Open AccessPhase contrast imaging interferometer for edge density fluctuation measurements on LHD
Author(s) -
K. Tanaka,
L. N. Vyacheslavov,
T. Akiyama,
A. Sanin,
K. Kawahata,
T. Tokuzawa,
Y. Ito,
S. Tsuji-Iio,
S. Okajma
Publication year - 2003
Publication title -
review of scientific instruments
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.605
H-Index - 165
eISSN - 1089-7623
pISSN - 0034-6748
DOI - 10.1063/1.1538361
Subject(s) - interferometry , optics , physics , wavelength , plasma diagnostics , phase (matter) , plasma , astronomical interferometer , range (aeronautics) , phase contrast imaging , laser , materials science , phase contrast microscopy , nuclear physics , quantum mechanics , composite material
A phase contrast interferometer employing a CO_2 laser (wavelength lambda_i = 10.6 ?m) is designed and installed in order to study density fluctuations on a large helical device. A 250×50 mm slab beam passes the edge of the plasma, where rho= r/a>0.65, and provides observations of edge density fluctuations. A spatial image of the integrated fluctuations is measured by a multichannel detector array, of which the effective spacing is 5 mm in the plasma. Measured wave number components are dominated by radial components, and within the range of 7.2×10^?2<=k<=0.63 mm^?1 and within the frequency range of 5?125 kHz. A clear difference in the fluctuation levels and peak wave numbers are observed between different discharges, which differ in the energy confinement
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