Transport simulations of helium exhaust in ITER using recent data from TFTR, TEXTOR and JT-60

Insufficient helium exhaust can seriously degrade the performance of any fusion reactor and has recently been identified as a potential significant issue for the International Thermonuclear Experimental Reactor (ITER). The effects of variations of the ratios DHe/χi, DHe/DD and vHe/DHe and of the sawtooth period on helium exhaust in ITER have been studied with BALDUR code transport simulations. Recent measurements of DHe/χi in TFTR, of DHe/DD in TEXTOR and of vHe/DHe in TFTR, TEXTOR and JT-60 are found to be compatible with the requirements of sustained ignition and helium exhaust for ITER. Ignition is found to be critically sensitive to the ratio vHe/DHe, particularly at the plasma edge, and to a reduced sawtooth period. These critical dependences are moderated for reduced helium recycling at the separatrix and for hollow particle diffusivity profiles. (author). 26 refs, 9 figs, 1 tab