Burn control simulation experiments in JT-60U

Burn control simulation experiments were conducted in non-burning DD plasmas by using a burning plasma simulation scheme in JT-60U. In the burning plasma simulation scheme, two neutral beam (NB) groups were used, where one simulates α-particle heating and the other simulates external heating. The stored energy and the neutron yield rate were controlled at nearly constant values in both ELMy H-mode plasma and reversed shear (RS) plasma with an Internal Transport Barrier. In these plasmas, the NB power for the external heating simulation increased/decreased when the NB power for the α-particle heating simulation decreased/increased. Variation of the NB power for the external heating simulation was larger in the RS plasma than that in the ELMy H-mode plasma, indicating that larger control margin is necessary for the RS plasmas. In order to understand the detailed physical mechanism for the difference between ELMy H-mode and RS plasmas, we conducted numerical analysis using a 1.5-dimensional transport code. This calculation indicates the larger variation experimentally observed in the RS plasma could not be explained by the difference of the thermal diffusivity profiles or its temperature dependence.