Plasma and Fusion Research

Volume 18, 2401082 (2023)

Regular Articles

Volumetric Recombination in the Linear ECR Plasma Device NUMBER
Konan YAGASAKI, Atsushi OKAMOTO, Takaaki FUJITA, Minami SUGIMOTO, Shunya HIGUCHI, Muneo KOIKE, Koki SATO and Yuto YAMADA
Nagoya University, Nagoya 464-8603, Japan
(Received 9 January 2023 / Accepted 26 June 2023 / Published 12 October 2023)

Abstract

A plasma recombination experiment was carried out using the linear electron cyclotron resonance (ECR) plasma device NUMBER as a preliminary step for forming a detached plasma. The electron density measured by an electrostatic probe in a divertor-simulated region was successfully increased up to approximately 6×1017 m−3. This increase was realized by installing an additional gas feed system to the region and using a circular polarizer to control the microwave polarization. Passive spectroscopic measurements performed on the high-density plasma yielded line spectra of He I 23P–n3D for the principal quantum number n ≤ 13, which are characterstic of helium recombining plasma. The line spectra were used to calculate an electron temperature of approximately 0.055 eV and an electron density of approximately 1.33 × 1018 m−3 by the Boltzmann plot method and Saha–Boltzmann equation, respectively.

Keywords

recombining plasma, volumetric recombination, ECR plasma, polarization, electron density

DOI: 10.1585/pfr.18.2401082

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