Changes of optical properties of retroreflector installed in LHD

T. Akiyama, K. Kawahata, N. Ashikawa, M. Tokitani, S. Okajima, K. Nakayama, N. Yoshida, A. Ebihara, K. Tokunaga, Y. Ohtawa, S. Tsuji-lio

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Abstract

This article describes changes of optical properties of retroreflectors installed on the inner wall of the vacuum vessel of the Large Helical Device. They were made of stainless steel and were used for a CO2 laser Polarimeter. The reflectivity for a CO2 laser beam dropped up to 40% after the start of glow discharge cleanings and main plasma experiments. Then it decreased gradually. The reflectivity in a wavelength range shorter than 10 μm decreased significantly through one experimental campaign (about 4 months). On the other hand the reflectivity in a wavelength range longer than 50 μm was larger than 70%. Decrease in the reflectivity in the central region of mirrors was more significant (the reflectivity for visible beams became almost zero) than that in the edge. The distribution of the reflectivity along the radial direction is expected to be related to the shape of the retroreflector. The parallelism of the reflected beam to an incident one also deteriorated. The changes in the polarization angle and in the ellipticity of reflected light polarization were not observed from the visible to the far infrared range.

Original languageEnglish
Article number103501
JournalReview of Scientific Instruments
Volume78
Issue number10
DOIs
Publication statusPublished - Nov 20 2007

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retroreflectors
Optical properties
reflectance
optical properties
Wavelength
Polarimeters
Glow discharges
ellipticity
polarimeters
polarization
Light polarization
wavelengths
glow discharges
cleaning
Laser beams
vessels
stainless steels
Cleaning
Stainless steel
laser beams

All Science Journal Classification (ASJC) codes

  • Instrumentation

Cite this

Akiyama, T., Kawahata, K., Ashikawa, N., Tokitani, M., Okajima, S., Nakayama, K., ... Tsuji-lio, S. (2007). Changes of optical properties of retroreflector installed in LHD. Review of Scientific Instruments, 78(10), [103501]. https://doi.org/10.1063/1.2786938

Changes of optical properties of retroreflector installed in LHD. / Akiyama, T.; Kawahata, K.; Ashikawa, N.; Tokitani, M.; Okajima, S.; Nakayama, K.; Yoshida, N.; Ebihara, A.; Tokunaga, K.; Ohtawa, Y.; Tsuji-lio, S.

In: Review of Scientific Instruments, Vol. 78, No. 10, 103501, 20.11.2007.

Research output: Contribution to journalArticle

Akiyama, T, Kawahata, K, Ashikawa, N, Tokitani, M, Okajima, S, Nakayama, K, Yoshida, N, Ebihara, A, Tokunaga, K, Ohtawa, Y & Tsuji-lio, S 2007, 'Changes of optical properties of retroreflector installed in LHD', Review of Scientific Instruments, vol. 78, no. 10, 103501. https://doi.org/10.1063/1.2786938
Akiyama T, Kawahata K, Ashikawa N, Tokitani M, Okajima S, Nakayama K et al. Changes of optical properties of retroreflector installed in LHD. Review of Scientific Instruments. 2007 Nov 20;78(10). 103501. https://doi.org/10.1063/1.2786938
Akiyama, T. ; Kawahata, K. ; Ashikawa, N. ; Tokitani, M. ; Okajima, S. ; Nakayama, K. ; Yoshida, N. ; Ebihara, A. ; Tokunaga, K. ; Ohtawa, Y. ; Tsuji-lio, S. / Changes of optical properties of retroreflector installed in LHD. In: Review of Scientific Instruments. 2007 ; Vol. 78, No. 10.
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