to improve the injection efficiency of the Advanced Light Source (ALS) in top off mode. The requirements for a multipole pole kicker injection scheme for ALS are to kick a 1.9 GeV beam by an angle of 10 mrad with a magnet of 1 meter length. Both quadrupole and sextupole magnets have been studied, as well as a dipole magnet with non-constant field magnitude across the center of the aperture. This paper describes the design and gives a comparison of each type of magnet as well as the modulators needed to drive them.
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.
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.
BNL, Upton, Long Island, New York
SimTrack is a simple C++ library designed for numeric particle tracking in high energy accelerators. It adopts a 4th order symplectic integrator for optical transportat in the magnetic elements. 4-D and 6-D weak-strong beam-beam treatments are included for beam-beam studies. It provides versatile functions to manage elements and lines. New type of elements can be easily created in the library. It calculates Twiss and coupling, fits tunes and chromaticities, and corrects closed orbits. During tracking, the parameters of elements can be changed or modulated on the fly.
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.
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
The electron cloud, which is initially presumed as a homogeneous distribution of static electrons, changes its transverse centroid position very fast during the passage of even a single bunch. This is due to the strong focusing transverse field of the highly relativistic positron bunch. As the density of the electrons near the beam axis grows, its impact on the beam becomes stronger. The interaction of the electron cloud with the bunch results with the shift of the betatron tune of the coherent dipole motion of the beam. In this paper we simulated the dipole tune shift of the beam interacting with the electron cloud by taking also in to account the own space-charge forces of the electrons which strongly affect the motion of the electrons during the passage of the bunch. We computed the tune shift for different transverse size and density of the electron cloud.
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.
CLASSE, Ithaca, New York
CERN, Geneva
ANL, Argonne
KEK, Ibaraki
SLAC, Menlo Park, California
Over the course of the CesrTA program, the Cornell Electron Storage Ring (CESR) has been instrumented with several retarding field analyzers (RFAs), which measure the local density and energy distribution of the electron cloud. These RFAs have been installed in drifts, dipoles, quadrupoles, and wigglers; and data have been taken in a variety of beam conditions and bunch configurations. This paper will provide an overview of these results, and give a preliminary evaluation of the efficacy of cloud mitigation techniques implemented in the instrumented vacuum chambers.
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.
KEK, Ibaraki
SLAC, Menlo Park, California
Grooved surfaces are effective to suppress the secondary electron emission, and can be a possible technique to mitigate the electron cloud instability (ECI) in positron/proton storage rings. Various types of triangular grooved surfaces have been studied in a laboratory, and also using an intense positron beam of the KEKB B-factory. The grooves have vertex angles of 20 ~ 30 degrees, and depths of 2.5 mm. In the laboratory, the secondary electron yield (SEY) of sample pieces were measured using an electron beam in a magnetic-free condition. The maximum SEY well below 1.0 was obtained after some extent of electron bombardment for most of grooved surfaces. To test he groove efficacy in magnetic field regions of particle accelerators, insertions with several types of grooved surfaces were installed into a test chamber in a wiggler magnet of KEKB positron ring. In a dipole-like chamber wit magnetic field (0.78 T), the reduction in the electron density around the beam was observed for a grooved section when compared to the case of a flat surface with TiN coating. An R&D effort is underway to optimize and manufacture the grooved surface in accelerator beam pipes for practical use.
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.
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.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
The Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB) proposes to construct an ERL test facility. To provide different operational modes for different scientific applications is one of the advantages of these new, linac-driven radiation sources. In contrast to the linear machine layouts of FELs, new challenges arise from incorporating the linac into a circular machine. One of them is the so called merger, a magnetic chicane that threads the low energy, low emittance, but high current bunch from the gun into the recirculator. The preservation of the ambitious gun parameters, the optimal collimation of dark current and flexibility to suit all user demands are the dominant design goals. Different design criteria and possible layouts are discussed and a preliminary merger design is proposed.
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.
SLAC, Menlo Park, California
LBNL, Berkeley, California
EPFL, Lausanne
In this paper we describe the technical design of an on-going proof-of-principle echo-enabled harmonic generation (EEHG) FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment was designed through late 2009 and built and installed between October 2009 and January 2010. We present the design considerations, the technical realization and the expected performances of the EEHG experiment.
HU/AdSM, Higashi-Hiroshima
We report that a lifetime of GaAs photocathode activated the surface to negative electron affinity (NEA) at various temperatures. An electron source with the NEA-GaAs photocathode is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac, in which a high power laser is illuminated to the photocathode for generation of the electron beam of 100mA. For example, the laser power of 15W should be needed for the quantum efficiency of 1% and the wavelength of 800nm. Consequently the high power laser causes to rise the GaAs temperature. The degradation of photo emission from the cathode is enhanced by a thermal desorption of Cs due to the temperature rise, even if the beam is not extracted. We have measured the cathode lifetime at various temperatures between room temperature and 100 C.
KEK, Ibaraki
SLAC, Menlo Park, California
In order to mitigate the electron cloud instability (ECI) in a positron ring, an electron clearing electrode with a very thin structure has been developed. The electrode has been tested with an intense positron beam of the KEKB B-factory using a test chamber. A drastic reduction in the electron density around the beam was demonstrated in a dipole magnetic field (0.78 T). The clearing electrode was then applied to the actual copper beam pipe (94 mm in diameter) with antechambers for wiggler magnets of KEKB. The feed-through was revised to improve reliability, and the length was modified to fit a real magnet. The input power into the electrode was estimated to be approximately 80 W/m. The clear reduction in the electron density was also observed by applying a voltage of +500 V to the electrode. The design of clearing electrodes has now reached a high reliability and it is suitable for accelerator applications.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
European industry has participated in the LHC Project for technology development, component design and system construction. A good relationship in academia-industry collaboration has led to successful results for the project. Industry plays an important role for component design, manufacture and system construction in the XFEL project. The long history of academia-industry collaboration in the accelerator field in Europe is presented.
LNLS, Campinas
We report on the status of SIRIUS (BR), the new 3 GeV synchrotron light source currently being designed at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas, Brazil. The new light source will consist of a low emittance storage ring based on the use of permanent magnet technology for the dipoles. An innovative approach is adopted to enhance the performance of the storage ring dipoles by combining low field (0.5 T) magnets for the main beam deflection and a short slice of high field magnet. This short slice will create a high bending field (2.0 T) only over a short longitudinal extent, generating high critical photon energy with modest energy loss from the complete dipole. There are several attractive features in this proposal, including necessity for lower RF power, less heating of the vacuum chambers and possibility to reduce the beam emittance by placing the longitudinal field gradient at a favorable place.
ISA, Aarhus
At Aarhus University in Denmark, a new synchrotron radiation source is being built. The 46-m circumference storage ring with 6-fold symmetry will operate at 580 MeV to produce bright UV and soft x-ray radiation. The storage ring will have a horizontal emittance of around 10 nm. Four straight sections will be available for insertion devices including a 12-pole wiggler with a field of 2 Tesla. ASTRID2 will operate in top-up mode with electrons from the present storage ring ASTRID, used as a booster. The insertion devices will have a strong influence on the lattice, and studies of dynamical aperture and compensation of tunes and beta beat will be presented. Also injection simulations will be given. The technical layout with details about magnetic arrangements on girders will be shown, including the vacuum system with extensive use of NEG. A 105 MHz RF system is being built together with a new LLRF system. At present, most major components have been ordered, and first injection will take place in the first half of 2011.
Cornell University, Ithaca, New York
CLASSE, Ithaca, New York
The proposed Cornell Energy Recovery Linac (ERL) is designed for bunches of 77pC and 100mA whose energy is recovered. However, the ERL linac can also be used for larger bunch charges of reduced average current whose energy does not have to be recovered. The proposed Cornell ERL lightsource currently uses a split linac arrangement connected by a turnaround arc. In order to avoid the detrimental effects of Coherent Synchrotron Radiation (CSR) in this arc, a high charge (1nC) bunch must remain relatively long (2ps), and be compressed at high energy (5GeV). An appropriate bunch compressor must take second order effects into account, which adds complications for the large energy spread associated with compression to 100fs or less. We have therefore designed a very simple four dipole bunch compressor at high energy, which uses second order time of flight terms in the turnaround arc rather than in the bunch compressor itself. This design is tested using particle tracking simulations incorporating CSR, as well as magnetic field errors and misalignments.
BNL, Upton, Long Island, New York
The shielding design for the NSLS-II will provide adequate protection for the full injected beam loss in two periods of the ring around the injection point, but the remainder of the ring is shielded for lower losses of <10% full beam loss. This will require a system to insure that beam losses don't exceed these levels for a period of time that could cause levels outside the shield walls. This beam containment system will measure, provide a level of control and alarm indication of the beam power losses along the beam path from the source (e-gun, linac) thru the injection system and the storage ring. This system will consist of collimators that will provide limits to (an potentially measure) the beam miss-steering and control the loss points of the charge and monitors that will measure the average beam current losses along the beam path and alarm when this beam power loss exceeds the level set by the shielding specifications. This will require some new ideas in beam loss detection capability and collimation. The initial planning and R&D program will be presented.
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.
INFN/LNF, Frascati (Roma)
CNAO Foundation, Milan
CNAO, the Italian Centre of Oncological Hadrontherapy located in Pavia, is under commissioning and will be soon fully operational. It is based on a synchrotron that can accelerate carbon ions up to 400 MeV/u and protons up to 250 MeV for the treatment of patients. In this paper we present the subsystem, called B-Train, which has the purpose of measuring the magnetic field in a dedicated dipole connected in series with the sixteen dipoles of the synchrotron and to provide instantaneous values of the synchrotron field to the dipole power supply, to the RF, diagnostics and dump bumpers control systems, via optical lines, using a custom communication protocol. In order to measure the magnetic field with the specified precision (0.1G over 1.5T @ 3 T/s), a different approach has been taken with respect to previous versions of the system. The field is obtained by digitizing the voltage induced on a pick-up coil inserted in the gap of the dedicated dipole through a 18 bit, 1.25 Msamples/s ADC and integrating it by numerical methods. This paper describes the final design and features of the B-Train system, as well as the results obtained on the magnetic field readings precision.
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.
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.
Fermilab, Batavia
In the Project X facility a 2.6 GeV, H- CW beam is delivered to three users simultaneously by way of selectively filling appropriate RF buckets at the front end of the linac and then RF splitting them to three different target halls. With the desire to split the H- beam three ways, an RF separator directs two quarters of the beam to one user (Mu2e), one quarter to another user (Kaon), and one quarter to the third (unidentified) user. The natural way is to use a SC structure with the deflecting TM110 mode. Basic requirements to the deflecting RF structure are formulated and design of the deflecting SC cavities is presented.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
The design and construction of electron-ion colliders will be facilitated by the development of an SRF "crab crossing" cavity with 0.5 to 1.5 GHz frequency and 20 to 50 MV integrated voltage. These RF cavities provide a transverse kick to the particle beam. Current state of the art crab cavities provide 2-5 MV of integrated voltage, and most of the existing designs require complex schemes to damp unwanted RF modes. We propose a novel system for implementing TEM-like two-bar structures. Two phase-locked sources 180° out of phase each drive a half-wavelength coax antenna inside of a cavity designed for the fewest possible unwanted modes. The cavity design will required a high-Q system composed of coax windows designed for maximizing the shunt impedance of the structure. A series of cavities could be installed in a beam line, and individual phase adjustment for each module will accommodate their longitudinal spacing and will provide the required integrated voltage.
CLASSE, Ithaca, New York
This paper discusses the optimization of superconducting RF cavities to be used in Cornell's Energy Recovery Linac, a next generation light source. We discuss the determination of a parameter corresponding to beam break-up current and the results of introducing a realistic higher-order-mode absorber constructed of carbon nanotubes rather than a ferrite based absorber. We conclude by comparing the threshold current of the new design and show differences are due to the new absorber material.
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.
LNLS, Campinas
"Green solutions" using permanent magnets are being proposed for the dipoles and quadrupoles of the second Brazilian Synchrotron Light Source - LNLS2 - magnetic lattice. The main purpose is to reduce as much as possible the electrical energy consumption, assuring the reliability of the magnets during several years. Sextupoles will have multiple functions due to the limited space in the lattice design.
NTHU, Hsinchu
NSRRC, Hsinchu
IUCF, Bloomington, Indiana
A novel gradient damping wiggler (GDW) was developed for the ALPHA storage ring in Indiana University. The GDW will be used to change the momentum compaction factor and the damping partition at ALPHA storage effectively. There is one middle pole and two outer poles that they have gradient field were assembled together on the same girder to be a full set of GDW magnet system. The dipole and gradient field strength of the middle (outer) pole is 0.67 T (-0.67) and 1.273 T/m (1.273 T/m), respectively. The magnet gap of the middle and outer pole is 40 mm and 35.87 mm, respectively, that the three combined function of dipole magnet can be charged by the same power supply. There is a trim coil on the three magnets to adjust the first and second integral field to zero. The good field region of middle pole and outer pole in transverse x-axis (deltaB/B=0.1%) are ±50mm and ±40mm separately. A prototype GDW magnet was fabricated and a Hall probe measurement system was set up to measure the magnet field to verify the magnet design and the magnet construction performance. The field cross-talk and the fringe field are also discussed herein by different methods.
JAEA, Ibaraki-ken
In J-PARC RCS, horizontal closed orbit distortion (COD) which is ±2 or 3mm in amplitude was observed all over the ring. Main component of the horizontal COD is 1kHz, phase variation period about 140 seconds. This paper demonstrates phase variation of the 1kHz horizontal COD caused by switching ripple from dipole magnet power supply. To suppress the phase variation of the horizontal COD, switching timing of the dipole magnet power supply was synchronized J-PARC timing system.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
CITCEA-UPC, Barcelona
ALBA is a 3 GeV third generation synchrotron light source under construction in Spain. The design and performance of the ALBA Storage Ring Power Converters will be described. A total of 122 power converters are required: 1 for the dipoles (all connected in series), 112 for the quadrupoles (each magnets with its own power supply) and 9 for the sextupoles (each family connected in series). All converters are switched mode with full digital regulation and a common control interface. The paper will describe the performance of the power converters and compare it with the design specifications.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
CITCEA-UPC, Barcelona
ALBA is a 3 GeV third generation synchrotron light source under construction in Spain. The injection system is composed of a 100 MeV Linac as pre-injector followed by a full energy booster synchrotron. The booster requires AC power converters operating at 3.125 Hz with a sinusoidal current waveform. All converters are switched mode with full digital regulation and a common control interface. The design specifications have been demonstrated and early tests on the Booster commissioning with beam will be presented
CERN, Geneva
The LHC was restarted on the 20th of November 2009 after 14 months of shutdown. The machine is composed of 8 powering sectors, each containing a main dipole circuit and two main quadrupole circuits. Each of these main circuits is entirely independent. To operate the LHC, the magnetic fields in the main magnets must be controlled with unprecedented accuracy. Indeed, the current in each power converter must be controlled with an accuracy of a few ppm (parts per million of nominal current) and the currents must be perfectly synchronised between sectors. To achieve the performance required of the LHC power converters, many challenges have been resolved. These include: measuring the power converter currents with an extreme absolute precision, control of these currents without tracking error or overshoot, perfect synchronisation of the current references sent to the power converters of the 24 main circuits. This paper details how these various problems have been resolved to obtain the performance required. Many experimental results are included, in particular the results of the tracking tests performed with the main circuits of the LHC.
NSRRC, Hsinchu
CMS/ITRI, Hsinchu
Based on the requirement of beam stability for the third-generation synchrotron radiation light source is more stringent, lower ripple and higher bandwidth of output current of corrector magnet power converters should be developed to implement the closed orbit correction of Taiwan Photo Source (TPS). The ±10A/±50V corrector magnet power converter uses a full bridge configuration, the switching frequency of power MOSFET is 40 kHz, in that each bridge leg has its own independent PWM controller and the output current bandwidth is 1 kHz when connected with the corrector magnet load. Using a DCCT as the current feedback component the output current ripple of this converter could be lower than 5 ppm. In this paper, we will describe the hardware structure and control method of the corrector magnet power converter and the test results will be demonstrated.
NSRRC, Hsinchu
The Taiwan Photon Source (TPS), a third-generation synchrotron radiation light source, should be installed with 1032 sets of magnet power supplies for the storage ring and 152 sets for the injector. All of the power supplies are preferred in PWM switched mode with IGBT or MOSFET. A high precision DC power supply for 48 dipoles of the storage ring; there are 240 quadrupole magnets and 168 sextupole magnets in storage ring, the main winding of quadrupole and 168 sextupole magnets are powered by individual power supplies. In the booster ring, one set of dynamic power supply for the dipole magnets and four sets for quadrupole magnets run at the biased 3Hz quasi sinusoidal wave. There are several hundred corrector (fast and slow) magnets and skew quadrupole magnets in storage ring and injector are powered by the same bipolar power converters.
CEA, Gif-sur-Yvette
The International Linear Collider reference design is based on a collision scheme with a 14 mrad crossing angle. Consequently, the detector solenoid and the machine axis do not coincide. It provokes a position offset of the beam at the Interaction Point in addition to a beam size growth. These effects are modified by the insertion of the anti-DID (Detector Integrated Dipole) aiming at reducing background in the detector. Furthermore a crab cavity is necessary to restore a 'head on' like collision, leading to higher luminosity. This introduces new beam distortions. In this paper, optics studies and simulations of beam transport in the Interaction Region taking these elements into account are presented. Correction schemes of the beam offset and beam size growth are exposed and their associated tolerances are evaluated.
CERN, Geneva
UMAN, Manchester
Uppsala University, Uppsala
The 1.5TeV CLIC beams, with a total power of 14MW per beam, are disrupted at the interaction point due to the very strong beam-beam effect. As a result, some 3.5MW reach the main dump in form of beamstrahlung photons. About 0.5MW of e+e- pairs with a very broad energy spectrum need to be disposed along the post-collision line. The conceptual design of this beam line will be presented. Emphasis will be on the optimization studies of the CLIC post-collision line design with respect to the energy deposition in windows, dumps and scrapers, on the design of the luminosity monitoring for a fast feedback to the beam steering and on the background conditions for the luminosity monitoring equipment.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
It is proposed to investigate the option of moving the positron source to the end of the main linac as a part of the central integration in the International Linear Collider project. The positron source incorporates an undulator at the end of the main linac and the photons generated in the undulator are transported to the target, located at a distance of around 400m. The dogleg design has been optimised to provide the required transverse off-set at the location of the target and to give minimum emittance growth at 500 GeV. The design of the dogleg and the tolerances on beam tuning as a result of locating this dogleg in the beginning of the beam delivery system are presented.
UMAN, Manchester
CERN, Geneva
Our earlier design* for an accelerating structure to suppress the wakefields in the CLIC main accelerating cavities has been modified. This structure combines strong detuning of the cell frequencies with waveguide-like damping by providing the structure with four attached manifolds which loosely couple a portion of the wakefields from each cell. The amended geometry reduces the surface pulse temperature heating by approximately 20%. We report on the overall parameters of the fundamental mode, together with details on damping higher order dipole modes. In order to adequately suppress the wakefield we interleave the frequencies of eight successive structures.
* Khan and Jones, TU5PFP007, PAC'09, Vancouver, Canada 2009.
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
DPNC, Genève
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Monitoring the muon beam properties in the final stage of the Neutrino Factory (the Decay Ring) is important for the understanding of the beam itself and a crucial piece of information for the downstream physics detectors. The main topics to be assessed are: knowledge of the muon beam energy, divergence of the muon beam and muon beam current. In the framework of the International Design Study for the Neutrino Factory (IDS-NF) a Race Track model Decay Ring based on G4beamline has been produced to understand how electrons from muon decays can be used to infer the energy properties of the beam via the spin depolarisation technique. The use of other codes, like Zgoubi, to generate a realistic beam including effects like spin polarisation, are considered. A general discussion on the remaining topics is presented.
IHEP Beijing, Beijing
In this paper, we made a new design for ILC 3.2 km damping ring with 2 arcs based on FODO cell and 2 straight sections which are nearly the same as the new version of the 6.4 km ring DCO4. This new lattice uses less dipoles and quadrupoles than the present SuperB like lattice and has an adequate aperture for the large injected emittance of the positron beam. The work of lattice design and DA optimization will be presented in detail.
PSI, Villigen
The application of various optics correction techniques at the SLS allows to reduce the vertical emittance to <3 pm.rad corresponding to an emittance coupling of <0.05 %. Beam sizes can be measured with a resolution of ~0.5 um allowing to resolve vertical beam sizes close to the quantum radiation limit of 0.55 pm.rad. The application of beam-based alignment/ calibration techniques on magnet girders (remotely controlled), quadrupoles and sextupoles can be used to center the beam in all relevant optical elements at a minimum expense of vertical dipole corrector strength. Furthermore a fast orbit feedback based on a high resolution digital BPM system allows to stabilize the closed orbit up to ~90 Hz and to perform precise orbit manipulations within this bandwidth. Furthermore the top-up operation mode guarantees very stable conditions for the various beam-based measurements. These conditions make the SLS an excellent "test-bed" for future damping ring optimization.
TUB, Beijing
Since being introduced to accelerator physics, I have had the privilege to study and work with some of the best physicists on some of the most exciting projects. My first assignment was to simulate transition-crossing in RHIC in which a shocking 86% beam loss led to a redesign of its RF system which later earned me a Ph.D. Participation in the design, R&D, construction, and the commissioning of RHIC, not only was I introduced to the fascinating world of accelerator physics but was also trained as a physicist for accelerator projects. Since then, I have had the opportunity to work and lead teams of physicists and engineers on accelerator projects: US-LHC/AP at BNL, SNS/AP at ORNL, SNS ring, CSNS in China, and now CPHS at Tsinghua. The accelerator profession is uniquely rewarding in that ideas and dreams can be turned into reality through engineering projects, through which one experiences endless learning in physics, technology, teamwork and friendship. An example of enjoying the fun and friendship is the work on crystalline beams as a hobby for the past 18 years.
*Wei, Li, Sessler, Okamoto PRL73(94)3089; 80(98)2606
*Wei, Harrison XVI RCNP Osaka(97)
*Wei et al PAC99 2921
*Wei et al PAC01(01)319
*Wei RMP75(03)1383
*Wei et al NIMA600(09)10
*Wei et al PAC09
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
As the dimensions of accelerating structures become smaller and beam intensities higher, the transverse wakefields driven by the beam become quite large with even a slight misalignment of the beam. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path. We propose a built-in tunable absorption mechanism for damping the parasitic transverse modes without affecting the operational modes in dielectric loaded accelerating (DLA) structures and wakefield power extractors. The new principle for HOM absorption is based on electron paramagnetic resonance. The dielectric tube of the DLA has to be doped with a material exhibiting high EPR, for example ruby, Al2O3 overdoped ~1% with Cr3+. The absorption frequency can be tuned by an external DC magnetic field to match the frequency of the transverse mode. At the resonance imaginary part of permeability becomes significant and the dielectric tube acts as an absorber for the transverse modes. The external DC magnetic field is solenoidal and has to have a magnitude of about 3 kG. This configuration in fact is desirable to focus the beam and provide additional control of beam break up.
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.
GSI, Darmstadt
IAP, Frankfurt am Main
With the ability to accelerate heavy ions up to an energy of 32 GeV/u, the SIS300 superconducting (sc) synchrotron is a central part of the new FAIR facility at GSI-Darmstadt. SIS300 will provide beams with a 20-fold increase in energy and, by means of a stretcher mode or a fast ramped mode (1 T/s), 100-10000 times higher average intensity. The beam from SIS300 will be extracted towards the experiments using resonant slow extraction, thus SIS300 becomes the first superconducting synchrotron worldwide with this feature. Coupling and persistent currents are the main practical limitation for operation of sc magnets at high ramping rates and long slow extraction plateaus. The effect of the persistent currents, which are time dependent and depend as well on the magnet's history, is especially critical for slow extraction at low energies. These effects determine the tolerances on magnetic components. In order to address this issue, detailed simulations of beam dynamics at slow extraction have been performed. In particular, the optimization of the lattice and its optical parameters for a low-loss extraction in the presence of steady and time-dependent field components will be presented.
CERN, Geneva
TU Vienna, Wien
EBG MedAustron, Wr. Neustadt
The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and different types of ions for cancer therapy and research. Ten different types of bumpers, septa and kickers will be used in the low energy beam transfer line, the synchrotron and the high energy extraction lines. They are presently being designed in collaboration with CERN. Both 2D and 3D finite element simulations have been carried out to verify and optimize the field strength and homogeneity for each type of magnet and, where applicable, the transient field response. The detailed designs for the injection and dump bumpers, the magnetic septa and the fast chopper dipoles are presented. A novel design for the electrostatic septa is outlined.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL, Chilton, Didcot, Oxon
JAI, Egham, Surrey
For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The general injection layout based on a cyclotron for proton and a Linac for carbon is considered. There are two options for pre-accelerating carbon ions for PAMELA, either accelerating carbon with the charge state 4+ from the ion source and stripping after the pre-accelerator or directly accelerating carbon 6+ ions all the way from the ion source. For both options solution has been investigated. Simulations of beam dynamics for both particle species are presented. The resulting schemes based on either the single turn or multiturn injection into the first FFAG ring are discussed.
Imperial College of Science and Technology, Department of Physics, London
JAI, Egham, Surrey
The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carbon beams for hadron therapy. Medium energy beam transfer(MEBT) of PAMELA consists of the proton beam line coming out of the injector cyclotron, carbon beam transfer from the independent carbon 6+ injector linac, switching dipole when both beam merge and transfer line toward the PAMELA NS-FFAG. The MEBT layout and design, which needs to incorporate the beam chopper for the intensity modulation are discussed. The careful matching of optical functions between various components in the MEBT and beam dynamics simulations are presented.
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.
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.
IKP, Mainz
Siemens AG, Erlangen
The university of Mainz institute for nuclear physics is operating the microtron cascade MAMI (Mainzer Mikrotron) since the late 1970ies. The microtron delivers a cw electron beam to users of the hadron physics community. The recent, fourth stage MAMI-C having a design energy of 1.5 GeV is operated since 2006*. This article deals with the recent developments and operational experiences of MAMI-C, as well as with the energy upgardes to 1.56 GeV** and as final step towards 1.6 GeV. The final increase of beam energy was due to user demands, since it is expected to raise the event rate of the eta prime production by an order of magnitude.
* A.Jankowiak, et al., EPAC08, Genoa, Italy, p.51 (MOZCM01)
** A. Jankowiak, et al., PAC09, Vancouver, Canada (WE6PFP111)
Lancaster University, Lancaster
The possibility of achieving higher accelerating gradients at higher frequencies with the reduction of the effect of HOMs, compared to conventional accelerating structures, is increasing interest in the possible use of Photonic Crystals (PC) for accelerator applications. In this paper we analyze how the properties of the lattice of a PC resonator can be engineered to give a specific band structure, and how by tailoring the properties of the lattice specific EM modes can either be confined or moved into the propagation band of the PC. We further go on to discuss the role of disorder in achieving mode confinement and how this can be used to optimize both the Q and the accelerating gradient of a PC based accelerating structure. We also examine the use of high disorder to give rise to Anderson Localization, which gives rise to exponential localization of an EM mode. Discussing the difference between the extended Bloch wave, which extends over the entire PC, and the Anderson localized mode.
University of Oslo, Oslo
CERN, Geneva
NTNU, Trondheim
The CLIC Test Facility 3 Test Beam Line is the first prototype for the CLIC drive beam decelerator. Stable transport of the drive beam under deceleration is a mandatory component in the CLIC two-beam scheme. In the Test Beam Line more than 50% of the total energy will be extracted from a 150 MeV, 28 A electron drive beam, by the use of 16 Power Extraction and Transfer structures. A number of experiments are foreseen to investigate the drive beam characteristics under deceleration in the Test Beam Line, including beam stability, beam blow up and the efficiency of the power extraction. General benchmarking of decelerator simulation and theory studies will also be performed. Specially designed instrumentation including precision BPMs, loss monitors and a time-resolved spectrometer dump will be used for the experiments. This paper describes the experimental program foreseen for the Test Beam Line, including the relevance of the results for the CLIC decelerator studies.
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
TUB, Beijing
Tsinghua University, Beijing
Wakefield excitation has been experimentally studied in a 3-cell X-band standing wave Photonic Band Gap (PBG) accelerating structure. Major monopole (TM01- and TM02-like) and dipole (TM11- and TM12-like) modes were indentified and characterized by precisely controlling the position of beam injection. The quality factor Q of the dipole modes was measured to be ~10 times smaller than that of the accelerating mode. A charge sweep, up to 80 nC, has been performed, equivalent to ~30 MV/m accelerating field on axis. A variable delay low charge witness bunch following a high charge drive bunch was used to calibrate the gradient in the PBG structure by measuring its maximum energy gain and loss. Experimental results agree well with numerical simulations.
CEA, Gif-sur-Yvette
GANIL, Caen
ANL, Argonne
S3 (Super Separator Spectrometer) [1] is a future device designed for experiments with the high intensity heavy ion stable beams of SPIRAL2 [2] at GANIL (Caen, France). It will include a target resistant to these very high intensities, a first stage momentum achromat for primary beam extraction and suppression, a second stage mass spectrometer and a dedicated detection system. This spectrometer includes large aperture quadrupole triplets with embedded multipolar corrections. To enable the primary beam extraction one triplet has to be opened on one side, which requires an appropriate design of such a multipolar magnet. The final mass separation power required for S3 needs a careful design of the optics with a high level of aberration correction. Multiple symmetric lattices were studied for this purpose. A 4-fold symmetric lattice and the achieved results are described in this paper.
[1] A. Drouart et al., Nucl. Phys. A 834 (2010) 747c. [2] SPIRAL2, http://pro.ganil-spiral2.eu/spiral2
USTC/NSRL, Hefei, Anhui
In order to meet the increasing requirements of synchrotron radiation users, an upgrading plan of hefei light source is undergoing by National Synchrotron Radiation Laboratory (NSRL). The emittance of storage ring is reduced from 166nm.rad to 36nm.rad. In this paper, we study the beam close orbit distortions' (COD) sensitivity to the field and alignment errors in magnets. Estimation of the COD from various error sources is investigated. The distribution of beam position monitors and the location of correctors are reported in the paper. Simulation proves that COD can be corrected down to 50 microns level. In the same time the corrector strengths are weaker enough in the correction scheme.
USTC/NSRL, Hefei, Anhui
To enhance the performance of Hefei Light Source, an upgrade project is undergoing. The magnet lattice of storage ring will be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. In order to assure smooth beam accumulation process under new low emittance lattice, the injector, which is composed of electron linac and beam transfer line, would be updated. The detail of upgrading Hefei Light Source transport line will be described in this paper. It include the upgrading of lattice, the orbit control of beam transfer line and others. It is hopeful to realize a high transfer efficiency and high injection efficiency for new lower beam emittance storage ring.
BINP SB RAS, Novosibirsk
Lattice correction based on orbit responses to dipole correctors and orbit correction based on orbit responses to field gradient variations in quads were successfully implemented on VEPP-2000 [*] for the flat-beam lattice. The round-beam lattice involves strong coupling of vertical and horizontal motions that require a full-coupling analysis in the orbit response technique. Programs used were modified to treat this task. Also, automation and speed enhancements were done that enable a routine use of this technique at VEPP-2000. New experimental results from VEPP-2000 are presented.
* Yu.M.Shatunov et al. Project of a New Electron-Positron Collider VEPP-2000, in: Proc. 7th European Particle Accelerator Conf. (EPAC 2000), Vienna, Austria, 439-441
CERN, Geneva
This paper describes a detailed analysis of various non-linear effects of the nominal Negative Momentum Compaction lattice for PS2. Chromaticity and orbit correction schemes together with dynamic aperture studies are presented. The impact of magnet errors is being assessed and tolerances are evaluated. Frequency and diffusion maps are produced and, combined with non-linear driving terms analysis, are used for working point optimization.
CERN, Geneva
BNL, Upton, Long Island, New York
A software package has been developed for the LHC on-line optics measurement and correction. This package includes several different algorithms to measure phase advance, beta functions, dispersion, coupling parameters and even some non-linear terms. A Graphical User Interface provides visualization tools to compare measurements to model predictions, fit analytical formula, localize error sources and compute and send corrections to the hardware.
ANL, Argonne
IHEP Beijing, Beijing
Nonuniform dipoles with bending field variation have been studied for reducing storage ring emittance in recent years. According to a new minimum emittance theory, the effects of an arbitrary dipole can be characterized by two parameters. To have a better idea of the potentials of nonuniform dipoles, here we numerically explore the values of these two parameters for optimal emittance reduction.
IUCF, Bloomington, Indiana
The Advanced eLectron-PHoton fAcility (ALPHA) is under construction to support Crane Naval Center's radiation effect testing program. This paper reports the design of injection and extraction beamlines for the ALPHA and discusses the nonlinear beam spreader which is used to convert transverse Gaussian beam distribution into uniform rectangular beam distribution.
SLAC, Menlo Park, California
We use measured or simulated magnetic fields for dipoles and quadrupoles to build a lattice model for SPEAR3. In a non-symplectic approach the phase space coordinate mapping on the fields is based on Runge-Kutta integration of the equation of motion. In a symplectic approach we approximate the fields with proper fringe field models. Complication of the use of rectangular gradient dipoles in SPEAR3 is considered. Results of the model is compared to measurements on the real machine.
BNL, Upton, Long Island, New York
We report recent experimental results on linear optics measurements and corrections using ac dipole. In RHIC 2009 run, the concept of the SVD correction algorithm is tested at injection energy for both identifying the artificial gradient errors and correcting it using the trim quadrupoles. The measured phase beatings were reduced by 30% and 40% respectively for two dedicated experiments. In RHIC 2010 run, ac dipole is used to measure beta* and chromatic beta function. For the 0.65m beta* lattice, we observed a factor of 3 discrepancy between model and measured chromatic function in the yellow ring.
SOLEIL, Gif-sur-Yvette
LAL, Orsay
One advantage of X-ray sources based on Compton Back Scattering (CBS) processes is that such compact machines can produce an intense flux of monochromatic X-rays. CBS results from collisions between laser pulses and relativistic electron bunches. Aiming at high X-ray flux, one possible configuration combining a low emittance linear accelerator with a compact storage ring and a high gain laser cavity has been adopted by the ThomX project. We present here the main ring lattice characteristics in terms of baseline optics, possible other tunings such as low or negative momentum compaction, and orbit correction schemes. In addition, non-linear beam dynamics aspects including fringe field components as well as higher multipole tolerances are presented.
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.
Diamond, Oxfordshire
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
JAI, Oxford
CERN, Geneva
The correct implementation of the nonlinear ring model is crucial to achieve the top performance of a synchrotron light source. Several dynamics quantities can be used to compare the real machine with the model and eventually to correct the accelerator. Most of these methods are based on the analysis of turn-by-turn data of excited betatron oscillations. We present the experimental results of the campaign of measurements carried out at the Diamond. A combination of Frequency Map Analysis and resonant driving terms measurements has allowed a precise calibration of the nonlinear model capable of reproducing and then correcting the nonlinear beam dynamics in the storage ring.