Development of reversed shear plasmas with high bootstrap current fraction towards reactor relevant regime in JT-60U

摘要

This paper reports the recent development of reversed shear plasmas with a high bootstrap current fraction (f_(BS)) towards the reactor relevant regime. The previous operation regime of high f_(bs) plasmas is limited at q_(95) > 8 because of the low beta limit, whereas q_(95) = 5-6 is envisaged in the DEMO reactor. In the 2008 JT-60U experimental campaign, the high f_(BS) plasma was emphasized in the lower q_(95) regime by developing the large volume configuration close to the conducting wall for wall stabilization. Thanks to the wall stabilization, high f_(BS) plasmas exceeding the no-wall beta limit are obtained at reactor relevant q_(95) ～ 5.3. Though the high f_(BS) plasmas are terminated by destabilization of the resistive wall mode, a highly integrated performance is obtained. High values of HH_(98y2) ～ 1.7, β_n ～ 2.7, f_(BS) ～ 0.92 and n_e_(GW) ～ 0.87 are simultaneously achieved under the reactor relevant conditions of low momentum input and electron temperature nearly equal to ion temperature.