Insensitivity of Rb3C60 to γ irradiation

The effects of 60Co γ irradiation on a granular sample of Rb3C60 have been examined, using magnetically modulated microwave absorption to measure the superconducting Rb3C60 component. The microwave responses indicate the sample consists of superconducting grains connected by intergranular weak links. No decrease in superconductivity was found up to doses of 5.1 Mrad.