Power deposition measurements in deuterium and helium discharges in JET MKIIGB divertor by IR-thermography

One of the outstanding problems for a next step fusion device is the handling of the power fluxes into the divertor, in particular regarding fast transient heat deposition by edge localised modes (ELMs). For a next step fusion device, such as ITER, type-I ELMy H-Mode is the reference discharge and therefore of particular interest. At JET a thermography system with high time resolution is able to resolve temperature evolution during and between ELM periods; here, the analysis is focussed so far on type-I ELMy H-Mode discharges with ELM frequencies of 10–35 Hz. Influences from surface layers on the target tiles are investigated in special discharges and taken into account. Results about the distribution of ELM and inter-ELM power deposition on the inner and outer divertor target plates are presented. Additionally, the characteristic ELM power deposition time (or temperature rise time) and its dependence on pedestal parameters are studied. The thermal impact due to ELMs for ITER is calculated together with predictions for relative ELM midplane losses and heat flux evolution on the divertor target. The predicted values based on conservative assumptions exceed the material limits.