Evaluation of cooling concepts and specimen geometries for high heat flux tests on neutron irradiated divertor elements

To assess the lifetime and the long term heat removal capabilities of plasma facing components in future thermonuclear fusion reactors, neutron irradiation and subsequent high heat flux (HHF) tests will be of great importance. The effect of neutron damage will be simulated in material test reactors. To investigate the behaviour of components subjected to heat loads during normal and off-normal conditions, a 60kW electron beam teststand (Juelich Divertor Test Facility in Hot Cells (JUDITH)) has been installed in a hot cell which can be operated by remote handling techniques. In this facility inertially cooled test coupons can be handled as well as small actively cooled mock-ups.The irradiation of complete divertor modules however requires greater efforts. To investigate specific problems such as neutron induced changes in the performance of the braze interface, small test coupons without active cooling capabilities may be suitable. ITER relevant temperature gradients and resulting stress fields can be established during transient heating by electron beam methods. The only reasonable alternatives to this procedure are actively cooled test specimens or small divertor modules. A special clamping mechanism for test samples with an integrated coolant channel has been developed and tested. This experimental procedure is an attractive and cost effective alternative comparing large scale tests on complete divertor modules. (orig.)