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Sugita, Moe; Takayanagi, Tomohiro; Ueno, Tomoaki*; Ono, Ayato; Horino, Koki*; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.519 - 522, 2023/11
In J-PARC RCS, paint bump magnets are used to displace the beam orbit during paint injection, which produces a high intensity beam. A pattern of command current and command voltage can be used to create an output current waveform that varies the beam orbit over time. The accuracy of beam orbit control is determined by the shape difference between the command current and output current waveforms. In the current paint pattern adjustment, a deviation of 
1% or less is achieved by manual adjustment after using software that adjusts the pattern according to the response function of the power supply control. However, we would like to reduce the adjustment time. In addition, since the accuracy of paint injection is determined by the adjustment system of the paint magnet power supply, we would like to achieve output current deviation 10 times more precise than before to reduce beam loss. An analytical model of the load-side impedance is necessary to create a high-precision paint pattern, but it is very difficult to construct an analytical model because the load-side impedance changes in a time-varying nonlinear paint pattern. We used machine learning to adjust the output pattern of the paint pattern and achieved a deviation of less than 0.5% through repeated learning. This presentation will report on the current status of the system and its prospects.
Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Morishita, Takatoshi; Nemoto, Yasuo*; Oguri, Hidetomo
Physical Review Accelerators and Beams (Internet), 26(3), p.032802_1 - 032802_12, 2023/03
Times Cited Count：0 Percentile：0.02(Physics, Nuclear)A bunch-shape monitor (BSM) is a useful device for performing longitudinal beam tuning using the pointwise longitudinal phase distribution measured at selected points in the beam transportation. To measure the longitudinal phase distribution of a low-energy negative hydrogen (H
) ion beam, highly oriented pyrolytic graphite (HOPG) was adopted for the secondary-electron-emission target to mitigate the thermal damage due to the high-intensity beam loading. The HOPG target enabled the measurement of the longitudinal phase distribution at the center of a 3-MeV H ion beam with a high peak current of about 50 mA. The longitudinal bunch width was measured using HOPG-BSM at the test stand, which was consistent with the beam simulation. The correlation measurement between the beam transverse and longitudinal planes was demonstrated using HOPG-BSM. The longitudinal Twiss and emittance measurement with the longitudinal Q-scan method was conducted using HOPG-BSM.
Takayanagi, Tomohiro; Ono, Ayato; Fuwa, Yasuhiro; Shinozaki, Shinichi; Horino, Koki*; Ueno, Tomoaki*; Sugita, Moe; Yamamoto, Kazami; Oguri, Hidetomo; Kinsho, Michikazu; et al.
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.242 - 246, 2023/01
At J-PARC, semiconductor short pulse power supplies to replace kicker power supplies and semiconductor long pulse power supplies to replace klystron power supply systems are under construction. We have fabricated a 40kV/2kA/1.2
s unit power supply that employs a linear transformer drivers (LTD) system for kickers. Currently, we are working on a high voltage insulating cylinder insulator that suppresses corona discharges using only the insulator structure, without using insulating oil. In addition, the MARX system was adopted for klystron power supply system. A main circuit unit for 8kV/60A/830s rectangular pulse output and an 800V/60A correction circuit unit that improves the flat top droop from 10% to 1% were manufactured. Furthermore, a 2.2kV/2.4kW high voltage SiC inverter charger has been fabricated for this MARX power supply. The presentation will report the evaluation results of each test and prospects for semiconductor pulse power supplies.
ion sourceShinto, Katsuhiro; Shibata, Takanori*; Okoshi, Kiyonori; Nammo, Kesao*; Ikegami, Kiyoshi*; Oguri, Hidetomo
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.675 - 679, 2023/01
In J-PARC, we have been conducting the test of a J-PARC-made internal antenna in order to establish the production method and understand the beam characteristics of the antenna. At this time, we investigated the outgas characteristics during the production of a high-density plasma by using the J-PARC-made antenna. It is confirmed that no remarkable impurities are emitted from the antenna by a residual gas analysis using a quadrupole mass analyzer installed downstream the ion source and a spectroscopic analysis of the plasma in the ion source. It is found that the emittances of the H beam extracted from the J-PARC radio-frequency H ion source by using the antenna was similar as those in case by using SNS antenna.
Shibata, Takanori*; Ishida, Masaki*; Nammo, Kesao*; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Shinto, Katsuhiro; Oguri, Hidetomo
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.863 - 867, 2023/01
Continuous operation duration of the J-PARC Radio Frequency (RF) ion source has been extended step by step these years for the goal to supply stable beam during the entire period of J-PARC user operation (around 7 months) each year. A 3651 hours (5 months) continuous ion source operation has been achieved from Nov. 2020 to Apr. 2021. As the lifetime of the ion source is mainly limited by failure on the RF antenna coil, detailed evaluation of the antenna surface condition is required to ensure the feasibility of the further extension of the operation time. In the present study, dimension measurements and SEM/EDS analyses were applied to understand the surface discoloration of the RF antenna. The discoloration after the long-term continuous operation is due to deposition of injected cesium (for H surface production process) and of stainless used steel (Fe, Cr, Ni) from the ion source components sputtered by plasma. The results show that the enamel coating of the RF antenna has not worn out in the long-term continuous operation for several months and, hence, extension of the ion source continuous operation duration can be extended.
ion source with new parts exposed to plasmaUeno, Akira; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Oguri, Hidetomo
Journal of Physics; Conference Series, 2244, p.012029_1 - 012029_5, 2022/04
Times Cited Count：0 Percentile：0.32(Engineering, Electrical & Electronic)The J-PARC cesiated RF-driven H ion source is stably suppling about 58 mA beam with a duty factor of 1.25 % (0.5 ms
25 Hz) for the J-PARC LINAC 50 mA operations. For them, only three plasma chambers (PCHs) of #7, #8 and #9PCHs among ten PCHs have been used since the transverse emittances are more superior than others for unknown reasons. However, the emittances were enlarged by 16 % with the #7PCH, in which the plasma electrode (PE) temperature control plate (PETCP) was replaced to brand-new one to solve the air leak at the VCR vacuum fitting. The impurities from the new parts exposed to the plasma seemed to cause the degradation. The beam with almost the best emittances was reproduced by #4PCH with a new PETCP, in which sapphire tubes were used instead of the 99.7 % alumina ceramics tubes, after a new 2-MHz RF power scanning impurities reduction conditioning for 48 hours.
Shibata, Takanori*; Okoshi, Kiyonori; Shinto, Katsuhiro; Nammo, Kesao*; Ikegami, Kiyoshi*; Oguri, Hidetomo
Journal of Physics; Conference Series, 2244, p.012041_1 - 012041_5, 2022/04
Times Cited Count：1 Percentile：0.32(Engineering, Electrical & Electronic)In the J-PARC user operation from Nov. 2020 - Apr. 2021, continuous operation of J-PARC Radio Frequency (RF) negative hydrogen ion (H) source up to 3,651 hours (5 months) has been achieved. The ion source was operated with the output H current of 60 mA, the duty factor (for plasma generation) 2% and the input RF power up to 30 kW. After the operation, phase space diagrams at the Radio Frequency Quadrupole (RFQ) entrance were measured by the emittance monitor at the ion source test stand (IS-TS) under the same operation condition as in the J-PARC Linac. Comparison of the phase spaces and the beam emittances between the ion sources in the present and the previous operations shows slight difference. From the direct observation of the antenna coil, no exhaustion or the decrease in the thickness of the enamel coating of the coil have been confirmed. The results indicate the possibility of the next goal of the long-run up to 7 months, which is the same as the full duration of the J-PARC user operation in 1 year.
Shibata, Takanori*; Hirano, Koichiro; Hirane, Tatsuya*; Shinto, Katsuhiro; Hayashi, Naoki; Oguri, Hidetomo
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.417 - 421, 2021/10
In J-PARC linac, the operation of an rf-driven high-intensity H ion source was initiated in 2014. For plasma ignition, the 2-MHz rf amplifier outputs the power of several tens kW. However the rf amplifier for the ion source and those for the accelerating cavities have not been synchronized. As a result, the wave hights in the beam waveforms were different in shot by shot. Therefore, we have developed an synchronization system between the rf system for the ion source and those for the cavity systems and succeeded the same wave hights in the waveforms.
Shibata, Takanori*; Shinto, Katsuhiro; Wada, Motoi*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*
AIP Conference Proceedings 2373, p.050002_1 - 050002_9, 2021/08
Oscillation of emittance and Twiss parameters in the negative ion beam from the J-PARC 2-MHz RF ion source is measured by applications of a double-slit emittance monitor located at the RFQ (Radio Frequency Quadrupole) entrance. The emittance monitor is equipped with a newly-developed 60 MS/s data acquisition system, so that beam current oscillation in a few MHz can be observed with enough time resolution. From the measurement, it is shown that the beam phase space consists of (1) a DC component in the beam core, (2) a 2-MHz oscillating component which takes place both in the beam core and the halo and (3) a doubled RF frequency (4 MHz) oscillation which slightly exists in the beam halo. The major component is the 2-MHz component, which resultantly decides the beam emittance oscillation frequency. A typical value of the beam emittance in the present experiment is 0.34 
mm-mrad, while the amplitude of the 2 MHz oscillation is around 0.04 mm-mrad. The results indicate that the high-frequency oscillation component occupying about ten-percent of the beam from the RF source travels a few meters passing through a magnetic lens focusing system.
Sarmento, T.*; W
nderlich, D.*; Fantz, U.*; Friedl, R.*; Rauner, D.*; Tsumori, Katsuyoshi*; Shenjin, L.*; Chen, W.*; Bollinger, D.*; Oguri, Hidetomo; et al.
AIP Conference Proceedings 2373, p.110001_1 - 110001_18, 2021/08
In preparation for NIBS 2020 various labs prepared reference sheets containing key information about their ion sources and the machines that they serve. The contents of the reference sheets have been formatted and edited into this paper for posterity and ease of access.
ion sourceUeno, Akira; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Shinto, Katsuhiro; Oguri, Hidetomo
AIP Conference Proceedings 2373, p.040002_1 - 040002_8, 2021/07
On 2018, the stable operation of the J-PARC cesiated RF-driven H ion source (IS) with a 62 keV 100 mA beam, whose emittances were suitable for the radio-frequency quadrupole LINAC (RFQ), was reported. In the J-PARC IS operation, the stable plasma production with a 50 kW 2 MHz RF power for more than 3 months, an RF power efficiency higher than 2.4 mA/kW and the possibility of the space charge limited beam intensity pulling up by increasing the extraction and acceleration voltages were proven. On the other hand, the withstand voltage for the stable operation with an RF plasma production of the present 2 MHz matching circuit and the high voltage power supply was measured as about 66 kV. In the operation with the presently highest beam energy of 65 keV, a 110 mA beam with emittances suitable for the RFQ was stably produced. Since 102.5 mA of the beam was measured inside the emittances used for the RFQ design, the next generation 100 mA LINAC will be possible with the IS.
Yamamoto, Kazami; Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*
JPS Conference Proceedings (Internet), 33, p.011016_1 - 011016_7, 2021/03
The Japan Proton Accelerator Research Complex (J-PARC) is a multipurpose facility for scientific experiments. The accelerator complex consists of a 400-MeV Linac, a 3-GeV Rapid-Cycling Synchrotron (RCS) and a 30-GeV Main Ring synchrotron (MR). The RCS delivers a proton beam to the neutron target and MR, and the MR delivers the beams to the neutrino target and the Hadron Experimental Facility. The first operation of the neutron experiments began in December 2008. Following this, the user operation has been continued with some accidental suspensions. These suspensions include the recovery work due to the Great East Japan Earthquake in March 2011 and the radiation leak incident at the Hadron Experimental Facility. In this report, we summarize the major causes of suspension, and the statistics of the reliability of J-PARC accelerator system is analyzed. Owing to our efforts to achieve higher reliability, the Mean Time Between Failure (MTBF) has been improved.
ion sourceOguri, Hidetomo; Okoshi, Kiyonori; Shinto, Katsuhiro; Shibata, Takanori*; Nammo, Kesao*; Ikegami, Kiyoshi*; Takagi, Akira*; Ueno, Akira
JPS Conference Proceedings (Internet), 33, p.011008_1 - 011008_7, 2021/03
A cesiated RF-driven negative hydrogen ion source was initiated to operate in September, 2014 in response to the need for upgrading J-PARC's linac beam current. The ion source mainly comprises a stainless-steel plasma chamber, a beam extractor and a large vacuum chamber equipped with two turbo molecular pumps, each having the pumping speed of 1500 L/s, for differential pumping. The user operation was started with the beam current of 33 mA from the ion source. We gradually increased both beam current and continuous operation time of the ion source. In July, 2018 (Run#79), approximately 2,200 hours operation was achieved with the typical beam current, pulse length and repetition rate of 47 mA, 300 s and 25 Hz, respectively. Since October, 2018 (Run#80), the ion source has been delivering a nominal beam current of approximately 60 mA.
beam with 3 MeV by the bunch-shape monitorKitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi; Oguri, Hidetomo
JPS Conference Proceedings (Internet), 33, p.011012_1 - 011012_6, 2021/03
The new bunch shape monitor (BSM) is required to measure the bunch size of the high-intensity H beam with 3 MeV at the front-end section in the J-PARC linac. The carbon-nano tube wire and the graphene stick are good candidates for the target wire of the BSM, because these materials have the enough strength to detect the high-intensity beam. However, since the negative high voltage of more than a few kV should be applied to the wire in the BSM, the suppression of the discharge is the challenge to realize the new BSM. After the high-voltage test to investigate the effect of the discharge from the wire, the detection of the signal from the BSM was successful at the beam core with the peak current of 55 mA using the graphene stick. The preliminary result of the bunch-size measurement is reported in this presentation.
beam with orifice in J-PARC front-endShibata, Takanori*; Ikegami, Kiyoshi*; Nammo, Kesao*; Liu, Y.*; Otani, Masashi*; Naito, Fujio*; Shinto, Katsuhiro; Okoshi, Kiyonori; Okabe, Kota; Kondo, Yasuhiro; et al.
JPS Conference Proceedings (Internet), 33, p.011010_1 - 011010_6, 2021/03
Together with the intensity upgrade in J-PARC Linac Front-End, improvement of RFQ transmission ratio is an important task. This RFQ transmission ratio depends strongly upon the solenoid current settings in the low energy beam transport line (LEBT). In the present study, high beam current cases (72 mA and 88 mA H beam current in LEBT) are investigated at a test-stand. Phase space distributions of the H beam particles at the RFQ entrance are measured and compared with numerical results by Particle-In-Cell simulation. As a result, it has been clarified that a 15 mm 
orifice for differential pumping of H
gas coming from the ion source plays a role as a collimator in these beam conditions. This leads to change the beam emittance and Twiss parameters at the RFQ entrance. Especially in the condition with the beam current up to 88 mA in LEBT, the beam collimation contributes to optimize the phase space distribution to the RFQ acceptance with relatively low solenoid current settings. As a higher solenoid current setting would be necessary to suppress the beam expansion due to high space charge effect, these results suggest that current-saving of the solenoids can be possible even in the higher beam intensity operations.
Okabe, Kota; Liu, Y.*; Otani, Masashi*; Moriya, Katsuhiro; Shibata, Takanori*; Chimura, Motoki*; Hirano, Koichiro; Oguri, Hidetomo; Kinsho, Michikazu
JPS Conference Proceedings (Internet), 33, p.011011_1 - 011011_6, 2021/03
To realize more stable operation of the J-PARC accelerators, we have a re-design plan of an MEBT1 (Medium Energy Beam Transport). At the J-PARC Linac, the MEBT1 has transverse and longitudinal beam matching section for the DTLs. However there are some locally activated spots in DTL area at the current beam power level. To reduce beam loss during a beam acceleration at the DTLs is a most important task for a stable user operation. The first thing we should do is investigation a connection between beam quality in the MEBT1 and parameters of the upstream hardware. In this presentation, we will report a high intensity beam study results at the MEBT1.
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
JPS Conference Proceedings (Internet), 33, p.011043_1 - 011043_5, 2021/03
The Japan Atomic Energy Agency (JAEA) has been working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. The ADS proposed by JAEA consists of a CW proton linac of 30 MW coupling with a subcritical core reactor. The accelerator will be operated with a beam current of 20 mA. Normal conducting Radio-Frequency Cavities (NRFC) and Superconducting Radio-Frequency Cavities (SRFC) will be used to achieve final energy of 1.5 GeV, and the SRFC will be employed for the main part of the acceleration: from 2 MeV to 1.5 GeV. In the first stage of the accelerator development, the focus was the design and optimization of the SRFC models and the beam optics. For the SRFC sections, the acceleration will be done by using Half Wave Resonators (HWR), Single Spokes (SS), and Elliptical cavities (Ellip) operating with a frequency of 162, 324, and 648 MHz, respectively. The beam optics were optimized satisfying the equipartitioning condition to control the emittance growth, which helped to reduce the beam halos and the beam loss.
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.33 - 37, 2020/09
Japan Atomic Energy Agency (JAEA)- Accelerator Driven System (ADS) linac consists of a CW proton accelerator with a beam current of 20 mA driven with the energy of 1.5 GeV. Most of the beam acceleration is achieved by using superconducting cavities to obtain high acceleration efficiency at CW mode. The main superconducting linac is composed of five families of cavities (Half Wave resonators, Spokes resonators, and Elliptical cavities) with theirs respectively magnets. Due to the large beam power in the linac of 30 MW and the high reliability required for the ADS project, a robust beam optic designed is necessary to have a stable beam operation and control the beam loss power. The JAEA-ADS linac is composed of several sections and components; thus, the misalignment of these elements together with field errors enhance the beam loss rate and compromises the safety of the linac. To this end, an error linac campaign was launched to estimate the error tolerance of the components and implement a correction scheme to reduce the beam loss power around the linac.
Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi; Oguri, Hidetomo
Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.251 - 253, 2020/09
A bunch-shape monitor (BSM) in the low-energy region is being developed in the J-PARC linac to accelerate the high-intensity proton beam with the low emittance. A highly-oriented pyrolytic graphite (HOPG) was introduced as the target of the BSM to mitigate the thermal loading. The stable measurement of the BSM was realized thanks to the HOPG target, while the tungsten target was broken by the thermal loading from the high-intensity beam. However, since the longitudinal distribution measured with the BSM using the HOPG target was wider than the expected one, the improvement of tuning parameters is necessary for the BSM. The BSM consists of an electron multiplier, a bending magnet, and a radio-frequency deflector, which should be tuned appropriately. Behavior of these components were investigated and tuned. The longitudinal distribution measured with the BSM after the tuning was consistent with the expected one.
Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.
Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12
Times Cited Count：1 Percentile：52.28(Physics, Particles & Fields)We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.
