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 potentially significant issue for the International Thermonuclear Experimental Reactor (ITER). The effects of variations of the ratios D_He/χ_i, D_He/D_D and v_He/D_He and of the sawtooth period on helium exhaust in ITER have been studied with BALDUR code transport simulations. Recent measurements of D_He/χ_i in TFTR, of D_He/D_D in TEXTOR and of v_He/D_He 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 v_He/D_He, 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.