Characteristic responses of a COTS CCD to α, β-, and neutron-induced triton radiations and strategies to reduce noise

Newton, Rosie and Joyce, Malcolm (2019) Characteristic responses of a COTS CCD to α, β-, and neutron-induced triton radiations and strategies to reduce noise. PhD thesis, Lancaster University.

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Abstract

The potential of commercially available CCDs to perform in-situ detection and spectroscopy of α radiation has been investigated. The CCDs used are Sony ICX825AL as part of an Ultrastar camera from Starlight Xpress, modified by BIC Technology Ltd.. The glass covering is removed and the CCD is covered with a thin, aluminised Mylar film to prevent light interacting with the device. Vertical streaks seen in images produced when exposed to a 210Po source provide a unique identifier for the presence of α radiation. The sizes of the clusters produced and intensities of the brightest pixel in each cluster have been used among other properties to distinguish between α and β- radiation, and noise caused by radiation damage in the CCD. It was found that the CCDs used are mostly insensitive to γ radiation. It is possible to detect neutrons using this device by covering the CCD with 6Li-enriched crystals and detecting the α particles and tritons produced by the interactions of neutrons with the 6Li. The properties of clusters produced by this method were also analysed and compared with the previous types of radiation. Distinguishing features were found for each type of radiation analysed. Simulations suggest that the cluster sizes will vary depending on the energy of the incoming radiation, but it was found that the cluster sizes from the two β- sources used could not be significantly separated, due to the small energy difference between them of 197 keV. Discrimination should still be possible for β- particles with a larger energy difference. Cluster sizes and streak lengths for α radiation should also vary depending on the energy of the incident α radiation. Annealing, cooling, and image processing techniques have been determined to mitigate the effects of radiation damage in these devices.