Electrical and structural R&D activities on high voltage DC solid insulators in vacuum

This paper describes the R&D work performed in support of the design of the ceramic (alumina) insulators for the MITICA Neutral Beam Injector. The ceramic insulators are a key part of the 1 MV electrostatic accelerator of the MITICA injector, as they are required to withstand both the mechanical loads due to the weight of the ion source and the high electric field between the accelerator grids. For this reason, the insulators are a critical element both from the structural and electrical point of view. Numerical Finite Element models have been adopted to study both the electrostatic and the structural problems respectively to calculate the electrostatic field and the distribution of the stress tensor. The numerical models have been benchmarked by experimental tests on samples and insulator prototypes, the experimental campaigns have concerned withstanding voltage tests and destructive structural tests on ceramic samples. The final insulator design has been optimized considering the different requirements coming from structural aspects and voltage withstand issues.