Modeling and analysis of breakdown EMI protection for MITICA insulation and embedded diagnostics

Highlights: ► A fast transient model of MITICA electrical system with all relevant conductors has been developed. ► MITICA insulations on Source and main Bushing are at high risk due to electrical breakdowns. ► The introduction of capacitances in some critical points is effective to reduce overvoltages. ► Signal cables must be screened at both ends to and follow the route of reference potential conductors. -- Abstract: On the Padova PRIMA facility the prototype of the ITER HNBs will be tested in the device called MITICA (Megavolt ITER Injector and Concept Advancement). During Beam operation breakdowns will occur across the accelerator grids and Source components causing transient high voltages between parts normally at low voltages, so stressing the electrical insulation of sensor cables, connectors and feedthroughs. The MITICA electrical model implemented to estimate the characteristics of the voltage transients is here described, with particular emphasis on the feedthroughs, on the source insulation and on the embedded diagnostic system. As severe stresses result with the present design mitigating measures are necessary to avoid damage and maintain proper operation. The solution proposed and supported by the analyses to introduce concentrated capacitances in some critical points turns out to be suitable in terms of electrical effects and of technical compatibility with the main requirements of MITICA environment