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| MO1003 | Commissioning of the J-PARC Linac | linac, rfq, 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) | linac, acceleration, 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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| MOP002 | Efficient Long-Pulse, Fully Loaded CTF3 Linac Operation | linac, beam-loading, acceleration, 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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| MOP012 | Upgrade Status and Commissioning of BEPCII Linac | linac, positron, gun, 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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| MOP021 | Recent Operation of the ORELA Electron LINAC at ORNL for Neutron Cross-Section Research | gun, electron, vacuum, target | 79 | ||
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The ORNL electron LINAC, ORELA, began operation in 1969 and has been instrumental in providing improved neutron cross section data for many isotopes over the 0.002-60 MeV energy range. The ORELA utilizes a 4-30 ns <1000 Hz pulsed gridded electron gun, a 4 section RF Linac, and a water-cooled and moderated tantalum target to generate short neutron pulses. The short pulse lengths and long flight path provide high neutron energy resolution. Beam energy can range up to 180 MeV and a neutron production rate of up to 1014 n/sec can be generated with 50 kW of beam power. Recent operation is a 8 ns, 525 Hz pulse and a target power of 5-10 kW. RF power for the accelerator sections are provided by four 24 MW 1300 MHz klystrons. Recent activities have included improvements to the accelerator vacuum, klystrons, interlocks and other upgrades. The current ORELA program is focused on cross-section measurements for the Nuclear Criticality Safety Program and for nuclear astrophysics. Detection and data analysis capabilities have been developed for making highly accurate measurements of neutron capture, neutron total, (n,alpha), and (n,fission) cross sections simultaneously on different beam lines.
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| MOP025 | Study on High-Current Multi-Bunch Beam Acceleration for KEKB Injector Linac | linac, 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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| MOP040 | Design of the PEFP 100-MeV Linac | proton, linac, rfq, quadrupole | 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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| MOP041 | Test Results of the PEFP 20-MeV Proton Accelerator | rfq, proton, power-supply, site | 133 | ||
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A 20 MeV proton accelerator has been developed by Proton Engineering Frontier Project (PEFP). The accelerator consists of a 50 keV proton injector, a 3 MeV radio frequency quadrupole (RFQ) and a 20 MeV DTL (Drift Tube Linac). The preliminary test is being performed at KAERI (Korea Atomic Energy Research Institute) site. A pulsed proton beam is extracted from the proton injector by switching the high voltage power supply of the ion source. The beam transmission rate through the RFQ was measured with respect to the vane voltage to set the operating point. The 20 MeV DTL consists of four tanks and the beam transmission characteristics have been checked for various parameters. In this paper, a test stand for a 20 MeV accelerator at KAERI site is introduced and the test results are discussed.
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| MOP050 | Construction Plans for the LENS Proton Linac | proton, rfq, target, linac | 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, linac, 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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| TUP001 | Linac Automated Beam Phase Control System | linac, controls, 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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| TUP004 | Intense L-Band Electron Linac for Industrial Applications | coupling, linac, electron, impedance | 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 | linac, electron, 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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| TUP045 | Photothermal Cathode Measurements at the Advanced Photon Source | cathode, laser, gun, electron | 349 | ||
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The Advanced Photon Source (APS) ballistic bunch compression (BBC) injector presently uses an M-type thermionic dispenser cathode as a photocathode. This “photothermal” cathode offers substantial advantages over conventional metal photocathodes, including easy replacement and easy cleaning via the cathode’s built-in heater. We present the results of quantum efficiency measurements as a function of cathode heater power, laser pulse energy, and applied rf field strength.
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| TUP092 | Emittance Exchange at FNPL | emittance, coupling, electron, pick-up | 478 | ||
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An experiment to attempt the exchange of the transverse emittance with the longitudinal emittance of the Fermilab/NICADD PhotoInjector electron beam is being developed. The emittance exchange occurs by placing a TM110 mode RF cavity in the maximum dispersive region of a magnetic chicane. Properly employed, the cavity's longitudinal shearing Electric field zeros the momentum spread at the cost of generating a non-zero betatron oscillation amplitude. We report on the beam line modeling, beam line design, the RF cavity design, present status as well as the future program.
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| WE2004 | 100 MeV High-Duty-Factor Proton Linac Development at KAERI | proton, rfq, linac, 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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| TH1002 | Cryomodule Test Facilities and Multicell Cavity Performance for the ILC | linac, linear-collider, 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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| TH2003 | Recent Developments in Pulsed High-Power Systems | pulsed-power, kicker, linear-collider, collider | 541 | ||
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Pulsed power systems are inherent in any high power accelerator system. Applications include, among others, modulators for powering high power klystrons, pulsed power systems to drive linear induction accelerating cells, kicker magnet drivers for storage rings, and a wide variety of beam deflection and pulsed focusing systems. As with many enabling technologies, component limitations and materials properties dominate the engineering tradeoffs that must be made during the system design. An overview of the state-of-the-art in major components of pulsed power systems will be presented. An examination of how those components are being integrated into linac systems will also be performed and an overview of these systems shall be given. The relatively recent shift toward solid-state power electronics solutions to pulsed power engineering problems will be emphasized. Finally, some future trends in the field will be examined.
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| THP001 | Conceptual LLRF Design for the European X-FEL | controls, feedback, diagnostics, resonance | 559 | ||
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The LLRF System for the superconducting cavities of the European X-FEL must support an amplitude and phase stability of the accelerating fields of up to 0.01% and 0.01 deg. respectively. The stability must be achieved in pulsed operation with one klystron driving 32 cavities. This goal can only be achieved with low noise downconverters for field detection, high gain feedback loops and sophisticated feedforward techniques. State-of-the art technology including analog multipliers for downconversion, fast ADCs (>100 MHz) with high resolution (up to 16 bit), and high performance data processing with FPGAs with low latency (few hundred ns) allow to meets these goals. The large number of input channels ( >100 including probe, forward and reflected signal of each of the 32 cavities) and output channels (>34 including piezo tuners for each cavity) combined with the tremendous processing power requires a distributed architecture using Gigalink interfaces for low latency data exchange.
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| THP002 | Exception Detection and Handling for Digital RF Control Systems | controls, linac, 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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| THP006 | Performance of a Digital LLRF Field Control System for the J-PARC Linac | controls, beam-loading, feedback, linac | 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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| THP009 | Performance of RF Reference Distribution System for the J-PARC Linac | controls, linac, 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, feedback, linac, 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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| THP013 | Adaptive Control of a SC Cavity Based on the Physical Parameters Identification | controls, feedback, radio-frequency, resonance | 595 | ||
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The paper presents preliminary results of SRF cavity control by FPGA system called "SIMCON". Algebraic model of the control system including calibration and correction procedure of the signal path was discussed. In particular, there were debated the following aspects of the automatic control procedures: compensation of the input offset, calibration of the cavity channel and correction of the klystron channel (linearization). Functional structure of FPGA based SIMCON board for LLRF Cavity Control System was explained. Alghoritm of adaptive control for cavity driven with FPGA controller supported by MATLAB system was discussed. Experimental results for 8 cavities of ACC1 module controlled by the SIMCON board were shown. The resuls lead to novel method of parameters identification of cavity system in noisy and no stationary conditions.
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| THP016 | Active Compensation of Lorentz Force Detuning of a TTF 9-Cell Cavity in CRYHOLAB | simulation, controls, feedback, radiation | 598 | ||
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Linear colliders and free-electron lasers projects based on the superconducting RF technology require high gradient pulsed operation of superconducting elliptical multicells. The cavities are subject to Lorentz force detuning which reflects on an increased RF power consumption when trying to stabilize the accelerating field during the beam passage. This pulsed detuning can be mechanically compensated using a fast piezoelectric tuner. A new tuner with integrated piezoelectric actuators has been developed in the framework of CARE/SRF european program. The tuning system has been tested on a fully equipped 9-cell TTF cavity in the CRYHOLAB horizontal cryostat using the pulsed 1.3 GHz 1 MW RF source. In virtue of the high pulse to pulse repeatability of the detuning, the compensation of Lorentz detuning was achieved successfully using a simple feed forward scheme.
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| THP022 | Status of RF Sources in Super-Conducting RF Test Facility (STF) at KEK | superconducting-RF, controls, acceleration, linac | 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 | linac, 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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| THP027 | Study of PPM-Focused X-band Pulse Klystron | cathode, linear-collider, simulation, collider | 628 | ||
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The R&D of PPM (Periodic Permanent Magnet)-focused X-band pulse klystrons has been conducted since 1999, originally for Global Linear Collider (GLC) project. So far six prototype tubes have been tested. Some of them successfully produce the power required in GLC (75MW, 1.6μsec pulse width). However their performance was not perfect as a GLC tube. The problems are the stability of RF output and the gun performance. Since GLC programs were terminated in 2004, some limited work on the improvement of the PPM tubes continues at X-Band Test Facility (XTF) in KEK. The work includes the test to evaluate the performance of revised (rebuilt) tubes as well as disassembling these tubes after the test for further inspection. Recent results are reported.
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| THP030 | Investigation of Ferroelectrics for High-Power RF Phase Shifters in Accelerator Systems | impedance, simulation, vacuum, SNS | 637 | ||
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High power vector modulators enable independent control of RF power to each accelerating cavity, allowing a fan-out configuration to be used to power many cavities from a single high-power klystron. Previously, ferrite materials have been used in high-power phase shifters and vector modulators. It is shown that ferroelectric materials such as barium-strontium titanate (BST) can also be used in such tunable structures. Since ferroelectrics are controlled by an electric, rather than magnetic field, tuning can be faster than tuning a ferrite-loaded device. A BST-loaded coaxial structure is investigated theoretically and experimentally. Good high voltage performance is critical since DC biasing voltages of up to 80 kV can be impressed on the BST sections for tuning. It can also be seen that matching structures around the BST can improve performance over a wider range of amplitudes and phases.
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| THP031 | Pulse Cables For XFEL Modulators | impedance, simulation, pulsed-power, radiation | 640 | ||
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For the XFEL, housed in a single tunnel, most of the modulators will be placed in a central modulator building outside of the tunnel. The pulse transformers and the klystrons will be positioned inside the tunnel near the superconducting linac. Therefore the energy has to be transported via pulse cables. These cables have lengths between 350m and 1.7 km. The power is up to 16.8 MW per pulse with a repetition rate of 10 Hz. In order to keep the rise time short and match the klystron impedance four 25Ohm cables will be put in parallel. A tri-axial design was chosen to prevent magnetic field outside of the cables in order not to disturb electronics or electron beam. A prototype of the cable was produced in industry and delivered to DESY. A set of four 1.5km long parallel cables is in test at present at one of the modulators of the TTF/VUV-FEL at DESY. The cable design criteria 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, quadrupole, linac | 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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| THP040 | New Concept of Small Delay Line Type RF Pulse Compressor Using Coupled Cavities | beam-loading, simulation, linac, 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, linac, power-supply, proton | 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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| THP043 | The RF System of the Sparc Photo-Injector @ LNF | gun, linac, 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 | linac, 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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| THP048 | Band Gap Structures of PBG and Rod-loaded Cavities | dipole, damping, lattice, quadrupole | 688 | ||
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The band-gap structures for rod loaded (RL) and photonic band gap (PBG) cavities are calculated with 2D and 3D frequency domain codes. It is shown that an RL cavity with a single circle of rods can exhibit similar behavior as a conventional single-defect PBG cavity. A systematic method of computing the unloaded Q factor using SUPERFISH has been implemented. Results are compared with GdfidL and Gd1 calculations.
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| THP060 | Capture Cavity II at Fermilab | vacuum, resonance, instrumentation, cryogenics | 719 | ||
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Capture Cavity II is a 9-cell high gradient TESLA Superconducting cavity intended to upgrade the existing Fermilab Photoinjector electron beam energy from 15MeV to 40Mev. DESY provided the cavity which performed to 33MV/m. Beam tube component preparation and installation onto the cavity was completed at DESY. The cavity was shipped to FNAL under vacuum. Installation and testing of this cavity has provided an opportunity to demonstrate Fermilab’s SCRF High Power Testing infrastructure. We report on the high power RF tests performed with Capture Cavity II at both 4.5K and 1.8K, Cryogenic System Performance, Piezo Electric based fast tuner, and low level RF control.
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| THP065 | High-Gradient Generation in Dielectric-Loaded Wakefield Structures | electron, simulation, laser, gun | 731 | ||
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Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 43 MV/m at 14 GHz. Short electron bunches (13 ps FWHM) of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. One of these structures consists of a 23 mm long cylindrical ceramic tube (cordierite) with a dielectric constant of 4.76, and inner diameter of 10 mm, inserted into a cylindrical copper waveguide. This standing-wave structure has a field probe near the outer edge of the dielectric to sample the RF fields generated by the electron bunches. The signal is sent to a mixer circuit, where the 14 GHz signal is down converted to 5 GHz and then sent to an oscilloscope. A similar structure, with smaller inner diameter and an operating frequency of 9 GHz, is ready for initial tests. Its accelerating fields will be twice as high as the fields in the 14 GHz structure, for the same bunch charge.
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| THP087 | Status of C-band Accelerating Section Development at the KEKB Injector Linac | linac, 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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| THP097 | FPGA BASED DIGITAL RF CONTROL FOR FLASH | controls, feedback, gun, cathode | 809 | ||
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Most parts of the LLRF control system used in FLASH are based on the DSP processors. Actual computation power of the system is close to the limit, the algorithm is performed in a time longer than 1μs. The only way to extend the system with new features was to add more DSP processors. This solution requires integration of new DSP board into existing system. It may cause some additional problems and delays in the machine operations. During past years very fast progress on the FPGA market was observed. Nowadays FPGA chips have reached the computation power that can be compared with DSP processors. These chips offer variety of the embedded solutions such as PowerPC, Microblaze, Nios which can be easily used in addition to fast, parallel signal processing. Moreover large number of user pins makes it possible to integrate all the elements necessary for the control into one PCB board. Therefore, for the evaluation purposes, some parts of the system were replaced by FPGA based boards. This article summarizes the FPGA boards that are currently in use and describes algorithms executed by these boards.
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| FR2003 | New Materials and Designs for High-Power, Fast-Phase Shifters | linac, 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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