Sorting a large set of heavily used LiF:Mg,Ti thermoluminescent detectors into repeatable subsets of similar response

Kimberlee J Kearfott; Jill P Newton; Muhammad Rafique

doi:10.1016/j.apradiso.2014.10.019

Sorting a large set of heavily used LiF:Mg,Ti thermoluminescent detectors into repeatable subsets of similar response

Appl Radiat Isot. 2015 Jan:95:180-187. doi: 10.1016/j.apradiso.2014.10.019. Epub 2014 Oct 30.

Authors

Kimberlee J Kearfott¹, Jill P Newton², Muhammad Rafique³

Affiliations

¹ Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48109-2104, USA. Electronic address: kearfott@umich.edu.
² Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48109-2104, USA.
³ Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48109-2104, USA; Department of Physics University of Azad Jammu and Kashmir Muzaffarbad, 13100 Azad Kashmir, Pakistan.

PMID: 25464196
DOI: 10.1016/j.apradiso.2014.10.019

Abstract

A set of 920 heavily used LiF:Mg,Ti thermoluminescent dosimeters (TLDs) was placed into a polymethyl methacrylate (PMMA) plate attached to a 40×40×15cm³ PMMA phantom and irradiated to 4.52mGy using a ¹³⁷Cs source. This was repeated three times to determine the mean and standard deviation of each TLD׳s sensitivity. Reader drift was tracked over time with 10 control dosimeters. Two test sets of 100 TLDs were divided into subsets with sensitivities within ±1% of their subset means. All dosimeters were re-irradiated four times to test the TLDs׳ response repeatability and determine the sensitivity uniformity within the subsets. Coefficients of variation revealed that, within a given subset, the dosimeters responded within ±2.5% of their subset mean in all calibrations. The coefficient of variation in any of the 200 TLDs׳ calibrations was below 6% across the four calibrations. The work validates the approach of performing three calibrations to separate heavily used and aged TLDs with overall sensitivity variations of ±25% into subsets that reproducibly respond within ±2.5%.

Keywords: (137)Cs source; Calibration; Sensitivity; Statistics; Thermoluminescent dosimeters.