Monte Carlo simulations of the heat load asymmetries on JET divertor plates

JET divertor load measurements using embedded thermocouples have indicated a large inner/outer target load asymmetry and a significant non-uniformity in the load to the outer target. Furthermore, under H-mode conditions, the load appears to be dominated by the ion component. While the inner/outer target load asymmetry can be understood in terms of the conventional fluid picture, the sharp structures in the deposition profile as well as the ion dominance of the load cannot be readily explained by the fluid approach. The guiding-centre orbit-following Monte Carlo code ASCOT is used to simulate the ion contribution to the target deposition profiles, and this is the first time a narrow structure in the divertor loads has been reproduced in simulations. The importance of the plasma edge collisionality, the atomic, molecular and ionic collisions in the scrape-off layer, and the radial electric field both inside and outside the separatrix are all studied individually in detail.