On Collapses In Strong Reversed Shear Plasmas During Or Just After Plasma Current Ramp-Up In Jt-60u

The advanced tokamak (AT) scenario with the strong reversed magnetic shear is an attractive candidate of the steady state tokamak because the strong internal transport barrier leads to the high bootstrap current fraction, resulting in the reduction of the cost of the fusion reactor. In this paper, the causes of the collapses during or just after plasma current ramp-up of the experimental campaign of the AT scenario [Y. Sakamoto et al., Nucl. Fusion 49, 095017 (2009)] in 2007 and 2008 are investigated and the initial results are reported. As the observations are consistent with characteristics of the stability on the resistive wall mode (RWM) and the results of MARG2D code, the RWM is suggested as the candidate of the cause of the collapses in the analyzed AT scenario. (C) 2021 The Japan Society of Plasma Science and Nuclear Fusion Research