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ion beams in a proof-of-principle accelerator for ITERInoue, Takashi; Taniguchi, Masaki; Dairaku, Masayuki; Hanada, Masaya; Kashiwagi, Mieko; Morishita, Takatoshi; Watanabe, Kazuhiro; Imai, Tsuyoshi
Review of Scientific Instruments, 75(5), p.1819 - 1821, 2004/05
Times Cited Count：11 Percentile：51.23(Instruments & Instrumentation)The paper reports progress of proof-of-principle test of negative ion accelerator for ITER. The accelerator structure is immersed in vacuum, surrounded by a FRP insulator column as the vacuum boundary. So far, the beam energy has been limited due to poor voltage holding capability of the FRP insulator column. By lowering the electric field strength at the triple junction (interface of FRP insulator, metal flange and vacuum) with large stress ring installed inside the insulator column, high voltage of 1 MV was stably sustained for more than 2 hours. In the following beam test, acceleration of 900 keV, 100 mA H ion beam was succeeded. Although the current was lower (70 mA) at 1 MeV, the beam of this level has been stably accelerated for 6 days, 130 shots in total (each pulse length: 1 s).
Morishita, Takatoshi; Inoue, Takashi; Iga, Takashi*; Watanabe, Kazuhiro; Imai, Tsuyoshi
Review of Scientific Instruments, 75(5), p.1764 - 1766, 2004/05
Times Cited Count：8 Percentile：42.73(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.
Hanada, Masaya; Kashiwagi, Mieko; Inoue, Takashi; Watanabe, Kazuhiro; Imai, Tsuyoshi
Review of Scientific Instruments, 75(5), p.1813 - 1815, 2004/05
Times Cited Count：24 Percentile：73.13(Instruments & Instrumentation)A proof-of-principle test on plasma neutralizer, that is capable of enhancing a system efficiency of neutral beam injector for future fusion reactors, has been carried out. A 2 m long and 0.6 m diamater neutralizer with multicusp magnet line was used, improving the confinement of primary electrons flowed from both ends of the neutralizer by a pair of magnets. This improvement produced relatively high density Ar plasma of 10
- 10
cm
at low operating pressure of 0.002 Pa - 0.03 Pa. In the neutralization experiment, 200 keV H ion beams were neturalized with the plasms and gas. Compared with the gas neutralization, the maximaum neutralization efficiency by the plasma was 6% higher than that by the gas. Further, an optimum Ar gas line density for maximizing the neutralization efficiency was 30% lower than that by the gas. These results are in good agreements with results analyzed from the cross-section data for neturalization. Thus, it was experimentally verified that the neutralization effiency can be enhanced at relatively low line density by using the plasma.
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：39.52(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.
Saito, Yuichi; Okoshi, Kiyonori; Arakawa, Kazuo
Review of Scientific Instruments, 75(5), p.1502 - 1505, 2004/05
Times Cited Count：8 Percentile：42.73(Instruments & Instrumentation)An extremely compact, all-permanent-magnet electron cyclotron resonance ion source was designed and manufactured mainly for materials development. The ion source was installed to the 400kV ion implanter, and heavy ion beam in a MeV energy region with high beam current was available using multiply charged ions from the ion source. In the preliminary result at the test stand, the Ar
beam of 80 microA and He
beam of 100 microA were available and the Ar
beam was obtained at the extraction voltage of 13.5kV with microwave power of only 8W.
