First results from the J-TEXT high-resolution three-wave polarimeter-interferometer

Journal Article · Mon Oct 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4729674· OSTI ID:22093919

Chen, J.; Zhuang, G.; Wang, Z. J.; Gao, L.; Li, Q.; Chen, W. ^[1]; Brower, D. L.; Ding, W. X. ^[2]

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1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)
2. Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States)

A laser-based far-infrared polarimeter-interferometer system utilizing the three-wave technique has been implemented on the J-TEXT tokamak. The polarimeter determines the Faraday effect by measuring the phase difference between two collinear, counter-rotating, circularly polarized laser beams. The first results of the polarimeter-interferometer designed for J-TEXT have been obtained in the most recent J-TEXT experimental campaign. Simultaneous polarimetric and interferometric measurement is achieved, with phase resolution up to 0.1 Degree-Sign , at bandwidth of 50 kHz. The temporal resolution, which is dependent on the laser's frequency offset, is {approx}1 {mu}s. Continual spatial measurement covering 45 cm (80% of the plasma cross-section) is realized by utilizing 1D parabolic beam expansion optics. Three initial test chords are installed and future plans call for expansion up to 30 chords with 1.5 cm chord spacing, providing high spatial resolution for measurement of electron density and current density profiles. Reliability of both polarimetric and interferometric measurement is confirmed by comparison with computation and data from a hydrocyanic acid (HCN) interferometer. With the high temporal and phase resolution, perturbations associated with the sawtooth cycle and MHD activity have been observed.

• OSTI ID: 22093919
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
BEAMS
CALCULATION METHODS
CROSS SECTIONS
CURRENT DENSITY
DISTURBANCES
ELECTRON DENSITY
EXPANSION
FARADAY EFFECT
INTERFEROMETERS
LASER RADIATION
MAGNETOHYDRODYNAMICS
OPTICS
PLASMA INSTABILITY
POLARIMETERS
RELIABILITY
SAWTOOTH OSCILLATIONS
SPATIAL RESOLUTION
TOKAMAK DEVICES
VISIBLE RADIATION