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Feasibility of a Multi-Pass Thomson Scattering System with Confocal Spherical Mirrors

Junichi HIRATSUKA, Akira EJIRI, Yuichi TAKASE and Takashi YAMAGUCHI

The University of Tokyo, Kashiwa 277-8561, Japan

(Received 12 April 2010 / Accepted 27 August 2010 / Published 30 November 2010)

Abstract

Multi-pass Thomson scattering is an attractive method for measuring electron temperature and density in low density plasmas. The feasibility of multi-pass laser optics consisting of two confocal spherical mirrors has been studied, and analytic expressions for the path have been obtained. These can be used to optimize the design under the given conditions. The effects of aberration, as well as positioning and alignment errors, were found to be critical for obtaining large transit numbers. Beam expansion resulting from aberration, surface roughness of the mirrors and diffraction is considered. Under practical conditions, transit numbers of about 37 (i.e., 19 round trips) are possible.

Copyright (c) 2010 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

Thomson scattering, multi-pass, confocal mirror, ECH start-up, low-density plasma

DOI: 10.1585/pfr.5.044

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References

• [1] A. Ejiri et al., Nucl. Fusion 49, 065010 (2009).
• [2] M. Yu. Kantor et al., Plasma Phys. Control. Fusion 51, 055002 (2009).
• [3] K. Hanada et al., IEEJ Trans. FM 129, 589 (2009).
• [4] A. Ejiri et al., to be published in Plasma Fusion Res. Special Issue (ITC-19).

This paper may be cited as follows:

Junichi HIRATSUKA, Akira EJIRI, Yuichi TAKASE and Takashi YAMAGUCHI, Plasma Fusion Res. 5, 044 (2010).