A multi-beamlet analysis of the MITICA accelerator

The thermo-mechanical analysis and themechanical design of the accelerator of MITICA (i.e. the full size prototype of the ITER neutral beam injector under construction at RFX [1]) are based on the calculation of the power deposition induced by particle impacts. This calculation is performed by EAMCC [2], a relativistic particle tracking code based on the Monte-Carlomethod for describing collisions inside the accelerator, under prescribed electric andmagnetic fields. Themagnetic fieldmaps are produced by 3D codes, while the electric fieldmaps come from the 2D axi-symmetric code SLACCAD [3]. In order to perform amulti-beamlet analysis, which allows to take into account the beamlet-beamlet repulsion, and to consider other effects neglected under the hypothesis of axi-symmetric beam, a fully 3D version of the code is required. In this paper, amodified version of EAMCC, fully 3D, capable ofmodifying themesh of the 3Dmaps and of dealing with unevenmeshes is presented. A finermesh is used just in the regions where amore detailed description of the fields is required, for amore realistic simulation. A comparison between the original code and themodified version is presented at first, as a validation of themodifications introduced in the latter. Subsequently, themain results of a single-beamlet analysis performed with the two versions of the code are shown and the differences between the 2D and the 3D simulations discussed. The last part is dedicated to themulti-beamlet simulation of the accelerator.