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| MO1002 | Commissioning and Initial Operating Experience with the SNS 1-GeV Linac | SNS, target, emittance, 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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| MO1003 | Commissioning of the J-PARC Linac | rfq, klystron, focusing, ion-source | 6 | ||
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rt in December, 2006. All the components have been installed in the linac tunnel and the klystron gallery, respectively. The preparation for the beam commissioning is under way as scheduled, except for the air-pressure control system, which delayed the powering of the cavities by one month. If no more serious trouble, the beam commissioning will start on schedule. The J-PARC linac comprises the 3-MeV, 324-MHz RFQ linac, the 50-MeV DTL, and the 181-MeV SDTL and the 400-MeV, 972-MHz ACS. It is unique by making use of many newly developed or invented accelerator technologies.
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| MO2001 | Status of the CLIC Test Facility (CTF3) | acceleration, klystron, beam-loading, extraction | 11 | ||
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The CTF3 project, being built within the frame-work of an international collaboration involving more than 12 institutions, is advancing as planned. To date, the electron linac with its sub-harmonic bunching system, the magnetic chicane for bunch-length variations, and the Delay Loop have been installed. The 1.5 GHz sub-harmonic bunching system with fast phase switching allows the longitudinal position of the bunches to be changed every 140 ns. This phase-coded beam has been successfully injected into the Delay Loop using an RF deflector and bunch interleaving of 140 ns long sub-bunch trains which double the bunch repetition frequency has been demonstrated in the extraction line. In addition to its role as a test bed for the CLIC RF power source, CTF3 is being used as a source of high-power RF at 30 GHz for the testing of CLIC accelerating structures. In this power-generating mode, about 100 MW of 30 GHz power is routinely extracted from the beam half-way up the linac by special-purpose power-extracting structures and transported to the high-gradient test area by low-loss waveguides. This paper describes the overall status of the CTF3 project and outlines the plans for the future.
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| MO3002 | Overview of TEM-Class Superconducting Cavities for Proton and Ion Acceleration | proton, ion, vacuum, cryogenics | 23 | ||
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Superconducting (SC) TEM-class cavities have been developed at laboratories and institututions worldwide for cw and pulsed proton and ion linac applications. New geometries spanning nearly the full velocity range from 0.1 < v/c < 0.8 include co-axial quarter- and half-wave and single- and multi-spoke cavities. Optimized designs have large beam acceptance, high shunt impedance and good microphonics properties. Rapidly evolving and improving clean surface processing techniques have been applied to TEM cavities where achieved surface fields and rf losses are comparable to the best results presently achieved in elliptical cavity designs. Recent results for a three-spoke cavity following hydrogen degassing after fabrication show very low rf losses even at high accelerating fields and now open the possibility for substantially reduced effective cryogenic load in 2 Kelvin, rather than the historically-used 4 Kelvin, operation. At present performance levels, SC TEM-class cavities constitute the technology of choice for most ion linac applications requiring cavities up to or beyond 60 percent of the speed-of-light.
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| MOP001 | Pressurized Hydrogen-Filled Linacs for Muon Cooling | emittance, 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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| MOP002 | Efficient Long-Pulse, Fully Loaded CTF3 Linac Operation | beam-loading, acceleration, klystron, gun | 31 | ||
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An efficient RF to beam energy transfer in the accelerating structures of the drive beam is on of the key points of the Compact Linear Collider (CLIC) RF power source. For this, the structures are fully beam-loaded, i.e. the accelerating gradient is nearly zero at the downstream end of each structure. In this way, about 96% of the RF energy can be transferred to the beam. To demonstrate this mode of operation, 1500 ns long beam pulses are accelerated in six fully loaded structures in the CLIC Test Facility (CTF3) Linac. In the paper we present the results of experimental studies on this mode of operation, compare them with theoretical predictions and discuss its potential use in CLIC.
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| MOP003 | A Shared Superconducting Linac for Protons and Muons | proton, factory, target, collider | 34 | ||
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A future Fermilab proton driver* based on TESLA superconducting linac modules can provide protons to produce the muons and also accelerate the muons to be used for a neutrino factory or muon collider. Recent advances in muon cooling** imply muon emittances that are compatible with the 1300 MHz accelerating structures that are the basis for the ILC design. In the example discussed here, H- ions are accelerated to 8 GeV in the superconducting linac, then stripped, stored and bunched in a ring while the linac cavities are rephased for muon acceleration. Then the protons are extracted from the ring to produce pions and muons which are cooled in about six hundred meters, accelerated to a few GeV and injected into the linac at the point for acceleration to add 7 GeV. By recirculating the muons in the constant frequency section of such a proton driver linac, even higher energies can be achieved quickly so that losses from muon decay are minimized. By adding additional refrigeration and RF power, the repetition rate of the linac can be increased to make large increases in the average flux of a neutrino factory and the average luminosity of a muon collider.
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*G. W. Foster and J. A. MacLachlan, Proceedings of LINAC 2002, Gyeongju, Korea |
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| MOP005 | Beam Dynamics for Intense L-band Electron Linac | electron, bunching, simulation, focusing | 37 | ||
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We are now developing an intense L-band electron linac with a traveling-wave accelerating structure for irradiation applications. It is capable to produce 10 MeV electron beams of 30 kW by a pulsed klystron of 25 MW with a 60 kW average power. Bunching and accelerating cavities operated with 2π/3 mode at 1.3 GHz are designed by the SUPERFISH code. Focusing solenoids are designed by the POISSON code. Using electromagnetic field configurations obtained by these codes, a simulational study on the beam dynamics is conducted by the PARMELA code. As results, the beam envelope supports a transmission efficiency over 91% with the E-gun current of 1.6 A.
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| MOP008 | Design and Performance of Optics for Multi-Energy Injector Linac | injection, optics, electron, quadrupole | 46 | ||
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Injector linac provides injection beams for four storage rings, KEKB high energy electron ring (HER), KEKB low energy positron ring (LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that common magnetic fields of bending magnets and quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for KEKB high energy electron ring (8 GeV, 1 nC/pulse) and PF electron ring (2.5 GeV, 0.1 nC/pulse) and present a performance of the multi-energy injector linac.
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| MOP009 | Dragon-I Linear Induction Accelerator | induction, emittance, electron, cathode | 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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| MOP012 | Upgrade Status and Commissioning of BEPCII Linac | positron, gun, klystron, electron | 55 | ||
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BEPCII- an upgrade project of the BEPC is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate (≥50 mA/min.). In five months from May 1st of 2005, we’ve installed and upgraded major parts of the machine, and then it ran for busy BSRF operation. We took a limited time to commission the machine and got a preliminary but satisfied result, the positron beam at the linac end was about 60mA. Now the linac is running smoothly, almost all design goals were reached. In this paper, we’ll present the upgrades for better beam quality, such as phasing system, beam feedback system, and report the present status of the BEPCII linac.
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| MOP013 | Low-Intensity, Pulsed-Beam Generation System Using the OPU Linac | electron, gun, radiation, cathode | 58 | ||
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An ultra low intensity pulsed electron beam generation system has been developed, which consists of an electron linear accelerator (linac), highly sensitive beam current monitors and beam profile monitors. The beam current has been attenuated to be about ten orders of magnitude weaker than the ordinary beam current by using several methods, e.g. the reduction of the cathode emission in an injector and the use of a narrow slit. The minimum beam charge so far obtained has been estimated to be about several attocoulomb in one beam macropulse. The beam from a linac is controllable, collimated and synchronized with the trigger signal of the linac. The features are much advantageous compared with those of β-rays from radioisotopes which have been used in low intensity beam irradiation experiments. The final goal of this work is to generate a single electron beam.
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| MOP015 | Linac Design for the FERMI Project | controls, laser, gun, electron | 61 | ||
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FERMI is a fourth generation light source under construction at Sincrotrone Trieste. This is based upon the conversion of the existing injector linac to a 1.2 GeV machine suitable to drive a seeded FEL. The linac will require significant improvements and the addition of several new accelerating modules. Important parameters are pulse to pulse energy stability and the jitter of the e-bunch time of arrival. This paper will cover the baseline design of the machine, as well as experimental results and the proposed technical solutions for the more critical sub-systems.
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| MOP016 | SRF Linac Solutions for 4GLS at Daresbury | damping, acceleration, electron, superconducting-RF | 64 | ||
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The proposed 4th Generation Light Source (4GLS) facility, anticipated to be located at Daresbury Laboratory in the UK, will extensively utilise Superconducting RF (SRF) Linacs for each stage of its multi-beam acceleration. IR, XUV and VUV FEL devices, and particularly the ability to combine these sources for users, provide a unique capability for this Energy Recovery Linac (ERL) based accelerator. The CW mode of operation for the SRF Linacs necessitates that adequate provision is made for delivering the required RF power and also damping of the beam induced HOMs to manageable levels. This paper outlines the RF requirements and proposed solutions for each of the 4GLS Linacs.
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| MOP017 | 4GLS Beam-Break-Up Investigations | focusing, recirculation, simulation, quadrupole | 67 | ||
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Beam Break Up (BBU) thresholds have been studied as part of the Linac focusing scheme for the proposed 4GLS accelerator. A graded gradient focusing scheme, with a triplet of quadrupoles between each of the modules within the Linac has been chosen. These quadrupoles are set-up in a defocusing – focusing – defocusing format with strengths of -1/2k, k, -1/2k. This value of k was altered and the BBU thresholds for the machine calculated using various BBU codes. Alternate cavity designs have also been investigated using CST’s Microwave Studio to see how the effects of higher order modes (HOMs) can be minimised whilst maintaining fundamental field flatness across theaccelerating cells. The number of cells/unit length and cell-to-cell geometries have also been parameterised and the corresponding BBU thresholds presented as a function of cavity geometry, with the intention of providing an optimum solution for 4GLS.
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| MOP018 | Upgrading the CEBAF Accelerator to 12 GeV: Project Status | controls, beam-transport, acceleration, dipole | 70 | ||
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Jefferson Lab is preparing to upgrade its 6 GeV Continuous Electron Beam Accelerator Facility (CEBAF) to 12 GeV as part of the 12 GeV Upgrade project. The doubled energy will significantly extend the scientific reach of the three existing Halls with upgraded experimental equipment, and will make possible a new research program in exotic mesons in a newly constructed fourth Hall. The acceleration of the present linacs will be roughly doubled through the addition of ten new cryomodules with performance ~5 times the original specification for CEBAF. The 2K helium plant will be roughly doubled; new rf systems, including digital controls, will be installed for the new cryomodules. The beam transport system’s capability will be doubled by strongly leveraging existing hardware (without incurring significant saturation) but must be enhanced with some replacement magnets, new power supplies, one new recirculation arc, and a beamline to the new Hall. Critical Decision 1 was approved by DOE for this project in February 2006. Technical status for the accelerator systems including R&D will be presented as well as the status of the 12 GeV Upgrade Project as a whole.
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| MOP019 | Methods to Reduce the Electron Beam Energy Spread at the S-DALINAC | electron, recirculation, controls, feedback | 73 | ||
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The S-DALINAC is a recirculating superconducting electron linac operating at 3 GHz. The accelerator delivers a cw beam with energies up to 130 MeV to serve electron scattering experiments where highest momentum resolutions, typ. below 1·10-4 are required. Current activities aim to reduce the energy spread of the accelerator by two methods: Long term drifts, mainly a result of temperature drifts, will be corrected by a feedback system which measures the energy variation of the extracted beam continuously using rf-monitors. By means of time-of-flight analysis in a modified beamline a correction signal can be generated as a feedback for the rf control of the accelerating cavities. This system was set-up recently and first results will be reported. Furthermore, the influence of short term fluctuations, e.g. triggered by micro-phonics, on the electron energy can significantly be reduced utilizing the inherent stability of a microtron, if the synchronous phase and longitudinal dispersion are chosen properly. The concept, particle simulations and the experimental verification will be shown as well as necessary modifications to the recirculation scheme to use it in an all-day operation.
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| MOP022 | Simulation and Design of a Small LIA Stand | electron, induction, simulation, gun | 82 | ||
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A small LIA experiment stand is designed and manufactured at Accelerator Lab, Tsinghua University. It consists of a thermal cathode DC gun, two induction acceleration cells, pulse power supply system, beam transportation and diagnostics. The electron gun can produce an electron beam of 80 ns, 1.2A and 80keV. Two induction cells accelerate beam energy up to 240keV. The time interval of each two pulses is 300 ns, and the beam pulse flat-top is 80ns. Simulations of the beam transportation by PARMELA code and the optimized results of the beam line will be presented in this paper.
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| MOP023 | Beam-Based Optics Correction for New Beam Transport Line from LINAC to Photon Factory in KEK | optics, luminosity, beam-transport, quadrupole | 85 | ||
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The e+/e- injector LINAC in KEK usually injects into four rings which are Low Energy Ring(LER) of KEKB(3.5GeV/e+), High Energy Ring (HER) of KEKB(8.0GeV/e-), Photon Factory(PF)(2.5GeV/e-) and Advanced Ring for pulse X-rays(PF-AR)(3.0GeV/e-). While LINAC continuously injects into LER and HER alternatively every about five minutes, both of KEKB rings usually storage almost full operating currents. Time for PF or PF-AR which includes switching time had taken about 20 minutes a several times in a day. This had made luminosity at KEKB lower. In summer of 2005, a part of transport line from LINAC to PF were renewed, in which a DC bending magnet only for PF apportions electron beam from the end of LINAC to the new line. We succeeded to reduce the occupancy time for PF injection to about five minutes and there is almost no affection to KEKB luminosity. In this paper optics of the new PF beam transport line is described. In practical performance there had been leakage magnetic field from ECS magnets in KEKB(e+) beam transport line neighboring the PF line. Furthermore we measured the horizontal dispersions along the line. We describe about the magnetic shielding and the optics correction.
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| MOP025 | Study on High-Current Multi-Bunch Beam Acceleration for KEKB Injector Linac | klystron, beam-loading, acceleration, simulation | 91 | ||
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The KEKB injector linac is usually operated to accelerate only two 10 nC electron bunches to generate positron, since more bunch cannot be equalized the beam energy using the conventional pulse compressor (SLED) and the simple phase modulation. The aim of this study is to find how to accelerate more bunches without any modification of high power RF distribution. One way is that a part of the acceleration units is used to compensate the beam energy difference. On the other hand, the recent electron linac is designed for the multi-bunch operation by compensating the beam loading. And this beam loading compensation method is usually realized by combining the output power of two or more klystrons. However our linac system consists of one 50 MW klystron in one acceleration unit, and eight klystrons are driven by a 100kW klystron. Another way to realize the multi-bunch acceleration in our linac is using the amplitude modulation of the klystron. This is realized using the I-Q modulation of the low level RF considering the non-linear characteristics of the total amplification system including klystrons. Further we developed a FPGA board with 100 MHz DACs and ADCs to realize this.
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| MOP030 | An Upgrade to NSCL to Produce Intense Beams of Exotic Nuclei | cyclotron, ion, acceleration, injection | 103 | ||
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A substantially less costly alternative to the Rare Isotope Accelerator (RIA) project has been developed at Michigan State University (MSU). By upgrading the existing facility at the National Superconducting Cyclotron Laboratory (NSCL), it will be possible to produce stable beams of heavy ions at energies of greater than 180 MeV/u with beam power in excess of >80 kW. The upgrade will utilize a cyclotron injector and superconducting driver linac at a base frequency of 80.5 MHz. Radioactive ion beams will be produced in a high-power target via particle fragmentation. A charge-stripping foil and multiple-charge-state acceleration will be used for the heavier ions. The 9 MeV/u injector will include an ECR source, a bunching system, and the existing K1200 superconducting cyclotron with axial injection. The superconducting driver linac will largely follow that proposed by MSU for RIA, using cavities already designed, prototyped, and demonstrated for RIA. The existing A1900 Fragmentation Separator and experimental areas will be used, along with a new gas stopper and reacceleration system.
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| MOP031 | Beam Distribution System for the MSU-RIA Driver Linac | kicker, emittance, 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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| MOP034 | Status of FS-FIR Project of the PAL | radiation, electron, gun, undulator | 112 | ||
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At the Pohang Accelerator Laboratory (PAL), a femto-second far infrared radiation (fs-FIR) facility is under construction. It is a THz radiation source using 60-MeV electron linac, which consists of an S-band photocathode RF-gun with 1.6 cell cavity, two S-band accelerating sturctures, two chicane bunch compressors, and a 1-m long planar undulator. We installed the gun and measured the characteristics. In this article, we will present the construction status of the fs-FIR facility as well as the simulation results and the measurement results of the electron gun.
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| MOP035 | Operational Aspects of High-Power Energy-Recovery Linacs | wiggler, quadrupole, vacuum, lattice | 115 | ||
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We have been operating a high power energy recovery linac (ERL) at Jefferson Lab for several years. In the process we have learned quite a bit about both technical and physics limitations in high power ERLs. Several groups are now considering new ERLs that greatly increase either the energy, the current or both. We will present some of our findings on what to consider when designing, building, and operating a high power ERL. These include space charge effects, halo, magnetic field quality, RF stability, short bunch formation, coherent synchrotron radiation and it effect on the beam, beam breakup instabilities, higher order mode production, and diagnostic requirements.
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| MOP036 | Status of the PAL-XFEL Project | electron, laser, undulator, radiation | 118 | ||
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PAL-XFEL, the new X-ray FEL machine that is going to be built at Pohang Accelerator Laboratory, is under intensive design study. The electron beam energy will be 3.7 ~ 4.0 GeV and the target wavelength will be 0.3 nm. The results as well as the strategy and the difficulties in the PAL-XFEL design are presented in this paper.
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| MOP037 | Applications of Time-of-Flight Measurements at FLASH | electron, vacuum, laser, undulator | 121 | ||
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As a prototype of the XFEL, VUV-FEL has been build and commissioned at DESY by an international collaboration. It is a linear electron accelerator with an undulator arrangement to produce laser pulses by the 'Self-Amplified Spontaneous Emission' (SASE) process. To generate the laser pulses, electron bunches are compressed in longitudinal direction to reach the necessary peak current of about 2.5 kA. To control the compression process a number of 'Phase Monitors' are installed at the accelerator. They measure the time of the bunch passages. Differences of the bunch passage times at different linac locations yield the 'Time-Of-Flight' (TOF) between these locations. The system is installed with regard to the planned installation of a further RF module operating at the third harmonic RF frequency. This 'third harmonic cavity' is required to optimize the longitudinal bunch charge distribution. Its effect is examined by the TOF measurements. The paper presents the Phase Monitor system to measure the TOF at VUV-FEL. The principle is shown, the determination of 'on-crest'-phases is demonstrated and first measurements of the momentum compaction coefficients, R56 and T566, are discussed.
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| MOP038 | 200-MHz, 1.5-MeV Deuteron RFQ Linac | rfq, ion, ion-source, controls | 124 | ||
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A 200-MHz, 1.5-MeV deuteron RFQ linac system is under construction at Linac Systems. The linac structure employs the four-bar, radial-strut design, where the four bars are supported by a series of radial struts emanating from the wall of a cylindrical cavity with four-pole symmetry. This structure looks and performs very much like the four-vane RFQ structure. This design is about twice the efficiency of the conventional four-bar RFQ design. Another important advantage of this design is that the dipole mode is higher in frequency than the quadrupole mode, thus eliminating any problems with the mixing of the dipole mode with the quadrupole mode. Injection of deuterons into the linac will be at 50 keV from a microwave ECR ion source. The linac structure is 2.72 meters long. The peak beam current out of the linac will be 20 mA. A pulse duty factor of 5% will yield an average beam current of 1 mA. The rf power requirement is 58 kW to excite the structure, plus 30 kW to accelerate the beam, for a total of 88 kW. This linac system is scheduled for completion in the spring of 2007.
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| MOP039 | The SPL (II) at CERN, a Superconducting 3.5-GeV H- Linac | proton, injection, target, simulation | 127 | ||
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A revision of the physics needs and recent progress in the technology of superconducting (SC) RF cavities have triggered major changes in the design of a SC H- linac at CERN. With 4 - 5 MW beam power, the SPL can be the proton driver for a next generation ISOL-type radio-active beam facility ("EURISOL") and/or supply protons to a neutrino facility (conventional superbeam + beta-beam or neutrino factory). Furthermore the SPL can replace Linac2 and the PS booster, improving significantly the beam performance in terms of brightness, intensity, and reliability for the benefit of all proton users at CERN, including LHC and its luminosity upgrade. Compared with the first conceptual design, the beam energy is almost doubled (3.5 GeV instead of 2.2 GeV) while the length is reduced by 40%. At a repetition rate of 50 Hz, the linac re-uses decommissioned 352.2 MHz RF equipment from LEP in the low-energy part. Beyond 90 MeV the RF frequency is doubled, and from 180 MeV onwards high-gradient SC bulk-niobium cavities accelerate the beam to its final energy of 3.5 GeV. This paper presents the overall design approach, together with the technical progress since the first conceptual design in 2000.
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| MOP040 | Design of the PEFP 100-MeV Linac | proton, rfq, quadrupole, klystron | 130 | ||
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The Proton Engineering Frontier Project (PEFP) is constructing a 100 MeV proton linac in order to provide 20 MeV and 100 MeV proton beams. The linac consists of a 50 keV proton injector, a 3 MeV radio-frequency quadrupole (RFQ), a 20 MeV drift tube linac (DTL), a medium energy beam transport (MEBT), and the higher energy part (20 MeV ~ 100 MeV) of the 100 MeV DTL. The MEBT is located after the 20 MeV DTL in order to extract 20 MeV proton beams as well as to match the proton beam into the higher energy part of the linac. The 20 MeV part of the linac was completed and is now under beam test. The higher energy part of the PEFP linac was designed to operate with 8% beam duty and is now under construction. This brief report discusses the design of the PEFP 100MeV linac as well as the MEBT.
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| MOP042 | Performance of Alternating-Phase-Focused IH-DTL | ion, acceleration, rfq, heavy-ion | 136 | ||
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Tumor therapy using HIMAC has been performed at NIRS since June 1994. With the successful clinical results over more than ten years, a number of projects to construct these complexes have been proposed over the world. Since existing heavy-ion linacs are large in size, the development of compact linacs would play a key role in designing compact and cost-effective complexes. Therefore, we designed a compact injector system consisting of RFQ and Interdigital H-mode DTL (IH-DTL) having the frequency of 200 MHz. For the beam focusing of IH-DTL, the method of Alternating-Phase-Focusing (APF) was employed. By using APF, no focusing element in the cavity, such as quadrupole magnets, is needed. Having employed APF IH-DTL, the injector system is compact; the total length of two linacs is less than 6m. The injector system can accelerate carbon ions up to 4.0 AMeV. The construction and installation of RFQ and APF IH-DTL has completed, and the beam tests were performed. We succeeded to accelerate carbon ions with satisfactory beam intensity and emittances. The design and performance of RFQ and APF IH-DTL will be presented.
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| MOP044 | The High-Intensity Superconducting Linac for the SPIRAL 2 Project at GANIL | ion, rfq, heavy-ion, ion-source | 142 | ||
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After a detailed design study phase (2003-2004), the Spiral 2 project at GANIL was officially approved in May 2005. The project group for the construction was launched in July 2005, with the participation of French laboratories (CEA, CNRS) and international partners. The Spiral 2 Driver Accelerator is composed of an injector (protons, deuterons and heavy ions with q/A=1/3), a room temperature RFQ, and a superconducting linac with two beta families of Quarter Wave Resonators. It will deliver high intensity beams for Radioactive Ions production by the ISOL method and stable heavy ions for nuclear and interdisciplinary physics. High intensity neutrons beams will also be delivered for irradiation and time of flight experiments. In this paper we focus on the High Intensity Driver Accelerator design and the results obtained with the first prototypes of several major components.
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| MOP045 | Performance of SNS Front End and Warm Linac | beam-losses, SNS, emittance, 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, ion-source, emittance | 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, emittance, ion, 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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| MOP048 | Installation of the French High-Intensity Proton Injector at Saclay | rfq, diagnostics, proton, shielding | 153 | ||
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The installation of the French high intensity injector “IPHI” is in progress on the Saclay site. The proton source, RF power system, cooling plant, diagnostics line as well as shielding are now in place. The first sections of the RFQ cavity are installed on their supports. Commissioning is planned during the first half of 2007. At the beginning of 2008, a beam chopper, developed at Cern, will be inserted between the RFQ and the diagnostics line and tested with a proton beam. At the end of 2008, part of IPHI will be moved from Saclay to Cern. New tests, intended for the LINAC4 project, will be carried out using a negative hydrogen beam. This paper describes the fabrication and assembly operations. The future of IPHI at Cern is evoked.
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| MOP050 | Construction Plans for the LENS Proton Linac | proton, rfq, klystron, target | 156 | ||
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The Low Energy Neutron Source (LENS) at Indiana University will provide moderated neutrons in the meV energy range for materials and neutron physics research as well as MeV energy range neutrons for creating a high flux neutron test environment. Neutrons will be generated by colliding 13 MeV or 21 MeV protons with a Be target. Since December 2004, we have used an existing RFQ and DTL, we have been able to deliver a 0.5% duty factor a 10 mA, 7 MeV beam to a Be target mounted next to a frozen methane moderator*. By early 2007, an additional 7 MeV to 13 MeV DTL section will be added and klystrons will be used to power the RFQ and DTL sections. This will improve the output to 3% duty factor with 20 mA at 13 MeV. A new 75 keV, 150 mA proton injector and 100 mA, high duty factor RFQ is being constructed to replace the original 3 MeV RFQ at a later date. The peak beam current available from the new injector and RFQ will increase to 50 mA with a duty factor of at least 5% or up to 100 mA with lower duty factor. In addition, a 13 MeV to 22 MeV DTL is planned to boost the maximum instantaneous flux available from the neutron source up to about 1012 n/s/cm2.
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V. P. Derenchuk, et al., "The LENS 7 MeV, 10 mA Proton Linac," PAC05, p. 3200. |
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| MOP057 | A Fault Recovery System for the SNS Superconducting Cavity Linac | SNS, klystron, beam-loading, proton | 174 | ||
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One of the advantages for the change of the Spallation Neutron Source (SNS) linac from copper to superconducting cavities, was the possibility of fault tolerance. Namely, the ability to rapidly recover from a cavity failure, retune the downstream cavities with minimal user disruption. While this is straightforward for electron machines, where beta is constant, it is more involved for the case of proton machines, where the beta changes appreciably throughout the Superconducting Linac (SCL). For SNS when the SCL is first turned on, each cavity’s RF amplitude and phase (relative to the beam) are determined with a beam based technique. Using this information a model calculated map of arrival time and phase setpoint for each cavity is constructed. In the case of cavity failure(s) the change in arrival time at downstream cavities can be calculated and the RF phases adjusted accordingly. Typical phase adjustments are in the 100 – 1000 degree range. This system has been tested on the SNS SCL in both controlled tests and a need based instance in which more than 10 cavity amplitudes were simultaneously reduced. This scheme and results will be discussed.
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| MOP058 | Heavy-Ion-Beam Emittance Measurements at the GSI UNILAC | emittance, ion, simulation, 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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| MOP059 | Long-Term Perspective for the UNILAC as a High-Current, Heavy-Ion Injector for the FAIR-Accelerator Complex | ion, heavy-ion, synchrotron, ion-source | 180 | ||
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The present GSI-accelerator complex, consisting of the linear accelerator UNILAC and the heavy ion synchrotron SIS 18, is foreseen to serve as an U28+-injector for up to 10+12 particles/s for FAIR. In 2003 and 2004 different hardware measures and careful fine tuning in all sections of the UNILAC resulted in an increase of the beam intensity to 9.5·10+10 U27+ ions per 100 mks (max. pulse beam power of 0.5 MW). In addition a dedicated upgrade program for the UNILAC will be performed until 2009. It is intended to fill the SIS 18 up to the space charge limit of 2.7·10+11 U28+ ions per cycle. After completion of the FAIR complex in 2015 the running time for the accelerator facility at least will be 20 years, while the UNILAC will then be in operation for more than 60 years as a high duty factor heavy ion linac. Different proposals for a new advanced short pulse, heavy ion, high intensity, high energy linac, substituting the UNILAC as a synchrotron injector, will be discussed. This new "High Energy-UNILAC" has to meet the advanced FAIR requirements, will allow for complete multi-ion-operation and should provide for reliable beam operation in the future.
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| MOP061 | The 70-MeV Proton Linac for the Facility for Antiproton and Ion Research FAIR | proton, rfq, emittance, 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, emittance, 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 | emittance, 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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| MOP067 | Higher Order Mode Wakefield Simulations and Beam Dynamics Simulations in the ILC Main Linacs | emittance, 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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| MOP068 | Beam-Loss Measurement and Simulation of Low-Energy SNS Linac | SNS, simulation, radiation, beam-losses | 202 | ||
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We have installed a number of Neutron detectors from the MEBT to the end of CCL [186 MeV]. These detectors are made in collaboration with INR. In this paper we present our implementation and simulation of the losses by inserting Faraday Cups at different energies. We also calibrated neutron detectors and their high voltage dependence. The measured losses are simulated by 3-D transport codes during SCL commissioning. We also discuss future improvements such as interpreting the loss signal in terms of beam current lost in warm part of SNS linac with accurate longitudinal loss distribution as well as plan to automate voltage dependence of the neutron detectors. We compare two different sets of Beam Loss Monitors: Ionization Chambers (detecting X-ray and gamma radiation) and Photo-Multiplier Tubes with a neutron converter (detecting neutrons). We outline such combination is better way to deal with the beam losses than relying on detectors of one type.
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| TU1003 | Modern Electron Induction Linacs | electron, target, induction, cathode | 208 | ||
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Several high power induction linacs are in existence and a couple are being built around the world. Typically, they are capable of delivering about 100 micro-coulombs of e-beam to the target in a single burst and are built for radiographic application. DARHT 2nd Axis induction linac under construction at Los Alamos National Laboratory is the first of its kind, designed to deliver multiple e-beam pulses to the target. This incorporates the latest advances in the induction linac technology. An overview of the existing as well as the DARHT induction linac will be presented in this paper.
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| TU2003 | China Spallation Neutron Source Linac Design | rfq, power-supply, ion, ion-source | 222 | ||
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Beijing Spallation Neutron Source has been approved in principle by the Chinese government. BSNS can provide a beam power of 100kW on the target in the first phase, and then 200kW in the second phase. The accelerator complex of BSNS consists of an H- linac of 81MeV and a rapid cycling synchrotron of 1.6GeV at 25Hz repetition rate. In the second phase, the linac energy will be upgraded to 134MeV and the average current will be doubled. The linac has been designed, and some R&D studies have been lunched under the support from Chinese Academy of Sciences. The linac comprises a H- ion source, an RFQ and a conventional DTL with EMQs. This paper will present our major design results and some progresses in the R&D of the linac.
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| TU3002 | Industrial Aspects of Linac Components | gun, radio-frequency, vacuum, electron | 237 | ||
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The industrial aspects of producing linac components from the particle sources, the accelerator structures, the magnet systems and RF systems will be discussed. The various aspects of working with national labs and universities will be covered. Such issues as to what type of Contract Form should be used; Organizational Conflict of Interest and Intellectual Property will be covered as well as how best to work with the labs and universities on SBIRs, CRADAs and Work for Others contract. Specific examples will be addressed including the unique issues for the ILC.
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| TUP001 | Linac Automated Beam Phase Control System | controls, klystron, gun, feedback | 241 | ||
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Adjustment of the rf phase in a linear accelerator is crucial for maintaining optimal performance. If phasing is incorrect, the beam will in general have an energy error and increased energy spread. While an energy error can be readily detected and corrected using position readings from beam position monitors at dispersion locations, this is not helpful for correcting energy spread in a system with many possible phase errors. Uncorrected energy spread results in poor capture efficiency in downstream accelerators, such as the Advanced Photon Source (APS’s) Particle Accumulator Ring (PAR) or Booster synchrotron. To address this issue, APS has implemented beam-to-rf phase detectors in the linac, along with software for automatic correction of phase errors. We discuss the design, implementation, and performance of these detectors and how they improved APS top-up operations. * Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.
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| TUP002 | High-Dynamic-Range Current Measurements in the Medium-Energy Beta Transport Line at the Spallation Neutron Source | SNS, Spallation-Neutron-Source, extraction, rfq | 244 | ||
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It is desired to measure the effectiveness of the LEBT (low energy beta transport) chopper system. Since this chopper is required to chop the H- beam to a 1% level, it is required therefore to accurately measure the beam during the chop. A system is developed with a high dynamic range that can both accurately measure the beam to tune the chopper system as well as provide an input to the MPS (machine protection system) to stop the beam in the event of a chopper system failure. A system description, beam based calibration, and beam measurements are included.
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| TUP003 | Spallation Neutron Source Linac Beam Position and Phase Monitor System | pick-up, SNS, controls, instrumentation | 247 | ||
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The SNS linac currently has 6x beam position monitors which allow the measurement of both beam position and phase from a single pickup. The signals from the pickup lobes are down converted from either 402.5MHz or 805 MHz to 50-MHz IF signals for processing. The IF signals are synchronously sampled at 40 MHz to generate I and Q signals from which the beam position and phase are calculated. Each BPM sampling reference frequency is locked to a phase-stable 2.5 MHz signal distributed along the linac. The system is continuously calibrated by generating and measuring rf bursts in the processor that travel to the BPM pickup, reflect off of the shorted BPM lobes and return to the processor for re-measurement. The electronics are built in a PCI card format and controlled vith LabVIEW. Details of the system design and performance are presented.
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| TUP004 | Intense L-Band Electron Linac for Industrial Applications | coupling, electron, impedance, klystron | 250 | ||
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An intense L-band travelling-wave electron linac is under development for irradiation applications. It is capable of producing 10 MeV electron beams of 30 kW average beam power. The operating energy is limited to prevent neutron production. On the other hand, the current is limited by the beam loading effect in the given structure. The accelerating structure operated with 2π/3 mode is constant-impedance and disk-loaded waveguides. We determined the optimum operating parameters by adjusting the duty factor, which is again governed by the available high-power pulsed klystron. The SUPERFISH code was used to design the bunching and accelerating cavities. The PARMELA code gives the result of beam dynamics. We present design details of the intense travelling-wave linac powered by a 1.3 GHz, 25 MW pulsed klystron with a duty factor of 0.21%. We also present cold test results for the prototype cavities.
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| TUP007 | Low-Energy Linacs and Their Applications in Tsinghua University | electron, klystron, positron, scattering | 256 | ||
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During these years, several kinds of low energy linacs were developed for cargo inspection, non-destructive-test and irradiation in Tsinghua University cooperated with NUCTECH company. The newly finished interlaced pulse dual energy 9/6MeV linac for material distinguishing cargo inspection and several others will be described here. The beam dynamics simulation and the experiment results together with some applications of these linacs will be given in this paper.
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| TUP009 | First Operation of the FLASH Machine Protection System with Long Bunch Trains | undulator, beam-losses, radiation, laser | 262 | ||
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The linac-based free electron laser facility FLASH at DESY Hamburg is designed to transport an electron beam with an average power of more than 50 kW. To avoid serious damage to accelerator components, a fast active machine protection system (MPS) stops the production of new bunches if hazardous machine conditions are detected. This paper gives an overview of the MPS topology and its subsystems. Furthermore, we present results from the commissioning of the fast beam interlock system that has for the first time allowed to operate the accelerator with macropulses of up to 600 bunches.
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| TUP011 | Upgrade of Beam Diagnostics in LEBT and MEBT of J-PARC LINAC | monitoring, diagnostics, vacuum, rfq | 268 | ||
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After tests in Tsukuba-site, Front end part (from an ion source upto the first drift tube linac) of J-PARC LINAC was transported to Tokai-site. From the coming December, testing with H- beam is planned. After the tests in Tsukuba, a few beam current monitors are added in the low and the medium energy transport line, and those monitors are used for the machine- and the person-protection system. In this paper, design and roles of each monitor are described.
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| TUP016 | BPM DAQ System Using Fast Digital Oscilloscope | controls, feedback, injection, factory | 280 | ||
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The KEK injector linac is planned to be upgraded to perform the simultaneous injection for four rings (KEKB e-/ e+, PF and PF-AR rings). In this operation mode, each rf pulse accelerates the beam with different charge and energy by controlling the low-level rf phase. For this purpose, it is strongly required to improve the BPM DAQ system. In the current system, maximum DAQ rate is strictly limited by the oscilloscope performance, and it should be improved for the 50-Hz measurement. We made decision to replace the current DAQ system by the fast digital oscilloscope. In this presentation, the system description of the new DAQ system and the result of the performance test will be presented.
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| TUP018 | Low-Intensity Electron Beam Monitoring and Beam Applications at OPU Linac | electron, monitoring, radiation, gun | 286 | ||
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Low intensity beams are generated with a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The minimum charge of electrons in a pulsed beam has been estimated to be about several attocoulomb. In order to measure the intensity and the profile of the beams with thermoluminescence dosimeters and two-dimensional radiation dosimeters, the characteristics of the dosimeters have been investigated by using the electron beams. For the charge of the beam above one picocoulomb, charge-sensitive type beam monitors have been used. The linear relation between the output signal of the dosimeter and the irradiation dose of the beam has been obtained. From the results it has been found that these dosimeters can be applied to monitoring the low intensity electron beam. The beam applications under preparation are presented.
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| TUP020 | The J-PARC L3BT Monitor System for RCS Injection | injection, electron, beam-losses, pick-up | 290 | ||
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The J-PARC linac-3GeV rapid cycling synchrotron (RCS) beam transport line (L3BT) monitor system will be used to tune the intensity of 5mA-50mA linac beam. The monitor system is composed of BPMs and multi wire profile scanners (MWPS) in L3BT line and RCS injection area. A non-destructive beam momentum spread monitor using a 4-stripline pickups is also developed in order to measure and control the momentum spread of linac beams. The spatial resolution of less than 0.3mm and momentum spread of less than 0.1% is required for RCS injection to avoid uncontrolled beam losses. In this paper, beam position monitor, profile monitor and momentum spread measurement for J-PARC linac is described. Preliminary results of beam size and m value measurement with quadrupole mode of the signal of 4-stripline BPMs in the KEK MEBT1 are also discussed.
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| TUP021 | Wire Profile Monitors in J-PARC Linac | electron, proton, simulation, rfq | 293 | ||
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We plan to install wire scanners for J-PARC linac in order to measure beam profile and emittance. They have been designed to capture electrons in H-, 7um-diameter carbon wires are used in 3MeV point and 30um-diameter tungsten wires are used for 50-181MeV point. We plan to set 36 wire scanners in linac and beam dumps. In this paper, we report the result of beam test with 3MeV beam at KEK and the calculation about signal and wire temperature.
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| TUP023 | Beam-Size Measurements in the IPNS 50-MeV Transport Line Using Stripline BPMs | quadrupole, diagnostics, controls, monitoring | 296 | ||
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Continuing with the work started two years ago, the technique of using a two-beamlet model to measure beam size is presented. Beam signals are detected on terminated 50-ohm, stripline BPMs located in the transport line between the 50 MeV linac and rapid cycling synchrotron. Each BPM is constructed with four striplines: top, bottom, left and right. Using a fast-sampling oscilloscope to compare the signals from opposite strip lines allows one to determine beam size assuming a two beamlet model. Measurements made with the two-beamlet approach are compared with other standard profile diagnostics such as wire-scanners, segmented Faraday cups, and scintillators. Advantages of the two-beamlet method are that it is non intrusive and does not require the presence of a background gas necessary for an IPM. Disadvantages of the technique are that it does not provide a detailed profile and the longitudinal beam pulse length must be short relative to the stripline length.
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| TUP029 | Performance and Early Operating Experience with the ISAC-II Cryogenic System | cryogenics, vacuum, ion, controls | 306 | ||
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A 500 W class refrigerator has been installed and commissioned at TRIUMF to cool the new 20MV superconducting linac. The refrigerator liquifies helium into a common supply dewar. The dewar feeds a common cold manifold and the five cryomodules are fed via parallel cold distribution circuits. The system operates at 4.5K. Measurements have been done to estimate the static loads of the cryomodules and the distribution system and to characterize plant performance. The paper will include a system description, performance results and early operating experience.
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| TUP030 | RF Cavity Performance and RF Infrastructure for the ISAC-II Superconducting Linac | controls, coupling, power-supply, acceleration | 309 | ||
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The ISAC-II superconducting linac is presently being commissioned. Twenty cavities have been prepared and characterized in single cavity tests before mounting in the on-line cryomodules. The cavities are specified to operate at a challenging peak surface field of 30MV to supply an accelerating voltage of 1.1MV/cavity. The cavity bandwidth of ±20Hz is achieved by overcoupling while a mechanical tuner actively maintains the cavity frequency within this bandwidth. An overview of the rf systems will be given. We will describe the early operating experience and compare the cavity on-line performance with the single cavity characterizations.
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| TUP031 | Beam Dynamics Studies on the ISAC-II Superconducting Linac | emittance, 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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| TUP034 | Development of a Superconducting RF Module for Acceleration of Protons and Deuterons at Very Low Energy | vacuum, proton, alignment, acceleration | 321 | ||
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A prototype superconducting accelerating module housing six 176 MHz half wave resonators and three superconducting solenoids is currently under production at Accel as part of a 40 MeV linear accelerator at the Soreq NRC. The module will accelerate protons and deuterons from energy of 1.5 MeV/u up to 6.5 MeV. The design is based on a peak electric field gradient of 25 MV/m and maximum 10 W of power dissipation in the helium bath by each cavity. Main design considerations of the cavities, solenoids, tuners and couplers as well as for the module especially in view of assembly and alignment will be presented. First cold cavity test results obtained in Accel’s new cold RF test facility will be presented. Prototypes of the tuner, helium vessel, solenoids and the couplers are under construction and partly under test.
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| TUP037 | Possible Upgrade Paths for the LANSCE H- Injector | rfq, ion, ion-source, target | 330 | ||
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The LANSCE linac presently provides both H- and H+ beams to several user facilities. The H- injector uses a cesiated, multi-cusp field, surface converter source operating at duty factors between 10 and 12%, coupled to a Cockcroft-Walton (CW) accelerator to provide peak beam currents of ~15 mA for the LANSCE linac. In an effort to raise the peak beam current available to the majority of the H- users, we are pursuing two options. The first is a low duty factor H- ion source and a 750 keV RFQ that would provide ~25 mA of peak current for use by the Lujan and pRad programs. The second is a low frequency buncher for the existing 80 keV beam transport located inside the CW dome that could provide about a factor of two increase in the peak beam current for the WNR program. This paper will present these two options.
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| TUP039 | Two-Charge-State Injector for a High Power Heavy-Ion Linac* | ion, emittance, 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 | emittance, 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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| TUP048 | Beam-Loading Effect in the Normal-Conducting ILC Positron Source Pre-Accelerator | positron, beam-loading, focusing, linear-collider | 355 | ||
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Significant positron bunch charge (several nC) in the ILC Positron Source results in high pulse beam loading for normal-conducting accelerating structures in Positron Pre-Accelerator (PPA). Time interval between bunches (~ 300 ns) is not negligibly small in comparison with accelerating structure time constant (rise time for Standing Wave (SW) or filling time for Traveling Wave (TW) options). As the result, beam loading effect has particularities both from stored energy acceleration regime and continuous beam loading one. Taking into account particular PPA beam structure, beam loading effect is estimated for the present ILC base line parameters, both for SW and TW PPA options. Possible solutions for beam loading compensation are discussed.
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| TUP060 | Status of the EBIS Project at Brookhaven | ion, rfq, electron, injection | 385 | ||
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The EBIS Project at Brookhaven National Laboratory will replace the Tandem Van de Graaff accelerators with an Electron Beam Ion Source, an RFQ, and short linac, as the heavy ion preinjector for RHIC. This project, jointly funded by DOE and NASA, will provide a modern preinjector which will have increased flexibility in providing beams to the various programs running simultaneously, will be capable of providing beams not presently available for RHIC and the NASA Space Radiation Laboratory, and will be simpler and less costly to operate. Presently in the first year of the four-year project, the detailed design is nearly complete, and some major procurements have been placed. The overall status of the project will be presented, as well as some unique features in the design, and results from the R&D using the prototype EBIS.
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| TUP063 | Commissioning of a New S-Band RF Gun for the Mark III FEL Facility at Duke University | gun, cathode, electron, emittance | 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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| TUP067 | Tune-up Scenario for Debuncher System in J-PARC L3BT | injection, simulation, monitoring, target | 406 | ||
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We plan to start beam commissioning of J-PARC linac and the succeeding beam transport line in December 2006. The beam transport line, to which we refer as L3BT, has two key functionalities to satisfy the requirements for the succeeding ring injection. One is to reduce the momentum jitter and momentum spread, and the other is to scrape off the transverse tail. To realize the former functionality, a debuncher system is installed in L3BT which enables longitudinal gymnastics of the beam to reduce the momentum spread at the ring injection. In this presentation, the tune-up scenario for the debuncher system is presented together with simulation results on the effects of debuncher system.
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| TUP068 | Tuning Strategy for Transverse Collimator in J-PARC L3BT | collimation, beam-losses, monitoring, injection | 409 | ||
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We plan to start beam commissioning of J-PARC linac and the succeeding beam transport line in December 2006. The beam transport line, to which we refer as L3BT, has two key functionalities to satisfy the requirements for the succeeding ring injection. One is to reduce the momentum jitter and momentum spread, and the other is to scrape off the transverse tail. To realize the latter functionality, a transverse collimator system is installed in L3BT which consists of four horizontal and four vertical collimators. In this presentation, the tuning strategy for the transverse collimator system is presented together with the main features of the collimator system.
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| TUP069 | Design of 132MeV DTL for CSNS | SNS, focusing, simulation, vacuum | 412 | ||
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A description is given to the drift-tube-linac (DTL) of the Beijing Spallation Neutron Source (BSNS). The DTL accelerate a 3MeV, 30mA H- beam from the RFQ to the LRBT. Tank body and drift tube configuration design using the SUPERFISH code has enabled efficient optimization of the effective shunt impedance and avoided high surface field. Accelerating cells design and particle tracking were made by using PARMILA code. Special emphasis is given to the transverse focusing system design, which was compared with two usual schemes, constant phase focusing and equipartitioning focusing. Details of beam dynamics analysis will be presented in this paper.
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| TUP070 | Comparison of Phase Scan vs Acceptance Scan for the SNS DTL | simulation, SNS, Spallation-Neutron-Source, target | 415 | ||
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There are two widely used techniques for setting the rf set-point of the Drift Tube Linac (DTL). The Phase Scan and the Acceptance Scan techniques were applied to the SNS DTL and were benchmarked against each other. Commissioning data indicate that both techniques produce quite consistent results and the model used is quite accurate. Both of the models are based on multiparticle tracking with space charge effects.
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| TUP071 | Beam-Loading Effects on Phase Scan for the Superconducting Cavities | simulation, beam-loading, SNS, impedance | 418 | ||
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When the beam is passing through superconducting cavities, it excites beam induced field in cavities. A systematic study was performed to study the beam loading effects by the nonrelativistic beam for β = 0.81 superconducting cavities of the SNS linac. The analysis indicates that the induced field level is quite close to the estimation and its effect on the phase scan is consistent with the model.
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| TUP072 | Beam Dynamics Studies of the 8-GeV Superconducting H- Linac | simulation, beam-losses, focusing, rfq | 420 | ||
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A 8-GeV H-minus linac has been proposed to enhance the accelerator complex at Fermilab as a high-intensity neutrino source.* The linac is based on 430 independently phased superconducting cavities. The front-end of the linac (up to 420 MeV) operating at 325 MHz is based on RIA-type multi-spoke cavities. The rest of the linac (from 420 MeV to 8 GeV) uses ILC-type elliptical cavities. We have performed large scale end-to-end beam dynamics simulations of the driver linac using the code TRACK** including all sources of machine errors and detailed beam loss analysis. The results of these simulations will be presented and discussed.
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* G. W. Foster and J. A. MacLachlan, Proceedings of LINAC-2002, p.826. |
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| TUP073 | Simulations of RF Errors in the SNS Superconducting Linac | simulation, emittance, 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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| TUP074 | Beam Dynamics Simulations of SARAF Accelerator including Error Propagation and Implications for the EURISOL Driver | simulation, proton, lattice, rfq | 426 | ||
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Beam dynamics simulations of the SARAF (Soreq Applied Research Accelerator) superconducting RF linear accelerator have bean performed in order to establish the linear accelerator design. The multi-particle simulation includes 3D realistic electromagnetic field distributions, space charge forces and fabrication, misalignment and operation errors. A 4 mA deuteron beam is accelerated up to 40 MeV with a moderated rms emittance growth and a high real-estate acceleration gradient of 2 MeV/m. An envelope of 40,000 macro-particles is kept under a radius of 11 mm, well below the beam pipe bore radius. The accelerator design for SARAF is proposed as an injector for the EURISOL driver accelerator. The basic Accel 176 MHz β0=0.09 and β0=0.15 HWR lattice was extended to 90 MeV based on the LNL 352 MHz β0=0.31 HWR. The matching between both lattices ensures smooth transition and the possibility to extend the accelerator to the required EURISOL ion energy.
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| TUP075 | Automatic Transverse and Longitudinal Tuning of Single and Multiple Charge State Ion Beams | beam-losses, focusing, emittance, 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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| TUP076 | First TRACK Simulations of the SNS Linac | simulation, SNS, lattice, focusing | 432 | ||
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In an effort to benchmark the code TRACK* against the recent commissionnig data from the SNS linac, we started updating the code TRACK to support SNS-type elements like DTL's and CCL's. 2D electric field tables were computed using SUPERFISH and 3D magnetic fields from PMQ's were calculated using EMS-Studio. A special DTL routine was implemented and successfully tested. The first results of TRACK simulations using a realistic beam will be presented. A comparison with the code PARMILA will also be presented and discussed.
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* "TRACK: The New Beam Dynamics code", V. N. Aseev et al, in Proceedings |
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| TUP077 | Transverse Beam Matching and Correction Procedures in INR Linac | quadrupole, controls, simulation, focusing | 435 | ||
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An interactive procedure for the transverse beam matching and correction has been developed and implemented in several areas of INR Linac. The profile measurements are used for determination of the main transverse beam parameters. These data are applied for calculation the dipole correction currents and quadrupole gradients to transport the beam with minimum sizes and off axis displacements. The user friendly interface and graphics support has been developed for data treatment and beam behavior presentation. The proposed algorithm of beam matching, beam steering and data treatment is discussed. Some experimental and simulation results for different INR Linac operation modes are presented.
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| TUP079 | RIAPMTQ/IMPACT: Beam-Dynamics Simulation Tool for RIA | simulation, emittance, 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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| TUP081 | Impact of a RF Frequency Change on the Longitudinal Beam Dynamics | emittance, 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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| TUP083 | Development of High-Power RF Vector Modulator Employing TEM Ferrite Phase Shifters | controls, SNS, impedance, vacuum | 451 | ||
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Construction and installation of cavity RF power distribution system in a high power superconducting RF accelerator can have cost savings if a fan-out configuration that feeds many cavities with a single high power klystron is realized. The configuration however requires independent control of RF amplitudes and phases to the cavities to perform properly. A prototype high power RF vector modulator for the control is built and tested. The vector modulator employs a quadrature hybrid and two fast ferrite phase shifters in square coaxial TEM transmission lines. The square coaxial format can provide the power handling capability and thermal stability. RF properties of the design and result of high power system testing of the design are presented.
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| TUP084 | Drifting Beam Application for SNS Superconducting Cavity Setting | SNS, controls, beam-loading, Spallation-Neutron-Source | 454 | ||
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A software application for tuning superconducting linac cavity has been developed and tested at the Spallation Neutron Source (SNS). The application is based on the drifting beam method and the XAL online model. The drifting beam method and the application were proved to be consistent with other cavity tuning method during the SNS commissioning runs. Detail algorithm and data acquisition for the application will be presented.
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| TUP085 | Beam Simulations for the MSU-RIA Driver Linac Using IMPACT Code | simulation, beam-losses, emittance, 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 | emittance, space-charge, simulation, 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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| TUP087 | Ion Charge Stripping Foil Model for Beam Dynamics Simulation | simulation, ion, scattering, heavy-ion | 463 | ||
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An efficient computer model for the stripping foil simulation was proposed at NSCL/MSU as part of the Rare Isotope Accelerator (RIA) development. The model was successfully implemented in the LANA beam dynamics simulation code. Later this model was also included in the IMPACT code as well as in some other beam dynamics simulation tools. The derivation of the algorithm is presented and the application of the model for the uranium beam stripping simulation in context of the RIA driver linac studies at NSCL/MSU is analysed in the paper.
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| TUP090 | Advances of NPK LUTS Contraband Detection System | rfq, proton, acceleration, radiation | 472 | ||
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Principle and project of NPK LUTS contraband detection technological complex (CDTC) was presented by authors at EPAC 2002. This paper reviews researches connected with 433 MHz ion linacs creation for the last four years. Main part is description of designing and testing of RFQ and APF resonators. State of affairs of other CDTC system is described briefly.
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| TUP091 | Choice of Ion Linac as Neutron Generator for Contraband-Detection System | proton, target, rfq, background | 475 | ||
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8 Mev proton linac and 4 Mev deuteron linac with working frequency 433 MHz are considered as neutron generator for detection system of explosive and fission. Required beam parameters, target materials, pulsed modulation and detection methods are discussed. Possible schemes of accelerating system of contraband detection complex are proposed. One supposes using of RFQ for deuteron linac and RFQ with IH cavity as proton one. Choice is determined by some few criterions: cost, sizes, safety, hardness of manufacturing and tuning.
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| WE1002 | The 4GLS at Daresbury | electron, radiation, simulation, undulator | 481 | ||
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4GLS is a next generation proposal for an advanced light source to be built at Daresbury Laboratory. The facility will consist of three integrated accelerator systems: a 25-60 MeV linear accelerator driving an Infra-Red Free-Electron Laser (FEL) at 13 MHz; a 750-950 MeV branch driving a 10-100 eV XUV-FEL at 1 kHz; a 600 MeV energy recovery linac carrying 100 mA current driving a suite of spontaneous sources at 1.3 GHz or a VUV-FEL (up to 10 eV) at 4 MHz. The latter two accelerator systems share a common superconducting linac based on 1.3 GHz TESLA technology, which will simultaneously accelerate the two bunch types (1 nC and 77 pC) whilst decelerating the returning 77 pC bunches. This paper will outline the project and its key features, including the 35 MeV ERL Prototype accelerator presently being commissioned, and will discuss the accelerator physics and technology challenges to be explored in the present Design Study.
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| WE1003 | The TTF/VUV-FEL (FLASH) as the Prototype for the European XFEL Project | laser, electron, free-electron-laser, radiation | 486 | ||
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The European X-ray Free-Electron Laser Facility (XFEL) is going to be built in an international collaboration at the Deutsches Elektronen-Synchrotron (DESY), Germany. The Technical Design Report was published recently. The official project start will be before end of this year. The new facility will offer photon beams at wavelengths as short as 1 Angstroem with highest peak brilliance being more than 100 million times higher than present day synchrotron radiation sources. The radiation has a high degree of transverse coherence and the pulse duration is reduced from ~100 picoseconds down to the ~10 femtosecond time domain. The overall layout of the XFEL will be described. This includes the envisaged operation parameters for the linear accelerator using superconducting TESLA technology. The complete design is based on the actually operated VUV Free-Electron Laser at DESY. Experience with the operation during first long user runs will be described in detail. Many of the different subsystems of the XFEL could be tested. Specially developed electron beam diagnostics was commissioned. A summary of the status of the XFEL preparation work will be given.
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| WE2003 | LLRF Systems for Modern Linacs: Design and Performance | controls, feedback, resonance, coupling | 498 | ||
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Near-future linac projects put yet unreached requirements on the LLRF control hardware in both performance and manageability. Meeting their field stability targets requires a clear identification of all critical items along the LLRF control loop as well as knowledge of fundamental limitations. Large-scale systems demand for extended automation concepts. The experience gained with present systems as well as dedicated experiments deliver the basis for a design of future systems. Digital hardware has evolved quickly over the past years and FPGAs became common not only in LLRF control. A high degree of digitization in various fields, as for example beam diagnostics, suggests to aim for a convergence of the digital platform designs. Channeling of efforts of different research laboratories may be the key to an affordable solution that meets all requirements and has a broad range of applications.
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| WE2004 | 100 MeV High-Duty-Factor Proton Linac Development at KAERI | proton, klystron, rfq, power-supply | 501 | ||
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The Proton Engineering Frontier Project (PEFP) is developing a 100 MeV high-duty-factor proton linac, which consists of a 50 keV proton injector, a 3 MeV radio frequency quadrupole, a 20 MeV drift tube linac, a 20 MeV beam transport line, a 100 MeV drift tube linac, and a 100 MeV beam transport line. It will supply proton beams of 20 MeV and 100 MeV to users for proton beam applications with the beam duty factor of 24% and 8% respectively. The 20 MeV front-end accelerator with CW RF systems had been constructed at KAERI test stand, and the rest part of the accelerator is being fabricated and will be installed in the new site at Gyeongju City. The preliminary results of the 20 MeV proton linac and the status of the 100 MeV proton linac will be presented.
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| WE2005 | HOM Damping and Power Extraction from Superconducting Cavities | damping, coupling, impedance, electron | 506 | ||
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Damping of Higher Order Modes plays an important role in achieving and preserving low emittance and low energy modulation of beams in accelerators based on the superconducting technology. In the overview, various damping schemes and damping devices and their advantages and disadvantages will be discussed.
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| TH1001 | The Linac Coherent Light Source (LCLS) Accelerator | electron, feedback, undulator, diagnostics | 511 | ||
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The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) based on the final kilometer of the Stanford Linear Accelerator. Such an FEL requires a high energy, high brightness electron beam to drive the FEL instability to saturation. When fed by an RF-photocathode gun, and modified to include two bunch compressor chicanes, the SLAC linac will provide such a high quality beam at 14 GeV and 1-micron normalized emittance. In this talk, we report on recent linac studies, including beam stability and tolerances, longitudinal and transverse feedback systems, conventional and time-resolved diagnostics, and beam collimation systems. Construction and installation of the injector through first bunch compressor will be complete by November 2006, and electron commissioning is scheduled to begin in December of that year.
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| TH1002 | Cryomodule Test Facilities and Multicell Cavity Performance for the ILC | linear-collider, klystron, superconducting-RF, controls | 516 | ||
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To address the ILC Main Linac gradient, which are greater than 35MV/m at vertical test and greater than 31.5MV/m in the operation of the cryomodule, ILC-GDE organized several task forces in the R&D board. They are S0 task force, S1 task force, and S2 task force. The charge of S0 is to achieve 35MV/m in the qualification with reasonable yield. S1 is to achieve 31.5MV/m operation of cryomodule. And S2 is to estimate how large test facility is required to test chain of cryomodules and to make industrialization of cryomodule production. The paper reports the task force activities status together with existing R&D of multicell cavity performance and cryomodule test facility status.
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| TH1003 | Initial Commissioning Results from the ISAC-II SC Linac | acceleration, emittance, 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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| TH1004 | A 70-MeV Proton Linac for the FAIR Facility Based on CH - Cavities | coupling, proton, rfq, quadrupole | 526 | ||
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Future Accelerators for fundamental and for applied research will need a significant improvement in injector capabilities. This paper will describe the concept and the status of the 70 MeV, 70 mA proton injector for GSI - FAIR and compare the CH - linac design with traditional DTL concepts. Improvements in the space charge routine of the LORASR code as well as CH - prototype cavity development and cavity grouping with respect to commercial 3 MW rf power amplifiers is reported. Additionally, the potential of robust superconducting low and medium energy high current linac sections will be explained on the basis of experimental results from a first 19 cell s.c. 350 MHz CH - prototype cavity.
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| TH2001 | High-Power Couplers for Linear Accelerators | vacuum, emittance, 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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| TH2002 | Timing and Synchronization in Large-Scale Linear Accelerators | laser, diagnostics, radiation, electron | 536 | ||
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New coherent light sources are based on large scale linear accelerator; the adopted single pass acceleration scheme allows the preservation of bunch 6D phase space leading to ultra short (<100fsFWHM) and ultra bright (average Brilliance = 1024 (1) ph/sec/mm2/mrad2/0.1%bw) pulses of coherent radiation in the DUV-x-ray regions. Femto-second lasers are deeply integrated in the electron bunch and photon pulse generation, in diagnostic set-ups and in time resolved experiments: the timing may be as low as 10% of pulse duration. The requirements on the stability of RF acceleration call for distribution of ultra-stable and ultra-low phase noise reference signal for the Low Level RF feedback loops. A non reversible breakthrough into the adoption of optical and O/E techniques is on-going which is taking advantage on five order of magnitude reduction in the period of the carrier. Being the current limit represented by the carrier-envelope stabilization techniques, sub-fs jitters have been demonstrated in the laboratory; the preservation of laboratory levels of jitters and stability over the whole accelerator premises is the next step. On-going efforts and results let us be optimistic.
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Interim Report of the Scientific and Technical Issues (XFEL-STI) Working Group ona European XFEL facility in Hamburg, January 11, 2005. |
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| TH3002 | Normal-Conducting Energy Recuperator | emittance, electron, 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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| THP002 | Exception Detection and Handling for Digital RF Control Systems | controls, klystron, radiation, feedback | 562 | ||
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Exception detection and handling routines will play an important role in future large scale accelerator to ensure high availability and beam stability in presence of interlock trips, varying operational parameters, and operation close to the performance limit. For superconducting linacs typical examples for exception situations include cavity quenches, coupler and klystron gun sparcs, operation close to klystron saturation, and errors in vector-sum calibration. The goal is to identify all possible exception situations which will lead to performance degradation or downtime, detect these situations and take appropriate actions as necessary.
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| THP003 | Integrated Optical Timing and RF Reference Distribution System for Large-Scale Linear Accelerators | laser, feedback, electron, controls | 565 | ||
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Highly-stable timing and RF reference distribution systems are required to meet the tight specifications in large scale accelerators for next generation light sources. In this paper, we present an approach based on the distribution of an optical pulse train from a mode-locked laser via timing stabilized fiber links. The timing information is contained in the precise repetition rate of the optical pulse train (~50 MHz), so RF can be extracted at end stations with a stability on the order of 10 fs. Less timing critical signals such as ADC clocks and trigger signals can be transmitted through the same stabilized fiber using a modulated cw laser operating at a different wavelength with sub-ps stability. As multiple wavelengths can propagate without interference through the fiber, it is also possible to integrate data communication in such a fiber system. This paper will review the timing system requirements and present a conceptual layout of an optical timing and reference frequency distribution system based on work done at MIT and DESY for the XFEL.
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| THP004 | Digital Low-Level RF Control Using Non-IQ Sampling | controls, feedback, SNS, rfq | 568 | ||
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The success of digital feedback with synchronous IQ sampling for cavity field control in recent accelerator projects make this LLRF control scheme a popular choice. This short-period synchronous sampling does not, however, average out well-known defects in modern ADC and DAC hardware. That limits the achievable control precision for digital IQ LLRF controllers, while demands for precision are increasing for future accelerators such as International Linear Collider. For this reason, a collaborative effort is developing a digital LLRF control evaluation platform to experiment using coherent sampling with much longer synchronous periods, on the order of the cavity closed-loop bandwidth. This exercise will develop and test the hardware and software needed to meet greater future RF control challenges.
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| THP005 | Digital Control of Cavity Fields in the Spallation Neutron Source Superconducting Linac | controls, SNS, feedback, beam-loading | 571 | ||
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Control of the pulsed RF cavity fields in the Spallation Neutron Source (SNS) superconducting Linac uses both the real-time feedback regulation and the pulse-to-pulse adaptive feed-forward compensation. This control combination is required to deal with the typical issues associated with superconducting cavities, such as the Lorentz force detuning, mechanical resonance modes, and cavity filling. The all-digital implementation of this system provides the capabilities and flexibility necessary for achieving the required performance, and to accommodate the needs of various control schemes. The low-latency design of the digital hardware has successfully produced a wide control bandwidth, and the developed adaptive feed forward algorithms have proved to be essential for the controlled cavity filling, the suppression of the cavity mechanical resonances, and the beam loading compensation. As of this time, all 96 LLRF systems throughout the Linac have been commissioned and are in operation.
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| THP006 | Performance of a Digital LLRF Field Control System for the J-PARC Linac | controls, beam-loading, feedback, klystron | 574 | ||
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Twenty high power klystrons are installed in the J-PARC linac. The requirements for the rf field stabilities are ±1% in amplitude and ±1 deg. in phase during a 500 us flat-top. In order to satisfy these requirements, we adopt the digital feedback and feed-forward system with FPGAs and a commercial DSP board. The FPGAs (Virtex-II 2000) enable a fast PI control for a vector sum of two cavity fields. The measured stability during rf pulse was ±0.15% in amplitude and ±0.15 deg in phase. The tuner control was successively operated by a way of the DSP board by measuring the phase difference between the cavity input wave and the cavity field. Beam loading effects were emulated using a beam-loading test box. By proper feed-forward, the rf stability was less than ±0.3% and ±.15 deg.
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| THP007 | Timing Distribution in Accelerators via Stabilized Optical Fiber Links | laser, controls, feedback, pick-up | 577 | ||
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We present progress on fiber-optic based systems for highly stable distribution of timing signals for accelerators. This system has application for linac-based sources of ultrafast radiation which require sub-100 fsec synchronization or for very large accelerators such as the linear collider. The system is based on optical fiber links that are stabilized with an optical interferometer with RF and timing signals distributed as modulations on the optical carrier. We present measurements of the stability of this link over distances of several hundred meters and discuss issues for testing the link over 10 km.
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| THP009 | Performance of RF Reference Distribution System for the J-PARC Linac | controls, klystron, feedback, injection | 583 | ||
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Installation of the J-PARC linac machines (Phase I) has been almost completed and the beam commissioning will be started in December this year. The error of the accelerating field must be within ±1 degree in phase and ±1% in amplitude. Thus, high phase stability is required as an RF reference. Our objective concerning the phase stability of the reference aims at less than ±0.3 degrees. Last year the installation of the RF reference distribution system was completed. The reference signal is optically distributed to all of the low-level RF control systems by using E/O, O/E, Optical Amplifier and Optical Couplers and so on. The performance of this system was evaluated. The phase stability of ±0.06 degrees was obtained.
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| THP010 | Low-level RF system for STF | controls, klystron, feedback, superconducting-RF | 586 | ||
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The Super-conducting RF Test Facility (STF) has been constructed to establish the production technique of a cavity having a high gradient and operated for the high power testing of the klystron and couplers being installed in the superconducting cavities. An accelerating electric field stability of 0.3% (rms) in amplitude and 0.3 degree (rms) in phase is also required for the RF system in STF. In order to satisfy these requirements, a digital LLRF control system using FPGA is adopted, and the components required for the digital LLRF system have been developed.
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| THP011 | High Gradient Operation with the CEBAF Upgrade RF Control System | controls, resonance, feedback, electron | 589 | ||
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The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. It is planned to increase the energy to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.
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| THP012 | Adaptive Tuner Control in TRIUMF ISAC 2 Superconducting LINAC using Kalman Filter | controls, feedback, superconducting-RF, pick-up | 592 | ||
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The TRIUMF ISAC 2 RF control system uses phase locking self-excited control. Amplitude, phase and frequency control is achieved with I/Q voltage injection, and forward RF power is minimized with a tuner feedback loop. The phase difference between the input coupler and the output pickup drives a velocity servo system to provide tuning control. However, the presence of microphonics in the cryomodule, although under control by the Quadrature loop, still presents a noisy interference on the phase difference for the tuner. The tuner will follow this noise and generate more microphonics as a result. A first-order Kalman filter is used for an estimation of the phase difference and reduces the movement of the tuner.
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| THP017 | Magnet Hysteresis Control at LANSCE | power-supply, quadrupole, controls, acceleration | 601 | ||
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We have investigated the effects of magnet hysteresis in various beamlines at LANSCE (Los Alamos Neutron Science Center) and have developed procedures to control the effects. Particular challenges are presented by sets of magnets with parallel boosting and bucking windings on the same yoke powered by two families of supplies and by magnets whose fields are routinely reversed for different operating modes. The results of the procedures are more rapid recovery from power-off conditions and rapid switching between operating modes, with minimized re-tuning. The latter improvement has been beneficial in controlling a beam instability that has adverse effects on the users’ experiments.
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| THP018 | Design Progress of the Re-bunching RF Cavities and Hybrid Quadrupoles for the RAL Front-End Test Stand (FETS) | quadrupole, impedance, simulation, proton | 604 | ||
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The proposed FETS project at RAL will test a fast beam chopper in a 3.0 MeV H- Medium Energy Beam Transport (MEBT) line. Space restrictions in the MEBT line place constraints on component length and drive the requirement to identify compact component configurations. Two candidate re-bunching RF cavity designs are considered: the space efficient Drift Tube Linac type (DTL) with integrated quadrupoles, and the high shunt impedance Coupled Cavity Linac type (CCL) with external quadrupoles. Preliminary RF simulations in 2D and 3D are presented, and a comparison, emphasising the advantages and disadvantages of each design is made. The compact hybrid quadrupole configurations considered are the 'tandem' combination of permanent magnet (PMQ) and electro-magnetic (EMQ) types, and the concentric combination of PMQ and laminar conductor (Lambertson) EMQ types. The suitability of the compact hybrid quadrupole for implementation in the low energy Drift Tube Linac (DTL) is suggested and discussed.
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| THP019 | Commissioning of the Digital LLRF for the CEBAF Injector/Separator | controls, feedback, insertion, instrumentation | 607 | ||
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The design and production of the CEBAF accelerator 499 MHz digital Low-Level RF control system has been completed. The first five systems were installed for use with the CEBAF Separator RF deflecting cavities operating at 499 MHz. The next four systems were installed in the injector on the chopping cavities (also 499 MHz deflecting cavities). The new LLRF system replaced an analog system that was over 15 years old. For initial testing an extensive acceptance plan along with a LLRF test stand was developed and incorporated to assure system performance as well as reliability. Various VHDL firmware was developed and modified to support operation of this system and included specific operational diagnostics. Once the acceptance tests were completed, the new systems were installed in the accelerator, in parallel with the existing analog LLRF, for extensive in-situ testing and comparison. After system commissioning, the new RF systems were assigned to the CEBAF accelerator and turned over to Accelerator Operations. This paper will address the VHDL firmware evolution, the automated tests and the performance measurements made through out the installation and commissioning process.
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| THP022 | Status of RF Sources in Super-Conducting RF Test Facility (STF) at KEK | klystron, superconducting-RF, controls, acceleration | 613 | ||
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Super-conducting rf test facility (STF) has been progessing in KEK since 2005. In this paper, we describe the current status of rf sources in STF. STF rf sources comprise of a long pulse modulator with bouncer circuit, a pulse transformer, an L-band 5MW klystron, power distribution system and low level rf system. We have completed the construction of the first rf system and have been testing for the system evaluation and for the coupler test of the super-conducting cavity. We have a schedule to feed a power to the cryomodule with 8 super-conducting cavities in December of 2006. We also describe the plan of the second rf sources of STF.
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| THP023 | Status of and Future Plan for the NSRL Microwave Power System | klystron, power-supply, controls, radiation | 616 | ||
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In this paper, 20MW microwave power system for NSRL (National synchrotron radiation Laboratory) Linac is introduced. The power system includes five s-band 20MW klystrons and their modulators. In 2002, the klystron modulators and the control system were upgraded. Constant-current, switching power supplies were employed to replace the old conventional LC resonant charging facilities. The new system has run for four years and played an important role in the operation of the 200MeV LINAC. A new soft x-ray FEL project (HTF) is now proposed in NSRL, the energy of electron beam will be increase from 200MeV to 800MeV. Seven s-band 80 MW klystrons and modulators will be employed as the new microwave power sources. The low energy spread specification of the Linac sets a stringent requirement to the stability of the klystron modulators. The paper also presents the technical considerations and preliminary design of the new system
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| THP026 | HIGH POWER TEST OF COUPLER WITH CAPACITIVE WINDOW | vacuum, coupling, linear-collider, collider | 625 | ||
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New type of coupler with capacitive-coupling inner conductor is designed in KEK. This coupler has a module structure, which is convenient for mass-production, assembling and repairing. Four samples of couplers were made and two of them were tested at high power level. The main parameters of the couplers and test results are presented in this paper.
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| THP032 | A Variable Directional Coupler for an Alternate ILC High-Power RF Distribution Scheme | coupling, polarization, klystron, quadrupole | 643 | ||
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We describe the design and functionality of an RF directional coupler for which the power division between the output ports is mechanically variable. In an alternate power distribution scheme for the ILC, power is delivered to cavities in pairs, through hybrids. Four pairs, or eight cavities, are fed from one waveguide feed, from which one fourth, one third, and one half of the power is coupled out at consecutive directional couplers. Three such feeds are powered by a single 10 MW klystron. Experience suggests that cavities considered useable will display some variation in the operational accelerating gradient they can sustain. With fixed distribution, the klystron power must be kept below the level at which the weakest cavity out of 24 receives its power limit. This problem can be solved by installing variable attenuators, but that means wasting precious power. With adjustable coupling, distribution can be optimized for more efficient use both of available power and of the accelerating cavities. This novel device, feeding cavities paired by similar performance, can provide such benefit to the ILC.
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| THP033 | Pulsed RF Heating Particularities in Normal-Conducting L-band Cavities | gun, booster, cathode, positron | 646 | ||
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For present projects, such as X-FEL and ILC, the SC technology is chosen for the main linacs. However, in some special parts, NC cavities are applied, operating with high electric and magnetic fields. RF gun cavities with an electric field up to 60 MV/m at the photo cathode are now under development. Capture cavities in the ILC positron source should operate with an accelerating gradient of up to 15 MV/m, practically the same value (14 MV/m), as for the CDS booster cavity in the Photo Injector Test Facility at DESY in Zeuthen (PITZ). High field strength leads to high specific RF heat loading. In combination with long RF pulses (~ 1ms) it results in substantial surface temperature rise, small cavity shape deformations and measurable frequency shifts. In this report we discuss both particularities and some general regularities related to long pulse operation of L-band cavities. Results of 3D numerical simulations for cavity surface temperature, displacements distributions and corresponding frequency shifts for different cavities are presented and compared with existing experimental data. The presented results will give the input for cavities optimization and sub-systems improvements.
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| THP034 | Effective Standing-Wave RF Structure for Charged-Particle Beam Deflector | RF-structure, coupling, simulation, impedance | 649 | ||
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In this report we describe new standing wave pi-mode rf structure for charged particles deflection. For L-band frequency range parameters of the proposed structure are compared with classical TM110 mode deflecting cavity ones. With originating TE11n mode, our proposal has several times higher rf efficiency, one order wider pass-band and smaller (in times) transverse dimensions. The cavity design idea and typical are parameters are presented. Some particularities of the beam dynamics in the proposed structure are pointed out. Preferable field of structure application is discussed.
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| THP035 | Design on Accelerating Tube of High-Power Electron Linac for Irradiation Processing | electron, beam-losses, bunching, simulation | 652 | ||
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There is an unstable phenomenon for high-power electron linacs for irradiation processing. The main source of the instability of this type of linac comes from the thermal effect of the accelerator tube under an intense heat load. If a lot of injected electrons are lost in the tube, they can cause an intense and uneven heat load on the tube that may deform the cavities of the accelerator tube and deviate the correct acceleration phase relationship. In this paper, a constant gradient accelerating structure is chosen to accelerate the electron beam, and the designed phase velocity is gradually increased along the tube. By adjusting the size of the accelerating cavities and the phase velocity function, a high capture-efficiency is reached. After a series of simulations studies, we obtained a 90% capture-efficiency, which minimizes the probability of the unstable phenomenon in the high power electron linac.
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| THP039 | Status of the RF Systems for the SPIRAL2 Linac at the Beginning of the Construction Phase | controls, rfq, ion, diagnostics | 664 | ||
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The Spiral 2 project uses an RFQ and a superconductiong linac to accelerate high intensity beams of deuterons and heavier ions. The accelatoror frequency is 88 MHz. The construction phase was approved in Mai 2005 and the project organization was recently finalized. The RF Systems activity includes power amplifiers and control electronics for all the accelerator and some of the RF devices on the beam line: the slow and fast chopper and the rebunchers. The paper describes the status of the amplifiers prototypes, the architecture chosen for the digital LLRF and the preliminary studies on the other RF devices.
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| THP040 | New Concept of Small Delay Line Type RF Pulse Compressor Using Coupled Cavities | beam-loading, klystron, simulation, coupling | 667 | ||
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I propose a new concept for the RF pulse compressor using the coupled cavities to make a small delay line. This new concept is a hybrid scheme of a cavity type and a delay line type of the RF pulse compressor. The delay line produces the pulse compression outputs through resultant RF beat between two inputs connected both ports of the coupled cavities. The time constant of the beat is matched to the time constant of the power flow of the coupled cavities. Further the special test stand for the coupled cavities was developed to easily adjust the resonant frequency of such high-Q coupled cavities.
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| THP041 | 400-kW RF Amplifier for a 201.5-MHz Deuteron RFQ Accelerator | rfq, power-supply, proton, klystron | 670 | ||
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The dedicated 400kW RF amplifier with hypervaportron TH781 tetrode for a 201.5MHz Deuteron RFQ accelerator has been manufactured and tested successfully. It can deliver 400kW pulse power over RF frequency range from 199MHz to 203MHz with maximum pulse duration of 1ms and 10% duty cycle. The exciter with solid state transistors can output 1kW at both CW and pulse modes. The driver stage can output maximum 20kW. The dummy load with CW 50kW and peak to average ratio of 10 has been modified to fit the requirements of amplifier test measurements.
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| THP042 | Development of High-Current 201.5-MHz Deuteron RFQ Accelerator | rfq, simulation, ion-source, ion | 673 | ||
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The beam dynamics for a 201.5MHz 50mA 2.0MeV Deuteron RFQ accelerator with duty cycle of 10% has been further improved by using equipartitioning method. The RFQ structure, mechanical design, thermal analysis and its cooling method have been investigated. The tuning of RF cavity for the field and other parameters has been simulated. A new developed ECR ion source and its setup have been completed and tested. The LEBT for the injection of RFQ is under the construction, and the HEBT at RFQ exit for the further applications has been designed and to be constructed in the near future. All the development results will be presented in this paper.
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| THP043 | The RF System of the Sparc Photo-Injector @ LNF | klystron, gun, vacuum, controls | 676 | ||
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The S-band linear accelerator SPARC is in advanced phase of installation and test at the INFN Frascati Laboratories. The purpose of the machine is to produce low emittance, high peak current electron beams to drive a SASE-FEL experiment. The SPARC RF system consists of an RF gun followed by 3 S-band room-temperature accelerating structures, supplied by 2 pulsed high power klystrons. The use of waveguide power attenuators and phase-shifters is foreseen to adjust independently the accelerating structures field amplitude and phase; this will be helpful for tuning the linac working point in the initial machine set-up. This paper reviews the experience in installation, RF conditioning, and commissioning of the normal conducting linac accelerating structures and RF subsystems.
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| THP044 | Design and Development of RF Structures for Linac4 | klystron, coupling, booster, quadrupole | 679 | ||
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Linac4 is a new 160 MeV H- linac proposed at CERN to replace the 50 MeV Linac2 as injector to the PS Booster, with the goal of doubling its brightness and intensity. The present design foresees after RFQ and chopping line a sequence of three accelerating structures: a Drift Tube Linac (DTL) from 3 to 40 MeV, a Cell-Coupled DTL (CCDTL) to 90 MeV and a Side Coupled Linac (SCL) up to the final energy. The DTL and CCDTL operate at 352 MHz, while in the SCL the frequency is doubled to 704 MHz. Although the injection in the PS Booster requires only a low duty cycle, the accelerating structures are designed to operate at the high duty cycle required by a possible future extension to a high power linac driver for a neutrino facility. This paper presents the different accelerating structures, underlining the progress in the design of critical resonator elements, like post-couplers in the DTL, coupling slots in the CCDTL and bridge couplers for the SCL. Alternative structures to the SCL are analysed and compared. Prototyping progress for the different structures is reported, including the RF design of a DTL tank prototype and results of low and high power tests on a CCDTL prototype.
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| THP049 | LANSCE DTL Longitudinal Field Measurements at High Power | insertion, resonance, proton, acceleration | 691 | ||
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Shifts in proton beam tuning were observed in the DTL portion of the Los Alamos Neutron Science Center (LANSCE) Accelerator corresponding with cooling system obstructions during the 2003 operational cycle. A diagnostic system was developed to measure longitudinal field changes at the operational field levels to confirm the source of the tune shifts and track the effectiveness of cooling system repairs. This paper describes the diagnostic system and the results of field distribution measurements at high RF power in the accelerating structures.
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| THP051 | Status of 3.9-GHz Superconducting RF Cavity Technology at Fermilab | superconducting-RF, vacuum, controls, higher-order-mode | 695 | ||
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Fermilab is involved in an effort to design, build, test and deliver 3.9 GHz superconducting RF cavities with a goal to deliver one 'third harmonic' cryomodule containing four cavities in early 2007 for use at the DESY TTF III Project. The design gradient of these cavities is 19 MV/m. This effort involves design, fabrication, intermediate testing, assembly, and eventual delivery of the four cavity cryomodule. We report on all facets of this enterprise from design through future plans. Included will be early test results of single 9-cell cavities, lessons learned, and other findings.
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| THP052 | Tests Results of Beta 0.12 Quarter-Wave Resonator for the SPIRAL2 Superconducting Linac | cryogenics, controls, heavy-ion, vacuum | 698 | ||
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New developments and tests have been carried out, at IPN-Orsay, on high β = 0.12, 88 MHz superconducting Quarter Wave Resonators. These resonators will be installed in the high beta section of the LINAC driver. RF tests results of the prototype cavity are reported. The fabrication of 2 pre-series cavities and their cryomodule is in progress in order to be ready for high power RF tests at 4.2 K at the beginning of 2007.
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| THP054 | Spoke Cavity Developments for the EURISOL Driver | vacuum, proton, cryogenics, diagnostics | 704 | ||
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EURISOL is the next generation of Radioactive Ion Beam (RIB) facility which aims at the provision of high intensity beams of radioactive nuclei with variable energy, from a few keV to greater than 100 MeV per nucleon, at an intensity several orders of magnitude higher than those currently available. The driver of EURISOL has to accelerate protons at a final energy of 1 GeV and 5 mA current, but also deuterons at 200 MeV (total energy). For the intermediate energy part of the driver, a solution based on superconducting (SC) spoke cavities is under study at the IPN Orsay laboratory. In this paper are presented the results of beam dynamics simulations for the linac, experimental results on the β = 0.15 spoke cavity, as well as achievements on the power coupler and cold tuning system. A new horizontal cryostat for performing a test of a fully equipped spoke cavity is detailed and an optimized design for a new β ~0.35 spoke prototype is also presented.
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| THP056 | Design of 325-MHz Single and Triple Spoke Resonators at FNAL | proton, vacuum, pulsed-power, target | 707 | ||
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We present the design of two 325 MHz superconducting single spoke resonators at β=0.22 and β=0.4 and a 325 MHz superconducting triple spoke resonator at β=0.62 for the front end of a 2 MW proton linac. We describe the optimization of the spoke resonator electromagnetic performance and how the resonator structural integrity and shape is ensured. We describe the mechanical design of the slow tuner mechanism and, via a coupled ANSYS-MWS analysis, how the mechanism adjusts the resonator operating frequency. The RF design of the power coupler is also presented
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| THP057 | Design of Normal Conducting 325-MHz Crossbar H-Type Resonators at Femirlab | lattice, focusing, vacuum, impedance | 710 | ||
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The warm section of the proposed High Intensity Neutrino Source at Fermilab is designed to accelerate H- ions and protons from 2.5 MeV to 10 MeV (β=0.0744 to β=0.1422). After the ion source, the beam will travel through a radio frequency quadrupole, a medium energy beam transport (two buncher cavities and a chopper) and finally 16 normal-conducting resonators, all separated by superconducting solenoids in individual cryostats. Over 10 MeV the design uses superconducting resonators and solenoids in common cryomodules. In this paper the electromagnetic design and optimization of all the 325 MHz Crossbar H-type normal-conducting resonators is presented. The mechanical design, performance and fabrication of the first prototype (β=0.0744) is presented in detail. The design of the prototype for the input coupler that will be used in the resonators is included.
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| THP058 | Proposed LLRF Improvements for Fermilab 201.25 MHz Linac | beam-loading, feedback, coupling, pick-up | 713 | ||
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The Fermilab Proton Plan, tasked to increase the intensity and reliability of the Proton Source for 10 or more years of operation, has identified the Low Level RF (LLRF) system as the critical component to be upgraded in the Linac. The current 201.25 MHz Drift Tube Linac was designed and built over 30 years ago and does not meet the higher beam quality demands required under the new Proton Plan. Measurement data, used to characterize the system, has been collected as input for a new computer model of the system. This model shows what improvements can be made by replacing the LLRF system to improve beam quality. The model includes RF driver amplifiers, a 5 MW 7835 triode power amplifier, the high voltage switch tube modulator, and the drift tube cavity. Complete system gain and bandwidth characterization data has been collected for the 7835 triode power amplifier, modulator and RF driver stages. This model will be a useful analysis tool for present and future Linac system upgrades.
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| THP061 | High Field Test Results of Superconducting 3.9-GHz Accelerating Cavities at FNAL | simulation, resonance, pick-up, pulsed-power | 722 | ||
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The XFEL facilities are planning to use section with a few third harmonic cavities (3.9GHz) to improve beam performance [1]. Fermilab is developing superconducting third harmonic section for the FLASH(TTF/DESY) upgrade. This section will include four cavities equiped with couplers and blade tuners installed in cryostat. Up to now, two cavities are completed and one of them is under vertical test. The gradient of the cavity was limited by multipactor in HOM coupler. The visual inspection of the HOM couplers after cold tests showed that both couplers were damaged. In paper we discuss the results of vertical tests, multipactoring analysis in HOM coupler and a new design for HOM coupler.
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| THP063 | First High-Power ACS Module for J-PARC Linac | vacuum, pick-up, ion, resonance | 725 | ||
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J-PARC Linac will be commissioned with energy of 181-MeV using 50-keV ion source, 3-MeV RFQ, 50-MeV DTL and 181-MeV SDTL (Separated DTL) on December 2006. It is planed to be upgraded by using 400-MeV ACS (Annular Coupled Structure), in a few years from the commissioning. The first high-power ACS module, which will be used as the first buncher between the SDTL and the ACS has been fabricated, and a few accelerating modules are also under fabrication until FY2006. Detail of cavity design and tuning procedure has been studied with RF simulation analysis and cold-model measurements. This paper describes RF measurement results, fabrication status, and related development items.
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| THP067 | Status of the Tuner for the 19-Cell Superconducting CH Prototype Cavity | simulation, cryogenics, radio-frequency, vacuum | 737 | ||
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The radio frequency tuning of the multi-cell superconducting CH structure for beta equal to 0.1 is investigated for a 19-cell niobium cavity operated at liquid helium temperature. By applying external mechanical forces the deformation of the structure is studied and the resulting change in frequency is analysed. The ruling equations of elasticity and the electromagnetic eigenvalue problem are solved by using commercial finite element tools. The quantitative results form the basis of an optimized tuning device. In order to guarantee a long lifetime of the cavity, fracture criteria are defined to avoid mechanical damage. Wherever possible the results are compared with experimental data obtained from measurements performed on the first CH prototype developed at the Institute of Applied Physics at Frankfurt. In addition a fast piezo device will be integrated into the slowly acting mechanical tuner. The whole system will operate in an existing horizontal cryostat for testing purposes.
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| THP068 | RF Characteristics of the SDTL for the J-PARC | insertion, proton, synchrotron, target | 740 | ||
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For the J-PARC linac, a Separated type DTL (SDTL) is used to accelerate an H- ion beam from 50MeV to 191MeV. The SDTL consists of 32 tanks and the operating frequency is 324MHz. It has 4 drift tubes and 2 half tubes (5cells), 2 fix tuners, 1 movable tuner and 1 RF input coupler. The inner diameter is 520mm and the length is approximately from 1.5m (SDTL1) to 2.5m (SDTL32). The focusing magnets are set between the tanks. We have measured the RF characteristics of the SDTL tanks and adjusted the field distribution since last summer. The measured Q value was above 90% of ideal SUPERFIS value, the field distribution was adjusted within ±1% for all the tanks. In this paper, the results of RF measurements of the SDTL tanks are described.
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| THP069 | DTL and SDTL Installation for the J-PARC | alignment, quadrupole, proton, synchrotron | 743 | ||
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Three DTL tanks and 30 SDTL tanks have been installed precisely in the under-ground tunnel of the J-PARC project. The alignment of the tank was mainly done by using an alignment telescope. The distance of the center axis of the tank from the beam axis was measured by the telescope of which axis is in the beam line. The distance is minimized by adjusting the position of the tank on the stand. The beam axis in the tank is defined by the two optical target which are put on the template fixed on both ends of the tank cylinder for the DTL. After the installation of the tanks the movable tuners and the input couplers were also fixed on the tank. In the paper the measured tank position will be described in detail.
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| THP072 | Fabrication and Low-Power Measurements of the J-PARC 50-mA RFQ Prototype | rfq, laser, vacuum, pick-up | 749 | ||
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In the Japan Proton Accelerator Research Complex (J-PARC) project, the beam commissioning of the H- linac will be started with a 30mA peak current. A 30mA type RFQ, which is developed for the former Japan Hadorn Facility (JHF) project, is used for the day-1 operation. However, it is required to accomplish the peak current of 50mA as soon as possible. For this purpose, we have developed an RFQ for the 50mA peak current, which is a four vane type RFQ and resonant frequency of which is 324MHz, same as the 30mA RFQ. In the R&D of this RFQ, we have adopted laser welding to join oxygen free copper blocks to be a cavity structure. The heat load of the laser welding can be more localized than that of the brazing, and the copper is not annealed, therefore, we think, it is possible to obtain more mechanical accuracy. We have developed a longitudinally 1/3 prototype cavity of the J-PARC 50mA RFQ. In this cavity, the distortion of the vane tips is measured to be less than 30 micro-meters, and the field uniformity of within 1% is obtained in a low power measurement after tuning. In this paper, we discuss about the fabrication and the low power measurement of this prototype cavity.
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| THP073 | High-Current Elliptical Cavity Design and Prototyping | pick-up, vacuum, simulation, injection | 752 | ||
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Beam instabilities due to undamped higher-order modes (HOMs) in the cavities can limit the performance of high-current superconducting accelerators, such as energy recovery linacs. If the accelerator is designed such that the bunch frequency is equal to the accelerating mode frequency and the beam pipe radius is chosen such that the cutoff frequency is less than twice that of the accelerating mode, all of the monopole and dipole HOMs that can be driven by the beam can be well-damped. A 6-cell elliptical cavity for speed-of-light particles and a 2-cell elliptical injection cavity have been designed for high-current accelerator applications. Both cavities have an aperture 29% larger than the TeSLA cavity, at the expense of peak surface fields about 10% higher for the same gradient. The injection cavity has a geometric β of 0.81 and was designed to accelerate electrons from 50 keV to 1 MeV, and the 6-cell cavity has a geometric β of 1 for further acceleration. Both cavities are designed for the purpose of accelerating hundreds of milliamps without HOM-induced beam breakup and to operate at 2.45 GHz. The cavity designs and prototype injection cavity results will be presented.
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| THP076 | Prototyping of a Superconducting Elliptical Cavity for a Proton Linac | proton, SNS, vacuum, radiation | 758 | ||
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A superconducting cavity has been designed for acceleration of particles travelling at 81% the speed of light (β = 0.81). Possible applications include the proposed Fermilab Proton Driver Linac. The cell shape is similar to the β = 0.81 cavity for the Spallation Neutron Source Linac, but the resonant frequency is 1.3 GHz rather than 805 MHz and the beam tube diameter matches that of the 1.3 GHz cavity for the TeSLA Test Facility. Six single-cell prototypes are being fabricated and tested. Three of these cavities are being formed from standard high purity fine grain niobium sheet. The rest are being fabricated from large grain niobium, following up on the work at Jefferson Lab to investigate the potential of large grain material for cost savings and/or improved RF performance. The fabrication of two 7-cell cavity prototypes (one fine grain, one large grain) is planned. A status report on this prototyping effort will be presented.
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| THP077 | A High-Gradient Test of a 30-GHz Copper Accelerating Structure | electron, pick-up, vacuum, acceleration | 761 | ||
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The CLIC study is investigating a number of different materials at different frequencies in order to find ways to increase achievable accelerating gradient and to understand what are the important parameters for high-gradient operation. So far a series of rf tests have been made with a set of identical-geometry 30 GHz and X-band structures in copper, tungsten and molybdenum. A new test of a 30 GHz copper accelerating structure has been completed in CTF3 with pulse lengths up to 100 ns. The new results are presented and compared to the previous structures to determine dependencies of quantities such accelerating gradient, material, frequency, pulse length, power flow, conditioning rate, breakdown rate and surface damage.
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| THP079 | High-Power Test of a 57-MHz CW RFQ | rfq, vacuum, acceleration, pick-up | 767 | ||
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High power heavy-ion drivers require a CW low-frequency RFQ for initial acceleration. The technique of high-temperature furnace brazed OFE copper cavities has proven to be very reliable for the production of high-quality CW accelerating structures. By appropriate choice of the resonant structure for the RIA driver RFQ we have achieved moderate transverse dimensions of the cavity and high quality accelerating-focusing fields required for simultaneous acceleration of multiple charge state ion beams. In our application the RFQ must provide stable operation over a wide range of RF power levels. To demonstrate the technology and high-power operation we have built an engineering prototype of one-segment of the 57-MHz RFQ structure [1]. The RFQ is designed as a 100% OFE copper structure and fabricated with a two-step furnace brazing process. The brazing process was successful and the cavity was shown to be vacuum tight. The errors in the tip-to-tip distances of the vanes average less than 50 microns. The RF measurements show excellent electrical properties of the resonator with a measured unloaded Q equal to 95% of the simulated value. Currently high-power tests are being performed.
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*J. W. Rathke et al., Preliminary Engineering Design of A 57.5 MHz CW RFQ for the RIA Driver LINAC. Proc. of the LINAC-2002, p. 467. |
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| THP084 | Design of an 8-Gev H- Transport and Multiturn Injection System | injection, lattice, proton, dipole | 779 | ||
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The baseline design of the transport and multiturn injection of 8 GeV H- to the FNAL Main Injector from a proposed 8 GeV superconducting linac will be discussed.
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| THP085 | Transportation of the DTL/SDTL for the J-PARC | acceleration, alignment, target, focusing | 782 | ||
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Three DTL tanks and 32 SDTL tanks for the Japan Proton Accelerator Research Complex (J-PARC) were assembled at KEK site. After the assembling, the aging of the DTL1 and 12 SDTL tanks and the beam acceleration test for the DTL1 was done. And then all the DTL and SDTL tanks have to be transported form KEK to JAEA. The distance is about 95km and special air suspension trailer is used. To confirm the effect to the accuracy of the drift tube alignment, we measured the displacement of the drift tube positions before and after the transportation by using a hot model tank. As a result of the test, the displacement of the drift tubes by the transportation was less than 0.02mm which meets our requirements. Based on this result, all the DTL and SDTL tanks were transported form KEK to JAEA. In this paper, the transportation results of the hot model tank and the DTL/SDTL tanks are described.
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| THP087 | Status of C-band Accelerating Section Development at the KEKB Injector Linac | klystron, impedance, positron, acceleration | 788 | ||
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This paper reports on C-band accelerating section development for future energy upgrade of the KEKB injector linac. Target field gradient is 42 MV/m, that is twice of the present S-band sections in the linac. Until now, we have developed four 1m-long sections based on a half-scale design of the S-band section with improvements in coupler cavity shape and in fabrication method. And the fifth accelerating section is in fabrication now. The four sections have already installed in the beam line of the linac. Together with a unit of C-band rf source (50 MW klystron, pulse modulator, rf-pulse compressor) installed in the linac, we will perform an operation test of a model C-band accelerator module that has almost same configuration as a design module in the upgrade. Results of the long-term operation test and beam acceleration study will be described. And present status of development of the fifth accelerating section will also be given.
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| THP089 | Testbench of the HICAT RFQ at GSI | rfq, ion, proton, RF-structure | 791 | ||
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In April 2006 the commissioning of the ion linac for the HICAT therapy facility in Heidelberg, Germany was started. In preparation of this commissioning process beam tests of the RFQ cavity with protons were carried out at GSI. The RFQ cavity for the HICAT facility was delivered to GSI in March 2005. The operation with an rf power up to 200 kW and a pulse width of 500 μsec could be accomplished successfully after a short time of rf-conditioning to assure the operation mode with carbon ions. A testbench for the RFQ cavity was constructed at GSI to allow for exact measurements of the output energy with the time of flight (ToF) method in addition to the beam tests at IAP Frankfurt. Due to the fact that the rebuncher is fully integrated into the RFQ rf-structure beam studies with different mechanical settings of the rebuncher had to be conducted. For each setting the effective voltage of the rebuncher could be estimated. The final mechanical setting was chosen with respect to required longitudinal matching to the IH structure behind of the RFQ.
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| THP091 | Experimental Study of Positron Production from Monocrystalline Targets at the KEKB Injector Linac | target, positron, electron, radiation | 797 | ||
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Intense positron sources are widely investigated for the next-generation of linear colliders and B-factories. A new method utilizing an axially-oriented crystal as a positron-production target is one of the bright schemes since it provides a powerful photon source through channeling and coherent bremsstrahlung processes when high-energy electrons penetrate the target. A series of positron-production experiments with tungsten crystal alone and diamond target combined with an amorphous tungsten plate have been carried out at the KEKB injector linac. The tungsten crystals with different thicknesses (2.2, 5.3, 8.9, 12.0 and 14.2 mm) and the diamonds with different thicknesses (4.57 and 7.25 mm) were tested on a goniometer by using 4 and 8-GeV electron beams, respectively. The positron-production yields were measured with a magnetic spectrometer at the positron momentum of 10 and 20 MeV/c. In this report the experimental results are summarized on the enhancements of the positron yield from these crystal targets compared to amorphous targets of the same thickness.
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*Email address: tsuyoshi.suwada@kek.jp |
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| THP092 | Control System for a Limitation of an Integrated Amount of Beam Charges Delivered from the KEKB Injector Linac | injection, controls, electron, positron | 800 | ||
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A new control system is under construction for radiation safety at the KEKB injector linac. The control system restricts the integrated amount of the beam charges delivered from an electron gun in order to keep the radiation safety with high reliability in a daily operation of the linac. The old control system of the radiation safety has been working based on a software control implemented on a UNIX-based workstation. However, this control system is not possible to be implemented for the long-term linac operation with high reliability. The new control system comprises a charge-integration-type analog circuit mounted along with a CPU chip and a data acquisition system based on programmable logic controllers. The fast analog circuit can detect the beam-charge signals delivered from a wall-current monitor, and control the beam-abort trigger pulses pulse-by-pulse. The new hardware-based control system may stabilize the radiation safety control for the long-term linac operation. In this report the design of the new control system is described along with preliminary test results.
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| THP093 | Polyhedral Cavity for Superconducting Linacs | coupling, collider, emittance, 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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| FR2003 | New Materials and Designs for High-Power, Fast-Phase Shifters | klystron, resonance, impedance, rfq | 829 | ||
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In the 100 MeV H- Linac to be constructed at Fermilab, the use of fast ferrite high power phase shifters will allow all accelerating RF cavities to be driven by a single 2.5 MW, 325 MHz klystron. This results in substantial cost savings. The tuners are coaxial with aluminum doped Yttrium Iron Garnet (YIG) ferrite. In combination with a branch line couplers, they will provide independent phase and amplitude control for each cavity. This is achieved by adjusting the solenoidal magnetic field applied to the ferrite. We report on our results in both low power (timing) and high power tests, for both 3'' and 1-5/8'' OD phase shifters. The low power measurements demonstrate that the rate of phase shift is well within the spec of 1 degree/us. The high power tests were performed at the Advanced Photon Source at Argonne National Lab. We measured phase shifts and the failure point (applied power) for tuners in various configurations. In addition, we performed phase and amplitude measurements for a setup consisting of a 1-5/8'' OD phase shifter along with a prototype branch line coupler.
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