Refine your search:     
Report No.
 - 
Search Results: Records 1-15 displayed on this page of 15
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Numerical analysis of the production profile of H$$^{0}$$ atoms and subsequent H$$^{-}$$ ions in large negative ion sources

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

Journal of Applied Physics, 103(5), p.053302_1 - 053302_12, 2008/03

 Times Cited Count:22 Percentile:32.62(Physics, Applied)

The production and transport processes of H$$^{0}$$ atoms are numerically simulated using a three-dimensional Monte Carlo transport code. The code was applied to the large JAEA 10 ampere negative ion source under the Cs-seeded condition to obtain a spatial distribution of surface-produced H$$^{-}$$ ions. In the H$$^{0}$$ atom transport process, the energy relaxation of the H$$^{0}$$ atoms, which affects the surface H$$^{-}$$ ion production rate, is taken into account. The result indicates that the surface H$$^{-}$$ ion production is enhanced near the high-electron-temperature region where H$$^{0}$$ atom production is localized.

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:36.12(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

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:1 Percentile:90.26(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

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:84.03(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:68.64(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:30.04(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

Negative ion production in high electron temperature plasmas

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

Plasma and Fusion Research (Internet), 2, p.022_1 - 022_4, 2007/06

no abstracts in English

Journal Articles

The Origin of beam non-uniformity in a large Cs-seeded negative ion source

Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki; Inoue, Takashi; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; Taniguchi, Masaki; Watanabe, Kazuhiro

Nuclear Fusion, 46(6), p.S318 - S323, 2006/06

 Times Cited Count:28 Percentile:27.66(Physics, Fluids & Plasmas)

The origin of the beam non-uniformity, that is one of the key issues in large Cs-seeded negative ion sources for JT-60U and ITER, was experimentally examined by measuring correlations between the intensity of the H$$^{-}$$ ion beam and plasma parameters such as an electron temperature and plasma density in the JAERI 10 A negative ion source. From the correlation between the beam intensity and the plasma parameters, it was foreseen that the beam non-uniformity was due to the localization of the plasma and/or H0 atoms caused by B x $$nabla$$B drift of the fast electron from filaments. The filament position was modified to suppress the B x $$nabla$$B drift, and then the spatial uniformity of the beam intensity was examined. By this modification, the root-mean-square deviation of the spatial beam intensity from the averaged value deceased to a half of that before modification while the beam intensity integrated along the longitudinal direction was kept to be constant. From this result, it was confirmed that one of the origin of the beam non-uniformity was caused by plasma localization.

Journal Articles

Improvement of beam uniformity by magnetic filter optimization in a Cs-seeded large negative-ion source

Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki*; Inoue, Takashi; Tobari, Hiroyuki; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Dairaku, Masayuki; Kashiwagi, Mieko; Sakamoto, Keishi; et al.

Review of Scientific Instruments, 77(3), p.03A515_1 - 03A515_3, 2006/03

 Times Cited Count:23 Percentile:26.09(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Numerical analysis of primary electrons in a tandem-type negative ion source

Kato, Kyohei*; Takado, Naoyuki*; Hatayama, Akiyoshi*; Hanada, Masaya; Seki, Takayoshi; Inoue, Takashi

Review of Scientific Instruments, 77(3), p.03A535_1 - 03A535_3, 2006/03

 Times Cited Count:12 Percentile:44.13(Instruments & Instrumentation)

To clarify physics mechanism of plasma spatial nonuniformity observed in tandem-type negative-ion sources, primary electron-transport process has been analyzed by a three-dimensional Monte Carlo simulation code. In the model, equations of motion for electrons are numerically solved. Geometry and magnetic-field configuration of the JAEA 10 Ampere negative ion source are taken into account. Various collision processes with neutral particles are also included in the model. The simulation results show that (1) the primary electrons have been lost from the source region to the extraction region due to magnetic drift in the magnetic filter, and then (2) there is another magnetic drift near the sidewalls, where a sum of magnetic field of the filter and the cusp field for plasma confinement allows electron drift towards the extraction region. A sequence of these magnetic drifts would increase the electron temperature in local area of extraction region, which resulted in loss of negative ions.

Journal Articles

Numerical analysis of the spatial nonuniformity in a Cs-seeded H$$^{-}$$ ion source

Takado, Naoyuki*; Hanatani, Junji*; Mizuno, Takatoshi*; Kato, Kyohei*; Hatayama, Akiyoshi*; Hanada, Masaya; Seki, Takayoshi; Inoue, Takashi

Review of Scientific Instruments, 77(3), p.03A533_1 - 03A533_3, 2006/03

 Times Cited Count:14 Percentile:39.63(Instruments & Instrumentation)

Surface production and transport process of H$$^{-}$$ ions are numerically simulated to clarify the origin of H$$^{-}$$ beam non-uniformity. A three-dimensional transport code using Monte Carlo method has been applied to productions of H$$^{0}$$ atoms and H$$^{-}$$ ions in a large negative ion source under the Cs seeded condition. The results show that a large fraction of hydrogen atoms are produced in a high electron temperature region. This leads to a spatial non-uniformity of H$$^{0}$$ atom flux to the plasma grid where H$$^{0}$$ atoms capture electrons and converted to H$$^{-}$$ ions. In addition, most surface-produced H$$^{-}$$ ions are extracted even through the high electron temperature region without destruction.

Journal Articles

Experimental study on spatial uniformity of H$$^{-}$$ ion beam in a large negative ion source

Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki*; Inoue, Takashi; Morishita, Takatoshi; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; et al.

Fusion Engineering and Design, 74(1-4), p.311 - 317, 2005/11

 Times Cited Count:7 Percentile:51.29(Nuclear Science & Technology)

no abstracts in English

Oral presentation

Dependence of the beam uniformity on the magnetic filter strength in a large Cs-seeded negative ion source for ITER

Seki, Takayoshi; Hanada, Masaya; Tobari, Hiroyuki; Inoue, Takashi; Takado, Naoyuki*; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Kashiwagi, Mieko; Taniguchi, Masaki; Watanabe, Kazuhiro; et al.

no journal, , 

no abstracts in English

Oral presentation

Improvement of beam uniformity in a Cs-seeded large negative ion source

Seki, Takayoshi; Hanada, Masaya; Tobari, Hiroyuki; Inoue, Takashi; Kashiwagi, Mieko; Taniguchi, Masaki; Watanabe, Kazuhiro; Sakamoto, Keishi; Takado, Naoyuki*; Mizuno, Takatoshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Improvement of uniformity of negative ion beam in a Cs-seeded large negative ion source and development of efficient radio-frequency ion source

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

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
  • 1