Tokamak-Independent Software Analysis Suite 
for Multi-Spectral Line-Polarization MSE Diagnostics

Authors:   S. D. Scott, R. T. Mumgaard

Abstract:  A new, tokamak-independent analysis suite has been developed to process data from Motional Stark Effect diagnostics. A major feature of the system is that unlike customary MSE systems that use analog lock-in amplifiers to measure the emission amplitude at the second harmonic of the photo-elastic modulator (PEM) drive frequencies, the amplitude at many harmonics is computed using a numerical-beat algorithm. The frequency and phase of the PEM drive signal is computed very accurately by examining the successive rise-times of the drive, then reference sinusiodal waveforms are constructed at multiple harmonics. The reference waveform is numerically beat against the measured MSE signal to obtain the signal amplitudes at various PEM harmonics. The software suite encompasses four major sequenced activities: (1) computing the PEM frequency and phase; (2) computing the beam on/off timing; (3) computing the signal amplitudes at various PEM harmonics; and (4) interpolating in wavelength to accurately subtract the polarized background and computing pitch-angles. The software is modularized (~150 IDL procedures) and parallelized so that each of the 40 channels is processed independently, thereby reducing both memory requirements and processing time. The entire system including userselected input parameters and output is based in MDSPLUS allowing straightforward porting to other tokamaks.
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Presented at:  High Temperature Plasma Diagnostics, Madison, WI, June 2016

Submitted to:  Reviews of Scientific Instruments
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Download PPPL-5240 (pdf 3.1 MB 4 pp)
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