DC electrical characteristics of polyimide at cryogenic temperature in vacuum

作者：Tu Youping^*; Tan Rong; Zhang Guifeng; Wang Cong; Zhang Hao

来源：Proceedings of the CSEE, 2013, 33(4): 194-200.

• Breakdown characteristics
• Breakdown field
• Cryogenic temperatures
• DC electrical
• Design and operations
• Discharge characteristics
• Electrical characteristic
• Field strengths
• In-vacuum
• Insulating properties
• Insulation structures
• Insulation system
• Liquid helium
• Polyimide film
• Room temperature
• Surface flashover
• Temperature rising
• Test systems

The insulation system of large superconducting magnets and other superconducting devices is an indispensable part, the invalidation of insulation structure which is working at the temperature of liquid helium or liquid nitrogen is the main reason of the failure of large-scale superconducting equipment. By using the home-made test system which is developed for testing cryogenic electrical characteristics of dielectrics, a series of tests for studying polyimide films' DC breakdown and surface flashover characteristics have been done at cryogenic temperature in vacuum. The test results show that the breakdown field strength of polyimide at cryogenic temperature has increased compared with at room temperature and the temperature, thickness and structure of polyimide all have some influence on the breakdown characteristics. And the surface flashover field strength of polyimide increase slightly with the flashover times and then trend to be a stable value. The temperature has almost no influence on the first-time flashover field strength of PI, but has definitive influence on the stable value of PI's flashover field strength. In the range of 78~200K, the value maintained unchanged while in the range of 225~250 K, the value dropped a little and then increased with temperature rising. The relevant data of insulating properties at cryogenic temperature and vacuum based on the research not only can be used for the exploration of the discharge characteristics at cryogenic temperature and vacuum, but also provide a reference for a reliable design and operation of large superconducting equipment.

• 出版日期2013
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