Development of Radiation-Resistant Warm Magnets Using Cyanate Ester Resin

We have been developing radiation-resistant warm magnets insulated by cyanate ester (CE) resins. A glass fiber cloth prepreg tape was fabricated using CE pre-polymers supplied by Mitsubishi Gas Chemical Company Inc. Proton beam irradiation tests were carried out for evaluation of the radiation hardness. We prepared cured resin samples of cyanate ester, bismaleimide triazine (BT), and epoxy resins using the same glass fiber cloth. The resin samples were irradiated by a 70-MeV proton beam at doses up to 10(9) Gy at the Cyclotron and Radioisotope Center, Tohoku University. The results of tensile tests after irradiation showed that the radiation resistance of the CE resins was almost same as that of BT resins and more than 10 times as high as that of epoxy resins. We also developed a CE putty for use in coil moldings. A curing test was performed on a coil mock-up made of a stack of hollow conductors wrapped with the CE prepreg tapes and putty. We successfully cured the coil mock-up without causing thermal runaway.