Mechanical design of the TFTR poloidal rotation diagnostic

In the spring of 1997, a poloidal rotation diagnostic was installed on TFTR for the final DT experiments. This spectroscopic diagnostic was designed to measure the poloidal velocity to determine the radial electric field in the plasma. The collecting optics consist of a quartz window vacuum interface, two vertically opposed fan-shaped arrays of 1 mm quartz fibers and lens system. The design requirements, as well as short design to implementation schedule, led to some unique design features. To minimize errors introduced by the toroidal velocity component of the measurement, tight position requirements were placed on the alignment of the fiber optic assemblies relative to the tokamak and to each other. Activation and contamination of the TFTR vacuum vessel presented unique design issues for installation and precise alignment of the optics to 1 part in 1000 from outside the vacuum vessel. The design progressed from concept to implementation in less than six months requiring a relatively simple design.