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Hemsworth, R. S.*; Inoue, Takashi
IEEE Transactions on Plasma Science, 33(6), p.1799 - 1813, 2005/12
Times Cited Count：125 Percentile：94.89(Physics, Fluids & Plasmas)The positive or negative ion sources which form the primary components of neutral beam injection systems used in magnetic fusion have to meet simultaneously several demanding requirements. This paper describes the underlying physics of modern positive ion sources, which provide the required high proton fraction (
90%) and high current density (
2 kA/m
) at a low source pressure (0.4 Pa) with a high electrical efficiency and uniformity across the accelerator grids. The development of negative ion sources, which are required if high energy neutral beams are to be produced, is explained. The paper reports that negative ion sources have achieved many of the parameters required of sources for the neutral beam injectors of future fusion devices and reactors, 200 A/m of D
at low pressure, 
0.3 Pa, with low co-extracted electron content. The development needed to meet all the requiremens of future systems is briefly discussed.
Inoue, Takashi; Taniguchi, Masaki; Morishita, Takatoshi; Dairaku, Masayuki; Hanada, Masaya; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; Seki, Takayoshi*; Watanabe, Kazuhiro
Nuclear Fusion, 45(8), p.790 - 795, 2005/08
The R&D of a 1 MeV accelerator and a large negative ion source have been carried out at JAERI. The paper presents following progress as a step toward ITER NB system. (1) Accelerator R&D: According to success in improvement of voltage holding capability, the acceleration test of H ions up to 1 MeV class energy is in progress. H ion beams of 1 MeV, 100 mA class have been generated with a substantial beam current density (100 A/m), and the current density is still increasing by the ion source tuning. (2) Large ion source R&D: One of major causes that limited the NB injection performance was spatial unifomity of negative ion production in existing negative-ion based NB systems. The present study revealed that the negative ions produced in the extraction region of the source were locally destructed by fast electrons leaking through magnetic filter. Some countermeasures and their test results are also described.
Morishita, Takatoshi; Inoue, Takashi; Iga, Takashi*; Watanabe, Kazuhiro; Imai, Tsuyoshi
Review of Scientific Instruments, 75(5), p.1764 - 1766, 2004/05
Times Cited Count：10 Percentile：47.34(Instruments & Instrumentation)Negative ion beams of high current density are required for accelerator and fusion. The H source utilizes surface production that produces H from H or H
. And hence, high proto yield ion source is required. Generally, a large volume plasma generator with strong plasma confinement is suitable to achieve high proton yield. On the contrary, production of high proton ratio plasma is not easy in small sources. However, in a small source (3.5 liter), high current H beam of 800 A/m was obtained. In this research, the proton ratio was investigated experimentally and analytically in a small source (1.4 liter). The measured proton ratio increased form 40% to 90% by applying the magnetic filter. From the numerical analysis, the proton ratio is low as 40% in the driver region. However, with the magnetic filter, flow of primary electrons is restrained, resulting in suppression of H
production at the extraction region. In addition, molecular ions are easily destroyed by thermal electrons in the filter region. Thus the proton ratio is enhanced by the magnetic field in the small sources.
Mizuno, Takatoshi*; Kitade, Yuki*; Hatayama, Akiyoshi*; Sakurabayashi, Toru*; Imai, Naoki*; Morishita, Takatoshi; Inoue, Takashi
Review of Scientific Instruments, 75(5), p.1760 - 1763, 2004/05
Times Cited Count：7 Percentile：38.44(Instruments & Instrumentation)Spatial non-uniformities of extracted negative ion beam were observed experimentally in tandem-type negative ion sources. To improve the beam uniformity, it is important to analyze the plasma profile in the ion source including magnetic filter effect. In the filter region, Lorentz force is important for both ions and electrons. However, their dynamics are completely different, i.e. electrons are magnetized and ions are not magnetized. Then, the system of two-dimensional two-fluid model equations is solved simultaneously to obtain self-consistent profiles of the plasma parameters. The result shows that a possible cause of spatial non-uniformity is the ion flow rather than ExB drift motion of electrons. This flow of ions is caused by synergetic effect of the force by electric field, Lorentz force and inertia force. To verify the results above and more quantitative comparisons with experiments, full 3D analysis is needed, because the electron loss along the field line is important for the plasma potential and the electric field in the filter region. Full 3D analysis is now in progress.
Morishita, Takatoshi; Inoue, Takashi; Iga, Takashi*; Watanabe, Kazuhiro; Kashiwagi, Mieko; Shimizu, Takashi; Taniguchi, Masaki; Hanada, Masaya; Imai, Tsuyoshi
JAERI-Tech 2003-007, 16 Pages, 2003/03
JAERI-Tech-2003-007.pdf:1.28MB
Recently the ion source for IFMIF (International Fusion Material Irradiation facility) achieved positive ion beams of 120 mA with the proton ratio of 90% by applying magnetic filter even in a small ion source. The mechanism of a high proton ration plasma production in such a small ion source has not been studied. Molecular ions are destroyed and the proton is produced from the dissociation of molecular ions in the filter region. Thus the proton yield is enhanced even in the small volume discharge. Using the same numerical method, the plasma production was calculated for the large ion source. The high proton ratio can be easily obtained, where the contribution of proton production by the ionization of H becomes high. From the negative ion production point of view, the negative ion beam current was numerically evaluated. The high atom flux to the plasma grid generates the large amount of negative ions rather than that by the positive ions in Cs-seeded large ion sources.
Takeda, Masayasu; Torikai, Naoya*; Ino, Takashi*; Tasaki, Seiji*
KENS Report-XIV, p.205 - 206, 2003/00
no abstracts in English
Miyamoto, Naoki*; Seki, Masakazu; Kinsho, Michikazu; Oguri, Hidetomo; Okumura, Yoshikazu
JAERI-Tech 99-010, 27 Pages, 1999/02
no abstracts in English
ion source for the JT-60U negative-ion-based neutral beam injectorOkumura, Yoshikazu; Hanada, Masaya; Inoue, Takashi; Kuriyama, Masaaki; Maeno, Shuichi*; Matsuoka, Mamoru; Miyamoto, Kenji; Mizuno, Makoto; Ohara, Yoshihiro; Suzuki, Satoshi; et al.
Proceedings of 15th IEEE/NPSS Symposium on Fusion Engineering, p.466 - 469, 1993/00
no abstracts in English
