TITLE

CO2 laser polarimeter for Faraday rotation measurements in the DIII-D tokamak

AUTHOR(S)
Van Zeeland, M. A.; Boivin, R. L.; Carlstrom, T. N.; Deterly, T. M.
PUB. DATE
October 2008
SOURCE
Review of Scientific Instruments;Oct2008, Vol. 79 Issue 10, p10E719
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
A tangential viewing, 10.59 μm CO2 laser polarimeter for electron density measurements based on plasma induced Faraday rotation has been installed on DIII-D. The system uses colinear right- and left-hand circularly polarized beams with a difference frequency of 40 MHz to generate the necessary signal for heterodyne phase detection. The high-resolution phase information required to adequately resolve degree level polarization rotation is obtained using an all-digital “real-time” phase demodulation scheme based on modern digital signal processing techniques. Initial application of the system to DIII-D disruption mitigation experiments utilizing “massive gas jet” injection exhibits reliable operation and excellent agreement with CO2 interferometer measurements; interestingly, the obtained Faraday rotation angles are in the range of those expected in ITER plasmas.
ACCESSION #
35150180

 

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