| Paper | Title | Other Keywords | Page |
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| MOPC062 | EMMA RF Comissioning | cavity, LLRF, acceleration, controls | 226 |
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| EMMA (Electron Model for Many Applications), the world’s first Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) accelerator is presently in operation at Daresbury Laboratory. The LLRF system is required to synchronize with ALICE (Accelerators and Lasers in Combined Experiments) its injector, which operates at 1.3GHz, and to produce an offset frequency of (+1.5 MHz to -4 MHz) to probe the longitudinal beam dynamics and to also maintain the phase and amplitude of the 19 copper RF cavities of the EMMA machine. The design, commissioning and results of the EMMA RF system is presented. | |||
| MOPC071 | Status of High Power Tests of Normal Conducting Short Standing Wave Structures* | coupling, klystron, electron, status | 241 |
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Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515 We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures. |
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| MOPC143 | A Reduced Gradient Output Design for SLAC's XL4 X-Band Klystron | simulation, klystron, cavity, impedance | 412 |
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Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515. X-band klystron work began at SLAC in the mid to late 1980's to develop high frequency (4 times the SLAC S-band klystron), high power RF sources for the linear collider designs under consideration at that time. This work culminated in the current workhorse X-band RF source, the XL4. To date 26 XL4 tubes have been built. The XL4 4-cell disk loaded traveling wave output structure has a high operating gradient. A new 6-cell structure has been designed to reduce breakdown and to further improve the klystron's robustness. Initial simulations show the 6-cell design reduces the gradient roughly 25% and that the structure is stable. A physical XL4 will be retrofitted with the new output cavity and hot tested in the near future. |
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| MOPC165 | Digital Low Level RF Development at Daresbury Laboratory | cavity, controls, LLRF, linac | 469 |
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| Digital LLRF development using Field Programmable Gate Arrays (FPGAs) is a new activity at Daresbury Laboratory. Using the LLRF4 development board, designed by Larry Doolittle of Lawrence Berkeley National Laboratory, a full featured control system incorporating fast feedback loops and a feed-forward system has been developed for use on the ALICE (Accelerators and Lasers in Combined Experiments) energy recovery linac. Technical details of the system are presented, along with experimental measurements. | |||
| MOPS035 | Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac | gun, electron, linac, bunching | 679 |
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Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program RF linacs for high power beams are operated in the fully beam-loaded condition for the power efficiency. In this condition, temporal energy spreads are induced by the transient beam loading effect. Irradiation sources require the beam energy of less than 10 MeV to prevent undesirable neutron production. In order to maximize the beam power and maintain the beam energy in a safe value, we need to suppress the temporal energy spreads. In an L-band traveling-wave linac for irradiation sources, the high energy electrons are suppressed by the beam current modulation with the RF power modulation. As a result, the average beam energy and the corresponding beam power are improved by nearly 60% compared to the case without any modulations. |
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| MOPS037 | High Intensity Transient Beam Dynamic Study in Travelling Wave Electron Accelerators with Accounting of Beam Loading Effect | simulation, linac, space-charge, electron | 682 |
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The beam loading effect is one of main problems limiting the beam current. The methods of beam dynamic simulation taking into account the beam loading effect were discussed previously. Simulation methods and the especial code version BEAMDULAD-BL was described in the paper*. The beam loading effect was considered only for traveling wave linacs and for stationary beam only. Now it is important to study the beam dynamics of short current pulses, i.e. for transient process. We can consider only one beam bunch (or a packet of bunches) in a long external RF field pulse in stationary case. The beam radiation and wave fields can be calculated in the quasi-statically approximation. This approximation can not be used for transient mode. The methods of beam dynamics simulation will be discussed in this paper for transient mode. New code version BEAMDULAC-BLNS will be described. The simple test simulations will be carried out.
* A.V. Voronkov et al., "Beam Loading Effect of High Current Trawling Wave Accelerator Dynamic Study", Proc. of IPAC’10, Kyoto, Japan, TUPEA012, p. 1348 (2010). |
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| TUPC059 | Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun | laser, electron, cavity, gun | 1132 |
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Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program. At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans. |
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| WEPS097 | Performance of Multi-harmonic RF Feedforward System for Beam Loading Compensation in the J-PARC RCS | cavity, impedance, acceleration, beam-losses | 2733 |
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| The beam loading compensation is a key part for acceleration of high intensity proton beams in the J-PARC RCS. In the wide-band MA-loaded RF cavity, the wake voltage consists of not only the accelerating harmonic component but also the higher harmonics. The higher harmonic components cause the RF bucket distortion. We employ the RF feedforward method to compensate the multi-harmonic beam loading. The full-digital feedforward system is developed, which compensates the first three harmonic components of the beam loading. We present the results of the beam test with a high intensity proton beam (2.5·1013 ppp). The impedance seen by the beam is greatly reduced, the impedance of the fundamental accelerating harmonic is reduced to less than 25 ohms in a full accelerating cycle, while the shunt resistance of the cavity is in the order of 800 ohms. The performance of the feedforward system is promising for achievement of the design beam power, 1 MW, in the future. | |||