Investigation of the Ion Energy Transport in the Scrape-Off Layer on the J-TEXT Tokamak Using a Retarding Field Analyzer

Radial profiles of the ion temperature, T_i, 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, B_t =1.8-2.0 T, I_p = 120 -180 kA, n_e = (2-2.5) × 10¹⁹ m^-3). Strongly declining T_i profiles in the SOL have been found. The different e-folding lengths, λ_T, of the T_i profiles in two experimental configurations with different magnetic connection lengths, L_c, reveal that a longer L_c results in weaker parallel energy transport and longer λ_T . In similarity with the particle transport across the SOL, λ_T is approximately proportional to the square root of L_c. Additionally, the poloidal asymmetry has been identified with enhanced ion energy transport across the SOL on the low-field side.