Far infrared laser interferometer system on the Large Helical Device

A multichannel far-infrared laser interferometer system has been developed for the measurement of the spatial and temporal behaviors of the electron d ensity on the Large Helical Device (LHD) at the National Institute for Fusi on Science. Of several candidates for high power laser sources a 119 mu m C H3OH laser was taken as a probing light. The optical configuration is of th e Michelson interferometer type with 13 channels. The optical system of the interferometer is mounted on a massive stainless frame floated on three vi bration isolating mounts. The resolution of the fringe counters is 1/100 fr inges, and it corresponds to a line averaged density of 5.6 X 10(16) m(-3) at the central chord. Preliminary results have been obtained in the initial experiments on the LHD. (C) 1999 American Institute of Physics. [S0034-674 8(99)63601-2].