Surface breakdown of gamma-ray irradiated polybutylene polymers under magnetic field

Polymer materials are usually used as insulation in nuclear systems and space-based electrical systems. For the use of materials in such regions, it must be confirmed whether the electrical performance was affected by radiation and magnetic field. This paper investigates surface breakdown of irradiated polybutylene polymers under magnetic field. The samples were irradiated in air up to 100 kGy and then up to 1000 kGy with dose rate of 10 kGy/h by using a ⁶⁰Co gamma source. The magnetic flux density (MFD) was 249 mT. The magnetic field was perpendicular to the electric field, which made the relative angle between the sample surface and the directions of E times B was 0, 90 and 180 degree. The effects of total dose of gamma-ray irradiation and the relative angle on the time to surface breakdown were discussed. Obtained results indicated that with the increase of the total dose of irradiation, the time to surface breakdown increased with PBN, but decreased with PBT. Under magnetic field, the time to surface breakdown of both PBN and PBT were delayed when the relative angles were 0 and 90 degree, but were shortened when the relative angle was 180 degree.