Assessment of current drive efficiency and the synergetic effect for ECCD and LHCD and the possibility of long pulse operation in ITER

Steady state operation is preferable for fusion reactors. The possibility of extending the pulse length in ITER is considered taking into account the capabilities of the planned electron-cyclotron current drive (ECCD) and low-hybrid current drive (LHCD). The ECCD efficiency for current drive at different locations is assessed. The possibility of extending the pulse length by the increase in the current drive efficiency due to the synergetic effect for combined ECCD and LHCD at the same location is assessed. The calculated synergetic effect of ECCD and LHCD on the current drive efficiency is less than 10% for ITER parameters. Long pulse operation with the energy multiplication factor Pfus/Paux = Q > 5 and duration t > 3000 s will be possible in the case of enhanced confinement with respect to the ELMy H-mode scaling HH98y,2 ∼ 1.3–1.4.