Thermo-oxidation and analysis of JET codeposits

Following the thermo-oxidation study of D removal from JET divertor codeposits, post oxidation surface analyses were performed using SIMS, NRA and profilometry. The analysis confirms that the D content was reduced by at least an order of magnitude after 8-h oxidation at 623 K (350 °C) and 21 kPa (160 Torr) O₂ pressure – in agreement with TDS measurements. The codeposits studied contain Be and C. Those on the vertical tile surfaces have a duplex structure with a C-D rich layer on the surface and a Be–C layer underneath; during oxidation the outer layer is removed and the inner layer remains. Codeposits with low Be content from the shadowed area have single-layer structures; during oxidation their thicknesses were reduced by about an order of magnitude. For the JET codeposits studied (with Be/C up to ∼1) it appears that Be does not affect the oxidative removal of deuterium from the codeposit in a significant way.