Gyrokinetic modelling of baseline H-mode JET plasmas with C Wall and ITER-like wall

摘要

Introduction A deterioration in global confinement is observed at JET in baseline H-mode experiments following the change from a carbon wall (CW) to an ITER-like wall (ILW) with beryllium and tungsten [1]. One cause is the high deuterium gas puffing rate necessary in ILW discharges in order to mitigate W accumulation. For low triangularity plasmas, this degradation of confinement with fuelling level was also observed for CW discharges [2]. The deterioration is correlated by a degradation of pedestal confinement with lower electron temperatures at the top of the edge barrier region. This leads to a lower electron temperature in the core, thereby changing the NBI heat deposition profiles in the core. As a result, the core energy confinement time is influenced with lower electron energy confinement time and similar ion confinement time in the ILW case [1]. To study the effect of the ILW on confinement, a database has been created comprising a set of JET discharges with ILW and matched CW discharges using the same criteria as in [3]. In the present work, transport due to Ion Temperature Gradient (ITG)/Trapped Electron Mode (TEM) turbulence is calculated for similar CW and ILW discharges using the gyrokinetic code GENE [4], in order to assess the differences seen in core energy confinement.