Measurement of Paα line from pellet ablation cloud in Heliotron J

A Iwata; S Kado; M Murakumo; T Shikama; G Motojima; A Mori; C Feng; H Okada; T Minami; S Ohshima; S Kobayashi; A Ishizawa; Y Nakamura; S Konoshima; T Mizuuchi; K Nagasaki

doi:10.1063/5.0101885

Measurement of Pa_α line from pellet ablation cloud in Heliotron J

Rev Sci Instrum. 2022 Nov 1;93(11):113537. doi: 10.1063/5.0101885.

Authors

A Iwata¹, S Kado², M Murakumo³, T Shikama³, G Motojima⁴, A Mori¹, C Feng¹, H Okada², T Minami², S Ohshima², S Kobayashi², A Ishizawa¹, Y Nakamura¹, S Konoshima², T Mizuuchi², K Nagasaki²

Affiliations

¹ Graduate School of Energy Science, Kyoto University, Kyoto, Japan.
² Institute of Advanced Energy, Kyoto University, Kyoto, Japan.
³ Graduate School of Engineering, Kyoto University, Kyoto, Japan.
⁴ National Institute for Fusion Science, Gifu, Japan.

PMID: 36461543
DOI: 10.1063/5.0101885

Abstract

The Pa_α line (1875.13 nm) in the near-infrared (NIR) region was evaluated to apply Stark broadening of the line spectrum to the electron density measurement of the small-pellet ablation cloud in Heliotron J, a medium-sized helical-axis heliotron device. Pa_α is three-to-four times broader than the visible H_β line (486.13 nm) for the same electron density. Using a portable NIR spectrometer, preliminary proof-of-concept experiments determined the marginal density, below which the broadening was undetectable. The lower detection density limit can be decreased using a narrower entrance slit or a denser grating.