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Yoshimoto, Masahiro; Saha, P. K.; Kato, Shinichi; Okabe, Kota; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.1048 - 1050, 2018/06
The charge exchange multi-turn beam injection scheme is adopted in the J-PARC 3GeV Rapid Cycling Synchrotron Accelerator (RCS) due to achieve 1MW beam power operation. In the conventional multi-turn beam injection scheme, which is provided by only the septum and bump magnets, injecting turn numbers are limited by the beam losses at the septum. On the other hand, charge exchange multi-turn beam injection does not cause the beam losses at the septum; there is no restriction in principle on the injecting turn number. However, high residual doses are observed around the stripper foil. During the charge exchange multi-turn beam injection, not only the injecting beam but also circulating beam hit the foil, and then a large number of secondary particles, namely protons and neutrons, are generated. PHITS simulation results indicate that the secondary particles cause the high residual doses around the foil. To verify this examination, secondary particles measurement is key issue. Then, a new independent type foil introducing device is installed in the 100-deg dump beam transport line in order to construct a simple experimental system for secondary particle measurements. We plan the two experiments by using this system; one is a directly secondary particle detecting method, and the other is a radioactivation analysis method with metal sample pieces. Now, we started the study of how the identification of species and energies of the secondary particles with PHITS code. Irradiation target of Cu is adopted and irradiated proton or neutron beam with various energy range. Then radio-nuclides emitted the 
-ray are picked up. Moreover, the radio-nuclides, whose reaction efficiencies due to beam species or energy are different, are searched for the indicator of the secondary particles. From the simulation results, 
Zn is extremely suitable for a proton beam indicator, and 
Co and 
Co are also suited for a neutron and proton indicator respectively.
Yoshimoto, Masahiro; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota
Proceedings of 6th International Beam Instrumentation Conference (IBIC 2017) (Internet), p.461 - 465, 2018/03
In the J-PARC RCS, a large fraction of our effort has been concentrated on reducing and managing beam losses to achieve 1MW high power proton beam operation. Standard beam loss monitor (BLM), which is installed outside of the magnet in every cell of beam optics and detect the beam loss at wide area in each cell, is insufficient to investigate finer beam loss mechanism in the ring. Thus we developed new scintillation type BLM to detect the beam loss at spot area on the vacuum chamber inside the magnet. The new BLM has separating structure a photomultiplier (PMT) from a plastic scintillator and connecting with optical fibres. Because small plastic scintillator is installed on the vacuum chamber directly, it has capability to have high sensitivity for localized spot area beam loss. On the other hand, the PMT can precisely be operated without being affected by magnetic field by keeping the PMT from the magnet. The new BLM leads the RCS to achieve the stable high power beam operation. In this presentation, we report the detail of the performance of the new BLM.
Harada, Hiroyuki; Yamane, Isao*; Saha, P. K.; Suganuma, Kazuaki; Kinsho, Michikazu; Irie, Yoshiro*; Kato, Shinichi
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.684 - 688, 2017/12
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 and report the current status.
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.95 - 99, 2017/12
no abstracts in English
Yoshimoto, Masahiro; Kato, Shinichi; Okabe, Kota; Harada, Hiroyuki; Kinsho, Michikazu
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.877 - 881, 2017/12
It is key issue to reduce the level of the radio-activation of the devices in high power proton accelerator, to achieve MW class high power beam operation. The 3 GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) adopted a beam collimation system which aims to localize the beam loss at the collimators and to reduce the level of residual doses at the other devices. However, relatively high residual doses are detected in not only the beam collimator area but also a vicinity of the stripper foil. The results of previous work, measurements of the detailed residual dose distribution and simulations of the radio-activation by the PHITS, indicate that the high level residual dose around the stripper foil is caused by secondary particles due to nuclear reaction at the foil. In order to suppress the secondary particles from foil, we try hard to reduce the number of foil hitting particles during the beam injection period. As a result, the level of the radio-activation around the foil can be decreased. At the same time, new beam loss monitor to detect the secondary particles from the foil is developed. In this presentation, we report the secondary particles detections and estimations of number of the foil hitting particles. In addition, we discuss the reduction of the radio-activation.
stripping to protons by using only lasers in the 3-GeV RCS of J-PARCSaha, P. K.; Harada, Hiroyuki; Yamane, Isao*; Kinsho, Michikazu; Miura, Akihiko; Okabe, Kota; Liu, Y.*; Yoshimoto, Masahiro; Kato, Shinichi; Irie, Yoshiro*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.866 - 870, 2017/12
Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12
The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.
Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; et al.
Physical Review Accelerators and Beams (Internet), 20(6), p.060402_1 - 060402_25, 2017/06
Times Cited Count：26 Percentile：87.8(Physics, Nuclear)The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10
. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro
Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2470 - 2473, 2017/06
For this past year, RCS beam tuning was focused on realizing a high-intensity low-emittance beam required from the downstream facility. The extraction beam emittance including its tail part was successfully decreased by optimizing transverse injection painting, and tune and chromaticity manipulations, where bipolar sextupole field patterns were newly introduced to simultaneously achieve emittance growth mitigation at the early stage of acceleration and beam instability suppression after the middle stage of acceleration. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.
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.
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.
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.61 - 65, 2016/11
After the RF power supply upgrade, the J-PARC 3-GeV RCS restarted a 1-MW beam test in October 2015. In the beam test in October, we successfully removed longitudinal beam loss by beam loading compensation as well as minimized space-charge induced beam loss by injection painting. In addition, in this beam test, beam instability was also well suppressed by controlling the tune and the chromaticity. Furthermore, in the following beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By these recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents recent progresses of 1-MW beam tuning with particular emphasis on our approaches to beam loss issues.
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.
Proceedings of 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams (HB 2016) (Internet), p.480 - 485, 2016/08
The J-PARC 3-GeV RCS has achieved a 1-MW beam acceleration in January 2015. Since then, a large fraction of our effort has been focused on reducing and managing beam losses. In the beam test in October 2015, we successfully minimized space-charge induced beam loss by optimizing the injection painting technique, as well as suppressed beam instability by controlling the tune and the chromaticity. In addition, in the recent beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By such recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. In this talk, recent progresses of RCS beam commissioning are reported with particular emphasis on our approaches to beam loss issues.
stripping to proton by using only lasers in the J-PARC RCSSaha, P. K.; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Irie, Yoshiro*; Yamane, Isao*
Proceedings of 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams (HB 2016) (Internet), p.310 - 314, 2016/08
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.
Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.592 - 594, 2016/06
The J-PARC 3-GeV RCS achieved a 1-MW beam acceleration in January 2015. Since then, a large fraction of our effort has been focused on reducing and managing beam losses. Major part of beam loss, such as space-charge induced beam loss, was well minimized by introducing injection painting. Uncontrolled beam loss arising from large-angle foil scattering during charge-exchange injection was also reduced drastically by the expansion of the transverse painting area, which was achieved by introducing quadrupole correctors and anti-correlated painting. By such recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents the recent progress of 1-MW beam tuning, especially focusing on our approaches to beam loss issues.
Hotchi, Hideaki; Tani, Norio; Watanabe, Yasuhiro; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Tamura, Fumihiko; Yoshimoto, Masahiro
Physical Review Accelerators and Beams (Internet), 19(1), p.010401_1 - 010401_11, 2016/01
Times Cited Count：12 Percentile：62.88(Physics, Nuclear)In the J-PARC 3-GeV RCS, transverse injection painting is utilized not only to suppress space-charge induced beam loss but also to mitigate foil scattering beam loss during charge-exchange injection. The space-charge induced beam loss is well minimized by the combination of modest transverse painting and full longitudinal painting. But, for sufficiently mitigating the foil scattering beam loss, the transverse painting area has to be further expanded. However, such a wide-ranging transverse painting had not been realized until recently due to beta function beating caused by edge focusing of pulsed injection bump magnets. This beta function beating additionally excites random betatron resonances, causing significant extra beam loss when expanding the transverse painting area. To solve this issue, we newly installed pulse-type quadrupole correctors to compensate the beta function beating. This paper presents recent experimental results on this correction scheme, while discussing the beam loss and its mitigation mechanisms.
Harada, Hiroyuki; Kato, Shinichi*
JPS Conference Proceedings (Internet), 8, p.012011_1 - 012011_6, 2015/09
The residual gas Ionization Profile Monitor (IPM) is developed in the J-PARC 3-GeV RCS. The IPM is a non-destructive beam profile monitor to observe a circulating transverse beam profile in the ring. It is very important to observe the beam profile turn-by-turn in the ring for identification of the beam loss and emittance growth source because the beam power of accelerator is limited by the beam loss from the view point of radio activation at these accelerator devices. The detail IPM system are introduced and latest results in beam commissioning will be reported in this presentation.
Kato, Shinichi; Takayanagi, Tomohiro; Harada, Hiroyuki; Horino, Koki; Tobita, Norimitsu; Ueno, Tomoaki*; Kinsho, Michikazu
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1180 - 1184, 2015/09
For the high intensity proton accelerator, the mitigation of the space charge force is most important because it causes the beam loss. For mitigation, the painting injection method which arranges the injection beam on the wide phase-space area during the multi-turn injection has been performed to expand the circulating beam in the J-PARC RCS. In the horizontal plane, the position and angle of the injection beam are fixed and these of the circulating beam are changed during the painting injection. Specifically, the time variation of the bump orbit height at the injection point is generated by the 4 paint bump magnet whose power supply are separate. Hence, the accuracy of the painting injection depend on the power conditioning precision of the magnet power supply. Therefore, the output characteristics of the power supply was examined for the precise power conditioning. In addition, the automatic conditioning tool has been developed based on that results.
Saha, P. K.; Harada, Hiroyuki; Hayashi, Naoki; Hotchi, Hideaki; Kinsho, Michikazu; Takayanagi, Tomohiro; Tani, Norio; Irie, Yoshiro*; Kato, Shinichi*
Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.518 - 520, 2014/07
Saha, P. K.; Shobuda, Yoshihiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Holmes, J. A.*; Kato, Shinichi*
Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.521 - 523, 2014/07
