Precision metrology of NSTX surfaces using coherent laser radar ranging

摘要

A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 (micro)m laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of 100(micro)m at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated.