SIMULTANEOUS MEASUREMENTS OF THE REFLECTION, REEMISSION AND PERMEATION OF PARTICLES DURING LOW-ENERGY DEUTERIUM BOMBARDMENT OF NIOBIUM

Quantitative data on the interaction of low energy hydrogen atoms with solids are of great importance in prediction of hydrogen recycling an d retention in fusion devices. For the low energy region only few expe rimental data are known on the particle reflection coefficient R(N) an d often reflected particles are not taken into account in discussing p ermeation experiments. In the present work, the permeation behavior of deuterium has been investigated for deuterium implanted into Nb membr ane with an incident ion energy 100-1500 eV. R(N) has been determined by means of the thermal desorption technique. The fluxes of reflected particles, reemission and permeation were monitored simultaneously by QMS. A mass balance of the above mentioned channels of deuterium relea se was confirmed at steady state in each bombardment, thus a high accu racy was achieved in evaluation of the R(N), The dependence of the mea sured values on surface contaminations has been investigated by means of AES and SIMS analyses of the upstream-side surface, The experimenta lly obtained particle reflection coefficient is in good agreement with the result of a binary collision computer simulation.