Fermilab, Batavia
DESY, Hamburg
FNAL has contributed to FLASH at DESY the third harmonic accelerating system, which will provide better beams for the FEL facility. The FNAL accelerating module has been qualified above specs and will be operational in FLASH in Spring.
DESY, Hamburg
The three stage bunch compression system proposed for the European XFEL will be able to achieve overall compression of about 100. This would lead to the reduction of the bunch length up to 2.5 10-5 m for the designed bunch charge of 1nC. It is anticipated that the final compression would be limited here mainly by rf tolerances (jitter) which are determined by technical specifications of the manufacturer. For a large variety of experiments it could be however desirable to go to shorter bunches even on cost of less radiation power. A good possibility to achieve this might be to operate the injector at lower than 1nC bunch charge. In this paper the possibility of the operation of the injector with low charge bunches was investigated. On this issue simulations with ASTRA code have been done in order to find suitable working points for the low charge regimes and to figure out the dependence of the bunch parameters on the initial bunch charge at the cathode. The results of these simulations for the injectors at FLASH and XFEL as well as the discussion about possible problems are presented.
SLAC, Menlo Park, California
CERN, Geneva
The Compact Linear Collider (CLIC) provides a path to a multi-TeV accelerator to explore the energy frontier of High Energy Physics. Its novel two-beam accelerator concept envisions rf power transfer to the accelerating structures from a separate high-current decelerator beam line consisting of power extraction and transfer structures (PETS). It is critical to numerically verify the fundamental and higher-order mode properties in and between the two beam lines with high accuracy and confidence. To solve these large-scale problems, SLAC's parallel finite element electromagnetic code suite ACE3P is employed. Using curvilinear conformal meshes and higher-order finite element vector basis functions, unprecedented accuracy and computational efficiency are achieved, enabling high-fidelity modeling of complex detuned structures such as the CLIC TD24 accelerating structure. In this paper, time-domain simulations of wakefield coupling effects in the combined system of PETS and the TD24 structures are presented. The results will help to identify potential issues and provide new insights on the design, leading to further improvements on the novel CLIC two-beam accelerator scheme.
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
JAEA, Ibaraki-ken
UTNL, Ibaraki
950 keV X-band Linac has the merits of compact system, and it does not need the radiation safety manager on-site in the public space. Therefore the system we have developed is suitable for the more safe circumstance in airport. Dual energy X-ray concept is introduced for material recognition with Linac these days, because it produce high energy X-ray which is available in case the target is thick and high atomic number material. We suggest two fold scintillator detector concept to induce dual energy X-ray effect. The design of two fold scintillator is decided by MCNP simulation with two scintillator code, CsI and CdWO4. The material recognition is confirmed using aluminium, iron and lead metal in conditions such as various thicknesses and containers.
GSI, Darmstadt
ITEP, Moscow
IAP, Frankfurt am Main
To provide for the high beam currents as required of the FAIR project, the GSI Unilac High Current Injector (HSI) must deliver 18 mA of U4+ ions at the end of the prestripper section. With the design existing up to 2008, the RFQ could not reach the necessary beam currents at the RFQ output, as simulations had shown. Furthermore, parts of the existing LEBT must be modified, and a new straight source branch must be added to provide for the full required beam current. As a first step of an HSI frontend upgrade, the RFQ has been modernized in summer 2009 with a completely new electrode design. Commissioning of the HSI has shown that the transmission of the RFQ increased significantly (from 55% to 85% in high current Uranium operation, 95% in medium current operation). As expected, further bottlenecks for the transmission of the complete HSI (matching LEBT-to-RFQ, matching to the Superlens) have been detected. An upgrade of LEBT magnets is foreseen for 2010, the additional linear source branch will follow.
GANIL, Caen
Three normal conducting rebunchers are located in the MEBT line of the SPIIRAL2 driver. The cavity are designed for a beta of 0.04, work at 88 MHz and have to supply beam voltages up to 120 kV in continuous mode or up to 190 kV in pulsed mode with 50%dutycycle. The paper describes the RF measurements and first results
CERN, Geneva
CEA, Gif-sur-Yvette
INFN/LASA, Segrate (MI)
In the framework of the preparatory phase for the luminosity upgrade of the LHC (SLHC-PP ) it is foreseen to characterize two superconducting RF cavities and demonstrate compliance of the required SPL field stability in amplitude and phase using a prototype LLRF system. We report on the preparation for testing of two super-conducting low-beta cavities at 50 Hz pulse repetition rate including the setting-up of the low level RF control system to evaluate the performance of the piezo-tuning system and cavity field stability in amplitude and phase. Results from tests with 50 Hz pulse repetition rate are presented. Simulations of the RF system are used to predict the necessary specifications for power and bandwidth to control the cavity field and derive specifications for the RF system and its control.
This project has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement no 212114
HIT, Heidelberg
The Heidelberg Ion Beam Therapy Centre (HIT) is the only medical facility in Europe for cancer treatment with protons and carbon ions. To broaden the range of available ion species towards helium the low energy beam transport (LEBT) will be extended by a third ion source and the associated spectrometer section. Following a novel ion optical approach the LEBT-branch has been redesigned. A dedicated test bench will be used to commission and validate the new design prior to its integration into the medical accelerator. In its final stage the test bench will comprise an ECR-ion source, a LEBT and an RFQ with diagnostics line. It opens up the unique opportunity to perform comprehensive investigations not only of the ion source but also of other devices like the RFQ which have been optimised in the frame of the LINAC upgrade. Here, particular emphasis will be placed on the new design of the analyser dipole and the macro pulse chopper. Furthermore results of beam optical simulations and first measurement results will be presented.
SINAP, Shanghai
TUB, Beijing
A compact hard X-ray FEL facility is on plan now at Shanghai Institute of Applied Physics (SINAP). This facility will be located close to Shanghai Synchrotron Radiation Facility(SSRF) which is a 3rd generation light source in China, in order to control the overall length less than 650m, this facility asks a compact linac with high gradient accelerating structure. C-band (5712MHz) accelerating structure is a compromised and good option for this compact facility. R&D of a C-band (5712MHz) high gradient traveling-wave accelerating structure has been in progress at Shanghai Institute of Applied Physics (SINAP). The structure is consisted of 53 regular disk-loaded cells and two waveguide couplers, and its length is about one meter. This paper introduces the study of the accelerating structure design method, its experimental model and the preliminary results of the RF cold test of the model structure.
MEPhI, Moscow
This paper presents the results of a research that analyzed the possibility of using a magnetic coupled disk-loaded structure (DLS-M) as an accelerating structure. DLS-M seems to have decent advantages comparing to the classical electrical coupled structure (DLS). The electrodynamics parameters of such a structure at various modes in C-band for a wide range of phase velocities as a function of aperture radii and coupling slot sizes are presented. Both forward and backward travelling wave regimes are considered. The essential parameters are compared to those of classical DLS. The design of an input coupler to the accelerator consisting of this type structure cells is also presented.
CERN, Geneva
EPFL, Lausanne
HIP, University of Helsinki
Optimizing the design and the manufacturing of the CLIC RF accelerating structures for achieving the target value of breakdown rate at the nominal accelerating gradient of 100 MV/m requires a detailed understanding of all the steps involved in the mechanism of breakdown. These include surface modification under RF fields, electron emission and neutral evaporation in the vacuum, arc ignition and consequent surface modification due to plasma bombardment. Together with RF tests, experiments are conducted in a simple DC test set-up instrumented with electrical diagnostics and optical spectroscopy. The results are also used for validating simulations which are performed using a wide range of numerical tools (MD coupled to electrostatic codes, PIC plasma simulations) able to include all the above phenomena. Some recent results are presented in this paper.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Fundación TEKNIKER, Eibar (Gipuzkoa)
The Medium Energy Beam Transport (MEBT) line for the Front End Test Stand (FETS) at Rutherford Appleton Laboratory (RAL) will transport a 60 mA, 2ms, 50 pps H- beam at 3 MeV. Its main components include a number of quadrupoles, re-bunching cavities and a fast-slow chopping system with dedicated beam dumps, as well as a diagnostics beam line. In this paper we present the design approach for the MEBT re-bunching cavities. A description is given for the proposed geometry and the main design choices are examined. In addition, the latest RF simulations results performed with 2D and 3D electromagnetic codes are presented including optimisation details and manufacturing plans.
IPN, Orsay
An Accelerator Driven System (ADS) for transmutation of nuclear waste requires a high power proton beam (several MWs) to reach the necessary spallation efficiency. Due to the induced thermal stress to the subcritical core, the high-power proton linac will have to fulfil stringent reliability requirements to minimise the number of unwanted beam trips (> 1 sec.) per operation cycle. In view of the construction of the MYRRHA ADS demonstrator, in Mol (Belgium), beam dynamic analyses were carried out to evaluate the fault tolerant capability of the superconducting linac, in the particular case of a radiofrequency (RF) cavity failure. This analysis was coupled with simulations on the RF behaviour of 700 MHz superconducting cavitiy as well as its tuning and feedback loop systems. Such considerations led to the development of a prototypical digital Low Level RF (LLRF) system to control the cavity phase and accelerating field, especially in the case of fast cavity retuning for failure compensation. In this paper we summarize the work which has been performed so far toward the development of such a fault-tolerant RF linac.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
For 400-MeV upgrade of the J-PARC Linac, ACS (Annular Coupled Structure) cavities, which are driven by 972-MHz RF, will be installed. The ACS cavity has complicated structure. Its Q-value is very low and the operation frequency is tree times higher in comparison with that of the SDTL cavity. So the stabilizing control of the ACS accelerating field will be more difficult than present 324-MHz RF system. Further more the chopped beam loading compensation is required. Especially, the debuncher will be located very far from the klystron, then the feedback loop delay will be about 1.5 us. This presentation will show the simulation results of the feedback control of the ACS cavity field including long loop delay and the effect of the chopped beam loading.
CEA, Bruyères-le-Châtel
GANIL, Caen
The high current driver accelerator of the SPIRAL 2 project uses a single-bunch selector to reduce the bunch repetition rate at the experimental target. The device works at almost 1 MHz and handles fast RF pulses of 18 ns with transient times shorter than 6 ns. The first electrode prototype, built in the framework of the Eurisol DS project, was used for thermal and RF tests and didn't show correct delay and matching. The paper describes the studies to improve these two important issues and the results of thermal tests
HIP, University of Helsinki
CERN, Geneva
Helsinki University, Department of Physics, University of Helsinki
The Compact Linear Collider (CLIC) is currently under development at CERN as a potential multi-TeV e+e' collider. The manufacturing and assembly tolerances for the required RF components are essential for the final efficiency and for the operation of CLIC. The proper function of an accelerating structure is sensitive to mechanical errors in the shape and the alignment of the accelerating cavity. The current tolerances are in the micron range. This raises challenges in the field of mechanical design and demands special manufacturing technologies and processes. Currently the mechanical design of the accelerating structures is based on a disk design. Alternatively, it is possible to create the accelerating assembly from quadrants, which has the potential to be favoured for the mass production due to simplicity and cost. In this case, the functional shape inside of the accelerating structure remains the same and a single assembly uses less parts. This paper focuses on the development work done in design and simulation for prototype accelerating structures and describes its application to series production.
KEK, Ibaraki
A new type of rotating anticathode X-ray generator has been developed, in which the electron beam up to 120keV irradiates the inner surface of a U-shaped Cu anticathode. A high-flux electron beam is obtained by optimizing the geometry of the combined function bending magnet. In order to minimize the sizes of the X-ray source, the electron beam is focused in a short distance by the combined function bending magnet, of which geometrical shape was determined by simulation with the codes of Opera-3D, General Particle Tracer (GPT) and CST STUDIO. The result of simulation clearly shows that the role of combined function in the bending magnet and the steering magnet is important to focus the beam in small sizes. FWHM sizes of the beam were predicted by simulation to be 0.45mm (horizontal) and 0.05mm (vertical) for a beam of 120keV and 75mA of which effective brilliance is about 500kW/mm2 with the supposition of a two-dimensional Gaussian distribution. The beam focus sizes on the target will be verified in the experiments by using the high-voltage power supply for the X-ray generator improved from 60kV to 120kV and 75mA.
Sokendai, Ibaraki
KEK, Ibaraki
We have designed Demountable Damped Cavity (DDC) as an ILC R&D. DDC has an axial symmetric structure, the coaxial waveguide HOM coupler and absorber at the end of beam pipe of SRF cavity. It is also demountable structure. These structures are expected to bring better cavity performance. However, DDC have many parallel faced surfaces and the multipacting might be a concerned issue. We have simulated MP on the DDC with CST-Studio and found MP could be not serious issue. In this paper we will report the simulation result in detail.
IAP, Frankfurt am Main
Recent international cw operated high-current applications with ambitious requirements regarding beam power and quality ask for new linear accelerator developments. In this context the CH-structure (Crossbar-H-mode) has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. It is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode and can be used for superconducting as well as for room temperature applications. Because of the large energy gain per cavity, which leads to high real estate gradients, the CH-cavity is an excellent candidate for the efficient acceleration in high power proton and ion accelerators with fixed velocity profiles. One possible application for this kind of cavity is the EUROpean research programme for the TRANSmutation (EUROTRANS) of high level nuclear waste in an accelerator driven system (ADS), which requires an efficient high-current cw-linac (600 MeV, 4 mA, protons, 352 MHz). The paper describes the status of the CH-cavity development and the actual beam dynamics results for the reference design of the 17 MeV EUROTRANS injector.
Imperial College of Science and Technology, Department of Physics, London
University of Warwick, Coventry
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
In order to contribute to the development of high power proton accelerators in the MW range, to prepare the way for an ISIS upgrade and to contribute to the UK design effort on neutrino factories, a front end test stand (FETS) is being constructed at the Rutherford Appleton Laboratory (RAL) in the UK. The aim of the FETS is to demonstrate the production of a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV with sufficient beam quality. The status of the FETS will be given and experimental results from the commissioning of LEBT and ion source will be presented. Previous measurements showed that the emittance of the beam delivered by the ion source exceeded our expectations by more than a factor of 3. Since then various changes in the beam extraction/post accelerator region reduced the beam emittance more than a factor of 2. The results from measurements will be compared with numerical simulations of the particle dynamics from the ion source to the end of the MEBT and the results discussed in respect to further work.
RLNR, Tokyo
A new type Linac, HSC (hybrid single cavity) linac for cancer therapy, which configuration combines RFQ (Radio Frequency Quadrupole) accelerating structure and DT (Drift Tube) accelerating structure is being finished designs and simulations now. This HSC linac design had adopted advanced power-efficiency-conformation, IH (Interdigital H) structure, which acceleration efficiency is extremely high in the low-middle energy region, and had also adopted most advanced computer simulation technology to evaluate cavity electromagnetic distribution. The study purposes of this HSC linac focus to design of injector linac for synchrotron of cancer radiotherapy facilities. Here, this HSC linac has an amazing space effect because of compact size by coupled complex acceleration electrode and integrated the peripheral device which is made operation easy to handle. The size of the HSC linac is very compact and is also easy to be adopted for cancer therapy in normal hospital.
IAP, Frankfurt am Main
Abstract A short RFQ prototype was built for tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-Simulations with CST Microwave Studio and measurements were done. The RF-Tests with continues power of 20 kW/m were finished successfully. Simulations of thermal effects with ALGOR are on focus now. First results and the status of the project will be presented.
IAP, Frankfurt am Main
NTG, Gelnhausen
The IH-type RFQ for the MAFF project at the LMU in Munich was operated at a beam test stand at the IAP in Frankfurt. It is the second IH-RFQ after the HIS at GSI and it has been designed to accelerate rare isotope beams (RIBs) with mass to charge ratios A/q up to 6.3 from 3 keV/u to 300 keV/u at an operating frequency of 101.28 MHz with an electrode voltage of 60 kV. Experimental results such as shunt impedance, energy spectrum and transmission will be presented.
Soreq NRC, Yavne
The SARAF 4-rod RFQ is operating at 176 MHz, designed to bunch and accelerate a 4 mA CW deuteron/proton beam to 1.5 MeV/u. The electrodes voltage for accelerating deuterons is 65 kV, a field of 22 MV/m. The RFQ injected power is induced by a loop coupler. The power needed to achieve this voltage is 250 kW, distributed along the 3.8 m RFQ length. This power density is approximately 3 times larger than that achieved in other 4-rod RFQs. At high power, local high surface currents in the RFQ might cause overheating which will lead to out-gassing and in turn to sparking. We used CST MWS to simulate the RF currents and fields in a 3D detailed model of the SARAF RFQ. The correct eigenmode was reproduced and both Qe and Qo are consistent with the measured values. The heat load generated by the simulated surface currents at critical areas along the RFQ was the input for thermal analysis using Ansys. Detailed results reproduced the experimental observation of several overheated regions in the RFQ, including the end flanges and the plungers. Further results predicted overheating at different regions which were subsequently measured and are now being improved by additional cooling.
ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
In radio frequency quadrupole (RFQ) structures, the fundamental quadrupole mode is used for focusing and acceleration of ion particles. The fields are maintained to have negligible interference with other unwanted modes of the structure using mode suppressors of different types especially in vane type RFQs that require dipole mode separation. The field distribution on the beam axis is usually measured and referenced using multiple loop-type magnetic probe antennas on the wall along the structure. Since the structures are equipped with many slug tuners on the outer wall for correction of fields, the tuner-probe interference can be a concern. In order to investigate the mode separation properties of the commonly used mode suppressors and the accuracies in field distribution with respect to localized perturbation due to the tuners, a systematic 3D simulation was carried out using a full-scale model of the SNS RFQ.
INFN/LNL, Legnaro (PD)
INFN- Sez. di Padova, Padova
In order to attain the stringent goals that assure the required performances of the IFMIF-EVEDA RFQ in terms of field uniformity, Q-value and RF-induced heat removal capability, the study of the 3D details of the cavity is particularly important. In this paper the main issues regarding the design of the slug tuners, cavity ends and vacuum grids are addressed, as well as the related optimization procedure.
INFN- Sez. di Padova, Padova
INFN/LNL, Legnaro (PD)
In the framework of the IFMIF/EVEDA project, the RFQ is a 9.8 m long cavity, with very challenging mechanicals specifications. In the base line design, the accelerator tank is composed of 18 modules that are flanged together. An RFQ prototype, composed of 2 modules with a reduced length, aimed at testing all the mechanical construction procedure is under construction. In this paper, the thermo-mechanical study by means of 2D thermo structural and 3D fluid-thermal-structural simulations will be described. The measurements made with a cooling water circuit on a part of the RFQ prototype and the comparison with fluid thermal simulation will be reported.
ANL, Argonne
An integral part of the ongoing ATLAS efficiency and intensity upgrade is an RFQ to replace the first section of the existing injector. The proposed RFQ is 3.8 m long made of 106 cells with 30 keV/u input energy and 260 keV/u output energy. The RFQ was designed using the DesRFQ code which produces a file consisting of the length, modulation and the 8 coefficients of the 8-term potential for every cell. To independently check the design we created full 3D models of the RFQ including cell modulation in both Micro-Wave Studio (MWS) and Electro-Magnetic Studio (EMS). The MWS model was used to verify the phasing and energy gain along the RFQ using particle tracking and the EMS model was used to extract the electric field cell by cell assuming the electrostatic approximation. A very good agreement was obtained between the full 3D model and the 8-term potential description in TRACK. In addition to the standard sinusoidal vane profile we studied the option of converting the cells with maximum modulation (~ 40 cells) into trapezoidal cells. The output energy was increased from 260 keV/u to ~ 300 keV/u with minimal change to beam dynamics. This option is the final RFQ design.
IHEP Beijing, Beijing
In the China Spallation Neutron Source project [1], the 324HMz Alvarez-type DTL will be used to accelerate the H- ion beam from 3 to 80.0MeV. The DTL linac has been designed as four tanks and the electromagnetic quadrupoles will be used for the transverse focusing inside the drift tubes. The geometries of the DTL cells were optimized by using SUPERFISH and the beam dynamics simulation was performed with PARMILA code. In this paper both the physical design and the engineering designs are presented.
IMP, Lanzhou
The separated function DTL in SSC(Separated Sector Cyclotron)-linac is being designed. According to the design requirements, 238U34+ ions are accelerated from 0.143MeV/u to 0.976MeV/u throught the DTL. The method coupling DAKOTA(Design Analysis Kit for Optimization and Terascale Application) and beam simulation code BEAMPATH is used to analyze tolerance of the structure. The tolerance of beam parameters to various type of random errors and misalignment are studied with Monte Carlo simulation,so as to de ne the engineering tolerance and alignment. In this paper, the beam dynamics simulation and the tolerance analysis of the SSC-linac are presented.
Southwest University of Science and Technology, Mianyang, Sichuan
A system ADS study program has been proposed and organized by Chinese Academy of Sciences. As part of the study program, concept design of a 10mA 1.5GeV Continue Wave (CW) superconducting proton linac has been started in the Institute of High Energy Physics (IHEP). In this paper the design of the 325MHz part of this linac, which is composed of a room temperature Radio Frequency Quadrupole (RFQ), eight 4-cell room temperature Cross bar H-type (CH) cavities and three kinds of spoke cavities with total number of 78, is presented. The main parameters and detailed beam dynamic simulation results of the CH and spoke section are introduced.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
X-ray radiation from the SDTL of J-PARC linac has been observed with the beam loss monitor by the cavity. The results show that the X-ray intensity depends not only on the RF power level of the tank but also on the RF structure of the tank. In the paper we will show the results of the investigation for the origin of the X-ray radiation from the tank.
INFN/LNL, Legnaro (PD)
CERN, Geneva
Post Couplers (PC's) are devices used in order to reduce the effect of perturbations on the operating mode of a DTL, using the resonant coupling stabilization method. In this paper an equivalent circuit for a DTL equipped with PC's is presented, together with a 3D simulation analysis, which can explain the post coupler stabilization principle and define a new tuning strategy for DTL cavities. The PC tuning procedure based on the equivalent circuit and on frequency measurements has been tested and validated with measurements on the Linac4 DTL aluminum model.
ITEP, Moscow
Intense heavy ion beam is very efficient tool to generate high energy density states in macroscopic amounts of matter. As result it enables unique methods to study astrophysical processes in the laboratory under controlled and reproducible conditions. For advanced experiments on high energy density physics the cylindrical target irradiated by hollow cylindrical beam is required. This combination provides extremely high densities and pressures on the axis of imploding cylinder. A new method for RF rotation of the ion beam is applied for required hollow beam formation. The RF system consisting of two four-cell H-mode cavities is under development for this purpose now. The cavities frequency has been chosen 298 MHz, which is sufficient for uniform target illumination at 100 ns pulse duration. The deflecting electrodes shape has been optimized to provide the uniform deflection of all particles in beam's cross-section. The prototype of the deflector cell was constructed. A measured electro-dynamics characteristic is presented. As well frequency corrections methods are considered in this paper.
Soreq NRC, Yavne
The SARAF front end is composed of a proton/deuteron ECR ion source and a LEBT to match the beam to a 4-rod RFQ. The LEBT is consisting of an analyzing magnet, an aperture, three magnetic solenoid lenses and a diagnostic system. The typical operation vacuum, downstream the analyzing magnet, is of the order of 10-6 mbar at 5 mA analyzed beam current. In the emittance measurement we identify a beam of secondary-species particles, differently affected by the solenoid and so arriving with a different phase-space profile at the emittance detector. The secondary beam is the result of a charge exchange interaction in which an ion interacts with residual gasses in the beam line, most likely hydrogen gas coming from the ion source, and become neutral. For 20 keV protons colliding with H2 the calculated ion neutralization rate is 1%/m/10-6 mbar. Since the neutral portion of the beam is not affected by the magnetic focusing / steering elements, a none concentric neural and ion beams in the phase-space is a measure of mistuned beam or misalign magnets. These effects were proved and followed by beam dynamics simulation and are used to match the beam to the RFQ.
Fermilab, Batavia
Fermilab is currently focusing its efforts toward the development of Stainless Steel (SS) helium vessels for its 1.3 GHz SRF cavities. The objective is to transition towards the concept of using SS helium vessels to dress the bare SRF cavities, thereby paving way for significant cost reduction and efficient production techniques for future accelerators. The biggest challenge has been to design a reliable interface between the niobium cavity end group and the stainless steel end flange that encloses the helium vessel. Fermilab has been pursuing a brazed joint design to allow this transition. Additional design challenges associated with this transition are ensuring proper cooling of the cavity, compensating for the difference in thermal contraction between the SS helium vessel and niobium cavities, and also modification of the tuning procedure and ensuring the safety and reliability of the blade and piezo tuners. Current efforts on the qualification of the niobium-SS braze joint, finite element simulations of the thermal design aspects, bench testing of actual cavity displacements, and study of the effects on the tuners will be presented.
DESY, Hamburg
The European XFEL, currently under construction at the DESY site in Hamburg, require high precision orbit control in the long undulator sections and in addition in some other locations of the machine, like bunch compressors, matching sections, or for the intra bunchtrain feedback system. Due to the pulsed operation of the facility the required high precision has to be reached by single bunch measurements. So far only cavity BPMs achieve the required performance and will be used at the European XFEL. We report on the development of two types of cavity BPMs for the intersection of the undulators with 10 mm beam pipe and for sections with a standard beampipe diameter of 40.5 mm. The prototypes for both types show the properties as expected for simulation results. The paper further concentrates on the industrialisation process. It points out some traps and their cures during the production process.
JAI, Egham, Surrey
CERN, Geneva
Compact Linear Collider (CLIC) is a multi-TeV electron-positron collider for particle physics based on an innovative two-beam acceleration scheme. The CLIC Test Facility 3 (CTF3, CERN) aims to demonstrate feasibility of this concept. The monitoring of a longitudinal profile will be very important for the CLIC. The optimization of the longitudinal charge distribution in a bunch is crucial for the maximisation of the luminosity and also for an optimal performance of a CLIC drive beam. A setup for the investigation of Coherent Diffraction Radiation (CDR) from targets with various configurations as a tool for non-invasive longitudinal electron beam profile diagnostics has been designed and installed in the CRM line of the CTF3 [1, 2]. In this report we present the status of the experiment and results on interferometric measurements of CDR from a single target configuration. Studies on downstream background contribution in the CRM line have been performed. Recently we have upgraded the system by installing a second target. In this report we shall also demonstrate the results on simulations of CDR spatial distribution from the two target configuration.
[1] M. Micheler et al., Longitudinal Beam Profile Measurements at CTF3 using CDR, PAC'09, "**".
[2] M. Micheler et al., Longitudinal beam profile monitor at CTF3 based on CDR, RREPS-09, "**".
Fermilab, Batavia
ANL, Argonne
Significant advances were demonstrated in the design and computer simulations of multi-GeV proton and H-minus linacs. Several codes were applied for the simulation of 8 GeV linac and resulted to extremely good coincidence of all beam parameters. New procedures such as stripping of H-minus ions due to various mechanisms were implemented into the tracking code. The author of this presentation has several publications in PRSTAB and Nuclear Instruments on various aspects of beam dynamics for 8 GeV linac.
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
CEA, Gif-sur-Yvette
Recent experiments at the Universal Linear Accelerator (UNILAC) at GSI provided evidence for space charge driven resonances along a periodic DTL. A transverse fourth order resonance has been detected by recording the four fold symmetry in phase space. As predicted in [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009)], the resonance dominates over the envelope instability. Additionally, evidence for resonant emittance transfer from the longitudinal to the transverse plane has been found for settings providing equal depressed tunes of the involved planes.
UMAN, Manchester
DESY, Hamburg
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Third harmonic superconducting cavities have been designed and fabricated by FNAL to minimise the energy spread along bunches in the FLASH facility at DESY. A module, consisting of four nine-cell 3.9 GHz cavities, has been installed in FLASH. The first measurement with beam excitation is presented, and the comparisons to transmission measurement without beam and simulations are made. Higher order modes (HOMs) are able to propagate to adjacent cavities through attached beam tubes. Modes from 1.3 GHz cavities in the module nearby also propagate into this module.
*Work supported by European Commission under the FP7 Research Infrastructures grant agreement No.227579.
UMAN, Manchester
DESY, Hamburg
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Transverse modes in the 3.9 GHz cavities designed and fabricated by FNAL are reported on. These modes have the potential to cause significant emittance dilution if they not sufficiently suppressed. Recent experiments, both probe-based and beam-excited, have indicated significant discrepancies between modes predicted in stand-alone 9-cell cavities compared to those in 4-cavity modules. We employ a suite of computer codes and circuit models to analyze these modes, coupled through beam tubes whose cut-off is above that of the first dipole band. We also report on preparations to instrument the higher order mode couplers with electronics suitable for diagnosing both the beam and cavity position, based on modes with sufficient R/Q values.
CERN, Geneva
KHLim, Diepenbeek
CERN is assembling a new vertical electropolishing facility in order to process several niobium cavities of beta 1 and beta 0.65 in the context of the HP-SPL R&D programme. Electrochemical simulations are being used in order to define the optimal cathode geometry to process the cavities in a vertical position. Macroscopic properties of fluid dynamics like the Reynolds number and thermodynamics linked to the power dissipated in the process are taken into account to dimension the main system components. All the materials from the different equipments must be compatible with all chemicals within the required working temperature and pressure. To provide safe operating conditions when handling chemicals or processing cavities, specific safety and protection equipment is also foreseen.
Cockcroft Institute, Lancaster University, Lancaster
BNL, Upton, Long Island, New York
CERN, Geneva
Multipactor is a limiting factor in many RF power couplers. The SPL coupler is proposed to have a conical matching section between the window and the coaxial section however this section must be checked for multipactor. Multipactor simulations of the coupler up to a few MW's of power were performed using a variety of different codes and the results were compared. Simulations were performed in the conical and straight coaxial sections.
KEK, Ibaraki
Fermilab, Batavia
The X-band pulse compression system has been developed for the high gradient experiment of the accelerating structure in the new X-band test facility (Nextef). The one channel circular polarized traveling wave delay line was selected to obtain the higher RF compression efficiency under limited delay line length and the easier operation than the cavity chain type. This delay line of the circular waveguide is also frequently used for the C-band feed line from the modulator floor to the accelerator test floor. Thus the delay line is tilted and has the limited length of around 20m. It is designed to obtain the three times compressed power which has the pulse duration of 150 ns. Further we also proceed the upgrade plan using the TE21 mode to double the pulse duration. In this paper, the design overview of this pulse compression system and the RF components including the mode launcher and the TE11-TE21 reflector will be presented.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
LBNL, Berkeley, California
For the beam current upgrade of the J-PARC linac, a new RFQ (RFQ III)is developing. The peak beam current of RFQ III is 50mA. To increase the peak current from the existing RFQ (RFQ I), the longitudinal and/or transverse emittances are expected to be increased. However, the increase of the longitudinal emittance will affect the performance of the RF chopper system. In this paper, detailed simulations of the RF chopper system are described and the requirement for the longitudinal emittance of the RFQ is clarified.
IAP, Frankfurt am Main
High intensity beams which are increasingly needed for a variety of applications pose new challenges for beam chopping. An ExB chopper system for proton beams of up to 200 mA and repetition rates of up to 250 kHz is under development at IAP. It will be tested and installed in the low energy section of the Frankfurt Neutron Source FRANZ at beam energies of 120 keV. The chopper consists of a static magnetic dipole field and a pulsed electric field in a Wien filter-type ExB configuration. The electric field temporarily compensates the magnetic deflection thus creating a proton pulse in forward direction, while the duty cycle of the electric field is minimized in order to reduce the risk of voltage breakdowns. Downstream of the chopper a septum will be used to separate the beams ensuring dumping outside the transport line in order to avoid uncontrolled power deposition and the resultant production of secondary particles. Numeric field optimizations and beam simulations including secondary electron effects are presented. Measurements of the high voltage pulse generator based on MOSFET technology and capable of generating 12 kV at 250 kHz as well as beam deflection experiments are shown.
KEK, Ibaraki
A new laser-based alignment system is under development in order to precisely align accelerator components along an ideal straight line at the KEKB injector linac. The new alignment system is strongly required in order to stably accelerate high-brightness electron and positron beams with high bunch charges and also to keep the beam stability with higher quality towards the next generation of B-factories. The new laser-based alignment system consists of the LD mounted on auto stage, vacuum duct, photo diode (PD) and PD detector. To eliminate the laser beam size dependent response of PD, the collimated laser beam propagation along the linac (around 500-m-long) is strongly required. In this paper, we will report the design of collimated laser beam optics for the KEKB injector linac alignment system in detail.
IAP, Frankfurt am Main
For the development of high energy and high duty cycle RFQs accurate particle dynamic simulation tools are important for optimizing designs, especially in high current applications. To describe the external fields in RFQs as well as the internal space charge fields with image effect, the Poisson equation has to be solved taking the boundary conditions into account. In PteqHI a multigrid Poisson solver is used to solve the Poisson equation. This method will be described and compared to analytic solutions for the Two-term-potential to verify the answer of the Poisson solver.
LANL, Los Alamos, New Mexico
Particle-core interaction is the well-developed model of halo formation in high-intensity beams. In present paper an analytical solution for averaged single particle dynamics around uniformly charged beam core is obtained. The problem is analyzed through sequence of canonical transformations of Hamiltonian describing nonlinear particle oscillations. An analytical expression for maximum particle deviation from the axis is obtained. Results of the study are in good agreement with numerical simulations and with previously achieved data.
INFN/LNL, Legnaro (PD)
As far as beam dynamics is concerned, the layout of the PIAVE-ALPI SuperConducting linac, it is injected either by a XTU tandem, up to 14 MV, or by the s-c PIAVE injector, made with 2 SC-RFQ. The linac (at the present 64 cavities for a total voltage up to 48 MV) is build up in two branches connected by an achromatic and isochronous U-bend. The PIAVE-ALPI complex is able to accelerate beams up to A/q = 7. The linac is quite complex due the presence of several accelerating, (SC RFQs and cavities), focusing and transport elements. The linac operation, optimized for the needs of the users, is described. In particular the effects of a flexible use of the cavities on the beam dynamics is addressed. The automatic tuning procedure of the Toutatis-Tracewin programs is used for the simulation, and the comparison with the actual linac performances is reported.
TEMF, TU Darmstadt, Darmstadt
TU Darmstadt, Darmstadt
The recirculating Superconducting Darmstadt Linear Accelerator S-DALINAC, installed at the institute for nuclear physics (IKP) at the TU Darmstadt, consist of a 10 MeV Injector and a 40 MeV linac. Utilizing two recirculations, the linac could be used up to three times, leading to a maximal energy for nuclear physics experiments of 130 MeV. This recirculating layout makes it pretty complicated to find an accurate setup for the various beam line elements, especially to match the path length of the recirculated beam with the phase of the accelerating fields. Fast online beam dynamics simulations can advantageously assist the operators because they provide a more detailed insight into the actual machine status. In this paper further developments of the moment based simulation tool V-Code enabling it to simulate recirculating machines are presented together with simulation results.
ANL, Argonne
A 100 MHz thermionic rf gun is under consideration as the electron source for the X-ray Free Electron Laser Oscillator*. Because the source must operate continuously, back-bombardment of the cathode is a serious concern. We present results of simulations of back-bombardment, as well as strategies for reducing the back-bombardment power on the cathode.
*K. J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008)
KEK/JAEA, Ibaraki-Ken
KEK, Ibaraki
On the beam line after linac in high power proton accelerators, like J-PARC, debuncher system plays an important role for beam injection to the succeeding ring. The debuncher system usually gives two functions, namely, to correct the center energy jitter and to minimize momentum spread and adjust beam energy at the injection. To mitigate the nonlinear effects of RF field, a debuncher system with two debuncher cavities was designed for the 181-MeV operation of J-PARC linac. In this design, the first debuncher is expected to deal with center energy jitter. Then, the second debuncher is utilized to control the injection momentum spread according to the requirements from the ring. Although the debuncher system was originally designed to minimize the momentum spread, beam-commissioning results show a different requirement for the injection momentum spread to minimize the beam loss in the ring. Based on the original design and the experimental findings with 181-MeV operation, we have designed a debuncher system for the energy upgrade of J-PARC linac to 400 MeV. In this paper, the beam dynamics design of the new debuncher system is presented together with some particle simulation results.
UMAN, Manchester
CERN, Geneva
The superconducting High Intensity and Energy (HIE) ISOLDE linac will replace most of the existing accelerating infrastructure of the Radioactive ion beam EXperiment (REX) at CERN, however, the 101.28 MHz RFQ and 5 MV IH cavity will remain in the role of injector for the upgrade, boosting the beam up to an energy of 1.2 MeV/u. We present the results of a beam dynamics investigation of the injector focused most critically on matching the longitudinal beam parameters from the RFQ to the SC machine, which is complicated largely by the IH cavity employing a Combined Zero Degree* (KONUS) beam dynamics design. The longitudinal beam parameters at the RFQ are reconstructed from measurement using the three-gradient method and combined with beam dynamics measurements and simulations of the IH structure to design the matching section for the SC linac.
*Ratzinger, U., "The IH-structure and its capability to accelerate high current beams," Particle Accelerator Conference, 1991
Soreq NRC, Yavne
Design of ion linacs with ion currents of several milli-amps necessitates detailed simulations of beam loss. At high intensities, even a small amount of beam loss can result in significant radio-activation of the linac components. Particle loss can result from longitudinal tails created in the bunching and pre-accelerating process, whereas strong transverse focusing and collimation limit the development of a transverse tail. In modern RF ion linacs, bunching and pre-acceleration take place in a radio frequency quadrupole (RFQ). We present a new approach for beam loss calculations that places emphasis on the tails of the particle distributions. This scheme is used for simulating the SARAF proton/deuteron linac, a 176 MHz complex designed to operate in CW mode at 4 mA beam current. We describe implementation of a RFQ accelerating element in the GPT 3D simulation code. We discuss our scheme for highlighting the tails of the particle distributions generated by the RFQ. These distributions are used as input to simulations of the RF superconducting linac, where subsequent particle loss is calculated. This technique allows us to increase beam loss statistics by a significant factor.
SLAC, Menlo Park, California
NSCL, East Lansing, Michigan
In the driver linac of the Facility for Rare Isotope Beams (FRIB), multipacting is an issue of concern for the superconducting resonators, which must accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. While most of the multipacting bands can be conditioned and eliminated with RF, hard multipacting barriers may prevent the resonators from reaching the design voltage. Using the ACE3P code suite, multipacting bands can be computed and analysed with the Track3P module to identify potential problems in the resonator design. This paper will present simulation results for multipacting in half-wave and quarter-wave resonators for the FRIB driver linac and compare the simulations with RF measurements on the resonators.
Diamond, Oxfordshire
Photocathode RF guns are widely used as injectors for accelerators requiring very high quality beams such as free electron lasers and linear colliders and recently used as ultrafast electron diffraction sources. Even with the limited repetition rate, normal conducting photocathode RF guns generate very low emittance and short pulse electron beams thanks to their high accelerating field and the efficient positioning of focusing solenoids. We report our activity of the design and production of an S-band normal conducting photocathode gun. The RF characteristics, thermal heating and vacuum analyses are discussed.
ANL, Argonne
The proposed injector design for the X-ray Free Electron Laser Oscillator* uses a 100 MHz thermionic rf gun in order to obtain beams with very small emittances at high repetition rates**. The required beam rate is only 1 to 10 MHz, so 90 to 99\% of the beam must be dumped. In addition, back-bombardment of the cathode is a significant concern. To address these issues, we propose using a laser to quickly heat the surface of a cathode in order to achieve gated thermionic emission in an rf gun. This may be preferrable to a photocathode in some cases owing to the robustness of thermionic cathodes and the ability to use a relatively simple laser system. We present calculations of this process using analysis and simulation. We also discuss potential pitfalls such as cathode damage.
*K. J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).
**P. N. Ostroumov et al., Proc. Linac08, 676-678.
SLAC, Menlo Park, California
SLAC has developed a comprehensive suite of 3D parallel electromagnetic codes based on the finite-element method to solve large-scale computationally challenging problem with high accuracy. The ACE3P (Advanced Computational Electromagnetic 3P) code suite includes the Omega3P eigenmode and S3P S-parameter solvers in the frequency domain for cavity prototyping and optimization, T3P time-domain solver for wakefields and impedances, Track3P particle tracking solver for simulating multipacting and dark current, and Pic3P Particle-in-cell code for RF Gun design. These capabilities with recent advances and the latest applications addressing important RF related accelerator phenomena will be presented.