An SF6 gas-insulated -500 kV DC conical insulator vacuum feedthrough

Area of Science:

• Physics
• Electrical Engineering
• Materials Science

Background:

• Spin-polarized electron sources require extreme high vacuum conditions.
• Conventional photogun designs use solid dielectric interfaces for high-voltage terminations, limiting operational voltage.
• Reducing vacuum chamber volume is crucial for efficient photogun operation.

Purpose of the Study:

• To develop and test a novel SF6 gas-insulated conical alumina insulator feedthrough for high-voltage DC biasing.
• To enable the operation of spin-polarized electron sources by meeting extreme high vacuum requirements.
• To extend the demonstrated operating voltage of solid feedthroughs using commercial hardware.

Main Methods:

• A novel SF6 gas-insulated conical alumina insulator feedthrough was designed and implemented.
• A test electrode was biased to -500 kV direct current (DC) using the feedthrough.
• The feedthrough design utilizes a pressurized SF6 volume between a conical alumina insulator and a commercial epoxy high-voltage cable receptacle.
• Testing was conducted within a chamber filled with SF6 at 170.3 kPa and later under vacuum.

Main Results:

• A maximum voltage of -500 kV DC was successfully applied to the test electrode.
• The system operated under SF6 gas pressure (170.3 kPa) and later under vacuum (-259 kV, limited by field emission).
• The novel design reduced photogun vacuum chamber volume compared to coaxial cylindrical insulators.
• Commercial high-voltage cable hardware was successfully integrated.

Conclusions:

• A custom-designed SF6 gas-insulated vacuum feedthrough combined with a commercial high-voltage cable can achieve -500 kV DC biasing for photogun electrodes.
• The design effectively reduces vacuum chamber volume, facilitating extreme high vacuum conditions.
• This approach extends the operational voltage capabilities of feedthroughs for advanced electron source applications.