Investigation of the Ion Energy Transport in the Scrape-Off Layer on the J-TEXT Tokamak Using a Retarding Field Analyzer**supported by National Natural Science Foundation of China (No. 11305070), the Ministry of Science and Technology (No. 2013GB106001) and the Open Foundation of the Key Laboratory of Geospace Environment, the CSA/SAFEA International Partnership Program for Creative Research Teams

Abstract

Radial profiles of the ion temperature, Ti, have been measured by a double-sided retarding field analyzer (RFA) in the scrape-off layer (SOL) of the J-TEXT tokamak (R = 105 cm, r = 25–29 cm, Bt = 1.8–2.0 T, Ip = 120–180 kA, ne = (2–2.5) × 1019 m−3). Strongly declining Ti profiles in the SOL have been found. The different e-folding lengths, λT, of the Ti profiles in two experimental configurations with different magnetic connection lengths, Lc, reveal that a longer Lc results in weaker parallel energy transport and longer λT. In similarity with the particle transport across the SOL, λT is approximately proportional to the square root of Lc. Additionally, the poloidal asymmetry has been identified with enhanced ion energy transport across the SOL on the low-field side.