Radioactive emission from high-index, optical glasses and atypical effects on CCDs

摘要

Large-amplitude anomalous events have been observed in CCDs due to radioactive emission from high-index optical glasses, some producing charge-trapping like artefacts. We have identified the source of these events from one glass (Ohara S-YGH51) as α-particles from trace amounts of nuclides in the actinium decay series, parent ~(235)U. We present measurements of the anomalous event rate for samples of 15 separate optical glasses with n_d ≥ 1.6. There is a variation in anomalous count rates of orders of magnitude range over these materials. Care should be taken in the selection of optical glasses to be located in close proximity to detectors.