Shock-tube study of fusion plasma-wall interactions

Theoretical and experimental studies have been made of phenomena which occur when a hot (T1 approximately equal to 6 x 1060K), dense (n approximately equal to 1016 cm-3), deuterium plasma containing a transverse magnetic field is brought into sudden contact with a cold metal wall. These studies are motivated by the need to understand plasma and metallurgical conditions at the first-wall of a fusion reactor. Experiments were carried out in the Columbia high energy electromagnetic shock tube. Computational simulation was used to investigate the detailed physics of the fusion plasma boundary layer which develops at the wall. The rate of energy transfer from the plasma to the wall was calculated and conditions under which surface melting occurs are estimated. Experimental measurements of plasma-wall heat transfer rates up to 3 x 105 watts/cm2 were obtained and agreement with computed values are good. Fusion reactor first-wall materials have been exposed to 6.0 x 1021 eV cm-2 (1,000 shots) of deuterium plasma bombardment. Scanning electron micrograph photographs show preferential erosion at grain boundaries, formation of deuterium surface blisters, and evidence of local surface melting. Some cracking is observed along grain boundaries, and a decrease in tensile ductiity is measured