Radiation hardness of polycrystalline ceramic scintillators for radioisotope batteries

The usefulness of GYGAG(Ce) transparent polycrystalline ceramic garnet scintillators as the conversion medium in alpha and beta-fueled radioisotope batteries was explored through 0.5 to 3.5 MeV helium ion, alpha, and 0.5-2 MeV electron irradiations. Absorption spectra and light yields were measured before and after irradiations. Within experimental error no degradation in light yield was observed for the electron-irradiated samples as measured via beta or gamma excitation. A small increase in optical absorption near the emission wavelength was observed following the largest dose electron irradiation. Significant reduction in light yield was observed following helium ion irradiation. Partial recovery of the light yield was observed following annealing in oxygen above 400 degrees C for helium ion irradiated samples. These results suggest that GYGAG(Ce) may prove useful for beta-fueled scintillation-based radioisotope batteries by allowing for higher energy beta emitters, increased power densities, and long service lifetimes.