Charge Exchange Neutral Particle Analyzer (CX-NPA) diagnostic measurements in ohmic as well as Ion cyclotron resonance heated plasma discharges in Aditya

Charge Exchange Neutral Particle Analyzer (CX-NPA) diagnostics is a well-established technique to study fusion plasma characteristics and has been effectively used in a number of forms at many magnetically confined plasma machines. CX-NPA measurements in ADITYA-tokamak (R/a=75cm/25cm) are based on ionizing the neutrals in a gas filled stripping cells and subsequent analysis of positive ions. CX-NPA diagnostics system in Aditya, provides the time resolved values of core-ion temperature for ohmic plasma as well as in the presence of Ion cyclotron resonance heating (ICRH). CX-NPA measurements in ohmically heated plasma of Aditya have shown that the core ion temperature lies in the range of 100 to 300 eV, for several observed plasma shots. During ICRH heating also, the core-ion temperature measurements have been performed and reported here in this paper. Though the idea of a parallel plate electrostatic analyser, which CX-NPA uses, is very simple, there are design challenges to be considered. A few of them are also briefly discussed in this paper. (author)