Quality Assurance on Un-Doped CsI Crystals for the Mu2e Experiment

TL;DR

This paper reports on the quality assurance of undoped CsI crystals used in the Mu2e experiment's calorimeter, focusing on their scintillation properties and radiation hardness to ensure they meet physics requirements.

Contribution

It provides detailed quality assurance data for undoped CsI crystals from multiple suppliers, demonstrating their suitability for high-energy physics experiments.

Findings

CsI crystals have a fast decay time of 30 ns.

Light output exceeds 100 p.e./MeV.

Crystals show adequate radiation hardness.

Abstract

The Mu2e experiment is constructing a calorimeter consisting of 1,348 undoped CsI crystals in two disks. Each crystal has a dimension of 34 x 34 x 200 mm, and is readout by a large area silicon PMT array. A series of technical specifications was defined according to physics requirements. Preproduction CsI crystals were procured from three firms: Amcrys, Saint-Gobain and Shanghai Institute of Ceramics. We report the quality assurance on crystal's scintillation properties and their radiation hardness against ionization dose and neutrons. With a fast decay time of 30 ns and a light output of more than 100 p.e./MeV measured with a bi-alkali PMT, undoped CsI crystals provide a cost-effective solution for the Mu2e experiment.