Comparison between high-energy proton and charged pion induced damage in Lead Tungstate calorimeter crystals

TL;DR

This study compares damage caused by high-energy protons and pions in Lead Tungstate crystals used in calorimeters, revealing damage proportionality to star densities and tracking recovery over two years.

Contribution

It provides a direct comparison of proton and pion induced damage in Lead Tungstate crystals, highlighting the proportionality to star densities and long-term recovery behavior.

Findings

Damage correlates with star densities from irradiation.

Proton and pion damage levels are comparable when normalized.

Crystals recover over a two-year period in dark storage.

Abstract

A Lead Tungstate crystal produced for the electromagnetic calorimeter of the CMS experiment at the LHC was cut into three equal-length sections. The central one was irradiated with 290 MeV/c positive pions up to a fluence of (5.67 +- 0.46)x10^13 /cm^2, while the other two were exposed to a 24 GeV/c proton fluence of (1.17 +- 0.11) x 10^13/ cm^2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed over two years. The comparison of the radiation-induced changes in light transmission for these crystals shows that damage is proportional to the star densities produced by the irradiation.