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Journal Articles

Improvement of high voltage rectifier of J-PARC klystron power supply

Chishiro, Etsuji; Sagawa, Ryu*; Toriyama, Minoru*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.400 - 402, 2016/11

Klystron power supplies in the J-PARC have been generated high voltage DC power by chopping 12-phase AC voltage power by thyristors, and boosting the voltage up to 110 kV in step-up transformer and rectifying the voltage in high voltage rectifiers. Some of the high voltage transformers (HVTR), which consist of the step-up transformer and the high voltage rectifier and the reactor, were often broken in the running time of over 30,000 hours. This failure caused the long-term shut down of the J-PARC facility. The high voltage rectifier composed diodes and condensers by a series connection of 66 stages. Investigation of the failed rectifier shows that the capacitors ware applied the overvoltage because the flashover occurred on the ceramic surface. We investigated the mechanisms applying the overvoltage and took measure for the overvoltage to the rectifier. The HVTR with the improved rectifier has been operating for long term to assess the modification effect.

Journal Articles

Laser storage ring with high power for realization of laser stripping injection

Harada, Hiroyuki; Saha, P. K.; Yamane, Isao*; Kato, Shinichi; Kinsho, Michikazu; Irie, Yoshiro*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.983 - 986, 2016/11

The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate.

Journal Articles

Cavity voltage variation at beam extraction in the J-PARC MR

Tamura, Fumihiko; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.808 - 810, 2016/11

J-PARC MR provides high intensity proton beams of 390 kW to the neutrino experiment. The proton beams are extracted by fast extraction. It has been found that the cavity voltage goes up for about 20 $$mu$$s just after extraction. It is because the rf feed forward system for beam loading compensation outputs compensation signals for its system delay. The MR cavity has a relatively low Q value of 22 and the cavity voltage can varies in the order of 10 $$mu$$s. The voltage variation of the cavity voltage increases with the beam intensity and it is a possible reason of the damage of the gap capacitors. A counter measure using the inhibit function of the summation amplifier in the LLRF system has been applied. In this presentation, we present the details of the cavity voltage variation and the results of the counter measure. Also, we present the analysis of beam loading using the voltage variation.

Journal Articles

Updating HBase/Hadoop in the J-PARC operation data archiver with making the data collection tool redundant by ZooKeeper

Ikeda, Hiroshi; Kikuzawa, Nobuhiro; Yoshii, Akinobu*; Kato, Yuko

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.637 - 640, 2016/11

no abstracts in English

Journal Articles

Current status of the kicker magnet power supply in 3-GeV RCS

Togashi, Tomohito; Takayanagi, Tomohiro; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.725 - 728, 2016/11

The 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC (Japan Proton Accelerator Research Complex) has the pulse kicker power supply system which use the thyratron switches for beam extraction. It has passed from operation starting for more than 10 years, but an exchange of a part and check are being put into effect periodically, so a kicker power supply also keeps operation smoothly now. I spent long time and studied how to use, so thyratron could be used now for more than 10,000 hours. But long years have passed, so selection of a substitute of a discontinuance part is a pending problem. Silicon oil has also degraded, so I have to consider a way of a performance recovery and a procedure of an exchange. This report explains the current state of the kicker magnet power supply from a result of the regular inspection and conditions.

Journal Articles

Improvement of the IPM for the high-intensity beam profile measurement in the J-PARC RCS

Kato, Shinichi; Harada, Hiroyuki; Hatakeyama, Shuichiro; Kawase, Masato; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1089 - 1093, 2016/11

In the J-PARC RCS, the residual gas ionization profile monitor (IPM) is adopted for the nondestructive detection of the 1D transverse distribution of the circulating proton beam. The IPM mainly consists of the divided electrodes generating the external electric field and the detection unit. For the profile measurement, the residual gas ionized by the beam is transported to the detection unit by the external transverse electric field and amplified by the Multi-Channel Plate (MCP) as the electron. After that, these electrons are detected and the 1D distribution is reconstructed. To improve IPM performance, some updates have been performed continuously such as the optimization of the electric field potential and the introduction of the new MCP which has the gradual gain response to the applied voltage. As a result, the IPM shows intended performance in the beam commissioning with the low current condition. However, the distribution cannot be measured in the high current condition such as over 100 kW because the noise increases and hides the signal. To solve this problem, we investigated the source of this noise and examined measures. To compare the simulation and the noise measurement results, we identified the cause of the noise as the electric field from the beam. Therefore, we developed additional electrode component to shield that field based on the simulation result. This component will be installed in 2016 summer. It is expected that the noise is reduced to be 1/100 compared with present one by the new component and the distribution measurement can be performed in the high current condition.

Journal Articles

Status of the J-PARC RF ion source

Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Ueno, Akira; Shibata, Takanori*; Nammo, Kesao*; Shinto, Katsuhiro; Oguri, Hidetomo

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.940 - 943, 2016/11

In 2014 October, operation of cesium-seeded Radio Frequency (RF)-driven negative hydrogen ion (H$$^{-}$$) source was started in J-PARC LINAC. Due to the skillful RF antenna screening and the proper pre-conditioning process, long term unscheduled beam stop due to the antenna failure did not occur for more than 1 year. The continuous operation of 1,350 hours with a peak beam current of 45 mA was achieved in the recent beam run. Moreover, the fluctuation of beam current in a low energy beam transport (LEBT) is kept within $$pm$$2% of target value by application of three feedback systems. An ion source test-stand was assembled to investigate the ion source beam characteristic, for example, the emittance at the position of the RFQ entrance. In the presentation, we will report the recent status of the ion source operation and some experimental results obtained at the ion source test-stand.

Journal Articles

Vacuum improvement of kicker magnet area in J-PARC 3 GeV synchrotron

Kamiya, Junichiro; Yanagibashi, Toru; Ogiwara, Norio; Kinsho, Michikazu

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1193 - 1196, 2016/11

In this study, we propose a new in situ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs towards the kicker magnet. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. The outgassing rage was reduced to one tenth comparing to the case without bake out.

Journal Articles

A Malfunction of the beam collimator system in J-PARC 3 GeV rapid cycling synchrotoron

Yamamoto, Kazami; Okabe, Kota; Kamiya, Junichiro; Yoshimoto, Masahiro; Takeda, Osamu; Takayanagi, Tomohiro; Yamamoto, Masanobu

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.314 - 318, 2016/11

The 3 GeV Rapid-Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) project generates 1MW proton beam for the neutron experiments and Main ring accelerator. In case of such high intensity hadron accelerator, the most important issue is to reduce the uncontrolled loss. The beam collimation system is designed for this purpose. In the present design, the physical aperture is 1.5 times wider than the primary collimator aperture and the beam loss can be enough localized on this condition. After a startup of RCS in 2007, the collimator system of RCS worked well. But vacuum leakage occurred during the maintenance period in April, 2016. Since it was expected that the beam collimator was radio-activated very much, we took the influence of radiation into consideration and designed the collimator (ie. a remote clamp system to connect/take off it with a vacuum flange away from itself). Therefore, during the recovery work of the collimator, we were able to reduce the worker dose to less than 60 micro Sv though the collimator block had a residual dose of 40 mSv/h.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Naito, Fujio*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1409 - 1412, 2016/11

After the summer maintenance in 2015, user operation for the hadron experimental facility (HD) and the life science experimental facility (MLF) was resumed in the middle of October after the tuning of accelerator at J-PARC. In December, we reduced the repetition cycle from 6.0 seconds to the 5.52 seconds at the main ring (MR) and therefore, we have improved beam power to 42 kW, while it was 24 kW in April. The peak beam current at the linac by December 2015 was 30 mA, but we have increased to 40 mA in January, and the tuning was followed by the 3 GeV synchrotron (RCS) and the MR for user operation condition. As a result we improved a beam power to the neutrino experimental facility (NU) to 390 kW by the tuning while it was ranged 300 to 330 kW at 30 mA. User program was performed at 500 kW at the MLF, but it was suspended by a defect of a target in November. It was replaced for a spare one and resumed at 200 kW in February. We have several faults to stop beam operations: ventilation system at the linac by a short circuit, a vacuum leak at the RCS collimator, a breakdown of bending magnet of the MR, etc.

Journal Articles

Present status of JAEA-Tokai tandem accelerator and booster

Matsuda, Makoto; Osa, Akihiko; Ishizaki, Nobuhiro; Tayama, Hidekazu; Nakanoya, Takamitsu; Kabumoto, Hiroshi; Nakamura, Masahiko; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1413 - 1417, 2016/11

The tandem accelerator was operated over a total of 140 days and delivered 22 different ions to the experiments in the fields of nuclear physics, nuclear chemistry, atomic physics, solid state physics and radiation effects in material. Maximum accelerating voltage is keeping up 18 MV and there was used for ten days on this voltage. However, electric discharge was occurred frequently in December and accelerating voltage fell to 12 MV. The damaged acceleration tubes were replaced with the spare tube at the regular maintenance period in March. The superconducting booster was not operated. This paper describes the operational status of the accelerators and the major technical developments.

Journal Articles

Development of a control system at a 3 MeV linac in J-PARC

Sawabe, Yuki*; Ishiyama, Tatsuya; Takahashi, Daisuke; Kato, Yuko; Suzuki, Takahiro*; Hirano, Koichiro; Takei, Hayanori; Meigo, Shinichiro; Kikuzawa, Nobuhiro; Hayashi, Naoki

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.647 - 651, 2016/11

In the J-PARC, a 3 MeV linac has been developed for the tests of beam scraper irradiation and charge exchange by high-power laser. To accomplish tests efficiently and safely, the control system for 3 MeV was designed and developed, and this system consists of four subsystems, personal protection system, machine protection system, timing system, and remote control system using the EPICS. In this paper, the details of control system for a 3 MeV linac are presented.

Journal Articles

Beam instability suppression in the 3-GeV RCS of J-PARC

Saha, P. K.; Shobuda, Yoshihiro; Hotchi, Hideaki; Harada, Hiroyuki

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.125 - 129, 2016/11

Journal Articles

Study of beam loading compensation with comb-like structure at J-PARC linac

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.

Journal Articles

Development of klystron perveance and gain monitor in J-PARC Linac

Hori, Toshihiko*; Shinozaki, Shinichi; Sato, Yoshikatsu; Mizobata, Satoshi; Fukui, Yuji*; Futatsukawa, Kenta*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.429 - 432, 2016/11

The triode klystrons with a modulating anode have been used for the J-PARC linac. Recently, we exchanged four klystrons due to the frequent discharge at a modulating anode in the klystron tube. In order to understand the discharge mechanism and to estimate the time to replace the klystron, we need to monitor the long term performance of the klystron such as the degradation of a cathode emission current and the RF gain of the klystron tube and so on. Therefore, we started to develop the klystron perveance and gain monitor module (NIM Standard one). In this paper, we will present the design concept of the monitor module, and the first performance test result using the module prototype.

Journal Articles

Development of beam scrapers using a 3-Mev linac at J-PARC

Hirano, Koichiro; Asano, Hiroyuki; Ishiyama, Tatsuya; Ito, Takashi; Okoshi, Kiyonori; Oguri, Hidetomo; Kondo, Yasuhiro; Kawane, Yusuke; Kikuzawa, Nobuhiro; Sato, Yoshikatsu; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.310 - 313, 2016/11

We have used a beam scraper with the incident angle of 65deg to reduce the beam power deposition density in the MEBT between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC linac. The 65$$^{circ}$$ scraper was irradiated by the H$$^{-}$$ beam up to particle number of 1.47E22. We observed a lot of surface projections with several hundred micrometers high in the beam irradiation damage on the scraper by using the laser microscope. In order to study the limits of scrapers, we constructed a new 3 MeV linac at J-PARC. We will conduct the scraper irradiation test at the end of this year.

Journal Articles

Development of a vertical collimator at the mebt1 of J-PARC linac

Sugimura, Takashi*; Maruta, Tomofumi*; Hirano, Koichiro

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.307 - 309, 2016/11

There is an upgrade plan of J-PARC (Japan Proton Accelerator Research Complex) Linac from currently operated beam parameters such as, beam current of 40 mA, beam pulse width of 0.5msec and repetition of 25 Hz, to 50 mA, 0.5msec and 50 Hz, respectively. To reduce beam loss during a beam acceleration is a must task to accelerate a high power beam. At J-PARC Linac, a beam from an ion source followed by RFQ (Radio Frequency Quadrupole) injected into a series of DTLs (Drift Tube Linac) through a MEBT1 (Medium Energy Beam Transport 1), where a beam matching and a beam pulse forming are carried out at the beam energy of 3 MeV. There are some locally activated spots in DTL area at the current beam power level so that some kind of mitigation measure is required. Beam simulation results show that the beam loss at the DTL area can be reduced if there is a pair of vertical beam collimators. This paper reports a design and fabrication status of new vertical collimators.

Journal Articles

The Muon linac for the precise measurement of muon g-2/EDM at J-PARC

Kondo, Yasuhiro; Hasegawa, Kazuo; Ito, Takashi; Artikova, S.; Otani, Masashi*; Mibe, Tsutomu*; Naito, Fujio*; Yoshida, Mitsuhiro*; Kitamura, Ryo*; Iwashita, Yoshihisa*; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.66 - 69, 2016/11

We are developing a muon linac for the measurement of the muon anomalous magnetic moment and search for the muon electric dipole moment to explore beyond the Standard Model of elementary particle physics. This muon linac accelerate from room temperature to 212 MeV with normalized transverse emittances of about 1.5 $$pi$$ mm mrad. The muon linac consists of an ultra-slow muon source, a radio frequency quadrupole (RFQ) linac, an inter-digital H-mode drift tube linac (IH-DTL), a disk and washer coupled cavity linac (DAW CCL), and disk loaded structure (DLS) traveling-wave linac. In this paper, the status of the muon linac development, especially, the beam dynamics simulation is descried.

Journal Articles

Inter-digital H-mode drift-tube linac design with alternative phase focusing for muon linac

Otani, Masashi*; Mibe, Tsutomu*; Yoshida, Mitsuhiro*; Hasegawa, Kazuo; Kondo, Yasuhiro; Hayashizaki, Noriyosu*; Iwashita, Yoshihisa*; Iwata, Yoshiyuki*; Kitamura, Ryo*; Saito, Naohito

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.858 - 862, 2016/11

We have developed an interdigital H-mode (IH) drift-tube linac (DTL) design with an alternative phase focusing (APF) scheme for a muon linac, in order to measure the anomalous magnetic moment and electric dipole moment (EDM) of muons at the Japan Proton Accelerator Research Complex (J-PARC). The IH-DTL accelerates muons from beta 0.08 to 0.28 at an operational frequency of 324 MHz. The output beam emittances are calculated as 0.315 $$pi$$ and 0.195 $$pi$$ mm mrad in the horizontal and vertical directions, respectively, which satisfies the experimental requirement.

Journal Articles

Current status of the muon initial acceleration with RFQ for muon g-2/EDM experiment

Kitamura, Ryo*; Otani, Masashi*; Fukao, Yoshinori*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Miyake, Yasuhiro*; Shimomura, Koichiro*; Kondo, Yasuhiro; Hasegawa, Kazuo; Ishida, Katsuhiko*; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.476 - 479, 2016/11

The muon linear accelerator for the muon g-2/EDM experiment in J-PARC is being developed. As the first step of the muon acceleration, the muon acceleration with J-PARC RFQ (Radio-Frequency Quadrupole)-II plans to be demonstrated at H-line of J-PARC MLF. The slow muon will be obtained by the deceleration using the thin metal foil target in the RFQ acceleration test. The intensity of the decelerated muon by the thin metal foil was measured. Based on this result, the beam intensity in the RFQ test at H-line is estimated to be a few /sec. The particle simulation of the RFQ and the following beam diagnostics system is conducted, and it is shown that the emittance measurement at the RFQ exit using the micro-channel plate based beam profile monitor is feasible.

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