Rogowski loop designs for NSTX

The Rogowski loop is one of the most basic diagnostics for tokamak operations. On the National Spherical Torus Experiment (NSTX), the plasma current Rogowski Loop had constraints of very limited space available on the center stack, 5000 volt isolation, flexibility requirements as it remained a part of the Center Stack assembly after the first phase of operation, and with a ±120°C temperature requirement. For the second phase of operation, four halo current Rogowski loops under the Center Stack tiles will be installed having +600°C and limited space requirements. Also as part of the second operational phase, up to ten Rogowski Loops will installed to measure eddy currents in the passive plate support structures with +350 °C, restricted space, and flexibility requirements. This presentation will provide the details of the material selection, fabrication techniques, testing, and installation results of the Rogowski loops that were fabricated for the high temperature operation and bakeout requirements, high voltage isolation requirements, and the space and flexibility requirements imposed upon the Rogowski loops. In the future operational phases of NSTX, additional Rogowski loops could be anticipated that will measure toroidal plasma currents in the vacuum vessel and in the passive plate assemblies