Observation of the Plasma Flow Effect on Ion Temperature Measurements using a Retarding Field Analyzer

Abstract

A retarding field analyzer (RFA) was designed for the ECR plasma device HYPER-I, making ion temperature (T_i) measurements possible for the first time. Using argon plasma, T_i was measured by rotating the RFA relative to the magnetic field lines in 90-degree increments, while maintaining a constant radial position and discharge conditions. Consistently higher T_i was observed when the RFA was exposed to axial and rotational plasma flows, whereas lower values were measured when it was oriented in the downstream directions. Such discrepancies in T_i are expected to remain robust across devices when RFAs are used in plasmas with significant flow.