Bench testing of a heterodyne CO 2 laser dispersion interferometer for high temporal resolution plasma density measurements.

Autor: Akiyama T; National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292, Japan., Van Zeeland MA; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Boivin RL; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Carlstrom TN; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Chavez JA; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Muscatello CM; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., O'Neill RC; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Vasquez J; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Watkins M; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Martin W; General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA., Colio A; Palomar College, San Diego, California 92069, USA., Finkenthal DK; Palomar College, San Diego, California 92069, USA., Brower DL; Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA., Chen J; Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA., Ding WX; Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA., Perry M; California State University, San Marcos, San Marcos, California 92096, USA.
Jazyk: angličtina
Zdroj: The Review of scientific instruments [Rev Sci Instrum] 2016 Dec; Vol. 87 (12), pp. 123502.
DOI: 10.1063/1.4969055
Abstrakt: A heterodyne detection scheme is combined with a 10.59 μm CO 2 laser dispersion interferometer for the first time to allow large bandwidth measurements in the 10-100 MHz range. The approach employed utilizes a 40 MHz acousto-optic cell operating on the frequency doubled CO 2 beam which is obtained using a high 2nd harmonic conversion efficiency orientation patterned gallium arsenide crystal. The measured standard deviation of the line integrated electron density equivalent phase resolution obtained with digital phase demodulation technique, is 4 × 10 17 m -2 . Air flow was found to significantly affect the baseline of the phase signal, which an optical table cover was able to reduce considerably. The heterodyne dispersion interferometer (DI) approach is found to be robustly insensitive to motion, with measured phase shifts below baseline drifts even in the presence of several centimeters of retroreflector induced path length variations. Plasma induced dispersion was simulated with a wedged ZnSe plate and the measured DI phase shifts are consistent with expectations.
Databáze: MEDLINE
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