Modelling studies of SOL-divertor plasmas in EAST tokamak with ohmic shots

摘要

Modelling studies of SOL-divertor plasmas are carried out using the edge plasma code package B2.5/Eirene-SOLPS5.0. The modelling results are compared with the experimental data of ohmic shots in the EAST tokamak. The profiles of plasma temperature, density, ion flux at the divertor target plates from the modelling are compared with the Langmuir probe profiles. D_a and CⅢ emissivities from the modelling are also matched to the experimental measurement. The model treats plasma species of deuterium (D) and carbon (C) impurities in a real divertor geometry and an magnetohydrodynamic equilibrium from an experimental shot. Neutral particles of D° and C° are traced with Eirene. Properties of low recycling, high recycling and detachment in the divertor plasmas during the density ramp-up are studied at first for an ohmic shot in a discontacted double null configuration. For two ohmic shots with a single null configuration, modelling results of profiles of electron density n_e, electron temperature T_e, total heat flux Q_t and ion saturation flux F_(sat) are similar to the experimental measurement. The calculated profiles at some positions on the target plates, however, differ from the measured profiles; the calculated n_e and T_e are one-two times lower than the measured n_e and T_e, and the calculated r_(sat) is three-four times lower than the measured F_(sat). The calculated Q_t profiles along the outer target plate are in better agreement with the measured profiles of Q_t but the peak values of the Q_t profiles from the modelling differ from the experimental measurement, which may result from the low spatial resolution of the experimental measurement and the difficulties of measuring peak values with narrow widths.