Abstract
Measurements are presented of the reduction of signal output due to radiation damage for two types of plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb−1. The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: a laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions. Results from several irradiation campaigns using 60Co sources are also discussed. The damage is presented as a function of dose rate. Within the range of these measurements, for a fixed dose the damage increases with decreasing dose rate.
Highlights
√ Radiation damage due to particles produced in pp collisions at s = 13 TeV in two types of plastic scintillator tiles in the CMS hadron endcap calorimeter has been studied using data from several sources: a laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions
Within the range of our measurements, the results from the various methods indicate that at a fixed dose the damage to the scintillators increases with decreasing dose rate
The dose-rate dependence is most accurately measured by the laser system, with larger uncertainties in the other measurements
Summary
For the purpose of our studies, we refer to the HCAL tiles as objects consisting of plastic scintillator, a WLS fiber, a TyvekTM wrapping, a clear fiber, and a transducer. The absorption maximum of the secondary fluor corresponds to the emission maximum of the primary fluor, and the de-excitation of the secondary fluor has a wavelength of maximum emission of approximately 440 nm (blue light) This visible light must traverse the scintillator to reach the WLS fiber, and can be reduced by imperfections in the material (color centers) along its path. [17], the authors saw no change in the signal output or attenuation length for SCSN−81 down to dose rates of 2 Gy/h, whereas the authors of refs. Damage to the substrate often results in the creation of radicals, conjugated double bonds, carbonyl species formed by reaction with oxygen, and trapped electrons, and other structures that can be color centers. Color centers that absorb the light output by the secondary fluor reduce the absorption length of the light in the scintillator.
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