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Improvements of CO₂ Laser Heterodyne Imaging Interferometer for Electron Density Profile Measurements on LHD

Kenji TANAKA, Clive MICHAEL, Leonid VYACHESLAVOV¹⁾, Andrei SANIN¹⁾, Kazuo KAWAHATA, Shigeki OKAJIMA²⁾, Takeshi AKIYAMA, Tokihiko TOKUZAWA and Yasuhiko ITO

National Institute for Fusion Science, Toki 509-5292, Japan

1)

Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia

2)

Department of Engimeering, Chubu Univertsity, Kasugai 487-8501, Japan

(Received 7 December 2006 / Accepted 4 June 2007 / Published 20 November 2007)

Abstract

After installation of CO₂ laser (wavelength 10.6 μm) heterodyne imaging interferometer (CO₂ HI) in 2001, continuous developments have been carried out to improve the measurements capability and stability of operation. The CO₂ HI works almost without phase jumping at high electron density (> 1 × 10²⁰ m^-3), where the existing far infrared laser (wavelength 118.9 μm) interferometer suffers from fringe jump due to the reduction of signal intensity caused by refraction. However a second interferometer is required to compensate mechanical vibration. A YAG laser (wavelength 1.06 μm) heterodyne imaging interferometer (YAG HI) is presently used for the vibration compensation. In the 10th LHD experimental campaign (2006∼2007), sixty four channels of CO₂ HI to measure electron density profile and ten channels of YAG HI to measure mechanical vibration are working. A measurement example of a pellet fuelled high-density discharge is reported.

Copyright (c) 2007 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

LHD, CO₂ laser, interferometer, density profile, least square method, Abel inversion

DOI: 10.1585/pfr.2.S1033

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References

• [1] N. Oyabu et al., Phys. Rev. Lett. 97, 055002-1 (2006).
• [2] T. Akiyama et al., Rev. Sci. Instrum. 74, 1683 (2003).
• [3] K. Tanaka et al., Rev. Sci. Instrum. 75, 3429 (2004).
• [4] Y. Jiang et al., Rev. Sci. Instrum. 68, 902 (1997).
• [5] A. Sanin et al., Rev. Sci. Instrum. 75, 3439 (2004).
• [6] C. Michael et al., this proeedings.
• [7] M. Anton et al., Plasma Phys. Control. Fusion 38, 1849 (1996).
• [8] K. Narihara, Rev. Sci. Instrum. 72, 1122 (2001).
• [9] K. Kawahata, Rev. Sci. Instrum. 70, 695 (1999).

This paper may be cited as follows:

Kenji TANAKA, Clive MICHAEL, Leonid VYACHESLAVOV, Andrei SANIN, Kazuo KAWAHATA, Shigeki OKAJIMA, Takeshi AKIYAMA, Tokihiko TOKUZAWA and Yasuhiko ITO, Plasma Fusion Res. 2, S1033 (2007).