Modelling of the Effect of the ITER-like Wall on NBI Heating in JET
Following the installation of the ITER-like wall (ILW) at JET, carbon has been replaced by beryllium and tungsten as the main core plasma impurity. Simultaneously, the neutral beams have been upgraded to achieve higher heating power. Understanding if and how the deposition of heating power from the neutral beams has changed with these upgrades will have an impact on the coming JET campaigns and on ITER operation. In this work we report numerical simulations which study the effect of the upgraded JET NBI and tungsten impurity content on beam deposition.We compare the deposition from the old and the upgraded beam configurations in plasmas with the C-wall and the ILW. Furthermore, we investigate the effect of an asymmetrically distributed tungsten impurity on beam stopping. We use the orbit-following code ASCOT, coupled to the JETTO transport code, to calculate the beam deposition including the slowing-down and pitch and scattering of the beam ions. To take into account the effect of tungsten, ASCOT has been updated to use the ADAS database to obtain effective beam stopping coefficients. The results of ASCOT are compared with the PENCIL code, in order to determine the significance of fast ion orbit effects.