We have used a variety of electrostatic, calorimetric and sample exposure probes to diagnose the edge plasma of neutral-beam heated discharges on the tokamak fusion test reactor (TFTR).
In the past, spatial profiles of electron density and temperature, and other edge parameters, were generated by repositioning probes between discharges during experiments consisting of a large number of nominally identical discharges. Recently, we have employed a probe which executes a relatively rapid stroke to generate spatial and temporal profiles during a single discharge. This has greatly enhanced our ability to perform systematic studies of the edge plasma as various operating variables are changed. In addition, this rapid radial motion permits withdrawal of the probe during portions of the discharge when the intense neutral beam heating would otherwise damage the measuring tips.
Applications of such a technique to low temperature, process plasmas will be discussed.