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Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Yoshikatsu; Shinozaki, Shinichi; Fang, Z.*; Fukui, Yuji*; Mizobata, Satoshi; Michizono, Shinichiro*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.327 - 331, 2016/11
In the J-PARC linac, an intermediate-pulse with the comb-like structure is shaped by kicking an unwanted beam by the chopper cavity. Therefore, the cavities lying downstream of the RF-chopper have the beam loading with this beam shape. The present feedforward system which assumes the averaged beam current and not the comb-like beam was operated in the present LLRF, because the beam current in the linac was lower than the design value. However, it has been difficult that the required precision for the RF system is satisfied with increasing beam current. Thus, we performed the beam study of the beam loading compensation with the same shapes as the intermediate-pulses. The positive results for the cavities of SDTL and DTL with high Q values were obtained compared to the present system. On the other hand, when this compensation system was used in the case of ACS cavities, the neighbor modes were excited by the input RF. We have to improve the FF system for the operation against the real beam.
Sakai, Hiroshi*; Enami, Kazuhiro*; Furuya, Takaaki*; Kako, Eiji*; Kondo, Yoshinari*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sato, Masato*; Shinoe, Kenji*; et al.
Proceedings of 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL 2015) (Internet), p.63 - 66, 2015/12
no abstracts in English
Numata, Naoto*; Asakawa, Tomoyuki*; Sakai, Hiroshi*; Umemori, Kensei*; Furuya, Takaaki*; Shinoe, Kenji*; Enami, Kazuhiro*; Egi, Masato*; Sakanaka, Shogo*; Michizono, Shinichiro*; et al.
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.566 - 570, 2015/09
no abstracts in English
Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Fumiaki; Shinozaki, Shinichi; Chishiro, Etsuji; Hirano, Koichiro; Fang, Z.*; Fukui, Yuji*; Hori, Toshihiko; Michizono, Shinichiro*
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1320, 2015/09
In the J-PARC linac, an RF deflector installed in 3-MeV Medium Energy Beam Transport (MEBT1) is used to kick the unnecessary beam and the intermediate-pulse like a comb is created. The kicked beam leads to a scraper downstream the RF deflector and lose all kinetic energy. When the beam current increases to 50 mA of the design value, the heat load of a scraper to irradiate the kicked beam increases and its surface is predicted to be damaged. Therefore, we are preparing the tandem scrapers to reduce the damage. The half of the kicked beam leads to a scraper and the residual is to the other. The chopping operation is achieved by rotating the phase of the RF deflector in the periodic cycles by the LLRF system. We will introduce the phase rotation system and the test results.
Hwang, J.-G.*; Kim, E.-S.*; Miyajima, Tsukasa*; Honda, Yosuke*; Harada, Kentaro*; Shimada, Miho*; Takai, Ryota*; Kume, Tatsuya*; Nagahashi, Shinya*; Obina, Takashi*; et al.
Nuclear Instruments and Methods in Physics Research A, 753, p.97 - 104, 2014/07
Times Cited Count：7 Percentile：48.36(Instruments & Instrumentation)Sato, Masato*; Enami, Kazuhiro*; Furuya, Takaaki*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sakai, Hiroshi*; Shinoe, Kenji*; Umemori, Kensei*; Sawamura, Masaru; et al.
Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2531 - 2533, 2014/07
For the main linac of ERL, high loaded Q (QL) operation is desirable to reduce the input generator power. In such operation mode, the suppression of the micophonics is important to stabilize RF amplitude and phase. One of reasons which causes microphonics is mechanical vibration, which changes the cavity frequency. The vibrations of the cavities, the cryomodule and the floor were investigated and compared with the microphnics data taken during cERL operation.
Enami, Kazuhiro*; Furuya, Takaaki*; Sakai, Hiroshi*; Sato, Masato*; Shinoe, Kenji*; Umemori, Kensei*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Arakawa, Dai*; et al.
Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2534 - 2536, 2014/07
We evaluated a slidejack tuner adopted as compact ERL Main Linac tuner. The tuner compensates the frequency by extending a cavity. Tuning is driven by two system, piezo and slidejack system. Slide-jack mechanism with long stroke drives coarsely piezo adjust precisely and fast. We tested performance of the tuners on operation.
Umemori, Kensei*; Enami, Kazuhiro*; Furuya, Takaaki*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sakai, Hiroshi*; Sato, Masato*; Shinoe, Kenji*; Sawamura, Masaru; et al.
Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2537 - 2539, 2014/07
We developed ERL main linac cryomodule for Compact ERL (cERL) project, which was constructed in KEK. The module includes two 9-cell L-band superconducting cavities. After construction of cERL recirculation loop, beam operation was started. First electron beam successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation, however, field emission was a problem for long term operation.
Futatsukawa, Kenta*; Ito, Yuichi; Kikuzawa, Nobuhiro; Kobayashi, Tetsuya*; Sato, Fumiaki; Shinozaki, Shinichi; Suzuki, Takahiro*; Fang, Z.*; Fukui, Yuji*; Michizono, Shinichiro*
Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1126 - 1129, 2014/06
no abstracts in English
Futatsukawa, Kenta*; Anami, Shozo*; Kobayashi, Tetsuya*; Fang, Z.*; Fukui, Yuji*; Michizono, Shinichiro*; Sato, Fumiaki; Shinozaki, Shinichi
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.765 - 768, 2013/08
no abstracts in English
Futatsukawa, Kenta*; Anami, Shozo*; Kobayashi, Tetsuya*; Fang, Z.*; Fukui, Yuji*; Michizono, Shinichiro*; Kawamura, Masato*; Sato, Fumiaki; Shinozaki, Shinichi; Chishiro, Etsuji; et al.
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.769 - 773, 2013/08
no abstracts in English
Fang, Z.*; Michizono, Shinichiro*; Anami, Shozo*; Yamaguchi, Seiya*; Naito, Fujio*; Fukui, Yuji*; Kobayashi, Tetsuya; Suzuki, Hiroyuki; Chishiro, Etsuji; Shinozaki, Shinichi
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.1068 - 1070, 2010/08
The output energy of the J-PARC proton Linac will be upgraded from 181 to 400 MeV in the next two years by adding 972-MHz high-beta acceleration sections. The RF signals are controlled by the FPGA-based digital feedback control systems installed in a compact PCI (cPCI). Recently, the LLRF control software has also been upgraded for the J-PARC Linac, especially for the 972-MHz high-beta systems. Many functions have been added to the LLRF control software, such as (1) gradually increasing the feedback gains in the feedback loop instead of fixed ones, (2) automatic chopped-beam compensation, (3) automatically switching the beam loading compensation in accordance with the different beam operation mode, (4) input RF-frequency tuning carried out by a FPGA to match the RF cavities during the RF start-up, (5) auto-tuning of the RF cavity tuner by detecting the phase curve of the RF cavity during the field decay instead of the phase difference between the cavity input and output signals.
Fang, Z.*; Michizono, Shinichiro*; Anami, Shozo*; Yamaguchi, Seiya*; Naito, Fujio*; Fukui, Yuji*; Kawamura, Masato*; Kubota, Chikashi*; Nammo, Kesao*; Kobayashi, Tetsuya; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1434 - 1436, 2010/05
The output energy of the J-PARC proton linac will be upgraded from 181 to 400 MeV in the next two years by adding high-b acceleration sections. The upgrade of the FPGA-based digital LLRF controller for the 400 MeV linac will be presented in this paper. This new LLRF controller works for both the 324-MHz low-b and 972-MHz high-b sections. Many functions have been added into the LLRF controller, such as (1) working for different RF systems, (2) gradually increasing the feedback gains in the feedback loop instead of fixed ones, (3) automatic chopped beam compensation, (4) automatically switching the beam loading compensation in accordance with different beam operation mode, (5) input RF-frequency tuning to match the RF cavities during RF start-up, and (6) auto-tuning of the RF cavity tuner by detecting the phase curve of the RF cavity during the field decay instead of the phase difference between the cavity input and output signals.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Kobayashi, Tetsuya; Anami, Shozo*; Michizono, Shinichiro*; Fang, Z.*; Suzuki, Hiroyuki; Yamaguchi, Seiya*
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1065 - 1067, 2010/03
In the J-PARC Linac LLRF, for the cavity start-up, the cavity resonance is automatically controlled to be the accelerating frequency (324 MHz and 972 MHz) with a mechanical tuner installed on the cavity. Figure 1: FPGA block diagram of the digital FB and FF control system for the J-PARC linac LLRF. We are planning to introduce a new method of the cavity-input frequency matching into the digital LLRF control system instead of the tuner control for the cavity start-up. In order to match the frequency with the detuned cavity, the output RF frequency is modulated by way of phase rotation with the I/Q modulator, while the cavity tuner is fixed. The detuning of the cavity is obtained from phase gradient of the cavity field decay at the RF-pulse end and the phase rotation is automatically controlled by a FPGA and a DSP. No hardware modification is necessary for this frequency modulation method.
Kobayashi, Tetsuya; Michizono, Shinichiro*; Fang, Z.*; Matsumoto, Toshihiro*; Suzuki, Hiroyuki; Yamaguchi, Seiya*; Okada, Yoshihito*
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1068 - 1070, 2010/03
A 972-MHz RF system is being developed for 400-MeV upgrade of the J-PARC linac. The accelerating field stabilities should be less than 
1% in amplitude and 1
in phase. The basic digital LLRF (Low-Level RF) concept is the same as that of the present 324-MHz system with a compact-PCI crate. The main alterations are RF and clock generator (RF&CLK), mixer and I/Q modulator (IQ&Mixer) and digital LLRF algorithm. Since the typical decay time of the new system is faster (because its operational frequency is higher than that of the present 324-MHz cavity), chopped beam compensation is essential. The performance study of the digital feedback system with a cavity simulator is summarized.
Kobayashi, Tetsuya; Suzuki, Hiroyuki; Anami, Shozo*; Yamaguchi, Seiya*; Michizono, Shinichiro*; Fang, Z.*
Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.2213 - 2215, 2009/05
In the J-PARC Linac LLRF, for the cavity start-up, the cavity resonance is automatically controlled to be the accelerating frequency (324 MHz and 972 MHz) with a mechanical tuner installed on the cavity. We are planning to introduce a new method of the cavity-input frequency matching into the digital LLRF control system instead of the tuner control for the cavity start-up. In order to match the frequency with the detuned cavity, the output RF frequency is modulated by way of phase rotation with the I/Q modulator, while the cavity tuner is fixed. The detuning of the cavity is obtained from phase gradient of the cavity field decay at the RF-pulse end and the phase rotation is automatically controlled by a FPGA and a DSP. No hardware modification is necessary for this frequency modulation method. The cost reduction or the high durability for the mechanical tuner production is expected in the future.
Michizono, Shinichiro*; Fang, Z.*; Matsumoto, Toshihiro*; Yamaguchi, Seiya*; Kobayashi, Tetsuya; Okada, Yoshihito*
Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.2201 - 2203, 2009/05
Upgrade of J-PARC linac has been planed using 972 MHz rf system. The rf eld regulation is required to be less than 1% in amplitude and 1. in phase. The basic digital llrf concept is same as the present 324 MHz llrf system using a compact PCI crate. The main alterations are rf and clock generator (RF&LK), mixer and IQ modulator (IQ&Mixer) and digital llrf algorithm. Since the typical decay time is faster (due to higher operational frequency than present 324 MHz cavity), chopped beam compensation is one of the main concerns. Performance of the digital feedback system using a cavity simulator is summarized.
Kobayashi, Tetsuya; Chishiro, Etsuji; Suzuki, Hiroyuki; Anami, Shozo*; Fang, Z.*; Michizono, Shinichiro*; Yamaguchi, Seiya*
Proceedings of 24th International Linear Accelerator Conference (LINAC 2008) (CD-ROM), p.1054 - 1056, 2009/00
For the J-PARC linac low level RF system, a new function that switches the feed-forward control parameters in every pulse was installed into the digital accelerating-field control system, in order to compensate beam-loading change by pulses in the operation of 25-Hz repetition. The linac provides a 50-mA peak current proton beam to a 3-GeV rapid-cycling synchrotron (RCS). Then the RCS distributes the 3-GeV beam into a following 50-GeV synchrotron (main ring, MR) and the Materials and Life Science Facility (MLF), which is one of the experimental facilities in the J-PARC. The 500-us long macro pulses from the ion source of the linac should be chopped into medium pulses for injection into the RCS. The duty (width or repetition) of the medium pulse depends on which facility the RCS provides the beam to the MR or MLF. Therefore the beam loading compensation needs to be corrected for the change of the medium pulse duty in the 25-Hz operation.
Fang, Z.*; Anami, Shozo*; Michizono, Shinichiro*; Yamaguchi, Seiya*; Kobayashi, Tetsuya; Suzuki, Hiroyuki
Proceedings of 24th International Linear Accelerator Conference (LINAC 2008) (CD-ROM), p.1039 - 1041, 2009/00
In the J-PARC proton linac, each klystron drives two RF cavities. The RF amplitude and phase of the cavities are controlled by an FPGA-based digital feedback control system. The test results show that the variations in the cavity amplitude and phase are less than 0.1% and 0.1 without beam loading, or 0.3% and 0.2 with beam loading. The tuning of each cavity is also controlled by a DSP of this control system. The cavity auto-tuning is successfully controlled to keep the detuned phase within 1 degree. In our RF system, the tuning information including detuned frequency and phase, and Q-value of each cavity are measured in real-time and displayed in the PLC touch panel of the control system.
