Effect of cross-field transport on H− density profile in magnetized plasmas: Comparison between measurement and simulation

Abstract

The radial density profile of negative hydrogen ions in magnetized plasma is investigated in the divertor simulator MAP (Material and plasma)-II [S. Kado et al., J. Plasma Fusion Res. 71, 810 (2005)] by measurement and numerical simulation. The laser photodetachment method is used to evaluate the H− density by considering the influence of the magnetic field. The density of H− has a hollow profile and exhibits a peak in the peripheral region, though the electron density and temperature exhibit a peak at the center of the plasma column. The density profile of H− does not agree with the calculation result obtained from the rate equation, in which the local production and extinction rates are balanced, under the present experimental condition. To understand the behavior of negative ions, their trajectories are calculated by numerically solving the equation of motion by considering the effect of collisions. The negative ion density profile calculated from the particle simulation agrees well with the measured negative ion density profile. It is shown that the cross-field H− transport due to the radial electric field with the assistance of the elastic collisions plays an important role in enhancing the negative ion density in the peripheral region.

Behavior of 23S metastable state He atoms in low-temperature recombining plasmas

“…To demonstrate the influence of transport quantitatively, motion of the metastable atoms are calculated by using a simulation code developed based on a particle transport code [27].…”