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Systematic Study of LED Stimulated Recovery of Radiation Damage in Optical Materials

The radiation damage in optical materials mostly manifests itself as the loss of optical transmittance. The optical materials recover from radiation damage to some extent when the radiation exposure is stopped. The recovery is at a faster rate in the presence of stimulating light. On the other hand, a systematic study of the dynamics of the recovery as a function of the stimulating light parameters such as its wavelength, intensity and exposure duration and method has not been performed in detail yet. We established an LED recovery station which provides pulsed and continuous light at various wavelengths at custom geometries. We irradiated soda lime glass samples at a rate of 87.5 Gy/min to a total dose of 3.5 kGy and 7.0 kGy. The optical transmittance of the samples were then measured in 200 nm - 1500 nm range for an extended period of time. The recovery from radiation damage is improved, both in terms of timing and quantity, as the wavelength of the stimulating light decreases. Around 50 % improvement was measured both in recovery rate and the permanent damage when UV LED with a wavelength of 396 nm was used for stimulation. The trend is such that wavelengths deeper in the UV range would result in faster and more effective recovery from radiation damage. The LED stimulated recovery technique from radiation damage is a feasible implementation for the optical active media of radiation and particle detectors which operate in high radiation environments.