KSTAR experimental results toward solving burning plasma issues

摘要

Aim of the nuclear fusion research is to realize the fusion reactor for solving energy problem in the world and ITER would be the big milestone for proving the scientific and engineering feasibility of nuclear fusion at burning plasma state. Moreover, the study on the reactor requires operation of the machine to be simple as well as producing high efficient fusion reaction which is to be in cost effective. In this regards, KSTAR has been looking forward to demonstrating the high performance long pulse discharge using highly advanced physics concept and steady state compatible superconducting magnets.[1] By highly elaborating engineering effort to operation of the superconducting machine based on the design concept of AT physics, KSTAR has shown the very outstanding experimental results which would impact on the design of the future reactor. While demonstrating the pulse-length of more than 40 sec H-mode flat-top in 2014 characterizing uniqueness of superconducting machine and achieving high beta(b_N~4) above no-wall limit transiently by optimal Ip/B_T and with P_(ex)t ~ 3 MW, KSTAR has also been exploring various means to achieve and sustain steady-state, ELM-suppressed/mitigated H-modes using versatile in-vessel control coils (IVCC), ECCD/ECH, and/or SMBI. The 40s sustaining time corresponds to more than 20 times of current diffusion time that is sufficient time to provide the current profile control by changing hardware of ECH actuator mirror mechanically. KSTAR also showed that the level of the intrinsic error field of the machine is very low and it is suggested that KSTAR may not need any error field correction coil to realize ITER baseline scenario.