Hydrogen isotope retention and release from copper

The Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory is considering the use of tritium neutral beams during the deuterium-tritium phase of operation in 1990. A concern is the tritium inventory that will develop in neutral beam components such as the copper calorimeter. In this paper we report on measurements and calculations of hydrogen isotope retention and release for copper under ion bombardment. Retention of deuterium trapped in the near-surface region is measured as a function of temperature using the D(³He,p) a nuclear reaction technique with an 800-keV ³He⁺ analysis beam. The rate of molecular recombination (K_r) at the copper-vacuum interface is determined from plasma driven permeation studies in our Tritium Plasma Experiment facility, The measurements indicate that K_r = 6.7 ±0.1 X 10^-18 cm4/s over the temperature range 575-825 K, in agreement with theory. These data are used as inputs to the DIFFUSE computer code to provide a model for tritium-copper interactions. The mode! is tested against measured pressure rises during discharges in the TFTR neutral beam line, and is then used to predict tritium inventory in the copper ion beam dumps during future TFTR tritium operation.