Development of a telescope detector for Sr-90 detection

Abstract

Nuclear catastrophes and accidents release harmful fission products containing long-lived (Se-79, Zr-93, Tc-99, Pd-107, Sn-126, I-129, and Cs-135) radioisotopes having half-life of hundreds of thousands or millions of years and short-lived (Kr-85, Sr-90, Ru-106, Cs-134, Cs-137, Pm-147, Sm-151, and Eu-155). After a few years, Cs-137 and Sr-90 radioisotopes with a half-life of around 30 years dominate. These dominating radioisotopes are potentially harmful for living creatures. They affect DNA, brain tissues, and even stick with bones. To study the possible radiation damages, one needs to prepare a sample which is an expensive, tedious, and long-awaited process.

A telescope detector system was proposed to solve this sample preparation problem. This thesis aims to develop and test a prototype DeltaE - E type telescope detector system for beta particles. The detector system is based on the beta energy gating period to distinguish Y-90 decay from Sr-90 decay. The detector identifies beta particles via DeltaE - E coincidences. The high energy of Y-90 beta particles are used to distinguish this decay from other radiations.

The detector system consists of Eljen technology pre-cut plastic scintillator of types EJ-200 and EJ-212. Two prototypes containing (85 mm x 1 mm + 75 mm x 10 mm) and (35 mm x 1 mm + 25 mm x 10 mm) were developed, out of which the smaller one gave better light collection efficiency. For light collection purposes, two silicon photomultipliers were used for each detector system. The performance of the silicon photomultiplier was also critically analyzed by checking the performance parameters. SiPM is a new device used in spectroscopy and will be used more and more in the future.