(FT/P5-2) Development of Strongly Focused High-Current-Density Ion Beam System and Its Application for the Alpha Particle Measurement in ITER

H. Sakakita1), S. Kiyama1), Y. Hirano1), M. Sasao2), K. Shinto2), H. Koguchi1), Y. Yagi1), T. Shimada1), K. Yambe1), L. Frassinetti1), A. Okamoto2), G. Fiksel3), B. Hudson3)
1) National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
2) Tohoku University, 6-6-01-2 Aoba, Aramaki, Sendai 980-8579, Japan
3) University of Wisconsin Madison, Madison, WI 53706, USA

Abstract.  Strongly focused and high-current density ion beam system was successfully developed using large concave electrodes. The beam with a diameter of 345 mm at the electrode is focused to a diameter of 36 mm at the focal point with a small total divergence angle of about 1.6 deg. In the cases of H+, He+ and HeH+ beams of 25 keV, it is estimated that the extracted ion current density achieves as high as 190, 86 and 13 mA/cm2, respectively. The HeH+ beam of 25 keV can be considered as a primary beam of a diagnostic helium neutral beam of 1-2 MeV for the alpha particle measurement in ITER, and it is demonstrated for the first time that the current density level of HeH+ beam is sufficient for this purpose.

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