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Journal Articles

Analysis of electron temperature distribution by kinetic modeling of electron energy distribution function in JAEA 10 ampere negative ion source

Shibata, Takanori; Terasaki, Ryo*; Kashiwagi, Mieko; Inoue, Takashi; Dairaku, Masayuki; Taniguchi, Masaki; Tobari, Hiroyuki; Umeda, Naotaka; Watanabe, Kazuhiro; Sakamoto, Keishi; et al.

AIP Conference Proceedings 1515, p.177 - 186, 2013/02

 Times Cited Count:8 Percentile:94.55

In the neutral beam injector in JT-60SA, one of issues is that negative ion beam is partially intercepted at acceleration grids due to a spatial non-uniformity of negative ion production on large extraction area (0.9$$times$$0.45m$$^{2}$$). Previous experiments showed that fast electrons emitted from filament cathodes are transported in a longitudinal direction by $$mathbf{B} times textrm{grad} mathbf{B}$$ drift and the spatial distribution of electron temperature ($$T_e$$) strongly relates with the non-uniformity. In this study, a three-dimensional electron transport analysis has been developed. Electron temperature in the analysis agreed well with measurements in JAEA 10A ion source. This study clarified that the bias of $$T_e$$ distribution are caused by the following reasons; (1) fast electrons drifted in the longitudinal direction survives near the end wall with energy up to $$E$$ = 25-60 eV and (2) they produces thermal electrons by collision with plasma particles there.

Journal Articles

Effect of non-uniform electron energy distribution function on plasma production in large arc driven negative ion source

Shibata, Takanori; Koga, Shojiro*; Terasaki, Ryo*; Inoue, Takashi; Dairaku, Masayuki; Kashiwagi, Mieko; Taniguchi, Masaki; Tobari, Hiroyuki; Tsuchida, Kazuki; Umeda, Naotaka; et al.

Review of Scientific Instruments, 83(2), p.02A719_1 - 02A719_3, 2012/02

 Times Cited Count:2 Percentile:13.93(Instruments & Instrumentation)

In the NBI for large fusion devices, production of uniform negative ion beam is one of important issues. A physical model is proposed to understand the non-uniformity. It has been qualitatively shown that the non-uniform beam intensity is due to the following process; (1) formation of non-uniform EEDF, (2) localized production of hydrogen atoms/ions (H$$^0$$/H$$^+$$) due to (1), (3) non-uniform flux of H$$^0$$/H$$^+$$ to the PG and (4) localized surface production of negative ions. However, in the past studies, the EEDF was assumed as two temperature Maxwellian distribution from measurements. Thus effects of high energy electrons are not taken into account precisely. In the present research, local EEDF is calculated by the 3D Monte-Carlo kinetic model which takes into account the spatial and magnetic configurations of the real negative ion source. The numerical result show that high energy component of the EEDF enhances the spatial non-uniformity in the production rate of H$$^0$$/H$$^+$$.

Journal Articles

3D modeling of the electron energy distribution function in negative hydrogen ion sources

Terasaki, Ryo*; Fujino, Ikuro*; Hatayama, Akiyoshi*; Mizuno, Takatoshi; Inoue, Takashi

Review of Scientific Instruments, 81(2), p.02A703_1 - 02A703_3, 2010/02

 Times Cited Count:20 Percentile:67.88(Instruments & Instrumentation)

In order to develop the large H$$^{-}$$ ion source for future fusion reactors, the uniform production of H$$^{-}$$ ions is one of the important issues. Recently, it has been shown experimentally in JAEA 10A negative ion source that the non-uniformity of the electron energy distribution function (EEDF) inside the source and the resultant non-uniformity of the H$$^{-}$$ production strongly affect the H$$^{-}$$ beam optics. Therefore, modeling of the EEDF and analysis of the spatial non-uniformity of the EEDF is necessary to optimize H$$^{-}$$ ion source and the beam optics. For this purpose, we are developing the 3D3V Monte Carlo modeling of the EEDF in realistic 3D geometry. The code reproduces the spatial non-uniformity of the EEDF observed in the experiments. Our developing code is a powerful tool for the design of the next generation sources.

Oral presentation

Magnetic and crystal structures of Ba$$_{3}$$Co$$_{1-x}$$Ca$$_{x}$$Ru$$_{2}$$O$$_{9}$$

Horie, Akihiro*; Yasui, Yukio*; Igarashi, Taichi*; Yatagai, Ryo*; Yamamoto, Takafumi*; Terasaki, Ichiro*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*; Igawa, Naoki

no journal, , 

The magnetic and crystal structures, and magnetic properties of Ba$$_{3}$$Co$$_{1-x}$$Ca$$_{x}$$Ru$$_{2}$$O$$_{9}$$ have been studied by using the neutron powder diffraction and the magnetization analysis. With increasing ${it x}$, an antiferromagnetic transition temperature $$T_mathrm{N}$$ decreases such as $$T_mathrm{N}$$ = 88 K (${it x}$=0.1), 82 K (${it x}$=0.2), and 76 K (${it x}$=0.3), respectively. We have observed magnetic reflections, which can not be explained by the collinear structure. Though the lattice volume increases, we have found that a Ru-Ru bond length decreases with increasing ${it x}$. It is considered to be related with the Ru-Ru dimerization. By the combined studies of the magnetic properties and neutron diffraction analysis, we will discuss the change of Ru$$^{5+}$$-spins with varying ${it x}$.

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