[Table of Contents]

Plasma and Fusion Research

Volume 5, 044 (2010)


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)


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.


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

DOI: 10.1585/pfr.5.044


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  • [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).