ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
An important aspect of this method is to measure the density simultaneously with the Faraday rotation in order to infer the magnetic field from the rotation. This measurement performed on several chords yields information on the density and poloidal field profiles. Heterodyne techniques are employed for the polarimetry as well as the interferometry because they are insensitive to spurious amplitude changes that can hamper other methods. On ZT-40M, amplitude changes exceeding 50% have been observed, thus precluding any other method for our application. We use a 185-μm laser, a rotating grating for heterodyning, and GaAs photoconductors and Schottky diodes for detection. An instrumental sensitivity of 3 mrad at a time resolution of 25 μs has been demonstrated, however vibration-induced structure limits the sensitivity to ∼50 mrad. Efforts to reduce each of these numbers are in progress. The simultaneous measurement has been made on ZT-40M, and effort is turning to system refinement and scaling up to multichord operation. Error propagation in the inversion process is being evaluated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1138053
Permalink