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Journal Articles

Beamlet deflection due to beamlet-beamlet interaction in a large-area multiaperture negative ion source for JT-60U

Kamada, Masaki; Hanada, Masaya; Ikeda, Yoshitaka; Grisham, L. R.*; Jiang, W.*

Review of Scientific Instruments, 79(2), p.02C114_1 - 02C114_3, 2008/02

 Times Cited Count:16 Percentile:57.79(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Long pulse production of high current D$$^{-}$$ ion beams in the JT-60 negative ion source

Hanada, Masaya; Kamada, Masaki; Akino, Noboru; Ebisawa, Noboru; Honda, Atsushi; Kawai, Mikito; Kazawa, Minoru; Kikuchi, Katsumi; Komata, Masao; Mogaki, Kazuhiko; et al.

Review of Scientific Instruments, 79(2), p.02A519_1 - 02A519_4, 2008/02

 Times Cited Count:6 Percentile:32.56(Instruments & Instrumentation)

A long pulse production of high-current, high-energy D$$^{-}$$ ion beams was studied in the JT-60U negative ion source that was designed to produce 22 A, 500 keV D$$^{-}$$ ion beams. Prior to the long pulse production, the short pulse beams were produced to examine operational ranges for a stable voltage holding capability and an allowable grid power loading. From a correlation between the voltage holding capability and a light intensity of cathodoluminescence from the insulator made of Fiber Reinforced Plastic insulator, the voltage holding was found to be stable at $$<$$ 340 kV where the light was sufficiently suppressed. The grid power loading for the long pulse operation was also decreased to the allowable level of $$<$$ 1 MW without a significant reduction of the beam power by tuning the extraction voltage (Vext) and the arc power (Parc). These allow the production of 30 A D$$^{-}$$ ion beams at 340 keV from two ion sources at Vacc = 340 kV. The pulse length was extended step by step, and finally reached up to 21 s, where the beam pulse length was limited by the surface temperature of the beam scraper without water cooling. The D$$^{-}$$ ion beams were neutralized to via a gas cell, resulting in a long pulse injection of 3.2 MW D$$^{0}$$ beams for 21 s. This is the first long injection of $$>$$ 20 s in a power range of $$>$$ 3 MW.

Journal Articles

Development and operation of a Cs-free J-PARC H$$^{-}$$ ion source

Oguri, Hidetomo; Ueno, Akira; Namekawa, Yuya; Okoshi, Kiyonori; Kondo, Yasuhiro; Ikegami, Kiyoshi*

Review of Scientific Instruments, 79(2), p.02A506_1 - 02A506_4, 2008/02

 Times Cited Count:8 Percentile:39.47(Instruments & Instrumentation)

A cesium-free negative hydrogen ion source driven with a LaB6 filament was developed for the J-PARC (Japan Proton Accelerator Research Complex). It is being operated for the J-PARC LINAC beam commissioning, which was started on 20 November 2006. Nine runs of 2-week beam commissioning will be done until the end of June 2007. The source is operated with a duty factor of 0.8 % (0.32 ms and 25 Hz) while providing a 5 mA beam typically. Each interval of the runs, optimizations, such as the filament position and so on, are examined. At present, a 39 mA beam is successfully extracted with a duty factor of 0.8 %.

Journal Articles

Uniform H$$^{-}$$ ion beam extraction in a large negative ion source with a tent-shaped magnetic filter

Tobari, Hiroyuki; Hanada, Masaya; Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Watanabe, Kazuhiro; Inoue, Takashi; Sakamoto, Keishi; Takado, Naoyuki*

Review of Scientific Instruments, 79(2), p.02C111_1 - 02C111_4, 2008/02

 Times Cited Count:17 Percentile:59.59(Instruments & Instrumentation)

In order to improve the spatial uniformity of negative ion beam, a novel magnetic filter, the tent-shaped filter was applied in the JAEA 10 ampere negative ion source as a replacement to the conventional external magnetic filter. The cusp magnetic field configuration for plasma confinement was changed to form a symmetric cusp field commonly used in many of positive ion sources for high proton yield. This configuration together with the tent filter allows fast electrons emitted from filaments drift azimuthally around the beam axis. This is a major advantage of the current configuration to prevent localization of fast electrons due to B $$times$$ grad B drift in the external filter field. As the result, the standard deviation of H$$^{-}$$ ion beam profile extracted from a wide area of 170 mm $$times$$ 340 mm decreased from 16% with the external filter to 7.9 % with the tent filter. Thus the ion source with the tent filter demonstrated the uniform beam extraction that fulfilled the requirement for ITER NBI.

Journal Articles

Direct plasma injection scheme with beam extraction in a radio frequency quadrupole linac cavity

Kashiwagi, Hirotsugu; Okamura, Masahiro*; Tamura, Jun*; Takano, Jumpei*

Review of Scientific Instruments, 79(2), p.02C716_1 - 02C716_4, 2008/02

no abstracts in English

Journal Articles

Acceleration of ampere class H$$^{-}$$ ion beam by MeV accelerator

Taniguchi, Masaki; Inoue, Takashi; Umeda, Naotaka; Kashiwagi, Mieko; Watanabe, Kazuhiro; Tobari, Hiroyuki; Sakamoto, Keishi; Dairaku, Masayuki

Review of Scientific Instruments, 79(2), p.02C110_1 - 02C110_3, 2008/02

 Times Cited Count:13 Percentile:51.96(Instruments & Instrumentation)

Journal Articles

Negative ion production in cesium seeded high electron temperature plasmas

Inoue, Takashi; Tobari, Hiroyuki; Takado, Naoyuki*; Hanada, Masaya; Kashiwagi, Mieko; Hatayama, Akiyoshi*; Wada, Motoi*; Sakamoto, Keishi

Review of Scientific Instruments, 79(2), p.02C112_1 - 02C112_4, 2008/02

 Times Cited Count:2 Percentile:14.68(Instruments & Instrumentation)

In experiments on uniformity improvement in a large negative ion source, steep gradients have been observed in the profiles of electron temperature and H$$^{-}$$ ion beam intensity. It has been observed that the gradient in the H$$^{-}$$ ion beam intensity is altered by seeding Cesium, though the electron temperature distribution is not affected by the Cs. Thus in the Cs seeded condition, the H$$^{-}$$ ion beam intensity is enhanced in local area illuminated by high-electron temperature plasmas. A brief analysis suggests possible advantages of high-electron temperature plasmas for the negative ion surface production, by enhancement of dissociation to yield proton or atoms as parent particles of the negative ions.

Journal Articles

Surface discharge related properties of fiberglass reinforced plastic insulator for use in neutral beam injector of JT-60U

Yamano, Yasushi*; Takahashi, Masahiro*; Kobayashi, Shinichi*; Hanada, Masaya; Ikeda, Yoshitaka

Review of Scientific Instruments, 79(2), p.02A524_1 - 02A524_4, 2008/02

 Times Cited Count:4 Percentile:23.9(Instruments & Instrumentation)

The JT-60U negative-ion-based NBI was designed to have 3-stage electrostatic accelerators with total accelerating voltage of 500kV. In order to hold such high voltage, three Fiberglass Reinforced Plastic (FRP) insulators of 1.8 m inner diameter and 31.5 cm height are used. Currently the hold-off voltage capability of 3-stage FRP insulators has been typically limited to $$<$$ 460 kV without beam acceleration. One of the possible reason is a surface discharges on the FRP insulators. This paper describes measurement results of surface resistivity and volume resistivity under vacuum and atmospheric conditions, secondary electron emission (SEE) characteristics and cathodoluminescence under some keV electron beam irradiation, gas analysis desorbed from the FRP insulator under irradiation of some keV-electron beam were also analyzed.

Journal Articles

Spectroscopic observations of beam and source plasma light and testing Cs-deposition monitor in the large area negative ion source for LHD-NBI

Oka, Yoshihide*; Tsumori, Katsuyoshi*; Ikeda, Katsunori*; Kaneko, Osamu*; Nagaoka, Kenichi*; Osakabe, Masaki*; Takeiri, Yasuhiko*; Asano, Eiji*; Komada, Seiji*; Kondo, Tomoki*; et al.

Review of Scientific Instruments, 79(2), p.02C105_1 - 02C105_4, 2008/02

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

In the present studies, we studied the cesium lines in the source plasma during beam shots on the LND MN-NBI system. It was found for the first time in the LHD-source 2, that both the amount of Cs I (neutral Cs) and Cs II (Cs$$^{+}$$) in the source plasma light rose sharply when beam acceleration began, and continued rising during a 10 s pulse. We think that this was because the cesium was evaporated/sputtered from the source backplate by the back-streaming positive ions.

Journal Articles

Effect of energy relaxation of H$$^{0}$$ atoms at the wall on the production profile of H$$^{-}$$ ions in large negative ion sources

Takado, Naoyuki*; Matsushita, Daisuke*; Fujino, Ikuro*; Hatayama, Akiyoshi*; Tobari, Hiroyuki; Inoue, Takashi

Review of Scientific Instruments, 79(2), p.02A503_1 - 02A503_4, 2008/02

 Times Cited Count:2 Percentile:14.68(Instruments & Instrumentation)

Production and transport process of the H$$^{0}$$ atoms are numerically simulated using a three-dimensional Monte Carlo transport code. The code was applied to the "JAEA 10 ampere negative ion source" under Cs-seeded condition to obtain a spatial distribution of surface-produced H$$^{0}$$ ions. In this analysis, we focus on the effect of the energy relaxation of the H$$^{0}$$ atoms at the wall on the H$$^{-}$$ ion production from the H$$^{0}$$ atoms. The result indicates that, by considering the energy relaxation of the H$$^{0}$$ atoms at the wall, the production profile of the surface-produced H$$^{-}$$ ion is well reflected in the production profile of the H$$^{0}$$ atom production.

Journal Articles

Numerical analysis of H$$^{-}$$ ion transport processes in Cs-seeded negative ion sources

Matsushita, Daisuke*; Takado, Naoyuki*; Hatayama, Akiyoshi*; Inoue, Takashi

Review of Scientific Instruments, 79(2), p.02A527_1 - 02A527_4, 2008/02

 Times Cited Count:5 Percentile:28.44(Instruments & Instrumentation)

The H$$^{-}$$ ion transport processes are numerically simulated to understand the extraction process of surface-produced H$$^{-}$$ ions. The three-dimensional transport code using Monte Carlo method has been applied to calculate the H$$^{-}$$ ion extraction probabilities in the model geometry of the JAEA 10 ampere negative ion source. The roles of (1) filter magnetic field and (2) collisions with neutrals (H$$^{0}$$ atoms and H$$_{2}$$ molecules) on the H$$^{-}$$ ion extraction are systematically studied. The results show that H$$^{-}$$ ions are extracted mainly by the filter magnetic field under the low gas pressure condition. The simulation results of extracted H$$^{-}$$ ion beam intensity in the JAEA 10 ampere negative ion source without the magnetic filter tend to be smaller than the experimental results, especially under the low pressure condition.

Journal Articles

Analysis of electron energy distribution of an arc-discharge H$$^{-}$$ ion source with Monte Carlo simulation

Fujino, Ikuro*; Hatayama, Akiyoshi*; Takado, Naoyuki*; Inoue, Takashi

Review of Scientific Instruments, 79(2), p.02A510_1 - 02A510_3, 2008/02

 Times Cited Count:21 Percentile:65.86(Instruments & Instrumentation)

For optimization and accurate prediction of the amount of H$$^{-}$$ ion production in negative ion source, analysis of electron energy distribution function (EEDF) is necessary. We developed a numerical code which analyzes EEDF in the tandem-type arc discharge source. It is a three-dimensional Monte Carlo simulation code with the effects of cusp, filter, and extraction magnets. Coulomb collision between electrons is treated with Takizuka's model and several inelastic collisions are treated with null-collision method. We applied this code to the JAEA 10 ampere negative ion source. As a result, the order of electron density is in good agreement with experimental results. In addition, the obtained EEDF is qualitatively in good agreement with experimental results.

Journal Articles

KEKCB electron cyclotron resonance charge breeder at TRIAC

Imai, Nobuaki*; Jeong, S.-C.*; Oyaizu, Mitsuhiro*; Arai, Shigeaki*; Fuchi, Yoshihide*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Miyatake, Hiroari; Tanaka, Masahiko*; Okada, Masayuki*; et al.

Review of Scientific Instruments, 79(2), p.02A906_1 - 02A906_3, 2008/02

 Times Cited Count:13 Percentile:51.96(Instruments & Instrumentation)

KEKCB is an 18 GHz Electron Cyclotron Resonance (ECR) ion source and is a charge breeder device for converting mass-separated 1$$^+$$ radioactive ions to multi-ionized ones by utilizing an axial injection technique to the ECR plasma. It is a part of the Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. Based on the developments so far, converting efficiencies for metal elements, such as barium and indium, and for gaseous elements, such as krypton and xenon, are improved to be 7 $$%$$ and 2 $$%$$, respectively. And it is confirmed that the efficiency is nearly the constant for short-lived (t$$_{1/2}$$ $$ge$$ 1 sec) isotopes. Background ions mixed in the output beams are supressed to be 600 pps from 10$$^8$$ pps by applying all aluminum electrodes and high pressure pure-water cleanings.

Oral presentation

KEKCB; ECR charge breeder at TRIAC

Imai, Nobuaki*; Jeong, S.-C.*; Oyaizu, Mitsuhiro*; Arai, Shigeaki*; Fuchi, Yoshihide*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Miyatake, Hiroari; Tanaka, Masahiko*; Okada, Masayuki*; et al.

no journal, , 

The KEKCB is an ECR ion source for converting singly charged ions to multi-charged ones at Tokai Radioactive Ion Accelerator Complex. By using the KEKCB, singly charged gaseous and non-gaseous ions were successfully converted to the multi-charged ones of A/q $$simeq$$7 with the efficiencies of 7% and 2% respectively. The efficiency was found to be independent of the lifetime of the radioactive nuclei with an order of second. Three collimators placed at the entrance and the exit of the KEKCB defined the beam axis and enabled us to easily handle the beam injection to the KEKCB. Griding and washing the surfaces of aluminum electrode and plasma chamber dramatically reduced the impurity originated from the ECR plasma of the KEKCB.

14 (Records 1-14 displayed on this page)
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