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

Here, 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.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ; ORCiD logo [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [3] ;  [4] ;  [4] ;  [4] ;  [5]
  1. National Institute for Fusion Science, Gifu (Japan)
  2. General Atomics, San Diego, CA (United States)
  3. Palomar College, San Diego, CA (United States)
  4. Univ. of California Los Angeles, Los Angeles, CA (United States)
  5. California State University, San Marcos, San Marcos, CA (United States)
Publication Date:
Grant/Contract Number:
FC02-06ER54875; FC02-08ER54972
Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 87; Journal Issue: 12; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Research Org:
Tech-X Corp., Boulder, CO (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION
OSTI Identifier:
1466040
Alternate Identifier(s):
OSTI ID: 1334833

Akiyama, T., Van Zeeland, M. A., Boivin, R. L., Carlstrom, T. N., Chavez, J. A., Muscatello, C. M., O’Neill, R. C., Vasquez, J., Watkins, M., Martin, W., Colio, A., Finkenthal, D. K., Brower, D. L., Chen, J., Ding, W. X., and Perry, M.. Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements. United States: N. p., Web. doi:10.1063/1.4969055.
Akiyama, T., Van Zeeland, M. A., Boivin, R. L., Carlstrom, T. N., Chavez, J. A., Muscatello, C. M., O’Neill, R. C., Vasquez, J., Watkins, M., Martin, W., Colio, A., Finkenthal, D. K., Brower, D. L., Chen, J., Ding, W. X., & Perry, M.. Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements. United States. doi:10.1063/1.4969055.
Akiyama, T., Van Zeeland, M. A., Boivin, R. L., Carlstrom, T. N., Chavez, J. A., Muscatello, C. M., O’Neill, R. C., Vasquez, J., Watkins, M., Martin, W., Colio, A., Finkenthal, D. K., Brower, D. L., Chen, J., Ding, W. X., and Perry, M.. 2016. "Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements". United States. doi:10.1063/1.4969055. https://www.osti.gov/servlets/purl/1466040.
@article{osti_1466040,
title = {Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements},
author = {Akiyama, T. and Van Zeeland, M. A. and Boivin, R. L. and Carlstrom, T. N. and Chavez, J. A. and Muscatello, C. M. and O’Neill, R. C. and Vasquez, J. and Watkins, M. and Martin, W. and Colio, A. and Finkenthal, D. K. and Brower, D. L. and Chen, J. and Ding, W. X. and Perry, M.},
abstractNote = {Here, a heterodyne detection scheme is combined with a 10.59 μm CO2 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 CO2 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 × 1017 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.},
doi = {10.1063/1.4969055},
journal = {Review of Scientific Instruments},
number = 12,
volume = 87,
place = {United States},
year = {2016},
month = {12}
}