Response of Radiophotoluminescence Dosemeters Irradiated at Cryogenic Temperatures

Abstract

For decades, radiophotoluminescence dosemeters (RPL) have been used at CERN for high level dosimetry around the high energy particle accelerators, up to doses of the order of a megagray (MGy). With the use of radiation sensitive items (polymer insulations, quench-protection diodes) in the cryostats of the future Large Hadron Collider (LHC), radiation tests and dosimetry calibrations have to be made at cryogenic temperatures. The standard radiophotoluminescence (RPL) and polymer alanine dosemeters (PAD) in use at CERN have been irradiated with 60 Co sources at 77 K up to doses of 300 kGy and at 4.6 K up to 5 kGy. The present report gives the results of the RPL dosemeter response measured at room temperature after cryogenic irradiations compared to their response after irradiation at room temperature. They show that, below 10 kGy, the RPL signal is unaffected by the irradiation temperature. Above that dose, the self-absorption of the luminescent signal is less important at low temperatures, leading to a flattening of the calibration curve and making the dosemeters unusable for cryogenic applications