Efficient and rigorous evaluation of fast particle losses in non-axisymmetric tokamak plasmas

Abstract

We present an analysis scheme called loss-map analysis that quantitatively connects the fast ion transport in 3D magnetic field to the underlying transport mechanisms. The loss-map analysis is generally applicable, but here its use is demonstrated by applying it to study alpha particle losses in the ITER baseline scenario and ICRH losses in the reduced-field scenarios. This demonstration addresses the issues raised by the earlier ITER fast ion confinement studies. The focus is in the analysis scheme itself which aids in interpreting and confirming the results of orbit-following simulations by providing a way to connect observed losses to known fast ion transport processes. The loss maps can also be used to estimate fast ion losses directly from the magnetic field structure, thus providing a fast alternative to orbit-following simulations. Furthermore, the loss maps connect the particle birth position in the phase space to the wall region where it is lost. This can be used to optimize marker initialization in simulations that estimate peak power loads or FILD signals, thus reducing the required computational time which otherwise might be prohibitive.