First results from the far-infrared polarimeter system on the Madison Symmetric Torus reversed field pinch

The far-infrared laser interferometer on the Madison Symmetric Torus has re cently been upgraded to allow simultaneous interferometry and polarimetry m easurements. Centered around a heterodyne laser system that operates at lam bda similar or equal to 432 mu m, the diagnostic has a frequency response o f 1 kHz for the polarimeter and up to 1 MHz for the interferometer. The dis tribution of laser power through the 11 chord system is managed with wire m esh beamsplitters. Concurrent with the system upgrade to polarimetry, a det ailed study of the effect of the wire mesh beamsplitters on beam polarizati on was conducted. The study shows that the mesh characteristics must be inc luded to extract the polarimetry phase measurement from the raw data. The m odifications to the data analysis as well as preliminary five chord polarim etry profile data are presented. (C) 1999 American Institute of Physics. [S 0034-6748(99)52901-8].