Paper | Title | Other Keywords | Page |
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MO203 | The SARAF CW 40 MeV Proton/Deuteron Accelerator | rfq, ion, cavity, proton | 26 |
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The Soreq Applied Research Accelerator Facility, SARAF, is currently under construction at Soreq NRC. SARAF is based on a continuous wave (cw), proton/deuteron rf superconducting linear accelerator with variable energy (5-40 MeV) and current (0.04-2 mA). SARAF is designed to enable hands-on maintenance, which implies beam loss below 10-5 for the entire accelerator. Phase I of SARAF consists of an ECR ion source, a LEBT section, a 4-rod RFQ, a MEBT section, a superconducting module housing 6 half-wave resonators and 3 superconducting solenoids, a diagnostic plate and a beam dump. Phase II will include 5 additional superconducting modules. The ECR source has been in routine operation since 2006, the RFQ has been operated with ions and is currently under characterization. The superconducting module rf performance is being characterized off the beam line. Phase I commissioning results, their comparison to beam dynamics simulations and Phase II plans will be presented. |
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MOP001 | A Coupled RFQ-Drift Tube Combination for FRANZ | rfq, coupling, DTL, resonance | 46 |
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Funding: Work supported by BMBF |
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MOP006 | Stability of Normal Conducting Structures Operation with High Average Heat Loading | cavity, coupling, DTL, linac | 61 |
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Instead of proved application of superconducting structures for high energy part of intense linear proton accelerators, normal conducting structures are still considered for medium and low energy parts below 200 MeV. Operation with accelerating rate ~4 MeV/m and duty factor ~5% results for standing wave normal conducting structure in an average heat loading ~30 kW/m. Due to the high heat loading an operating mode frequency shift is significant during operation. In this paper conditions for field distribution stability against small deviations in time of individual cell frequencies are considered. For pi/2 structures these conditions were formulated by Y. Yamazaki and L. Young. General case of 0, pi/2 and pi operating modes is considered with common approach. |
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MOP010 | A Fast Chopper for the Fermilab High Intensity Neutrino Source (HINS) | linac, impedance, vacuum, high-voltage | 73 |
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A fast chopper capable of kicking single 2.5 MeV H- bunches, spaced at 325 MHz, at rates greater than 50 MHz is needed for the Fermilab High Intensity Neutrino Source (HINS). Four 1.2 kV fast pulsers, designed and manufactured by Kentech Instruments Ltd., will drive a ~0.5m long meander made from a copper plated ceramic composite. Test results showing pulses from the prototype 1.2 kV pulser propagating down the meander will be presented. |
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MOP029 | Beam Dynamics Studies for the SCREX-ISOLDE Linac at CERN | cryomodule, linac, emittance, cavity | 127 |
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For the REX-ISOLDE upgrade a superconducting linac based on 101.28 MHz Quarter Wave Resonators (QWRs) is foreseen downstream the normal conducting (NC) linac. Currently the REX-ISOLDE linac can accelerate ions with a mass to charge ratio in the range of 3 < A/q < 4.5 and up to an energy of 3 MeV/u. The upgrade aims to reach a final beam minimum energy of 10 MeV/u for A/q=4.5 in two main stages. The first stage consists of installing two cryomodules loaded with 10 cavities able to reach 5.5 MeV/u at the end of the present linac and the second consists of replacing part of the existing NC linac and adding further cryomodules. We report here on a beam dynamics study of the accelerator for the two installation stages and the transport line to the experimental station. |
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MOP030 | Multiple User Beam Distribution System for FRIB Driver Linac | kicker, septum, linac, emittance | 130 |
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Funding: Work was supported by DOE grant DE-FG02-04ER41324 *D.Gorelov, et al, proc of EPAC 2002, Paris, France, 2002. |
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MOP032 | Upgrade of the Unilac High Current Injector RFQ | rfq, emittance, ion, focusing | 136 |
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Funding: Work supported by the European Community INTAS Project Ref. no. 06-1000012-8782. |
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MOP037 | RF Design of the IFMIF-EVEDA RFQ | rfq, vacuum, coupling, cavity | 148 |
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The RFQ of IFMIF-EVEDA project is characterized by very challenging specifications, with 125 mA of deuteron current accelerated up to 5 MeV. Upon beam dynamics studies, it has been chosen a law for the variation of R0 and voltage along the structure; this law provides a significant reduction in terms of structure length, beam losses and rf power consumption. Starting from these outcomes, the rf study of the RFQ, aimed at determining the optimum design of the cavity shape, was performed. The stabilization issues were also addressed, through the analysis of the RFQ sensitivity to geometrical errors, by means of perturbative theory-based algorithms developed for this purpose . Moreover the determination of the main 3D details of the structure was also carried out. In this article the results of the rf studies concerning the above-mentioned topics are outlined. |
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MOP041 | The Fabrication and Initial Testing of the HINS RFQ | rfq, vacuum, quadrupole, emittance | 160 |
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Fermilab is designing and building the HINS front-end test facility. The HINS proton linear accelerator consists of a normal-conducting and a superconducting section. The normal-conducting (warm) section is composed of an ion source, a 2.5 MeV radio frequency quadrupole (RFQ), a medium energy beam transport, and 16 normal-conducting crossbar H-type cavities that accelerate the beam to 10 MeV. Production of 325 MHz 4-vane RFQ is recently completed. This paper presents the design concepts for this RFQ, the mechanical design and tuning results. Issues that arose during manufacturing of the RFQ will be discussed and specific corrective modifications will be explained. The preliminary results of initial testing of RFQ at the test facility will be presented and comparisons with the former simulations will also be discussed. |
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MOP042 | Complete RF Design of the HINS RFQ with CST MWS and HFSS | rfq, linac, quadrupole, radio-frequency | 163 |
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Similar to many other linear accelerators, the High Intensity Neutron Source requires an RFQ for initial acceleration and formation of the bunched beam structure. The RFQ design includes two main tasks: a) the beam dynamics design resulting in a vane tip modulation table for machining and b) the resonator electromagnetic design resulting in the final dimensions of the resonator. The focus of this paper is on the second task. We report complete and detailed rf modeling on the HINS RFQ resonator using simulating codes CST Microwave Studio (MWS) and Ansoft High Frequency Structure Simulator (HFSS). All details of the resonator such as input and output radial matchers, the end cut-backs etc. have been precisely determined. Finally in the first time a full size RFQ model with modulated vane tips and all tuners installed has been built, and a complete simulation of RFQ tuning has been performed. Comparison of the simulation results with experimental measurements demonstrated excellent agreement. |
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MOP043 | Simulation of Multipacting in HINS Accelerating Structures with CST Particle Studio | cavity, electron, accelerating-gradient, background | 166 |
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Recently high power tests of the room temperature cross-bar H-type resonators (CH resonators) and high gradient tests of a superconducting single spoke resonator (SSR) have been performed under the High Intensity Neutrino Source (HINS) project at Fermilab. The resonators have shown a tendency of having multipacting at various levels of input power and therefore longer processing time. To provide insights for the problem, detailed numerical simulations of multipacting for these resonators have become necessary. New generation of accelerating structures like superconducting spoke resonators and room temperature CH resonators need a full 3D treatment. Simulations and study of multipacting in the resonators have been carried out using CST Particle Studio. The problematic regions and power levels have been identified for both types of resonators. This presentation will give the result of simulations and comparison with experimental data. |
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MOP048 | DTL Tank Development of 132 MeV Linac for CSNS | DTL, quadrupole, linac, vacuum | 181 |
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A conventional 324 MHz DTL has been designed for China Spallation Neutron Source (CSNS) to accelerate H- ion from 3 MeV to 132 MeV. There are 7 tanks in the DTL and currently the R&D of tank-1 is under proceeding. In our design, Tank-1 has a tilt field distributed partially in order to obtain most effective energy gain and low Kilpatric parameter. The tank has been fabricated and the manufacture technique was verified by the measurement results. Because of the difficulty of tuning a partial tilt field distribution, a complex rf measuring and tuning procedure are introduced. The analysis on calculating the perturbation in a new method is also proposed. |
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MOP052 | Re-phasing of the ISAC Superconducting Linac with Computed Values | linac, cavity, emittance, ISAC | 193 |
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The ISAC superconducting linac is a fully operational machine that routinely provides beam to experiments. The linac consists of twenty superconducting independently phased cavities housed in five cryomodules. The initial tune is done manually aided by MATLAB routines to phase the linac and set the correct optics. From the initial tune we calculate the gradient at which each cavity operates based on the energy gain, the transit time factor and the geometry of the cavity itself. Then in the event of a gradient change of one or more cavities we can calculate the rf phase shift of each downstream cavity using the initial gradients, the known geometry of the entire linac and assuming linearity of the rf controls. This possibility has been investigated and we have demonstrated that the calculated phase shift can be implemented automatically thus avoiding a complete retune of the machine. In this paper we will present the calculations and the results of the online tests. |
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MOP064 | Bent Solenoid Tuning Simulations for the COMET Beamline | solenoid, target, dipole, electron | 226 |
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The COMET experiment beamline uses bent solenoids for the muon transport and the spectrometer used to analyse the decay electrons from stopped muons. The bent solenoid includes not just a solenoid field but also a vertical dipole field. It is therefore important to have the ability to tune the field distribution. However, since the field distribution is mainly determined by the geometry it is difficult to adjust once the solenoids have been constructed. A cost effective method to provide tuning capability of the field distribution of the bent solenoids is proposed and the results of simulations presented. |
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MOP068 | Trains of Sub-Picosecond Electron Bunches for High-Gradient Plasma Wakefield Acceleration | plasma, wakefield, electron, emittance | 235 |
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Funding: Work Supported by US Department of Energy *P. Muggli et al., to appear in Phys. Rev. Lett. (2008). |
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MOP069 | Beam Dynamics Simulations for a 15 MeV Superconducting Electron Linac Coupled to a DC Photo-Injector | cathode, focusing, target, solenoid | 236 |
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A 15 MeV accelerator scheme based on a dc photo-injector and a rf superconducting linac as been proposed as a new facility for radiography applications. The overall beam dynamics simulation process based on SUPERFISH and PARMELA codes will be reviewed. We present the results for the following beam operating conditions; acceleration of limited number of bunches, up to twenty electron micro-pulses of 100 ps time duration and 200 nC bunch charge, at 352 MHz repetition rate. |
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MOP072 | Beam Dynamics Simulation of the Low Energy Beam Transport Line for IFMIF/EVEDA | emittance, rfq, space-charge, injection | 242 |
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The purpose of the IFMIF-EVEDA (International Fusion Materials Irradiation Facility-Engineering Validation and Engineering Design Activities) demonstrator is to accelerate a 125 mA cw deuteron beam up to 9 MeV. Therefore, the project requires that the ion source and the low energy beam transport (LEBT) line deliver a 140 mA cw deuteron beam with an energy of 100 keV and an emittance of 0.25 π .mm.mrad (rms normalized) at the entrance of the RFQ. The deuteron beam is extracted from a 2.45 GHz ECR source based on the SILHI design*. A LEBT with a two solenoids focusing system is foreseen to transport and adapt the beam for the RFQ injection. In order to validate the LEBT design, intensive beam dynamics simulations have been carried out using a parallel implementation of a particle-in-cell 3D code which takes into account the space charge compensation of the beam induced by the ionisation of the residual gas. The simulations results (in particular from the emittance growth point of view) performed under several conditions of gas species or gas pressure in the beam line are presented. *R. Gobin et al, Rev. Sci. Instrum. 79, 02B303 (2008). |
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MOP074 | Beam Dynamics Simulations of Sub-ps Electron Bunch Produced in a Photo-Injector | emittance, electron, laser, gun | 248 |
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A growing number of experiments require low emittance ultra-short electron bunches in the 100 fs range (rms value) for the production of coherent light or the injection in plasma for laser-plasma acceleration. Especially in the last case it is highly desirable to have a compact accelerator; hence a strong experimental activity is carried out to get such a beam directly from a photo-injector. We have performed beam dynamic simulations using the PARMELA code to study the performances of the alphaX photo-injector installed in the University of Strathclyde in UK. This rf gun is aimed to produce electron bunches of 100 pC bunch charge, 100 fs bunch length and 1 mmmrad transverse emittance. We will show the results of systematic parametric studies as a function of charge and laser pulse duration as well as the natural evolution of the beam phase space as a function of the distance from the photo-cathode. |
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MOP075 | Benchmarking of Measurement and Simulation of Transverse RMS-Emittance Growth Along an Alvarez DTL | DTL, emittance, quadrupole, linac | 251 |
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Funding: CARE, contract number RII3-CT-2003-506395) European Community INTAS Project Ref. no. 06-1000012-8782 |
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MOP076 | Integration of Fringe Field Alpha Magnets into the V-Code Beam Dynamics Simulation Tool | multipole, dipole, electron, focusing | 254 |
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Funding: This work was partially funded by DESY Hamburg and DFG (SFB 634). |
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MOP082 | Multipacting Simulation in RF Structures | multipactoring, electron, cavity, linac | 266 |
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A new computer code for 3D simulation of multipacting phenomenon in axisymmetric and non-axisymmetric rf structures is presented. The goal of the simulation is to determine resonant electron trajectories and electron multiplication in rf structure. Both SW and TW structures of normal- and superconductivity have been studied. Simulation results are compared with theoretical calculations and experimental measurements. |
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MOP083 | Analysis of Input Coupler Asymmetry Influence on Beam Dynamics in Accelerators with Superconducting Cavities | emittance, cavity, electron, superconducting-cavity | 269 |
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Analysis of input coupler asymmetry influence on beam dynamics in superconducting cavities of Energy Recovery Linac (ERL) injector is presented. Both coaxial and waveguide, single and twin input couplers were analyzed. Using computer simulation electromagnetic fields distribution in accelerating cavity was obtained and recalculated to the transverse-kick to the bunch passing the coupler. Also calculation of external coupling was done. RTMTRACE code was adapted for particle beams dynamic simulation. Acceptable transverse emittance growth was achieved for twin-coaxial (4%) and waveguide (5%) input coupler designs. |
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MOP087 | Status of Longitudinal Beam Dynamics Studies in CTF3 | wakefield, electron, space-charge, cavity | 278 |
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The aim of the CLIC Test Facility CTF3, built at CERN by an international collaboration, is to address the main feasibility issues of the CLIC electron-positron linear collider technology by 2010. One key-issue studied in CTF3 is the generation of the very high current drive beam, used in CLIC as the rf power source. It is particularly important to simulate and control the drive beam longitudinal dynamics in the drive beam generation complex, since it directly affects the efficiency and stability of the rf power production process. In this paper we describe the ongoing effort in modelling the longitudinal evolution of the CTF3 drive beam and compare the simulations with experimental results. |
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MOP088 | Particle Dynamics Calculations and Emittance Measurements at the FETS | rfq, emittance, ion, ion-source | 281 |
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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 results of numerical simulations of the particle dynamics from the charge separation dipole behind the ion source to the end of the MEBT 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 by a factor of 2. Simulations of the particle dynamics in the FETS based on distributions gained from recent measurements of the transversal beam emittance behind the ion source will be presented and the results for different input distributions discussed. |
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MOP089 | Beam Dynamics and Wake-field Simulations for High Gradient ILC Linacs | cavity, linac, emittance, wakefield | 284 |
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Higher order modes (HOMs) are simulated with finite element and finite difference computer codes for the ILC superconducting cavities currently under investigation for the ILC. In particular, HOMs in KEK's Ichiro type of cavity and Cornel University's Re-entrant design are focussed on in this work. The aim, at these Universities and laboratories, is to achieve an accelerating gradient in excess of 50 MV/m in 9-cell superconducting cavities whilst maintaining a high quality and stable electron beam. At these high gradients, electrical breakdown is an important cause for concern and the wakefields excited by the energetic electron beams are also potentially damaging to the beam's emittance. Here we restrict the analysis to performing detailed simulations, on emittance dilution due to beams initially injected with realistic offsets from the electrical centre of the cavities and due to statistical misalignments of the cavities. We take advantage of the latest beam dynamics codes in order to perform these simulations. |
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MOP090 | Scattering Matrix Simulations of Fields and Dispersion Relations in Superconducting Cavities for XFEL and ILC | scattering, coupling, cavity, impedance | 287 |
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The globalised scattering matrix (GSM) method provides an efficient means of obtaining the electromagnetic field in interconnected multi-cavity structures. In the proposed XFEL at DESY and the ILC facilities, energetic electron beams can readily excite higher order modes which if left unchecked can dilute the emittance of the beams. The GSM in conjunction with finite element modelling of the scattering matrices of the linac cavities is used to enable the characteristic eigenmodes to be rapidly obtained and the potential for trapped modes is investigated. This characteristic eigensystem allows the wakefield experienced by the beam to be analysed and the consequences on beam quality ascertained. The impact of fabrication errors on the transverse electromagnetic field and corresponding resonant frequencies of the modes is also explored in detailed simulations. |
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MOP091 | End-to-End Simulation of the SNS Linac Using TRACK | linac, rfq, emittance, DTL | 290 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357. *"First TRACK Simulations of the SNS linac", B. Mustapha et al., in Proceedings of Linac-06 Conference, Knoxville, Tennessee, August 21-25, 2006. |
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MOP092 | Monte Carlo Simulation of Touschek Effects in a Linac Beam | scattering, electron, beam-losses, linac | 293 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
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MOP097 | Orthogonal Basis Function Approximation of Particle Distribution in Numerical Simulations of Beams | linac, synchrotron | 299 |
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Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University. |
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MOP099 | An Innovative Graphic User Interface for PARMILA 2 | linac, optics, DTL, drift-tube-linac | 305 |
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A new graphic user interface (GUI) has been created for the PARMILA 2 program. PARMILA 2 is an advanced version of the historical PARMILA program originally developed to design and model drift tube linear (DTL) accelerators. PARMILA 2 expands upon that capability to support the design and simulation of coupled cavity linear (CCL) accelerator structures, coupled-cavity drift tube linac (CCDTL) structures, superconducting accelerator structures, as well as DTL structures and transport lines that can include magnetic, radiofrequency and electrostatic beam optics elements. The Open Architecture Software Integration System, or OASIS, has been used to develop a custom module for the PARMILA 2 program that runs along with a suite of other optics codes in the Particle Beam Optics Laboratory (PBO Lab). OASIS development tools were utilized to define the innovative GUI for the PARMILA 2 module. Existing PARMILA 2 executables, including Parmila.exe, Lingraf.exe and readdst.exe, have been implemented via GUI commands utilizing other OASIS tools without any compilation or linking required. This paper presents an overview of the PARMILA 2 module and illustrates some of the GUI features. |
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MOP101 | Simulation of Emittance Growth Using the UAL String Space Charge Model | emittance, space-charge, electron, synchrotron | 308 |
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Evolution of short intense electron bunches passing through bunch-compressing beamlines is simulated using the UAL (Unified Accelerator Libraries) string space charge formulation. Excellent agreement is obtained with results obtained experimentally at CTF-II, the CERN "Compact Linear Collider'' test facility. The 40 MeV energy of these data is low enough for Coulomb and Biot-Savart forces to be important and high enough for coherent synchrotron radiation and centrifugal space charge forces to be important. UAL results are also compared with CSRtrack results for emittance growth in a 40 MeV 'standard' chicane. Vertical space charge forces are found to be important in this (low energy) case. |
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MOP104 | Parallel 3D Finite Element Particle-In-Cell Code for High-Fidelity RF Gun Simulations | gun, wakefield, space-charge, emittance | 317 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. |
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MOP106 | Prediction of 4ν=1 Resonance of a High Intensity Linac | resonance, emittance, linac, space-charge | 323 |
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The 4ν=1 resonance of a linac is found when the depressed tune is around 90 deg. It is observed that this fourth order resonance is dominating over the better known envelope instability and practically replacing it. Simulation study shows a clear emittance growth by this resonance and its stopband. Experimental measurement of the stopband of this resonance is proposed and conducted in early 2008 using the UNILAC at GSI. This study will serve as a excellent benchmarking. |
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TUP016 | Status of an Automatic Beam Steering for the CLIC Test Facility 3 | linac, quadrupole, lattice, emittance | 422 |
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An automatic beam steering application for CTF 3 is being designed in order to automatize operation of the machine, as well as providing a test-bed for advanced steering algorithms for CLIC. Beam-based correction including dispersion free steering have been investigated. An approach based on a PLACET on-line model has been tested. This paper gives an overview of the current status and the achieved results of the CTF3 automatic steering. |
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TUP018 | A 150 MeV Pulse Electron Linac with a 1 mA Average Current | electron, linac, target, emittance | 428 |
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Funding: The present work is supported by the STCU project #P233 |
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TUP019 | Injector of Intense Electron Beam | electron, bunching, cavity, emittance | 431 |
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The results of beam dynamic simulation in an S-band injector that can be used for creation of the powerful electron linac are presented in the report. The injector consists of a diode electron gun with beam current of up to 2 A at energy of electrons of 25 keV, the klystron type prebuncher and the three cavity buncher. In the buncher, due to the special choice of eigen frequencies of resonators, maximal amplitude of the field on the axis of resonators exponentially increase from the first (downstream of the beam) resonator to the last resonator. It allows effective bunching the intensive electron beam and accelerating it to relativistic velocities. For providing of low transversal beam emittance the injector is placed in the external magnetic field. The injector provides more than 1 A of beam current at particle energies of about 1 MeV. Attention is paid to research of transients and stability of injector work. |
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TUP024 | Growth of Density Modulations in an Energy Recovery Linac Light Source due to Coherent Synchrotron Radiation and Longitudinal Space Charge | lattice, linac, emittance, dipole | 444 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
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TUP027 | Simulation of Linear Lattice Correction of an Energy-Recovery Linac Designed for an APS Upgrade | lattice, quadrupole, sextupole, optics | 450 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
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TUP042 | High Repetition Rate Electron Injectors for FEL Based Next Generation Light Sources | gun, emittance, cavity, SRF | 489 |
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Several laboratories concentrate their efforts on development of high repetition rate FEL based next generation light sources. One particular concept under development at STFC Daresbury Laboratory specifies high brightness electron bunches with a charge of 0.2-1 nC which arrive with a frequency up to 1 MHz. As emittance of the bunches should not exceed 1 um, traditional high repetition rate thermionic injectors, similar to the ones used at high micropulse repetition rate FELs like ELBE or FELIX, may not be used. We consider three options of high repetition rate injectors based on photocathode guns - a high voltage dc gun, a one and half cell superconducting rf gun and a normal conducting VHF gun, recently proposed at LBNL. We consider practical injector schemes for all three guns and provide the results of beam dynamic simulations. We also discuss the photocathodes which may be used in each gun, as this critical component defines achievable beam parameters and operational efficiency of the injectors. |
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TUP043 | Development of a Beam Loss Monitor System for the LCLS Undulator Beamline | undulator, electron, beam-losses, radiation | 492 |
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Funding: Work Argonne supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357. |
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TUP045 | Generation of Femtosecond Bunch Trains Using a Longitudinal-to-Transverse Phase Space Exchange Technique | emittance, dipole, cavity, electron | 498 |
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Funding: Work supported by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DOE and by Northern Illinois University under Contract No. DE-FG02-08ER41532 with the U.S. DOE *P. Emma, Z. Huang, K.-J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006). |
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TUP047 | Manipulating the Two-Stream Instability for Efficient Terahertz Generation | electron, bunching, radiation, coupling | 504 |
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Particle beams have exhibited a two-stream instability for many decades; this undesirable trait has been well-understood for many years. We propose creating a scheme that uses a beam of electrons with two distinct energies that will develop the two-stream instability as a bunching mechanism. By controlling the beam parameters and seeding them with a low-level rf signal, a gain as high as 2.5 dB per centimeter is predicted. We show the theory behind this concept and recent progress in a developing experiment. |
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TUP096 | RF Gun Development with Improved Parameters | cavity, gun, cathode, vacuum | 627 |
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During development and operation of DESY L-band rf gun cavities, desires for further improvements were formulated. The next step of development is based on the proven advantages of existing cavities, but includes significant changes. The L-band 1.6 cell rf gun cavity is intended for operation in pulse mode with electric fields at the cathode of up to 60 MV/m, rf pulse length of ~1 ms and average rf power higher than existing gun cavities. In the new design the cell shape is optimized to have the maximal surface electric field at the cathode and lower rf loss power. The cavity cells are equipped with rf probes. Cooling circuits are designed to combine cooling efficiency with operational flexibility. In the report, the main design ideas and simulation results are described. |
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TUP097 | Measurements and Modeling at the PSI-XFEL 500 kV Low-Emittance Electron Source | emittance, cathode, electron, laser | 630 |
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Paul Scherrer Institute (PSI) is presently developing a low emittance electron source for the PSI-XFEL project. The electron gun consists of an adjustable diode configuration subject to pulses of 250 ns (FWHM) with amplitude up to 500 kV from an air-core transformer- based high-voltage pulser. The facility allows high gradient tests with different cathode configurations and emission processes (field emission and photo emission). In the first stage, the beamline is only made up of focussing solenoids followed by an emittance monitor. Selected beam characterization measurements, from photo-cathode operation driven by a 266 nm UV laser system delivering 4 uJ energy during 6.5 ps (FWHM), are presented and compared to the results of 3D particle tracking simulations. |
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TUP105 | Simulation of the Upgraded Photoinjector for the 10 kW JLAB IR-FEL | laser, emittance, cavity, FEL | 649 |
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Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University |
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TUP106 | Simulation of Field-Emission Cathodes for High Current Electron Injectors | cathode, electron, FEL, gun | 652 |
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Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University |
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TH301 | Beam Dynamics Studies of the 8 GeV Linac at FNAL | linac, cavity, focusing, proton | 760 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Scince, under contracts number DE-AC02-06CH11357 and No. W-31-109-ENG-38. |
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TH302 | Transport Limits in Periodic Focusing Channels | focusing, lattice, space-charge, beam-transport | 765 |
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It has been empirically observed in both experiments and particle-in-cell simulations that space-charge-dominated beams suffer strong growth in emittance and particle losses in alternating gradient quadrupole transport channels when the undepressed phase advance increases beyond about 85 degrees per lattice period. Although this criterion has been used extensively in practical designs of strong focusing intense beam transport lattices, the origin of the limit has not been understood. We propose a mechanism for the transport limit resulting from strongly chaotic classes of halo particle resonances near the core of the beam that allow near-edge particles to rapidly increase in oscillation amplitude when the space-charge intensity and the flutter of the matched beam envelope are both sufficiently large. A core particle model is applied to parametrically analyze this process and the results are compared with extensive particle simulations. |
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TH303 | Towards a Model Driven Accelerator with Petascale Computing | linac, beam-losses, rfq, emittance | 766 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357. |
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THP008 | A Novel Frequency Tuning System Based on Movable Plunger for SPIRAL2 High-Beta Superconducting Quarter-Wave Resonator | cavity, cryomodule, niobium, insertion | 789 |
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SPIRAL2 aims at building a multi-purpose facility dedicated to nuclear physics studies, including the production of rich-neutrons isotopes. The multi-beam linear accelerator is composed of superconducting accelerating modules and warm focusing magnets. IPN Orsay is in charge of the high energy accelerating modules, each hosting two superconducting (β = 0.12) quarter-wave resonators operating at an accelerating field of 6.5 MV/m at 88 MHz. The static and dynamic frequency tuning is achieved by the insertion and motion of a niobium plunger into the magnetic field area. The efficiency of the tuning (1 kHz/mm) has been validated during the tests of the cryomodule. In this paper we discuss the impact of such a tuning system, based on experimental results on Spiral2 cavities, on the different aspects: maximum accelerating field, Qo slopes, quench, multipacting and microphonics. |
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THP018 | Successful Qualification of the Coaxial Blade Tuner | cavity, insertion, superconducting-cavity, SRF | 818 |
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Cavity tuners are needed to precisely tune the narrow-band resonant frequency of superconducting cavities. The Blade Tuner presented is installed coaxially to the cavity and changes the resonator frequency by varying its length. Piezoceramic actuators add dynamic tuning capabilities, allowing fast compensation of main dynamic instabilities as Lorentz Forces, under pulsed operations, and microphonic noise. A prototype piezo Blade Tuner has been assembled on a TESLA cavity and extensively cold tested inside the horizontal cryostats CHECHIA (DESY) and HoBiCaT (BESSY). Then, as suggested by results, a few minor modifications have been implemented thus achieving the current Blade Tuner design. The introduction of thicker blades re-distributed along the circumference allows to increase its stiffness and fulfill European and American pressure vessel codes, while ensuring requested performances and cost. The paper will present the successful characterization tests performed on the prototype, the extensive mechanical analyses made to validate the final model and the results from qualification tests of first revised Blade Tuner produced, to be installed in the second module of ILCTA at FNAL. |
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THP022 | SC Nb Sputtered QWRs for the REX-ISOLDE Accelerator at CERN: Prototype Design and Manufacturing | cavity, niobium, linac, vacuum | 827 |
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The HIE-ISOLDE activity aims at the construction of a superconducting linac based on 101.28 MHz Nb sputtered Quarter Wave Resonators (QWRs), which will be installed downstream the present REX-ISOLDE linac. The present design considers two basic geometries of the cavities (geometric β0 = 6.26% and 10.84%) for which a mechanical, chemical treatment and Nb coating design study has been performed. We report here on the status of the prototype cavity and sputtering tests. |
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THP030 | High Gradient Test Results of 325 MHz Single Spoke Cavity at Fermilab | cavity, vacuum, linac, accelerating-gradient | 851 |
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The High Intensity Neutrino Source (HINS) project represents the current effort at Fermilab to develop 60 MeV Proton/H- Linac as a front end for possible use in the Project X. Eighteen superconducting β=0.21 single spoke resonators (SSR), operating at 325 MHz, comprise the first stage of the HINS cold section. Two SSR cavities have now been fabricated in industry under this project and undergone surface treatment that is described here. We report the results of high gradient tests of the first SSR in the Vertical Test System (VTS). The cavity successfully achieved accelerating gradient of 13.5 MV/m; higher than the design operating gradient of 10 MV/m. The history of multipacting and conditioning during the VTS tests will be discussed. Experimental measurements of the cavity mechanical and vibration properties including Lorenz force detuning and measurements of X-rays resulting from field emission are also presented. |
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THP035 | Multipactor in Minimum Electric Field Regions of Transmission Lines and Superconducting RF Cavities | cavity, electron, multipactoring, superconducting-RF | 860 |
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Funding: Work is supported by the National Science Foundation grant PHY 0131508 *S. Belomestnykh and V. Shemelin, "Multipacting-free Transitions between Cavities and Beam-pipes," submitted to Nuclear Instruments and Methods in Physics Research A. |
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THP040 | A New TEM-Type Deflecting and Crabbing RF Structure | cavity, impedance, vacuum, damping | 873 |
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Funding: Supported by US DOE Contract No. DE-AC05-06-OR23177 |
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THP045 | Twisted Structures and Their Application as Accelerating Structures | cavity, superconducting-cavity, electron | 888 |
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Funding: This work has been sponsored by ORNL-SNS. The Spallation Neutron Source is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
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THP047 | Design of the MEBT Rebunchers for the SPIRAL2 Driver | cavity, rfq, ion, linac | 894 |
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The SPIRAL2 project uses a RFQ, normal conducting rebunchers and a superconducting linac to accelerate high intensity beams of protons, deuterons and heavier ions. All cavities work at 88 MHz, the beta after of the RFQ is 0.04 and 3 rebunchers are located in the MEBT line, which accepts ions with A/q up to 6. The paper describes the RF design and the technological solutions proposed for an original 3-gap cavity, characterised by very large beam holes (60 mm) and providing up to 120 kV of effective voltage. |
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THP049 | Optimization of Spiral-Loaded Cavities Using the 3D Code OPERA/SOPRANO | cavity, resonance, impedance, insertion | 900 |
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Rebunching cavities are today routinely used for matching a beam of charged particles between different accelerator structures, and thus optimizing the overall transmission and beam quality. At low resonance frequencies, unnecessary large dimensions of these cavities can be avoided by using spiral-loaded cavities. The optimization of these structures is a complicated process in which a wide range of different parameters have to be modified essentially in parallel. In this contribution, we investigate in detail the characteristics of a model structure with the 3D code OPERA/SOPRANO. This includes the optimization of the structure in terms of the spiral geometry for a given resonance frequency, the investigation of power losses on the inner surfaces, and the possibility of cavity tuning by means of a tuning cylinder. |
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THP056 | Improvement in the ACS Cavity Design for the J-PARC Linac Energy Upgrade | coupling, cavity, linac, background | 915 |
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The ACS (Annular-ring Coupled Structure) cavities were under development for the J-PARC Linac from 190 MeV to 400 MeV. We have fixed the cavity specification, taking into account the results of the high-power conditioning and the fabrication experience. The mass production of the ACS with a tight time schedule is now an issue, since the user community strongly requests the beam power upgrade as early as possible. Therefore, the design and the fabrication process of the ACS cavity have been reexamined on the basis of the experience, stored during the course of the fabrication and the tuning of the prototype ACS tanks. Here, we also discussed about the key issues on the mass production with a manufacturer. The cavity shape, that required complicated machining, was simplified to some extent, while the frequency tuning strategy was reconsidered to reduce the production period. The paper describes these recent activities on the ACS development. |
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THP065 | Shunt Impedance Studies in the ISIS Linac | linac, DTL, impedance, cavity | 942 |
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The ISIS linac consists of four DTL tanks that accelerate a 50 pps, 20 mA H- beam up to 70 MeV before injecting it into an 800 MeV synchrotron. Over the last decades, the linac has proved to be a strong and reliable injector for ISIS, which is a significant achievement considering that two of the tanks are more than 50 years old. At the time the machine was designed, the limited computing power available and the absence of 3D electromagnetic (EM) simulation codes, made the creation of a linac optimized for power efficiency almost impossible, so from this point of view, the ISIS linac is quite simple by today's standards. In this paper, we make a shunt impedance comparison study using the power consumption data collected from ISIS and the results obtained when simulating each of the four DTL tanks with 2D and 3D EM codes. The comparison will allow us to check the accuracy of our simulation codes and models and to assess their relative performance. It is particularly important to benchmark these codes against real data, in preparation for their use in the design of a proposed new linac, which will replace the currently aging ISIS injector. |
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THP066 | Breakdown in Pressurized RF Cavities | cavity, electron, vacuum, emittance | 945 |
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The performance of many particle accelerators is limited by the maximum electric gradient that can be realized in rf cavities. Recent studies have shown that high gradients can be achieved quickly in 805 MHz cavities pressurized with dense hydrogen gas, because the gas can suppress, or essentially eliminate, dark currents and multipacting. In this project, two new test cells operating at 500 MHz and 1.3 GHz will be built and tested, and the high pressure technique will be used to suppress the vacuum effects of evacuated rf cavities, so that the role of metallic surfaces in rf cavity breakdown can be isolated and studied as a function of external magnetic field, frequency, and surface preparation. Previous studies have indicated that the breakdown probability is proportional to a high power of the surface electromagnetic field, in accordance with the Fowler-Nordheim description of electron emission from a cold cathode. The experiments will be compared with computer simulations of the rf breakdown process. |
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THP069 | Design and Test of the Triple-Harmonic Buncher for the NSCL Reaccelerator | cavity, rfq, emittance, linac | 948 |
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To meet the requirement of a small output longitudinal beam emittance from the reaccelerator, a triple-harmonic buncher operating at the fundamental frequency of 80 MHz upstream the Radio Frequency Quadrupole (RFQ) linac has been designed, manufactured and tested at the National Superconducting Cyclotron Laboratory (NSCL). The buncher consists of two coaxial resonators with a single gridded gap. One cavity provides both the fundamental and the third harmonic simultaneously with l/4 and 3l/4 modes respectively, while the other for the second harmonic with a l/4 mode. This buncher combines the advantages of using high quality factor resonator and only a pair of grids. Details on design considerations, electromagnetic simulations, and test results are presented. |
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THP076 | Last SPIRAL 2 10 kW CW RF Coupler Design | cryomodule, cavity, linac, resonance | 969 |
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The first tests of the SPIRAL 2 coupler have been done successfully in the B-cryomodule of the SPIRAL2 linac. It led to an updated design. We present the new design as well as the results of the last test and conditioning. |
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THP077 | Studies on Input Couplers for Superconducting Cavities | interlocks, vacuum, superconducting-cavity, cavity | 972 |
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Drastic conditioning time reduction was successfully achieved for the TTF-III couplers at LAL. This was carried out by a systematic study of the different parameters that play a role in the conditioning process. Moreover, many investigations were made in order to have a better understanding of the couplers behaviour. These activities represent some aspects of a larger technology program that is being developed at LAL to study power couplers and multipacting. This paper will give an overview of some of these studies, the future experiments on couplers at LAL and the development of the associated technology program. |
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THP080 | Elimination of Parasitic Oscillations in RF Tube Amplifier for High Power Application | cavity, linac, ion, controls | 981 |
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For the heavy ion therapy center HIT in Heidelberg a 1.6 MW power amplifier for 217 MHz was built to supply the 7 MeV/u IH cavity. The inherent parasitic oscillations of the RF tube increases rapidly the anode current until the system switches off. For the elimination of those parasitic oscillations ferrite material is used. The electro magnetic fields are simulated to find an optimal positioning of the ferrite material in the anode cavity such that only the parasitic oscillations are attenuated without affecting the fundamental mode. |
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THP081 | Development of All Solid State Bouncer Compensated Long Pulse Modulators for LEP 1MW Klystrons to be Used for LINAC4 Project at CERN | klystron, linac, high-voltage, controls | 984 |
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Funding: Department of Atomic Energy, India. The work is done under DAE CERN Collaboration under NAT Protocol. |
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THP086 | Cold Cathode Electron Tube Toward Plenty Multi Beam Tube | cathode, cavity, electron, high-voltage | 990 |
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The multi beam electron tube with a lot of beam pipes is required for the low applied voltage and the high frequency because the efficiency has a limit according to the perveance. However, the total heater power becomes too high if many thermal cathodes are used. Thus the cold cathode such as the carbon nano tube (CNT) is suitable for such a multi beam electron tube. Further the cold cathode has the advantage to work as a switching device since the metal grid close to the cathode can be used. The design and the fundamental test of the partial model will be presented. |
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THP096 | Next Generation IGBT Switch Plate Development for the SNS High Voltage Converter Modulator | high-voltage, pulsed-power, plasma, diagnostics | 1012 |
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Funding: Work supported by the U.S. Department of Energy under contract DE-AC05-00OR22725 |
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THP116 | Real Time RF Simulator (RTS) and Control | cavity, controls, LLRF, beam-loading | 1072 |
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A multi cavity real time rf simulator and PID control has been implemented on a Xilinx Virtex-4 FPGA. The rf simulator simulates an entire rf unit with up to 4 cavities connected to a single simulated klystron. Each cavity is allowed to have its own set of parameters, set point gradients, synchronous phases, and beam loadings. The simulator is built based on an interdependent electrical and mechanical model of a cavity. The electrical model is a 1st order differential equation in the complex phase space. The mechanical model is a 2nd order differential equation of the Lorentz force detuning on the cavities. Other spurious effects as microphonics and noises can be added using an external source or a memory table. The simulator has been optimized for size and utilizes only one Xilinx DSP block per cavity. A typical Virtex-4 has of the order of 100 DSP blocks. The simulator bandwidth is 1MHz which is plenty for niobium type superconducting cavities which have a loaded Q of about 3 million and a half bandwidth of about 250 Hz. The Real Time simulator is currently running on hardware comprised by an ESECON LLRF controller* and a Linux based VME processor. *ESECON, 14 channel LLRF controller, Low Level Radio Frequency Workshop (LLRF07), Knoxville, Tennessee, October 22-25, 2007, presentation 031. |
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FR105 | Billion Particle Linac Simulations for Future Light Sources | linac, electron, space-charge, FEL | 1110 |
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Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC03-76SF00098. |
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FR201 | The IFMIF 5 MW Linacs | rfq, linac, target, emittance | 1114 |
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The International Fusion Materials Irradiation Facility (IFMIF) is based on two high power cw accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV to the common lithium target. The present design of the 5 MW IFMIF Linacs, as well as the description of the prototype accelerator to be built in Japan are presented: the injector including the 140 mA ion source and the magnetic focusing LEBT, the RFQ for the bunching and acceleration to 5 MeV, the MEBT for the proper injection into the Drift-Tube-Linac where the beam is accelerated to the final energy of 40 MeV. Recently, the Alvarez type DTL was replaced by a superconducting Half-Wave Resonator Linac to benefit from the advantages of the SRF technology, in particular the rf power reduction, plug power saving, ability to accelerate high intensity cw beams with high flexibility and reliability. Last, a HEBT section transports and tailors the beam as a flat rectangular profile on the flowing Lithium target. The design and technology choices will be validated during the EVEDA phase, which includes the construction of one full-intensity deuteron linac, but at a lower energy (9 MeV) at Rokkasho Mura in Japan. |
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