Fast Neutral Pressure Gauges in NSTX
Authors: R. Raman, H.W. Kugel, R. Gernhardt, T. Provost, T.R. Jarboe, and V. Soukhanovskii
Date of PPPL Report: April 2004
Date of Revised PPPL Report: September 2004
Presented at: the 15th APS High Temperature Plasma Diagnostics Conference, 19-22 April, 2004, San Diego, CA. Published in Review of Scientific Instruments 75:10 (Oct 2004) 4347-4349.
Successful operation in NSTX of two prototype fast-response micro ionization gauges during plasma operations has motivated us to install five gauges at different toroidal and poloidal locations to measure the edge neutral pressure and its dependence on the type of discharge (L-mode, H-mode, CHI) and the fuelling method and location. The edge neutral pressure is also used as an input to the transport analysis codes TRANSP and DEGAS-2. The modified PDX-type Penning gauges are well suited for pressure measurements in the NSTX divertor where the toroidal field is relatively high. Behind the NSTX outer divertor plates where the field is lower, an unshielded fast ion gauge of a new design has been installed. This gauge was developed after laboratory testing of several different designs in a vacuum chamber with applied magnetic fields.