Effects of plasma-wall self-organization on density limit and ignition condition of a burning tokamak plasma*

The impurity radiation in a tokamak affects the amount of heat flux reaching the wall target plates, determining the plasma conditions in the target region and the subsequent impurity production and radiation inside plasma. Such a plasma-wall self-organization (PWSO) has been proposed as a potential machanism for the tokamak density limit [D.F. Escande NF 2022]. In this work, the PWSO model has been extended to evaluate the effects of PWSO on the density limit and the ignition condition of a burning tokamak plasma. Based on a 1D transport model including the PWSO, the α-particle heating is found to enhance the tokamak density limit. On the other hand, the results reveal that the inclusion of the PWSO leads to an increased value of the fusion triple product required for ignition, which can be attributed to the power deposition on the wall target plates that is excluded from the transport energy loss. The impurity fraction near density limit and ignition condition can be self-consistently determined based on the power deposition on the wall target plates and the sputtering properties of the target material in our calculation.