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 98 y 2 ∼ 1.7, β N ∼ 2.7, f BS ∼ 0.92 and n e / n GW ∼ 0.87 are simultaneously achieved under the reactor relevant conditions of low momentum input and electron temperature nearly equal to ion temperature.
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Sakamoto et al. (2009) studied this question.