[Table of Contents]

Plasma and Fusion Research

Volume 4, 034 (2009)

Regular Articles

Characterization of Dust Particles Ranging in Size from 1 nm to 10 µm Collected in the LHD
Kazunori KOGA, Shinya IWASHITA, Satoru KIRIDOSHI, Masaharu SHIRATANI, Naoko ASHIKAWA1), Kiyohiko NISHIMURA1), Akio SAGARA1), Akio KOMORI1) and LHD Experimental Group1)
Department of Electronics, Kyushu University, Fukuoka, 819-0395, Japan
1)
National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
(Received 27 June 2008 / Accepted 10 May 2009 / Published 15 July 2009)

Abstract

We collected dust particles ranging in size from 1 nm to 10 µm from the Large Helical Device employing two methods: an ex-situ filtered vacuum collection method and an in-situ dust collection method. The size distribution from 1 nm to 10 µm is well expressed by the Junge distribution. Dust particles are classified into three kinds: small spherical dust particles below 1 µm in size, agglomerates consisting of primary particles of 10 nm, and large dust particles above 1 µm in size and irregular in shape; this suggests three formation mechanisms of dust particles: chemical vapor deposition growth, agglomeration, and peeling from walls. In-situ collection shows that agglomeration between dust particles takes place in main discharges. The primary dust particles in agglomerates are around 10 nm in size, suggesting agglomeration between a negatively charged large agglomerate and a positively charged dust particle 10 nm in size. We have also confirmed the important fact that a large number of dust particles move during vacuum vent. Therefore, the in-situ dust collection method is needed to reveal the generation-time and -processes of dust particles and their deposition position during discharges.

Keywords

plasma-material interaction, dust, Large Helical Device, hydrogen plasma, carbon

DOI: 10.1585/pfr.4.034

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This paper may be cited as follows:

Kazunori KOGA, Shinya IWASHITA, Satoru KIRIDOSHI, Masaharu SHIRATANI, Naoko ASHIKAWA, Kiyohiko NISHIMURA, Akio SAGARA, Akio KOMORI and LHD Experimental Group, Plasma Fusion Res. 4, 034 (2009).