Erosion and deuterium retention investigation of mixed W-Be layers on Be in experiments on plasma disruption simulation

The mixed W-Be layers were prepared by deposition of Be and W atoms on a Be substrate under simultaneous sputtering of Be and W targets by 20 keV Ar+- ions. The thickness of the deposited mixed W-Be layer was similar to 500 nm . The element composition analysis of these layers showed that the mixed la yer contains up to 35 at.% W, up to 35 at.% Be and up to 30 at.% O. The W-B e films on Be were irradiated by pulsed deuterium plasma flux in the electr odynamic plasma MKT-accelerator with a deuterium plasma concentration of 10 (21) m(-3), maximal ion energy of (1-2) keV and with the energy flux densit y Of 0.2 MJ/m(2) per pulse. The pulse duration was equal to 60 Ccs After ir radiation by two plasma pulses the W-Be film is melted and removed complete ly from the local surface areas. The element distributions in a mixed layer after an effect of the pulsed plasma are essentially changed. For the surf ace areas with the removed film the Be concentration is about 75 at.%, W - about 15 at.%, O - about 10 at.% and the penetration of W and O atoms is up to 1000 nm deep of Be substrate. For the surface areas with the retained m elted film the Be surface concentration increase up to 90 at.%, tungsten an d oxygen concentration decrease about 2-3 times. The method of Elastic Reco il Detection Analysis was used to study D retention. The integral deuterium concentrations are equal to 0.6 10(20) and 2.2.10(20) m(-2) for the remove d film areas and for the retained melted film ones, correspondingly. Conseq uently, deposited W-Be film promotes the essential reduction of D retention in Be substrate. Transmission electron microscopy was used to study the er osion product size distribution. The erosion products were collected on bas alt filter fibers located in a shadow of the pulsed plasma flux around the exposed W-Be film target. The erosion product size distribution has two max ima located in the ranges 0.1-0.2 mum and 2.5-5.0 mum.