Evaluation of power loads on MITICA beamline components due to direct beam interception and electron backscattering

The MITICA (Megavolt ITER Injector Concept Advancement) experiment is the full scale prototype of the Heating and Current Drive Neutral Beam Injectors for ITER, planned to be built at Consorzio RFX. The injector is designed to accelerate and neutralize high density beams of H- or D- up to 1 MeV. During the acceleration stage the beam is expected to interact with the residual background gas and with the material surfaces of the electrodes, resulting in the production of secondary particles, mainly electrons, which are accelerated together with the primary beam. These particles, having a large divergence, tend to impact on the MITICA components located after the accelerator, causing significant heat loads. Moreover, as there is a high probability of backscattering some particles can also reach components which are not in the direct line of sight of the accelerator, making the evaluation of the distribution of heat loads on the various components not straightforward. This paper discusses the main sources of power loads to the MITICA beamline components downstream of the accelerator, and the implementation of a 3D code tracking the particles in order to evaluate the associated power deposition.