title: Bench testing of a heterodyne CO2laser dispersion interferometer for high temporal resolution plasma density measurements.
abstract: A heterodyne detection scheme is combined with a 10.59 μm CO2laser 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 CO2beam 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 × 1017m-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.
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Akiyama
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Van Zeeland
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Boivin
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: T N
authors.initials: TN
authors.lastname: Carlstrom
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Chavez
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Muscatello
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: O'Neill
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: J
authors.initials: J
authors.lastname: Vasquez
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: M
authors.initials: M
authors.lastname: Watkins
authors.affiliation: General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
authors.forename: W
authors.initials: W
authors.lastname: Martin
authors.affiliation: Palomar College, San Diego, California 92069, USA.
authors.forename: A
authors.initials: A
authors.lastname: Colio
authors.affiliation: Palomar College, San Diego, California 92069, USA.
authors.forename: D K
authors.initials: DK
authors.lastname: Finkenthal
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Brower
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: W X
authors.initials: WX
authors.lastname: Ding
authors.affiliation: California State University, San Marcos, San Marcos, California 92096, USA.
authors.forename: M
authors.initials: M
authors.lastname: Perry