Multichannel far-infrared laser interferometer for electron density measurements on the tokamak fusion test reactor

A ten-channel far-infrared laser interferometer which is routinely used to measure the spatial and temporal behavior of the electron density profile on the tokamak fusion test reactor is described, and representative results are presented. This system has been designed for remote operation in the very hostile environment of a fusion reactor. The possible expansion of the system to include polarimetric measurements is briefly outlined.