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ion sourceShinto, Katsuhiro; Shibata, Takanori*; Okoshi, Kiyonori; Nammo, Kesao*; Kawai, Isao*; Ikegami, Kiyoshi*
Journal of Physics; Conference Series, 2743, p.012023_1 - 012023_5, 2024/05
We have been conducting the test of a new J-PARC-made internal antenna for the J-PARC RF-driven cesiated H ion source. After the development of the first J-PARC-made antenna, the composition of the porcelain enamel coating of the antenna was changed because we were afraid of the outgassing of the impurities from the previous antenna coating. During the test of high-density plasma production by the new antenna, we monitored the outgassing characteristics of the new antenna by measuring mass spectrometry and optical spectrum analysis. It is confirmed that no remarkable impurities were emitted from the new antenna. We also carried out the H beam extraction and measured the H beam characteristics by using the new antenna. It is found that the emittances of the H beam extracted from the J-PARC RF-driven cesiated H ion source by using the new antenna were similar to those in the case by using the SNS-made antenna. To accelerate the endurance test of the new antenna, we applied the antenna for the high-density plasma production to the 5% duty factor (1 ms pulse width with 50 Hz repetition rate) with the 2 MHz RF input power of approximately 60 kW, whose values were much higher than those in the J-PARC nominal operation; 0.8 ms pulse width with 25 Hz repetition rate (the duty factor of 2%) with the RF input power of approximately 30 kW. This presentation shows the results of the characteristics of the new J-PARC-made antenna and discusses the feasibility of the new antenna for use in the J-PARC accelerator operation.
ion beam extracted from an RF wave excited ion source plasmaWada, Motoi*; Shibata, Takanori*; Shinto, Katsuhiro
Journal of Physics; Conference Series, 2743, p.012031_1 - 012031_5, 2024/05
An internal antenna type RF driven negative hydrogen (H) ion source supplies beams to the J-PARC accelerator facility. The H ion beam current exhibits high stability, while it fluctuates with less than 5% amplitude of the DC current when a Faraday cup measures the current extracted from the source mounted on a test stand. Two frequencies are identified as the main oscillation components, 2 MHz and 4 MHz which are the driving RF frequency and the second harmonics, respectively. The amplitude levels of these components appear larger as parts of the beam directing specific angles passing through a slit are detected. A possible reason for observing a small amplitude oscillation in the total beam intensity is the averaged phase-shift of the local beam depending upon the position of the H ion production and the succeeding trajectory reaching the Faraday cup. To confirm if the phase-shift is the main reason for diminishing the oscillation amplitude for the total beam, the phase-shift between the 2 MHz and 4 MHz components were measured for beams passing through a 0.1 mm slit coupled to a Faraday cup having a 0.1 mm entrance slit. The result indicated the phase-shift changed substantially depending upon the position, but no simple model can explain the measured spatial distribution of the phase-shift. Further attempts will be made to clarify the beam dynamics relevant to the H ion beam transport including the measurements of the beam current phase-shift with respect to the RF antenna current, and the time evolution of Balmer-
light emission.
Shibata, Takanori*; Shinto, Katsuhiro; Nammo, Kesao*; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Oguri, Hidetomo; Ishida, Masaki*; Wada, Motoi*
Journal of Instrumentation (Internet), 19, p.C01009_1 - C01009_8, 2024/01
From Nov. 2020 to Apr. 2021, the continuous ion source operation for 3,651 hours (5 months) was achieved. As the lifetime of the RF ion source is mainly limited by failure on the enamel coating of the RF antenna, detailed evaluation of the antenna surface is required to ensure feasibility of the further extension of the operation time. In the present study, surface discoloration on the RF antenna coil observed after the 5 months operation is investigated by application of digital microscope and SEM/EDS analyses. The material mapping and the line spectrum obtained by the EDS analysis show that depositions of the sputtered source chamber wall materials and the injected cesium on to the enamel coating are the most possible candidate for the discoloration. The dimension measurements of the RF antenna thickness before and after the long-term operation support the idea that the discoloration is due to the deposited materials and hence insulation of the RF antenna coil by enamel coating is maintained. The emittance measurement after the operation also shows that the RF plasma and the beam formations are not affected by the deposition on the antenna.
Shinto, Katsuhiro; Okoshi, Kiyonori; Shibata, Takanori*; Nammo, Kesao*; Kawai, Isao*; Ikegami, Kiyoshi*; Ueno, Akira
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.928 - 931, 2023/11
J-PARC initiated the operation of the high-intensity rf-driven negative hydrogen (H) ion source in 2014 autumn. The ion source produces the H beam with the beam current of 60 mA and the beam energy of 50 keV in order to inject the H beam into the 3 GeV RCS with the beam current of 50 mA and the beam energy of 400 MeV from the J-PARC linac. We have achieved the longest continuous operation time of 4001 hours in the previous (2021/2022) campaign. The 2022/2023 campaign was the first time that the continuous operation of the H ion source without any exchanges of the ion source until the end of the campaign was examined. We present the operation status of the J-PARC H ion source in this campaign as well as the status of the J-PARC-made internal antenna test.
Shinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.392 - 395, 2023/11
Negative hydrogen (H) ion sources which are used at high-intensity proton accelerator facilities such as J-PARC or neutral beam injection system for plasma heating in the fusion devices such as ITER produce plasmas by using RF sources driving with the frequency of 1-2 MHz. We have shown that the H beams extracted from the RF-driven H ion source with the frequency of several MHz have some fluctuations with the frequency of the fundamental and second harmonics. The reason is that the high plasma density is produced in the ion source with the low driving frequency. Therefore, we propose the driving RF frequency same as the RF sources with that of 324 MHz in the J-PARC linac, which is much higher than the ion plasma frequency, is used for producing the plasma to suppress the H beam fluctuations. As a first step, we performed a design of a matching circuit for the higher frequency driven H ion source. We present the background for decision of a new RF amplifier with much higher frequency and the design results.
Yamamoto, Masanobu; Nomura, Masahiro; Okita, Hidefumi; Shimada, Taihei; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Yoshii, Masahito*
Progress of Theoretical and Experimental Physics (Internet), 2023(7), p.073G01_1 - 073G01_16, 2023/07
Times Cited Count：0 Percentile：0.01(Physics, Multidisciplinary)The Japan Proton Accelerator Research Complex (J-PARC) Rapid Cycling Synchrotron (RCS) employs Magnetic Alloy (MA) loaded cavities. We realize multi-harmonic rf driving and beam loading compensation owing to the broadband characteristics of the MA. The currently installed cavity is the conventional type one which is designed to be driven by tube amplifiers in a push-pull operation. The push-pull operation has some advantages, i.e., suppressing a higher harmonic distortion without the beam acceleration and shortening the cavity length. However, a disadvantage arises at the high intensity beam acceleration where the multi-harmonic rf driving causes a severe imbalance of the anode voltage swing and restricts the tube operation. Although we have achieved an acceleration for the design beam power of 1 MW, the imbalance becomes an issue to further increase the beam power. We have developed a single-ended MA cavity to avoid such difficulty. The cavity has no tube imbalance intrinsically and it is found that the power consumption to drive the cavity can be reduced compared with the conventional one.
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.
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：69.82(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.
Tamura, Fumihiko
Kasokuki, 18(3), p.151 - 160, 2021/10
The LLRF control system for the J-PARC RCS plays an important role in acceleration of high intensity beams. The original system had been working well without significant problems for more than a decade, however, the long term maintenance became difficult due to the obsolesce of the old FPGAs in the system. Therefore we developed and deployed the next-generation LLRF control system. The next-generation system is based on the modern platform, MTCA.4. The most important new function of the system is the multiharmonic vector rf voltage control feedback, which compensate the heavy beam loading in the wideband cavity better than the feedforward at the beam intensity of the design beam power, 1MW. The commissioning results are reported. The next-generation system has been successfully deployed.
beam extracted from an RF-driven high-intensity H ion sourceShinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.230 - 233, 2021/10
In most proton accelerator facilities such as J-PARC, SNS, CERN, a H ion source equipped with a 2-MHz rf driver for plasma generation produces H beams. We have reported H beam characteristics extracted from the J-PARC rf-driven high-intensity H ion source. We have been developing an emittance measurement apparatus equipped with a highly time-resolved data acquisition system in order to observe fluctuation of the beam emittance in association with the frequency of the rf driver. By using this apparatus, we found that the beam emittance is fluctuated with the frequency with the rf driver and higher harmonics. We will show some obtained results of the emittance fluctuation.
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.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Yamamoto, Masanobu; Okita, Hidefumi; Omori, Chihiro*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.170 - 174, 2021/10
A stable and precise LLRF (Low Level RF) control system is indispensable for acceleration of high intensity proton beam in the J-PARC RCS. The original LLRF control system had been operated without major problems for more than ten years since the start of operation of the RCS, while maintenance of the system became difficult due to the obsolesce of the old FPGAs in the modules. We developed and installed the next-generation LLRF control system based on MTCA.4. The key function of the system is the multiharmonic vector rf voltage control feedback. We describe the system overview and the commissioning results. The performance of the beam loading compensation is significantly improved.
ion sourceWada, Motoi*; Shinto, Katsuhiro; Shibata, Takanori*; Sasao, Mamiko*
Review of Scientific Instruments, 91(1), p.013330_1 - 013330_5, 2020/01
Times Cited Count：4 Percentile：27.22(Instruments & Instrumentation)The ions are extracted from an ion source through a plasma sheath where a low frequency electromagnetic induction drives transport of charged particles including the target ions. High frequency alternating current commonly excites plasmas in sources for negative hydrogen (H) ions at a frequency in the MHz range. A high-speed beam current monitor system coupled to a narrow entrance slit enabled the investigation of the special distribution of the AC component intensity of the H ion beam extracted from an ion source driven by a 2 MHz radio frequency (RF) power. The distribution showed a smaller oscillation of the beam at the center.
Fuwa, Yasuhiro; Shinozaki, Shinichi; Chishiro, Etsuji; Hirane, Tatsuya; Fang, Z.*; Fukui, Yuji*; Futatsukawa, Kenta*; Mizobata, Satoshi*; Iwama, Yuhei*; Sato, Yoshikatsu*; et al.
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.611 - 613, 2019/10
In the J-PARC linac, a proton accelerator is operated using 45 units of 324 MHz and 972 MHz klystrons. In the future stabilization and advancement of the accelerator, it is important to acquire the klystron output characteristics near the maximum output accurately. In order to understand this characteristics, measurement of the characteristics of the replaced klystron for some reason such as discharge, as well as the new klystron. However, such measurements have not been performed because of the risk of damage including peripheral equipment due to discharge and the temporal interference with the operation of the accelerator. Therefore, we set up a klystron test stand in the linac building and measured the high-voltage characteristics and input/output characteristics of the klystron under various operating parameters. By using this measurement result, the characteristics of klystron can be obtained before installation, and it becomes possible to determine the optimum operation parameters and make effective plan of klystron replacements. In addition, basic data for predicting the degradation tendency of klystron was acquired by comparing the characteristics of the used and used klystron.
Shinto, Katsuhiro; Okoshi, Kiyonori; Shibata, Takanori*; Nammo, Kesao*; Ikegami, Kiyoshi*; Takagi, Akira*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2052, p.050002_1 - 050002_7, 2018/12
Times Cited Count：6 Percentile：93.67(Physics, Applied)In the 2017/2018 campaign, the J-PARC cesiated rf-driven negative hydrogen (H) ion source producing H beam with the beam current of 47 mA accomplished three long-term operations more than 2,000 hours without any serious issues. On the final day of this campaign, the ion source produced an H beam current of 72 mA so that the linac commissioning group could demonstrate the beam current of 60 mA at the linac exit. We are also conducting an endurance test of a J-PARC-made antenna at a test bench. The antenna achieved the operation time approximately 1,400 hours.
ion sourceShinto, Katsuhiro; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Shibata, Takanori*; Nammo, Kesao*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2011, p.050018_1 - 050018_3, 2018/09
Times Cited Count：3 Percentile：81.69(Physics, Applied) ion sourceShinto, Katsuhiro; Shibata, Takanori*; Miura, Akihiko; Miyao, Tomoaki*; Wada, Motoi*
AIP Conference Proceedings 2011, p.080016_1 - 080016_3, 2018/09
Times Cited Count：6 Percentile：93.67(Physics, Applied)Shibata, Takanori*; Shinto, Katsuhiro; Takagi, Akira*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*; Naito, Fujio*
AIP Conference Proceedings 2011, p.020008_1 - 020008_3, 2018/09
Times Cited Count：5 Percentile：91.41(Physics, Applied)Shinto, Katsuhiro
Kasokuki, 14(4), p.248 - 250, 2018/01
The 17th International Conference on Ion Sources (ICIS 2017) was held on 15th - 20th October 2017 at Geneva in Switzerland. This conference is held biennially. Most of scientists and engineers for ion sources in the world meet at the conference in order to share results of research and development.
