High-voltage breakdown in the injection-extraction region of the CANREB EBIS: A possible mechanism

• Published in: Journal of physics. Conference series 2022-04, Vol.2244 (1), p.12073
• Main Authors: Charles, Chris R.J., Cavenaile, Mathieu, Harford, Paige, Ames, Friedhelm, Schultz, Brad, Kester, Oliver
• Format: Article
• Language: English
• Subjects: Breakdown; Drift tubes; Electric field strength; Electrons; High voltages; Insulation; Magnetic mirrors; Magnetic shielding; Physics; Room temperature; Wiring
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2244/1/012073

OmniTrak simulations were performed in the 40°K injection-extraction region near the collector trumpet of the CANREB EBIS to understand the nature of chronic electrical breakdowns of PEEK feedthroughs. These feedthroughs are designed to route high-voltage wires (up to +15 kV) from room temperature to each drift-tube at 4°K, while operating in the strong superconducting semi-Helmholtz field. The electric field strength |E| at the PEEK feedthroughs are ∼ 7 × 10 5 V/m within about 2-3 mm of the surroundings at ground potential. When simulating only bare wires (with no PEEK feedthroughs), |E| increases by about 1 order-of-magnitude to > 10 6 V/m in the same region. Assuming a 3 Tesla magnetic field, electrons starting with 0 eV near the PEEK feedthroughs undergo helical motions due to E → × B → -drift and demonstrate reflections from magnetic mirror effects. A combination of this helical motion, reflecting mirror trajectories, and attraction of electrons to exposed HV wires may be responsible for the ongoing HV breakdown of insulating feedthroughs in this region of the EBIS. Solving this problem requires complete ground-shielding of all HV wiring to eliminate |E| and should encapsulate all wires to prevent breakdown paths.