Deuterium Recycling Rate Constants Derived from Plasma Implantation/Desorption Shots in a Martensitic Steel Surface

Abstract

The recombination (K 2 ) and dissociation rate constants (K 1 ) are essential magnitudes for the tracking of tritium at the First Wall (FW) of Fusion Reactors (FR). This paper presents our plasma implantation/recycling test, the modelling of the experiment and the results obtained for K 2 and K 1 in the case of a deuterium (D þ 3 /D þ 2 ) plasma in the martensitic steel DIN 1.4914 (MANET). Once parasitic contributions were accounted, the D 2 release from the target was seen to be surface limited. The values obtained for K 1 and K 2 show low dispersion on impinging flux and ion energies. For K 1 a roughly constant value of 7 Â 10 --6 mol Pa --1 m --2 s --1 is derived. The obtained K 2 is written as: K 2 = 2.414 exp (--1571/RT) (m 4 mol --1 s --1 ), with R = 8.314 J mol --1 K --1 . Our activation energies agree with those existing in the literature derived from permeation experiments. High reflection coefficients are derived, which are in good agreement with the classical theory of ion scattering at low energy.