LOW-ENERGY NEUTRAL PARTICLE FLUXES TO THE WALLS OF ASDEX DURING HE AND D2 DISCHARGES

Neutral particle fluxes onto the walls of ASDEX have been investigated using a time-of-flight (TOF) method. The energy distributions of the neutrals could be determined in the range of 10-100 ev/amu. Ohmic divertor and limiter discharges with equal plasma currents and densities have been compared for He and D//2. The He**0 outflux at approximately 2000 ev from He discharges is 1/ 10 of the corresponding D**0 flux in D//2 discharges. At lower energies this difference is much smaller. In all cases many more He neutrals were observed than was anticipated from the CX rate-coefficients for He**2** plus . The impurity fluxes due to sputtering by the CX-neutrals show no significant difference for He and D//2 discharges. For divertor discharges CX-sputtering can fully account for the Fe impurity content determined spectroscopically.