Effect of Nuclear Radiation on Magnet Insulation in High-Energy Accellerators

Magnet coil insulation consists of inorganic materials such as glass fiber, fillers, and organic thermosetting resins. Most of the usual insulation systems are damaged if subjected to high radiation levels such as those anticipated at the Stanford Linear Accelerator, where the expected dose rate may be as high as 1011 rads per year. This paper describes tests carried out at SLAC in which several commercially available insulations were found to deteriorate severely at total absorbed doses of as low as 1010 rads. Changes in molecular structure induced by radiation effects and degradation of electrical and mechanical properties are discussed. The development and testing of an organic insulation using pure Al2O3 filler which retained about 25% of its original strength at an absorbed radiation level of 3.25×1014 ergs.gr-l will be described. This insulation required minor changes in the usual winding and potting technique prevalent in the industry.