ELM physics and ELM mitigation in ITER

Edge Localised Modes are characteristic of the high performance, H-mode plasmas that are required for the attainment of Q = 10/500MW fusion power in the first phase of ITER operation. The energy released by a type I ELM, in good confinement plasmas, is typically 510% of the plasma stored energy; with low collisionality plasmas at the upper end of the range. Dimensional analysis, experiment and modeling all show that the thermal load limit of, where evaporation or sublimation of the divertor surface occurs, is likely to be exceeded by at least an order of magnitude by ELMS in ITER. The consequence this will be unacceptably rapid erosion of the divertor target, core plasma pollution and, possibly, increased disruption frequency. Thus it is required that ELMs be eliminated or mitigated in ITER. This paper details the background to this requirement, the physical basis for the available mitigation methods and the technical measures that have been undertaken, so far, to implement them on ITER.