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Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.
AIP Conference Proceedings 1390, p.466 - 475, 2011/09
Times Cited Count：2 Percentile：53.22(Physics, Atomic, Molecular & Chemical)Voltage holding tests by using JT-60 negative ion source and small electrodes was carried out because JT-60 negative ion source had a critical problem about low voltage holding capability for long time. As a result, the voltage holding capability is decreased with the increase of area where local electric field is generated, as well as the surface area according to existing scaling low about surface area. Therefore, in order to improve the voltage holding without changing the existing accelerator, the voltage holding test was carried out by extending gap lengths of the negative ion source. In order to improve the voltage holding, beam radiation shield needs to be optimized additionally. As a result, the voltage holding has been improved to 500 kV and stabilized. By using this modified ion source, negative ion beams of 500 keV up to 3A has been successfully produced.
Hanada, Masaya; Kojima, Atsushi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Akino, Noboru; Kazawa, Minoru; et al.
AIP Conference Proceedings 1390, p.536 - 544, 2011/09
Times Cited Count：7 Percentile：84.66(Physics, Atomic, Molecular & Chemical)no abstracts in English
Shinto, Katsuhiro; Wada, Motoi*; Nishida, Tomoaki*; Demura, Yasuhiro*; Sasaki, Daichi*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Kaneko, Osamu*; Kisaki, Masashi*; Sasao, Mamiko*
AIP Conference Proceedings 1390, p.675 - 683, 2011/09
Times Cited Count：0 Percentile：0.19(Physics, Atomic, Molecular & Chemical)
ion sourceUeno, Akira; Namekawa, Yuya; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Oguri, Hidetomo
AIP Conference Proceedings 1390, p.292 - 299, 2011/09
Times Cited Count：3 Percentile：63.26(Physics, Atomic, Molecular & Chemical)A Cs free H ion source driven with a LaB
filament is being operated at the J-PARC. Although it satisfies the J-PARC first stage requirements of an H ion beam current of 30 mA and a life-time of 500 hours, it was proven that the current was not increased by seeding Cs. In order to satisfy the second stage requirements of an H ion beam current of 50 mA and a life-time of 2000 hours, the development of a 13.56 MHz-rf-driven H ion source was started by using an antenna developed at the SNS. As the first step, the impedance of an antenna with hydrogen plasma was measured. For an rf-power of 1.25 kW or 7.45 kW, it was measured as 11.82+80.22j 
or 21.16+58.24j , respectively, which has a high real-part and positive rf-power dependence unexpectedly. By using the measured impedance, the circuit to produce rf-plasma in the plasma chamber on the -50kV potential with a 13.56 MHz-rf on the ground potential was designed by LTSpice IV.
Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Namekawa, Yuya; Ueno, Akira
AIP Conference Proceedings 1390, p.235 - 244, 2011/09
Times Cited Count：0 Percentile：0.19(Physics, Atomic, Molecular & Chemical)A cesium-free H ion source driven with a LaB filament is being operated for J-PARC for about 4 years. Although the ion source can produce the H ion current of 36 mA, the maximum current is restricted to 16 mA for the stable operation of the RFQ linac which has serious discharge problem from September 2008. The beam run is performed during 1 month cycle, which consisted of a 4-5 weeks beam run and a few days down-period interval. At the recent beam run, approximately 700 h continuous operation was achieved, which is satisfied with the requirement of the ion source lifetime for the J-PARC first stage. At every runs, the beam interruption time due to the ion source failure is a few hours, which correspond to the ion source availability of 99%. The R&D work is being performed in parallel with the operation in order to enhance the further beam current by using an ion source test stand.
Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Dairaku, Masayuki; Yamanaka, Haruhiko; Tsuchida, Kazuki; Kojima, Atsushi; et al.
AIP Conference Proceedings 1390, p.449 - 456, 2011/09
Times Cited Count：2 Percentile：53.22(Physics, Atomic, Molecular & Chemical)At JAEA, MeV accelerator has been developed as a proof-of-principle accelerator for ITER NBI. To achieve the acceleration of 1 MeV, 200 A/m
beam required for ITER, improvement of the voltage holding capability is essential. Review of voltage holding results ever obtained with various geometries of the accelerators showed that voltage holding capability was about a half of that for ideal small electrode. This is due to local electric field concentration in the accelerators, such as edge and corner between grids and its support structures. Based on these results, accelerator was modified to reduce the electric field concentration by reshaping the support structures and expanding the gap length. After the modifications, voltage holding capability in vacuum was increased from 835 kV to 1 MV. Voltage holding progressed the energy and current to 879 keV, 0.36 A (157 A/m).
Kashiwagi, Mieko; Inoue, Takashi; Taniguchi, Masaki; Umeda, Naotaka; Grisham, L. R.*; Dairaku, Masayuki; Takemoto, Jumpei; Tobari, Hiroyuki; Tsuchida, Kazuki; Watanabe, Kazuhiro; et al.
AIP Conference Proceedings 1390, p.457 - 465, 2011/09
Times Cited Count：9 Percentile：88.83(Physics, Atomic, Molecular & Chemical)In a five stage multi-aperture and multi-grid (MAMuG) accelerator in JAEA, beam acceleration tests are in progress toward 1 MeV, 200 A/m H ion beams for ITER. The 1 MV voltage holding has been successfully demonstrated for 4000 s with the accelerator of expanded gap length that lowered local electric field concentrations. The led to increase of the beam energy up to 900 keV-level. However, it was found that beamlets were deflected more in long gaps and direct interceptions of the deflected beamlet caused breakdowns. The beamlet deflection and its compensation methods were studied utilizing a three-dimensional multi beamlet analysis. The analysis showed that the 1 MeV beam can be compensated by a combination of the aperture offset of 0.8 mm applied in the electron suppression (ESG) and the metal bar called a field shaping plate with a thickness of 1 mm attached beneath the ESG. The paper reports analytical predictions and experimental results of the MAMuG accelerator.
