Thermal effects of divertor sweeping in ITER

Abstract

Thermal effects of magnetically sweeping the separatrix strike point on the outer divertor target of the ITER are calculated. For the 0.2 Hz*+or-12 cm sweep scenario proposed for ITER operations, the thermal capability of a generic target design is found to be slightly inadequate (by approximately 5%) to accommodate the full degree of plasma scrape-off peaking postulated as a design basis. The principal problem identified is that the 5-s sweep period is long relative to the 1.4-s thermal time constant of the divertor target. An increase of the sweep frequency to approximately 1 Hz is suggested; this increase would provide a power handling margin of approximately 25% relative to present operational criteria.<>