Knowing the ion temperature in the scrape-off layer (SOL) of tokamaks is of great importance for understanding the heat flux to plasma facing components. Few measurements are available for SOL ion temperatures compared with electron temperatures due to the relative complexity of the measurement. Two retarding field energy analysers (RFEAs) have been used in the mega amp spherical tokamak (MAST) to measure the ion temperature at both the midplane and the divertor in ohmic L-mode plasmas with a range of densities. Midplane SOL Ti was found to be higher than Te by a factor of about 2 or greater. Divertor Ti measurements at the target showed Ti ≈ Te having considered the effect of plasma flows on the divertor RFEA measurements.
Ion temperature measurements in the tokamak scrape-off layer with high temporal resolution