Ion energy measurements on MAST using a midplane RFEA

TL;DR

This study uses a midplane RFEA to measure ion energies in MAST's scrape-off layer during various plasma conditions, revealing ion temperature profiles and ratios during ELMs and inter-ELM periods.

Contribution

First detailed ion energy measurements in MAST's scrape-off layer during ELMs using a midplane RFEA, providing new insights into ion temperature behavior.

Findings

Ion temperatures of 20-70 eV during inter-ELM periods.

Ion temperatures of 30-50 eV during ELMs at various distances.

Ion to electron temperature ratio averages around 4.

Abstract

Ion energy measurements have been made in the scrape off layer of the Mega Amp Spherical Tokamak (MAST) using a midplane retarding field energy analyser (RFEA) in H-mode plasmas during the inter-edge localised mode (ELM) period and during type I and type III ELMs. During the inter-ELM period at distances of 3 to 8 cm from the last closed flux surface (LCFS), ion temperatures of 20 to 70 eV have been measured giving an ion to electron temperature ratio of 2 to 7 with a mean of 4. During type III ELMs, an ion temperature of 50 eV has been measured 3 to 6 cm from the LCFS which decreases to 30 eV at distances 11 to 16 cm from the LCFS. During type I ELMs, an ion temperature of 40 eV has been measured at a distance of 10 to 15 cm from the LCFS.