Tamura, Fumihiko; Hotchi, Hideaki; Schnase, A.*; Yoshii, Masahito*; Yamamoto, Masanobu; Omori, Chihiro*; Nomura, Masahiro; Toda, Makoto*; Shimada, Taihei; Hasegawa, Katsushi*; et al.
Physical Review Special Topics; Accelerators and Beams, 18(9), p.091004_1 - 091004_8, 2015/09
The RCS in the J-PARC was originally designed to accelerate two high intensity bunches, while some of neutron experiments in the MLF and a muon experiment using MR beams require a single bunch operation mode. The beam intensity in the single bunch operation has been limited by longitudinal beam losses due to the rf bucket distortions by the wake voltage of the odd harmonics in the wide band MA cavities. We installed an additional rf feedforward system to compensate the wake voltages of the odd harmonics (h=1,3,5). The longitudinal beam losses during the single bunch acceleration disappeared with feedforward for the odd harmonics. We also confirmed that the beam quality in the single bunch acceleration are similar to that of the normal operation with two bunches. Thus, high intensity single bunch acceleration at the intensity of 2.310 protons per bunch has been achieved in the J-PARC RCS.
Bulanov, S. S.*; Esarey, E.*; Schroeder, C. B.*; Leemans, W.*; Bulanov, S. V.; Margarone, D.*; Korn, G.*; Haberer, T.*
Physical Review Special Topics; Accelerators and Beams, 18(6), p.061302_1 - 061302_6, 2015/06
Kondo, Yasuhiro; Morishita, Takatoshi; Yamazaki, Saishun; Hori, Toshihiko; Sawabe, Yuki; Chishiro, Etsuji; Fukuda, Shimpei; Hasegawa, Kazuo; Hirano, Koichiro; Kikuzawa, Nobuhiro; et al.
Physical Review Special Topics; Accelerators and Beams, 17(12), p.120101_1 - 120101_8, 2014/12
We performed a beam test of a new radio frequency quadrupole linac (RFQ III) for the beam current upgrade of the Japan Proton Accelerator Research Complex. First, the conditioning of RFQ III was conducted, and after 20 h of conditioning, RFQ III became very stable with a nominal peak power and duty factor of 400 kW and 1.5%, respectively. An off-line beam test was subsequently conducted before installation in the accelerator tunnel. The transmission, transverse emittance, and energy spread of the 50-mA negative hydrogen beam from RFQ III were measured and compared with simulation results. The experiment and simulation results showed good agreement; therefore, we conclude that the performance of RFQ III conforms to its design.
Shobuda, Yoshihiro; Chin, Y. H.*; Takata, Koji*
Physical Review Special Topics; Accelerators and Beams, 17(9), p.091001_1 - 091001_41, 2014/09
Shobuda, Yoshihiro; Chin, Y. H.*
Physical Review Special Topics; Accelerators and Beams, 17(9), p.092801_1 - 092801_8, 2014/09
Zhidkov, A.*; Masuda, Shinichi*; Bulanov, S. S.*; Koga, J. K.; Hosokai, Tomonao*; Kodama, Ryosuke*
Physical Review Special Topics; Accelerators and Beams, 17(5), p.054001_1 - 054001_7, 2014/05
Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*
Physical Review Special Topics; Accelerators and Beams, 17(5), p.053401_1 - 053401_17, 2014/05
Saha, P. K.; Harada, Hiroyuki; Hayashi, Naoki; Horino, Koki; Hotchi, Hideaki; Kinsho, Michikazu; Takayanagi, Tomohiro; Tani, Norio; Togashi, Tomohito; Ueno, Tomoaki; et al.
Physical Review Special Topics; Accelerators and Beams, 16(12), p.120102_1 - 120102_11, 2013/12
Tamura, Fumihiko; Omori, Chihiro*; Yamamoto, Masanobu; Yoshii, Masahito*; Schnase, A.*; Nomura, Masahiro; Toda, Makoto*; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*
Physical Review Special Topics; Accelerators and Beams, 16(5), p.051002_1 - 051002_12, 2013/05
Beam loading compensation is a key for acceleration of a high intensity proton beam in the MR of J-PARC. Magnetic alloy loaded rf cavities with a Q value of 22 are used to achieve high accelerating voltages. The cavity is driven by a single harmonic (h = 9) rf signal while the cavity frequency response also covers the neighbor harmonics (h = 8, 10). Therefore the wake voltage induced by the high intensity beam consists of the three harmonics, h = 8, 9, 10. We employ the rf feedforward method to compensate the beam loading ofthese three harmonics (h = 8, 9, 10). The full-digital multiharmonic feedforward system was developed for the MR. The commissioning of the feedforward system has been performed by using high intensity beams with 1.010 protons per pulse. The longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, stable high power beam operation is achieved.
Kondo, Yasuhiro; Morishita, Takatoshi; Hasegawa, Kazuo; Chishiro, Etsuji; Hirano, Koichiro; Hori, Toshihiko; Oguri, Hidetomo; Sato, Fumiaki; Shinozaki, Shinichi; Sugimura, Takashi*; et al.
Physical Review Special Topics; Accelerators and Beams, 16(4), p.040102_1 - 040102_8, 2013/04
We performed a high-power test of a new radio-frequency quadrupole (RFQ II) for the J-PARC linac. RFQ II was developed as a spare RFQ because the operating J-PARC RFQ has suffered from a sparking problem. First, the conditioning of RFQ II was carried out; after 50 h of conditioning, RFQ II became very stable with a nominal power and duty of 330 kW and 3%, respectively. Next the thermal properties were measured because the resonant frequency of RFQ II is tuned by changing the temperature of the cooling water. The frequency response was measured and compared to finite-element method simulation results, confirming that the simple two-dimensional model reproduces the experimental data well. The differences in the field distribution with changes in the rf loading and the cooling-water temperature were also measured, and no serious field distortion was observed. Therefore, we conclude that RFQ II can perform well as a high-power rf cavity.
Mizuta, Yoshio*; Hosokai, Tomonao*; Masuda, Shinichi*; Zhidkov, A.*; Makito, Keigo*; Nakanii, Nobuhiko*; Kajino, Shohei*; Nishida, Akinori*; Kando, Masaki; Mori, Michiaki; et al.
Physical Review Special Topics; Accelerators and Beams, 15(12), p.121301_1 - 121301_10, 2012/12
Kondo, Yasuhiro; Hasegawa, Kazuo; Morishita, Takatoshi; Jameson, R. A.*
Physical Review Special Topics; Accelerators and Beams, 15(8), p.080101_1 - 080101_6, 2012/08
We have performed the beam-dynamics design of an H radio frequency quadrupole (RFQ) for the beam-current upgrade of the Japan Proton Accelerator Research Complex linac (RFQ III). LINACSrfqDES was set up to support the conventional design method, i.e., design with CURLI-type shaper followed by constant bore radius and with constant intervane voltage, supplemented by keeping the equipartitioned condition in the gentle buncher section. For the particle simulation, LINACSrfqSIM was used. The obtained transmission, transverse and longitudinal emittance are 98.5%, 0.21 mm mrad, and 0.11 MeV deg for the input beam current of 60 mA and normalized rms emittance of 0.20 mm mrad. This design satisfies the requirements of RFQ III.
Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yamamoto, Masanobu; Yoshimoto, Masahiro; et al.
Physical Review Special Topics; Accelerators and Beams, 15(4), p.040402_1 - 040402_15, 2012/04
The J-PARC 3-GeV RCS was commissioned in October 2007. Via the initial beam tuning and a series of underlying beam studies with low-intensity beams, since December 2009, we have intermittently been performing beam tuning experiments with higher-intensity beams including the injection painting technique. By optimizing the injection painting parameters, we have successfully achieved a 420 kW-equivalent output intensity at a low-level intensity loss of less than 1%. In this paper, we present the experimental results obtained in the course of the RCS beam power ramp-up, especially on the beam loss reduction achieved by employing the injection painting.
Okada, Masashi*; Niki, Kazuaki*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Ishiyama, Hironobu*; Jeong, S. C.*; Katayama, Ichiro*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Watanabe, Yutaka*; et al.
Physical Review Special Topics; Accelerators and Beams, 15(3), p.030101_1 - 030101_10, 2012/03
Ao, Hiroyuki; Yamazaki, Yoshishige
Physical Review Special Topics; Accelerators and Beams, 15(1), p.011001_1 - 011001_13, 2012/01
A prototype cavity for the annular-ring coupled structure (ACS) for use in the Japan Proton Accelerator Research Complex (J-PARC) linac has been developed to confirm the feasibility of achieving the required performance. This prototype cavity is a buncher module, which includes ten accelerating cells in total. The ACS cavity is formed by the silver brazing of ACS half-cell pieces stacked in a vacuum furnace. The accelerating cell of the ACS is surrounded by a coupling cell. We, therefore, tuned the frequencies of the accelerating and coupling cells by an ultraprecision lathe before brazing, taking into account the frequency shift due to brazing. The prototype buncher module was successfully conditioned up to 600 kW, which corresponds to an accelerating field that is higher than the designed field of 4.1 MV/m by 30%. We describe the frequency-tuning results for the prototype buncher module and its high-power conditioning.
Saha, P. K.; Hatakeyama, Shuichiro; Yamamoto, Kazami; Yoshimoto, Masahiro; Harada, Hiroyuki; Hotchi, Hideaki; Shobuda, Yoshihiro; Kinsho, Michikazu; Sato, Kenichiro*; Irie, Yoshiro*
Physical Review Special Topics; Accelerators and Beams, 14(7), p.072801_1 - 072801_10, 2011/07
Tamura, Fumihiko; Yamamoto, Masanobu; Omori, Chihiro*; Schnase, A.; Yoshii, Masahito*; Nomura, Masahiro; Toda, Makoto*; Shimada, Taihei; Hara, Keigo*; Hasegawa, Katsushi*
Physical Review Special Topics; Accelerators and Beams, 14(5), p.051004_1 - 051004_15, 2011/05
For the acceleration of very high intensity protons in the 3 GeV RCS of the J-PARC, the beam loading compensation in the rf accelerating cavities is implemented. The wake voltage in the wide-band MA cavity consists of not only a component of the fundamental accelerating rf, but also the higher harmonics. We developed a multi-harmonic feedforward compensation system, which handles the most important three harmonics ( = 2, 4, 6). The function of the multi-harmonic feedforward is described. Adjustments of the amplitude and phase patterns for the cancellation of the wake voltage during the acceleration period are not trivial. We developed the commissioning methodology of the feedforward. We describe the methodology in the cases without and with driving the accelerating rf. We describe the commissioning results and the beneficial effects of the feedforward compensation in the beam operation.
Shimada, Miho*; Hajima, Ryoichi
Physical Review Special Topics; Accelerators and Beams, 13(10), p.100701_1 - 100701_5, 2010/10
We propose inverse Compton scattering (ICS) of coherent synchrotron radiation (CSR) from arelativistic short electron bunch in energy recovery linacs (ERL) as a high-flux subpicosecond X-ray and -ray source. An advantage of the CSR scheme over a conventional ICS source is that no externallaser is required, and synchronization between CSR pulses and electron bunches is obtained automatically. Moreover, higher-flux X-rays can be generated from the ICS of CSR in an ERL operated at a highrepetition rate, 100 MHz to 1.3 GHz. Using parameters of the Compact ERL at KEK, 110 phs/sb.w. 10% X-ray with a 100 fs-1 ps pulse duration can beobtained, for an energy range from 0.04 to 4 keV. In the case of a 5-GeV ERL, rays with energy aroundtens of MeV are generated with 110 phs/pulse b.w. 10% at a repetition rate of several hundredsof MHz.
Nishiuchi, Mamiko; Sakaki, Hironao; Hori, Toshihiko; Bolton, P.; Ogura, Koichi; Sagisaka, Akito; Yogo, Akifumi; Mori, Michiaki; Orimo, Satoshi; Pirozhkov, A. S.; et al.
Physical Review Special Topics; Accelerators and Beams, 13(7), p.071304_1 - 071304_7, 2010/07
A laser-driven repetition-rated 1.9 MeV proton beam line composed of permanent quadrupole magnets (PMQs), a radio frequency (rf) phase rotation cavity, and a tunable monochromator is developed to evaluate and to test the simulation of laser-accelerated proton beam transport through an integrated system for the first time. In addition, the proton spectral modulation and focusing behavior of the rf phase rotationcavity device is monitored with input from a PMQ triplet. In the 1.9 MeV region we observe very weakproton defocusing by the phase rotation cavity. The final transmitted bunch duration and transverse profile are well predicted by the PARMILA particle transport code. The transmitted proton beam duration of 6 ns corresponds to an energy spread near 5% for which the transport efficiency is simulated to be 10%. The predictive capability of PARMILA suggests that it can be useful in the design of future higher energy transport beam lines as part of an integrated laser-driven ion accelerator system.
Sawamura, Masaru; Furuya, Takaaki*; Sakai, Hiroshi*; Takahashi, Takeshi*; Umemori, Kensei*; Shinoe, Kenji*
Physical Review Special Topics; Accelerators and Beams, 13(2), p.022003_1 - 022003_9, 2010/02
An eccentric-fluted beam pipe is proposed to damp quadrupole modes in a cavity. The eccentric-flutes act as a mode converter from quadrupole to dipole. Optimizing the parameters of the eccentric-fluted beam pipe allows sufficient damping of both degenerate quadrupole modes. The external Q-values of the eccentric-fluted beam pipe measured with a low power model cavity agree well with those calculated with the 3D electromagnetic field simulation code, MAFIA.