High heat flux tests on beryllium and beryllium-copper joints

A large test program has been set up to evaluate the performance of beryllium as a plasma facing material for the divertor in thermonuclear fusion devices. Simulation of steady state heat loads of 5 MW m−2 and above on actively cooled divertor modules, and off-normal plasma conditions with energy densities in the range 1–7 MJ m−2, have been investigated. Thermal shock tests were carried out with the ITER reference grade S65-C and several Russian grades of beryllium. At incident energies up to 7 MJ m−2 the best erosion behaviour is observed for S65-C and for TGP-56. Steady state heating tests with actively cooled Be/Cu mock-ups were performed at incident powers of up to 5.8 MW m−2. All samples investigated in these tests did not show any indications of failure. A Be/Cu mock-ups with Incusil braze was loaded in thermal fatigue up to 500 cycles at an incident power of 4.8 MW m−2. Up to the end of the experiment no temperature increase of the surface and no indication of failure was observed.