| Paper | Title | Other Keywords | Page | ||
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| MO1002 | Commissioning and Initial Operating Experience with the SNS 1-GeV Linac | linac, SNS, target, beam-transport | 1 | ||
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The Spallation Neutron Source accelerator complex consists of a 2.5 MeV H- front-end injector system, a 186 MeV normal-conducting linear accelerator, a 1 GeV superconducting linear accelerator, an accumulator ring and associated beam transport lines. The SNS linac was commissioned in five discrete runs, starting in 2002 and completed in 2005. The remainder of the accelerator complex was commissioned in early 2006. With the completed commissioning of the SNS accelerator, the linac has begun initial low-power operations. In the course of beam commissioning, most beam performance parameters and beam intensity goals were achieved at low duty factor. A number of beam dynamics measurements have been performed, including emittance evolution and sensitivity to mismatch of the input beam. The beam commissioning results, achieved beam performance and initial operating experience of the SNS linac will be presented.
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| MOP001 | Pressurized Hydrogen-Filled Linacs for Muon Cooling | linac, collider, radiation, scattering | 28 | ||
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New techniques for muon ionization cooling require low-Z energy absorber, strong magnetic fields for focusing and emittance exchange, and high gradient RF cavities to replace the energy lost in the absorber. RF cavities pressurized with hydrogen gas are being developed to provide the most muon beam cooling possible in the short lifetime of the muon. We report the status of the cavity development, including the breakdown suppression due to the gas and new results showing that pressurized cavities show no degradation of performance in strong magnetic fields. We also comment on the development of the designs of the associated muon cooling linacs.
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| MOP006 | A Bunch Compressor for the CLIC Main Beam | radiation, electron, synchrotron, synchrotron-radiation | 40 | ||
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The second bunch compressor chicane in the main beam line of the multi TeV linear collider CLIC is foreseen to compress the electron bunches from 250 μm to 30 μm. It is specified that the emittance growth in this chicane, which is mainly due to incoherent and coherent synchrotron radiation, should not exceed 30 nm·rad in the horizontal plane and 1 nm·rad in the vertical plane. To achieve these values the chicane layout and the optics functions have been optimized and the influence of shielding due to the vacuum chamber including resistive wall wake fields has been studied. A chicane layout and the corresponding electron beam parameters are presented, which allow to preserve the emittance within the specifications.
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| MOP007 | Turn Around Loop and Chicane for Bunch Compression and Path Length Tuning in the CLIC Drive Beam | electron, kicker, simulation, dipole | 43 | ||
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The phase feedback of the CLIC drive beam consists of phase and energy measurement stations in front of the turn around loops and chicanes for bunch compression and path length correction behind the loops. The chicanes are foreseen to compress the bunches from 4 mm to 0.4 mm and should allow a path length tuning of at least 0.1 mm. Suitable layouts for the turn around loops and the chicanes and results of beam dynamics simulations including incoherent and coherent synchrotron radiation are presented.
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| MOP009 | Dragon-I Linear Induction Accelerator | induction, electron, cathode, linac | 49 | ||
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The best quality induction linac in the world, named Dragon-I, has been built at Institute of Fluid Physics, China Academy of Engineering Physics. It can produce 2.5~3kA high current electron beam with energy of 20MeV and pulse width of 70ns. The spot size of about 1mm diameter has been achieved with beam current greater than 2.5kA. The design of Dragon-I facility is introduced briefly. The commissioning and results of Dragon-I are presented in the paper including the most recent time resolved measurements of beam parameters.
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| MOP020 | Status of the PITZ Facility Upgrade | gun, cathode, diagnostics, booster | 76 | ||
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The upgrade of the Photo Injector Test Facility at DESY in Zeuthen towards the PITZ2 stage is continuously ongoing. In Spring 2006, an intermediate stage was taken into operation (PITZ1.6), including a new gun cavity that has been tuned and conditioned. Currently, three new emittance measurement systems are being installed along the beamline. After their commissioning, studies of the emittance conservation principle will be possible when using the available booster cavity. In the paper, the results of the RF commissioning of the new gun and the first beam measurements using recently installed diagnostics devices will be presented. The ongoing developments of further new diagnostics components will be discussed as well.
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| MOP031 | Beam Distribution System for the MSU-RIA Driver Linac | kicker, linac, target, simulation | 106 | ||
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The proposed Rare Isotope Accelerator (RIA) facility will deliver up to 400 kW of any stable isotope to multi-target areas to create radioactive ion beams using either Isotope Separation On Line or Particle Fragmentation methods. Operational and programmatic efficiency will be best served by a system that can simultaneously distribute the beam current over a large dynamic range to several targets. The proposed RIA beam switchyard uses an rf kicker-magnetic septum system to distribute the beam to multi-target areas on a micro-bunch by micro-bunch basis. The micro-bunches can be differentially loaded in the RIA driver linac front end utilizing a scheme similar to that successfully used at Mainz and JLAB CEBAF facility. In these cases, consecutive electron micro-bunches are deflected by an rf kicker and their intensity separately adjusted through variable apertures with an identical second rf kicker returning the micro-bunches on-axis. The feasibility of using a similar system in RIA driver linac front end was explored. The overall concept of the RIA beam distribution system including the differential bunch loading system and the results of the beam dynamics studies will be presented.
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| MOP045 | Performance of SNS Front End and Warm Linac | linac, beam-losses, SNS, focusing | 145 | ||
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The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006. Injector and warm linac performance results will be presented including transverse emittance evolution along the linac, longitudinal bunch profile measurements at the beginning and end of the linac, and the results of a beam loss study.
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| MOP046 | Commissioning of the 7-MeV/u, 217-MHz Injector Linac for the Heavy Ion Cancer Therapy Facility at the University Clinics in Heidelberg | ion, rfq, linac, ion-source | 148 | ||
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A clinical synchrotron facility designed by GSI for cancer therapy using energetic proton and ion beams (C, He and O) is under construction at the university clinics in Heidelberg, Germany. In this contribution the current status of the injector linac is reported. The installation and commissioning of the linac is performed gradually in three steps for the ion sources and the LEBT, the 400 keV/u RFQ and the 7 MeV/u IH-type drift tube linac. Two powerful 14.5 GHz permanent magnet ECR ion sources from PANTECHNIK as well as the LEBT and the linac RF system have been installed in Heidelberg between November 2005 and March 2006. A test bench with versatile beam diagnostics elements has been designed and installed for the commissioning phase. In April 2006 the two ion sources produced the first ion beams on the site. Extensive RFQ tests using proton beams have been performed at test benches at the IAP and at GSI already during 2004-2006. The 1.4 MW 217 MHz amplifier for the IH tank has also been commissioned at a test setup at GSI in advance to the installation in Heidelberg. The RF tuning of the 20 MV IH-DTL cavity is performed by the IAP in close cooperation with GSI.
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| MOP047 | An RFQ-Decelerator for HITRAP | rfq, ion, linac, vacuum | 151 | ||
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The HITRAP linac at GSI will decelerate ions from 5 MeV/u to 6 keV/u for experiments with the large GSI Penning trap. The ions are decelerated at first in the existing experimental storage ring (ESR) down to an energy of 5 MeV/u and will be injected into a new Decelerator-Linac consisting of a IH-structure, which decelerates down to 500keV/u, and a 4-Rod RFQ , decelerating to 5 keV/u. The properties of the RFQ decelerator and the status of the project will be discussed.
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| MOP051 | Development of an Intense Neutron Source FRANZ in Frankfurt | rfq, proton, space-charge, ion | 159 | ||
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The Stern-Gerlach-Center recently founded at the University of Frankfurt gives the possibility for experiments in accelerator physic, astrophysic and material sience research. It is planned to develop an intense neutron generator within the next 4 years. The proton driver linac consists of a high voltage terminal already under construction to provide primary proton beam energies of max. 150 keV. A volume type ion source will deliver a DC beam current of 100-250 mA at a proton fraction of 90%. A low energy beam transport using two solenoids will inject the proton beam into an RFQ while a chopper at the entrance of the RFQ will create a pulse length of 50 ns and a repetition rate up to 250 kHz. A drift tube cavity for the variation of the beam energy in a range of 1.9 – 2.4 MeV will be installed downstream of the RFQ. Finally a bunch compressor of the Mobley type forms a proton pulse length of 1 ns at the Li target. The maximum energies of the neutrons being adjustable between 100 keV and 500 keV by the primary proton beam. The detailed concept of the high current injector, numerical simulation of beam transport and losses will be presented together with first experimental results.
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| MOP054 | Status of the SARAF Project | rfq, ion, ion-source, diagnostics | 168 | ||
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Soreq NRC recently initiated the establishment of SARAF – Soreq Applied Research Accelerator Facility. SARAF will be a multi-user facility for basic, medical and biological research, non-destructive testing (NDT) and research, development and production of radio-isotopes for pharmaceutical purposes. An on going major activity is research and development of high heat flux (up to 80 kW on a few cm2) irradiation targets. 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. The commissioning of the Phase I of SARAF (full current, energy up to 4-5 MeV) is taking place during 2006 at Soreq. This paper describes the SARAF project and presents commissioning of the normal conducting injector (i.e., ECR ion source and RFQ). Test results of the β=0.09 half wave superconducting resonators are presented, and resonator geometry improvements with respect to electron multipacting behavior is discussed. An outlook on the project regarding reaching the final energy of 40 MeV is given.
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| MOP055 | Transport of LANSCE-Linac Beam to Proposed Materials Test Station | target, quadrupole, diagnostics, dipole | 171 | ||
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Refurbishment of Experimental Area A and installation of a Materials Test Station is planned at the Los Alamos Neutron Science Center (LANSCE). This paper describes the beamline to transport 800-MeV protons from the accelerator to Area A. The beamline has the minimum number of quadrupoles necessary to achieve the desired instantaneous beam parameters at the target, the appropriate beam-centroid excursions at the split target for painting the two target halves, and a beam-centroid crossover upstream of the target to facilitate shielding of upstream components from backstreaming neutrons. Options in the composition of the raster-magnet section represent trade-offs between the number of magnets and the severity of the effects of magnet failures. Beam diagnostics are an integral part of the beamline design. Instantaneous and painted beam sizes at the target can be inferred by observing the beam at properly chosen upstream locations. A beamline spur to a tune-up beam dump is planned.
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| MOP058 | Heavy-Ion-Beam Emittance Measurements at the GSI UNILAC | ion, simulation, linac, heavy-ion | 177 | ||
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The GSI UNILAC, a linac for high current heavy ion beams, serves as an injector for the synchrotron SIS 18 and hence being a part of the future FAIR (Facility for Antiproton and Ion Research) project. The UNILAC post stripper section consists of an Alvarez accelerator with a final energy of 11.4 MeV/u. In order to meet the requirements of the FAIR project (15emA U28+, transversal normalised emittances of ex = 0.8 and ey = 2.5 mm mrad) a part of the UNILAC upgrade program is the increase of the beam brilliance. A detailed understanding of the correlation between space charge forces and focusing during acceleration of high intensity ion beams is necessary. A suited quantity to study is the beam brilliance dependency on the phase advances in the Alvarez section. Measurements are planned in 2006 and coincide with the beam dynamics work package of the European network for High Intensity Pulsed Proton Injector (HIPPI). Results of the measurements are presented as well as corresponding beam dynamics simulations.
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| MOP060 | A New LEBT and RFQ Radial Matcher for the UNILAC Front End | rfq, ion, ion-source, heavy-ion | 183 | ||
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The UNILAC heavy ion accelerator will serve as a high current injector for the future FAIR accelerator complex of GSI. This requires to inject 2.7x1011 ions/0.1x10-6s of U28+ into the existing synchrotron (SIS). Additionally, the UNILAC serves in multi beam operation experiments with high duty factor beams of different species. To meet all future demands a dedicated upgrade programme of the UNILAC is in work. This paper focuses on front end improvements. A new beam transport system will provide achromatic deflection and high mass resolution for the heavy ion beams from both existing ion source terminals. A new terminal for high current ion sources with a straight line solenoid based beam channel will be added. E.g. U3+ and U4+ ions with and a total beam current of 55mA will be injected into the RFQ for a maximum intensity yield of U4+-beam at the exit. To optimize the total front end beam transmission a redesigned radial input matcher of the RFQ is already implemented. It enables a smoother RFQ input matching of the high current beam resulting in smaller beam diameter and in lower particle losses. Beam measurements comparing old and new input radial matchers are presented.
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| MOP061 | The 70-MeV Proton Linac for the Facility for Antiproton and Ion Research FAIR | proton, linac, rfq, simulation | 186 | ||
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A significant part of the experimental program at FAIR is dedicated to antiproton (pbar) physics requiring up to 7·1010 cooled pbars per hour. Taking into account the pbar production and cooling rate, this is equivalent to a primary proton beam of 2·1016 protons per hour to be provided by a 70 MeV proton linac preceding two synchrotrons. It has to deliver a pulsed proton beam of 70 mA of 36 μs duration at a repetition rate of 4 Hz. The normalized transverse emittances must not exceed 2.8 mm mrad and the total relative momentum spread must be less than 0.1%. The normal conducting DTL comprises 12 Crossed-bar H-cavities (CH) fed by six rf-power sources in total. The basic layout of the linac as well as the overall cost estimate has been completed including several reviews by external committees. A technical report has been completed in May 2006. This paper gives a general overview on the status of the project.
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| MOP063 | Deceleration of Highly Charged Ions for the HITRAP Project at GSI | ion, rfq, linac, heavy-ion | 189 | ||
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The highly charged heavy ion trap (HITRAP) project at GSI is a funded mid term project and is planned to be operational end of 2007. Highly charged ions up to U92+ provided by the GSI accelerator facility will be decelerated from 4 MeV/u down to 6 keV/u and subsequently be injected into a large Penning trap for further deceleration and phase space cooling. The deceleration is done in a combination of the GSI experimental storage ring (ESR) and a linac based on an IH-structure and a RFQ. In front of the decelerator linac a double drift-buncher-system provides for phase focusing and a final de-buncher integrated in the RFQ-tank reduces the energy spread in order to improve the efficiency for beam capture in the cooler trap. The paper reports the beam dynamics design along the entire decelerator down to the trap injection point, as well as and the status of the cavities. Finally the time schedule and ESR and linac commissioning are discussed.
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| MOP064 | Emittance Preservation for the Curved ILC Main Linac | linac, coupling, quadrupole, alignment | 192 | ||
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It is envisaged in Baseline Configuraation Document that the main linear accelerator of ILC will follow the earth curvature instead of being laser-straight. Beam based alignments will be imperative for preserving the small vertical beam emittances through the main linac. Various beam based algorithms have been developed during the last decade. However, most of the simulation studies assumed the straight geometry of the linac. In this work we present the results on single bunch emittance dilution in the curve ILC main linac, using Dispersion Free Steering under the nominal misalignment of the beam line components. We present the comparison of the curve linac with laser stright geometry. We have studied the sensitivity of the DFS to the various misalignments and also considered the effect of incoming beam jitter and quadrupole vibration jitter. Further, robustness of DFS to the failure of corrector magnets or BPM is investigated. The beneficial effect of the dispersion bumps on the emittance dilution performance is also discussed.
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| MOP066 | Wake Fields and Beam Dynamics Simulations for the 3.9-GHz Cavities of the ILC | simulation, luminosity, dipole, damping | 196 | ||
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Crab cavities are used for the ILC in order to increase the luminosity of the colliding beams. These cavities operate at the 3rd harmonic of the accelerating frequency (1.3GHz). We study the LOM (Lower Order Modes) and HOM (Higher Order Modes) excited by the beam. The corresponding wake field is calculated and simulations are conducted on the beam dynamics of the interaction of the wake field with the multi-bunch beam train.
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| MOP067 | Higher Order Mode Wakefield Simulations and Beam Dynamics Simulations in the ILC Main Linacs | linac, simulation, electron, superconductivity | 199 | ||
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The progress of approximately 3000 electron (and positron) bunches down the main linacs of the ILC (International Linear Collider) can readily give rise to dipole modes which distrupt the progress of the beam. We investigate the transverse modes which are excited and monitor the resulting emittance dilution which occurs down the linac. At present there are two design configurations for the ILC: the BCD (Baseline Configuration Design) and the ACD (Alternate Configuration Design). We investigate the wake fields and beam dynamics for both configurations. In particular, the influence of trapped modes on the emittance of the beam is studied.
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| TU1002 | Technologies Toward a 100-kW Free-Electron Laser | wiggler, electron, gun, extraction | 205 | ||
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The challenges of a high-average-power (100 kW and above) FEL are not insurmountable. Some of these challenges however require technological solutions beyond the incremental improvements of existing mature technologies. Efforts are underway to develop novel technologies that could lead to a new level of FEL performance, e.g. 100-kW average power. These technologies include a high-average-current RF photo-injectors, spoke resonator RF cavities with energy recovery, high-gain amplifiers driven by high-brightness electron beams, beam-breakup instability suppression, and new concepts of tapered wiggler designs, e.g. stair-step taper, for efficient energy extraction. In this talk, these technologies, potential benefits and issues will be discussed.
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| TU1004 | Development of High-Current, High-Duty-Factor H- Injectors | SNS, ion, electron, plasma | 213 | ||
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SNS, FNAL, and CERN have projects that require the production of H- beams with increased intensity and increased duty factors. The most demanding requirements are set by SNS, which plans to upgrade its power to 3 MW. This power level requires a LINAC peak current of 59 mA, which results from an RFQ input current between 67 and 95mA when injecting with rms-emittances between 0.20 and 0.35 Pi-mm-mrad, respectively. Predicted downstream losses exclude the use of higher emittance beams. Ion source lifetime and reliability requirements are also stringent to meet the 99.5% availability goal for the injector of a user facility with 95% availability. LEBT options are currently being studied to optimally match the ion source output into the RFQ with a minimal distortion of the beam emittance. Several ion source and LEBT options under consideration will be discussed.
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| TU2004 | Results on the Beam Commissioning of the Superconducting-RFQ of the New LNL Injector | rfq, simulation, ion, beam-losses | 227 | ||
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A new injector for the heavy ion superconducting linac ALPI has been built at LNL. This new accelerator, named PIAVE, is designed to accelerate ions with A/Q=<8.5 up to 1.2 MeV/u. The main components are an ECRIS source operating on a high voltage platform, a three harmonic buncher, a superconducting RFQ cryomodule containing two bulk niobium structures and two QWR cryomodules housing 4 cavities each. In the last year the injector has been commissioned, with O, Ar, Ne and Xe beams, and put into operation. The beam performances, and the results of longitudinal and transverse emittance measurements will be shown and compared with simulations. Neon and argon beams have been delivered to the experiments (after acceleration with PIAVE and ALPI) for a total of about 400 hours. It should be noted that this is the first superconducting RFQ in operation; the design opportunities offered by this technology for a wider field of applications will be briefly discussed. The heart of these opportunity is given by the high intervane voltage in a cw RFQ (PIAVE can operate cw with an intervane voltage higher than 250 kV).
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| TU3001 | High-Current Proton Beam Investigations at the SILHI-LEBT at CEA/Saclay | ion, proton, space-charge, ion-source | 232 | ||
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For the injection of a high current proton beam into the future proton LINAC at GSI for FAIR the ion source and the low energy beam transport system have to deliver a 100 mA proton beam with an energy of 95 keV within an acceptance of 0.3 mm mrad (normalized, rms) at the entrance of the RFQ. Besides the ion source a 2-solenoid focusing system is foreseen as an injection scheme for the subsequent RFQ. The beam parameters of the SILHI ion source and the 2-solenoid LEBT setup generally meet these requirements. Therefore joint emittance measurements on various beam parameters have been performed at the end of the LEBT system. In the frame work of the design study for the future proton LINAC it was a unique possibility to investigate the injection of a high current proton beam into a low energy beam transport system under the influence of space charge. The measurements reveal that a proton current of 100 mA can be achieved at the end of the LEBT while the emittance (95 %, rms, normalized) is as high as 0.3 to 0.5 mm mrad.
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| TUP008 | The Low Emittance Photoinjector in Tsinghua University | cathode, gun, laser, electron | 259 | ||
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A photocathode rf gun system is under developing in Tsinghua University for Thomson scattering. The microwave properties and the high power processing of this rf gun were finished. The UV laser system can provide a 266nm laser pulse with 1~10ps and 200μJ photo energy per pulse. The beam experiments are under way. This paper gives a general description of this photocathode rf gun and its preparation.
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| TUP031 | Beam Dynamics Studies on the ISAC-II Superconducting Linac | linac, acceleration, bunching, diagnostics | 312 | ||
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The ISAC-II superconducting linac is presently in the beam commissioning phase. The linac lattice consists of modules of four quarter wave cavities and one superconducting solenoid. Beam steerers between cryomodules compensate for steering effects due to misalignments in the solenoids. Beam dynamics aspects of linac commissioning will be highlighted.
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| TUP038 | Status of the Sparc Photoinjector | laser, gun, electron, cathode | 333 | ||
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The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam have been installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We will report also about first tests made on RF gun and on the emittance meter device. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials . We will also discuss studies on solenoid field defects, beam based alignments and exotic electron bunch production via blow-out of short laser pulses.
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| TUP039 | Two-Charge-State Injector for a High Power Heavy-Ion Linac* | ion, linac, heavy-ion, rfq | 336 | ||
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A permanent magnet (PM) ECR ion source and following low energy beam transport (LEBT) system with the capability to deliver two-charge-state heavy-ion beams (2Q-LEBT) for high-power linacs is being prototyped at Argonne. The injector consists of the PM ECR ion source, transport line with beam diagnostics including emittance measurements and a multi-harmonic buncher. Recently the ECR ion source has been installed on a high voltage platform to increase the accelerating voltage up to the design value of 100 kV. The unique feature of the 2Q-LEBT layout is that the charge separation is performed off of the platform after acceleration of a multi-component ion beam. This layout allows us to analyze and recombine two-charge-state beams using an achromatic bending system. Improvements of the PM ECR performance and beam optics studies based on measurements of various heavy-ion beams will be discussed in this paper.
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*This work was supported by the U. S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38 |
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| TUP042 | A Proposal for Post Acceleration, Matching and Measuring the H- Ion Beam at CERN's Linac 4 Test Stand | linac, simulation, ion, rfq | 343 | ||
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CERN's proposed future Linac 4 is a 160 MeV H- Linac injecting into the Proton Sychrotron Booster. We propose that the ion source parameters (80mA, 500us pulse length, 2Hz repetition rate, 0.25 mm.mrad normalised emittance at 1 σ) may be achieved by improving an existing 2MHz RF multicusp source. In this report, we explain the proposal to post-accelerate the beam from 35keV to 95keV, and to focus the beam into the RFQ with solenoids, with the aimof avoiding substantial emittance growth. Finally, details of the diagnostics required to test the source are given.
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| TUP046 | Experimental Studies of Electrostatic and Solenoidal Focusing of Low-Energy, Heavy-Ion ECRIS Beams at the NSCL/MSU | dipole, focusing, ion, injection | 352 | ||
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Replacement of the focusing solenoids between both ECR Ion Sources and the beam analysis dipoles with electrostatic triplets has resulted in a large increase in net accelerator output. 2D emittance scans explain some but not all of this increase. Further improvement is anticipated with a new optical device consisting of an electrostatic quadrupole doublet-octupole-doublet-magnetic sextupole arrangement, which has been built and is being tested in place of a triplet. Motivations and results of measurements and operating experience are discussed.
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| TUP057 | A Compact, Normal-conducting, Polarized Electron, L-band PWT Photoinjector for the ILC | electron, cathode, vacuum, gun | 376 | ||
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The International Linear Collider (ILC) needs a polarized electron beam with a low transverse emittance. High spin-polarization (>85%) is attainable with a GaAs photocathode illuminated by a circularly polarized laser. Low emittance is achievable with an rf photoinjector. DULY Research has been developing an rf photoinjector called the Plane Wave Transformer (PWT) which may be suitable as a polarized electron source for the ILC. A 1+2(1/2) cell, L-band PWT photoinjector with a coaxial rf coupler is proposed for testing the survivability of GaAs cathode. It is planned to produce a high-aspect-ratio beam using a round-to-flat-beam transformation. In addition to its large vacuum conductance, the modified PWT has a perforated stainless steel sieve as a cavity wall, making it easy to pump the structure to better than 10-11 Torr at the photocathode. An L-band PWT gun can achieve a low emittance (0.45 mm-mrad for a 0.8nC round beam) with a low operating peak field (<25MV/m). A low peak field is beneficial for the survivability of the GaAs photocathode because electron backstreaming is greatly mitigated.
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| TUP058 | The RF Design of a HOM Polarized RF Gun for the ILC | gun, cathode, electron, vacuum | 379 | ||
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The ILC requires a polarized electron beam. While a highly polarized beam can be produced by a GaAs-type cathode in a DC gun of the type currently in use at SLAC, JLAB and elsewhere, the ILC injector system can be simplified and made more efficient if a GaAs-type cathode can be combined with a low emittance RF gun. Since this type of cathode is known to be extremely sensitive to contamination including back bombardment by ions, any successful polarized RF gun must have a significantly improved operating vacuum compared to existing RF guns. We present a new RF design for an L-Band NC RF gun for the ILC polarized electron source. This design incorporates a higher order mode (HOM) structure, whose chief virtue in this application is an improved conductance for vacuum pumping on the cathode. Both 2-D and 3-D models have been used to optimize the RF parameters with two principal goals: first to minimize the required RF power; second to reduce the peak surface field relative to the field at the cathode in order to suppress field emitted electron bombardment. The beam properties have been simulated initially using PARMELA. Vacuum and cooling considerations for this design are discussed.
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| TUP059 | Photoinjector Production of a Flat Beam with Transverse Emittance Ratio of 100 | quadrupole, simulation, laser, electron | 382 | ||
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The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultrashort x-ray pulses or Smith-Purcell free electron lasers. In this paper, we report on the experimental generation of a flat beam with a measured transverse emittance ratio of 100±20 for a bunch charge of ≅0.5~nC*. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws. Possible improvement of the experiment along with application for such a flat beams are discussed
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* P. Piot, Y.-E. Sun and K.-J. Kim, Phys. Rev. ST Accel. Beams 9, 031001 (2006) |
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| TUP062 | Experimental Optimization of TTF2 RF Photoinjector for Emittance Damping | booster, gun, laser, damping | 391 | ||
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To get lasing and saturation at FEL facilities, we should generate high quality electron beams with a low emittance, a high peak current, and a low energy spread. Generally, the RF photoinjector is a key component to generate such a high quality beams. During DESY TESLA Test Facility (TTF) phase 2 commissioning, we optimized our L-band RF photoinjector and bunch compressor by comparing measurement results and simulation ones. In this paper, we describe our optimization experiences to get about 1.1 mm.mrad transverse normalized emittance for 1.0 nC single bunch charge and 4.4 ps RMS bunch length from TTF phase 2 RF photoinjector.
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| TUP063 | Commissioning of a New S-Band RF Gun for the Mark III FEL Facility at Duke University | gun, cathode, linac, electron | 394 | ||
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At the Free Electron Laser (FEL) Laboratory of Duke University, there is an S-band linac based Mark III FEL facility which can supply coherent FEL photon in the infrared wavelength range. To supply high quality electron beams and to have excellent pulse structure, we installed one S-band RF gun with the LaB6 cathode for the Mark III FEL facility in 2005. Its longest macropulse length is about 6 us, and maximum repetition rates of macropulse and micropulse are 15 Hz and 2856 MHz, respectively. Therefore our new RF GUN can generate maximum 17142 bunches within a bunch train and maximum 257130 bunches within one second. In this paper, we describe recent commissioning experiences of our newly installed S-band RF GUN for the Mark III FEL facility.
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| TUP065 | Longitudinal Beam Dynamic Simulation of S-DALINAC Polarized Injector | electron, gun, simulation, polarization | 400 | ||
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In future, a polarized gun will extend the experiment possibilities of the superconducting recirculating linear electron accelerator S-DALINAC. Therefore a new injector has to be designed where a new 100 keV polarized source SPIN will be added to the present unpolarized thermionic source. A polarization degree of 80%, a mean current of 60 uA and a 3 GHz cw structure are required. All features of the new source will be tested and measured at an offset beam line. The longitudinal beam dynamics of the injector are studied. The electron bunch length behind the gun is about 50 ps. The electrons has to be bunched to 5 ps for capturing the electrons to the main linac. Therefore a chopper/prebuncher system based on the devices used at MAMI is designed. The system consists of a harmonic chopper cavity, a slit, a first and a second harmonic prebuncher. The recent simulation results will be presented here.
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| TUP066 | Particle Dynamics Calculations and Emittance Measurements at the FETS | simulation, rfq, ion, ion-source | 403 | ||
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High power proton accelerators in the MW range have many applications including drivers for spallation neutron sources, neutrino factories, transmuters (for transmuting long-lived nuclear waste products) and energy amplifiers. In order to contribute to the development of HPPAs, 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 front end test stand is to demonstrate the production of a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV with sufficient beam quality. An overview on the status of the project together with the results of numerical simulations of the particle dynamics from the ion source to the RFQ exit will be presented. The particle distributions gained from the particle dynamics simulations will be compared with recent measurements of the transversal beam emittance behind the ion source and the results discussed.
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| TUP073 | Simulations of RF Errors in the SNS Superconducting Linac | linac, simulation, SNS, beam-losses | 423 | ||
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Minimizing beam emittance growth in the SNS superconducting linac due to RF errors, either correlated or uncorrelated, is essential since it can lead to beam loss in the linac and in the downstream ring. From multi-particle simulation studies of both matched and mismatched linac lattices, for the design peak beam current of 38 mA, as well as a typical commissioning beam current of 20 mA, we conclude that the linac may tolerate much higher non-correlated RF errors, especially in the second half of the superconducting linac, where errors in synchronous phase up to 10 degrees and that of cavity field amplitude up to 10% is acceptable. However, tolerance to correlated RF errors in the linac is within only 0.5 degree and 0.5 %, from simulations using a simple longitudinal linac model. Beam parameter measurement results acquired during linac beam commissioning confirmed the simulations.
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| TUP075 | Automatic Transverse and Longitudinal Tuning of Single and Multiple Charge State Ion Beams | linac, beam-losses, focusing, simulation | 429 | ||
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Extensive end-to-end beam dynamics simulations of the RIA driver linac using the code TRACK and including all sources of machine errors and detailed beam loss analysis* showed that the losses could be significantly reduced for a fine-tuned linac. For this purpose we have developed an automatic longitudinal tuning proceedure for multiple charge state heavy-ion beams.** For a complete tuning tool, we have recently developed an automatic transverse tuning proceedure to produce smooth transverse beam dynamics by minimizing the RMS beam sizes after each focusing period. We have also extended the automatic longitudinal proceedure to produce smooth longitudinal beam dynamics for single and multiple charge state ion beams. In addition to improving an existing tune, this powerful automatic beam tuning tool can be used to retune the linac and restore the beam after one or more elements failures and to develop new tunes for ion beams with different Q/A ratios. After presenting the method, the results from some applications will be presented and discussed.
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* P. Ostroumov, V. Assev and B. Mustapha, Phys. Rev. ST-AB 7 (2004) 090101 |
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| TUP078 | Status of the End-to-End Beam Dynamics Simulations for the GSI UNILAC | rfq, simulation, ion, synchrotron | 438 | ||
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The heavy ion high current GSI linac UNILAC serves as an injector for the synchrotron SIS18. The UNILAC mainly consists of a High Current Injector (HSI), the stripper section at 1.4 MeV/u, and the Alvarez postaccelerator (11.4 MeV/u). During the last years the systematic experimental and numerical studies resulted in an increase of the U73+ beam intensity of up to a factor of seven. The needs of the FAIR project (Facility for Antiproton and Ion Research at Darmstadt) require further improvement of the beam brilliance coming from UNILAC up to a factor of five. End-to-end beam dynamics simulations with the DYNAMION code have already been started. The general goal is to establish a simulation tool which can calculate the impact of the planned upgrade measures on the performance of the whole UNILAC. The results of the HSI calculations including influence of the beam intensity on the beam parameters (current, emittance, Twiss-parameters) at the stripper section are presented. Recent calculations and measurements of the beam matching to the Alvarez section under space charge conditions are discussed in the paper.
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| TUP079 | RIAPMTQ/IMPACT: Beam-Dynamics Simulation Tool for RIA | linac, simulation, beam-losses, rfq | 441 | ||
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We describe a multiple-charge-state simulation-code package for end-to-end computer simulations of the RIA heavy-ion driver linac, extending from the low-energy beam transport after the ECR source to the end of the linac. The work is being performed by a collaboration including LANL, LBNL, ANL, and MSU. The package consists of two codes, the code RIAPMTQ for the linac front end including the LEBT, RFQ, and MEBT, and the code IMPACT for the superconducting linac. This code package has been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The simulation tool will allow high-statistics runs on parallel supercomputing platforms, such as NERSC, as well as runs on desktop PC computers for low-statistics design work. It will address an important near-term need for the RIA project, allowing evaluations of candidate designs with respect to beam-dynamics performance including beam losses, which can be compared with predictions of other existing simulation codes.
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| TUP080 | Tuning the Magnetic Transport of an Induction Linac Using Emittance | simulation, background, diagnostics, optics | 444 | ||
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The Lawrence Livermore National Laboratory Flash X-Ray (FXR) machine is a linear induction accelerator used to produce a nominal 20-MeV, 3-kA, 60-ns pulse width electron beam for hydrodynamic radiographs. A common figure of merit for this type of radiographic machine is the x-ray dose divided by the spot area on the bremsstrahlung converter. Several characteristics of the beam affect the minimum attainable x-ray spot size. The most significant are emittance, chromatic aberration, and beam motion. FXR is in the midst of a multi-year optimization project to reduce the spot size. This paper describes the effort to reduce beam emittance by adjusting the fields of the transport solenoids. If the magnetic transport is not correct, the beam will be mismatched and undergo envelop oscillations increasing the emittance. We measure the divergence and radius of the beam in a drift section after the accelerator by imaging the optical transition radiation (OTR) and beam envelope on a foil. These measurements are combined with transport simulations to calculate an emittance. Relative changes in the emittance can be quickly estimated allowing for an efficient, real-time study.
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| TUP081 | Impact of a RF Frequency Change on the Longitudinal Beam Dynamics | linac, focusing, acceleration, ion | 447 | ||
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A frequency jump in a high-intensity linac could have some impact on the longitudinal beam dynamics and could therefore introduce some filamentation and even some beam loss if the transition is not done properly. This point is especially important when comparisons of cavity performances are performed. We show in this paper two techniques in order to render transparent for the beam such frequency jump. A few examples which show the efficiency of the two techniques are given.
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| TUP085 | Beam Simulations for the MSU-RIA Driver Linac Using IMPACT Code | linac, simulation, beam-losses, ion | 457 | ||
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Previous end-to-end three-dimensional (3D) beam dynamics simulation studies at Michigan State University (MSU) utilizing the LANA code and including experimentally-based ion source beam parameters, alignment and rf errors, and the effect of charge-stripping foils have indicated that the MSU Rare Isotope Accelerator (RIA) driver linac has adequate transverse and longitudinal acceptances to accelerate light and heavy ions to final energies of ≥ 400 MeV/u with beam powers of 100 to 400 kW. Recently, to evaluate beam dynamics performance under various error scenarios with high statistics, the end-to-end 3D beam dynamics simulation studies for the driver linac were performed on the high performance parallel computers at MSU using the parallel code IMPACT that is an element of the advanced beam dynamics simulation tool: RIAPMTQ/IMPACT. The results of these beam dynamics studies will be presented.
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| TUP086 | Linac Code Benchmarking for the UNILAC Experiment | space-charge, simulation, linac, lattice | 460 | ||
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In the framework of the European network HIPPI (High Intensity Pulsed Proton Injectors) a linac code comparison and benchmarking program have been promoted. An intermediate goal is to compare different space charge solvers and lattice modelling implemented in each code in preparation of experimental validations from future measurements to be carried out at the UNILAC of GSI. In the last two years a series of different tests and comparisons among several codes (DYNAMION, HALODYN, IMPACT, LORASAR, PARMILA, PATRAN, PATH and TOUTATIS) have been undertaken. The quality of Poisson solvers has been evaluated and a number of code adjustments has been carried out to obtain the best agreement in terms of RMS moments. In this paper we report on the status of this program.
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| TUP088 | Benchmarking of Simulation Codes TRACK and ASTRA for the FNAL High-Intensity Proton Source | simulation, space-charge, rfq, proton | 466 | ||
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The FNAL High Intensity Proton Source is an 8-GeV superconducting H-minus Linac conceived with the primary mission of enabling 2 MW beam power from the Main Injector at 120 GeV for the Fermilab neutrino program. The main tool used for the design of this accelerator is the beam dynamics code TRACK developed by Argonne National Laboratory to fulfill the requirements of proton and heavy-ion linacs. ASTRA, developed by DESY (Hamburg, Germany) and mainly used for the design of electron photo-injectors, also offers the possibility to simulate acceleration of hydrogen ions. Benchmarking of TRACK and ASTRA is presented in this paper for a zero current and a 30 mA beam from the exit of the RFQ (2.5 MeV) to the end of the accelerating section (8 GeV).
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| TUP089 | Computer Simulations of a High-Current Proton Beam at the SILHI-LEBT | ion, proton, simulation, space-charge | 469 | ||
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For the injection of a proton beam into the future proton LINAC for FAIR the ion source and the low energy beam transport system have to deliver a 100 mA proton beam with an energy of 95 keV at the entrance of the RFQ within an acceptance of 0.3 π mm mrad (normalized, rms). A 2-solenoid focusing system is foreseen as an injection scheme. The beam parameters of the SILHI ion source and the 2-solenoid LEBT setup at CEA/Saclay fulfill these requirements. Therefore joint emittance measurements on various beam parameters have been performed at the end of 2005. This article presents the computer simulations of the ion source extraction and LEBT, which supplemented these measurements using the KOBRA3-INP computer code in order to study the influence of space charge effects. These simulations have been performed for various solenoid settings and for different space charge compensation degrees clearly revealing that the ion beam transport within the LEBT is influenced by space charge forces.
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| TUP092 | Emittance Exchange at FNPL | coupling, klystron, electron, pick-up | 478 | ||
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An experiment to attempt the exchange of the transverse emittance with the longitudinal emittance of the Fermilab/NICADD PhotoInjector electron beam is being developed. The emittance exchange occurs by placing a TM110 mode RF cavity in the maximum dispersive region of a magnetic chicane. Properly employed, the cavity's longitudinal shearing Electric field zeros the momentum spread at the cost of generating a non-zero betatron oscillation amplitude. We report on the beam line modeling, beam line design, the RF cavity design, present status as well as the future program.
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| TH1003 | Initial Commissioning Results from the ISAC-II SC Linac | linac, acceleration, ion, heavy-ion | 521 | ||
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TRIUMF has installed 20MV of superconducting heavy ion linac as part of the first phase of the ISAC-II project. The linac consists of five cryomodules each with four 106MHz quarter wave cavities and one superconducting solenoid. The cavities and ancillaries operate cw with a demonstrated peak surface field exceeding 30MV/m at 7W rf cavity power. The solenoid produces fields up to 9T. In an initial beam test with a single module cavity performance exceeded design by over 20%. The full linac was installed by early 2006 with full linac beam commissioning tests starting in April 2006. The linac hardware will be described and the commissioning tests and results will be summarized.
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| TH2001 | High-Power Couplers for Linear Accelerators | linac, vacuum, impedance, simulation | 531 | ||
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High power input couplers are a fundamental component of the linear accelerating structures and in particular of the superconducting structures. In fact, in this case, the power couplers function is not only the power transfer and the vacuum separation but includes also the thermal transition and the integrity of the cavity cleanliness. A lot of activity has been recently worked out in the framework of different project on both CW (KEK and Cornell) and pulsed (SNS and TTF) power couplers. Particular attention has been devoted to the design phase to take care about the thermo mechanical and electromagnetic performances, the multipacting thresholds, the preparation procedures and, last but not least, the cost that in the case of high energy linacs is a fundamental parameter. In this framework not only the design phase but also the conditioning of the couplers has stimulated different studies. Partial reviews of the existing designs and of the couplers characteristics will be presented taking into account the different challenges.
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| TH3001 | Photoinjectors R&D for Future Light Sources and Linear Colliders | gun, electron, cathode, laser | 549 | ||
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Linac-driven light sources and linear proposed colliders require high brightness electron beams. In addition to the small emittances and high peak currents, linear colliders also require spin-polarization and possibly the generation of asymmetric beam in the two transverse degree-of-freedom. Other applications (e.g. high power free-electron lasers) call for high duty cycle and/or angular-momentum-dominated electron beams (electron cooling). We review on-going R&D programs aiming at the production of electron beams satisfying these various requirements. We especially discuss R&D on photoemission electron sources (especially based on radio-frequency gun) along with the possible use of emittance manipulation techniques.
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| TH3002 | Normal-Conducting Energy Recuperator | electron, linac, free-electron-laser, optics | 554 | ||
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Energy recovery linacs (ERLs) for different applications were discussed intensively at last decade. The normal conducting RF ERLs offer the possibility to provide high average currents at relatively low beam energies and long electron bunches. The comparison of normal conducting and superconducting RF is described briefly. To illustrate some interesting features of normal conducting ERLs some details of design, operational experience and prospects of the Novosibirsk FEL ERL are presented.
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| THP083 | Generation of Ellipsoidal Beam Through 3-D Pulse Shaping of a Photoinjector Drive Laser | laser, simulation, electron, gun | 776 | ||
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Due to the linear space-charge force, an ellipsoidal beam is expected to have much smaller emittance in comparison with beams of other geometries, which is critical for many accelerator applications. Up to now, no practical way of generating such beams is available. In this paper we present a few schemes for 3-D laser pulse shaping that can be used to generate ellipsoidal laser pulses that in turn can be applied for generating ellipsoidal electron bunches from a photoinjector. Our simulations show that 3D laser pulse shaping can be realized through laser phase tailoring in combination with properly designed refractive and diffractive optics. Performance of an electron beam generated from such shaped laser pulses is compared with that of the ideal flat-topped and Gaussian electron bunches by numerical simulation, showing improvement in both beam dynamics and performance.
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| THP093 | Polyhedral Cavity for Superconducting Linacs | linac, coupling, collider, brightness | 803 | ||
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A polyhedral cavity structure has been devised for use in superconducting linacs. It has the same ellipsoidal side contour as a TESLA cavity but is configured as a polyhedron in its end view. Each segment of the polyhedron consists of a Nb foil bonded to a Cu wedge that has been machined to the desired ellipsoidal inner contour. There are no welds, and the seams between adjacent segments do not affect the high Q of the accelerating mode but block the azimuthal currents of deflecting modes. The power coupled into deflecting modes can be slot-coupled at the seams into dielectric-loaded waveguides integrated in the copper segments and conveyed to warm termination. The inner surface of each segment is accessible for polishing and characterization. It accommodates application of improved superconducting surfaces, such as the multi-layer thin-film Nb3Sn proposed by Gurevich. Refrigeration can be provided by gun-bored channels within the copper segments. The copper segments provide a rigid assembly that eliminates Lorentz detuning. The talk will discuss the mode properties and coupling strategies, the strategy for Nb/Cu bonding, and plans for building and testing of prototype cavities.
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| FR1002 | SPring-8 Compact SASE Source | electron, undulator, cathode, radiation | 813 | ||
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The 8-GeV Japanese XFEL Project has been funded in 2006. Construction is scheduled 2006-2010, first beam in 2010. In order to develop technology required to XFEL, we have been carrying out R&D program at RIKEN since 2002, where thelow emittance thirmionic-gun and various key technologies were developed. To verify technologies, SCSS Prototype Accelerator has been constructed. The first lasing was obserbed in the prototype accelerator at June 20 at 60 nm.
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SCSS-Web Site: www-xfel.spring8.or.jp. |
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