Investigation of neutral hydrogen transport by means of Hsub(α)-resonance fluorescence measurements at the tokamak UNITOR

The investigations reported here were performed at the tokamak device UNITOR. The plasma is under normal operational conditions limited by a toroidal limiter. A poloidal limiter can be installed, too. Space and time resolved Hsub(α)-fluorescence measurements enabled us to determine the local density of excited H-atoms. Using a collisional radiative model the ground state neutral density varying from 1012 cm-3 at the wall to 109 cm-3 in the plasma core could be deduced. A Monte Carlo code for neutrals taking into account reflection, trapping and re-emission of neutral hydrogen at the walls was used to interpret the measurements. The local fluxes from and to the wall needed to fit the measured density are of the order of 1018 cm-2 s-1. (orig.)