Characterisation of scintillator-based gamma spectrometers for determination of sample dose rate in OSL dating applications

Minqiang Bu*, Andrew Sean Murray, Myungho Kook, Louise Maria Helsted, Jan-Pieter Buylaert, Kristina Jørkov Thomsen

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

A recent inter-comparison (Murray et al., 2015) has helped to highlight variability in the measurement of dose rate between luminescence laboratories. Part of this variability probably reflects the difficulties of homogenising and dissolving samples so that the<500 mg used in e.g. ICP-MS and NAA is representative. High resolution gamma spectrometry is the obvious alternative because it can measure samples 100–1000 times larger, but the instrumentation is low-throughput, high capital and running cost, and requires skilled personnel to maintain operation over many years. Here we investigate the potential of traditional low-cost, low maintenance alternatives based on a 3”×3” NaI(Tl) scintillation crystal. The temperature stability is investigated, and a linear (with intercept) correction for spectra drift based on the 1.46 MeV peak from 40K and the ∼100 keV composite X-ray peak from uranium and thorium is shown to minimise this problem. Using a calibration based on wax impregnated standards, the minimum detection limits (MDL) are 25 Bq/kg 40K, 4.8 Bq/kg (238U), 2.5 Bq/kg (232Th) for 250–300 g of sample; systematic deviations around the expected values are also shown to be acceptable as the MDL is approached. Finally, we compare the activity concentrations and resulting dry dose rates derived from our NaI-based system with those from routine high resolution gamma spectrometry, and conclude that the new analytical facility is very suitable for accurate and precise dose rate determination.
Original languageEnglish
JournalRadiation Measurements
Volume120
Pages (from-to)253-259
ISSN1350-4487
DOIs
Publication statusPublished - 2018

Keywords

  • Dose rate measurement
  • NaI(Tl) detector
  • OSL dating
  • Scintillation gamma spectrometry
  • Spectrum drift correction

Cite this

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title = "Characterisation of scintillator-based gamma spectrometers for determination of sample dose rate in OSL dating applications",
abstract = "A recent inter-comparison (Murray et al., 2015) has helped to highlight variability in the measurement of dose rate between luminescence laboratories. Part of this variability probably reflects the difficulties of homogenising and dissolving samples so that the<500 mg used in e.g. ICP-MS and NAA is representative. High resolution gamma spectrometry is the obvious alternative because it can measure samples 100–1000 times larger, but the instrumentation is low-throughput, high capital and running cost, and requires skilled personnel to maintain operation over many years. Here we investigate the potential of traditional low-cost, low maintenance alternatives based on a 3”×3” NaI(Tl) scintillation crystal. The temperature stability is investigated, and a linear (with intercept) correction for spectra drift based on the 1.46 MeV peak from 40K and the ∼100 keV composite X-ray peak from uranium and thorium is shown to minimise this problem. Using a calibration based on wax impregnated standards, the minimum detection limits (MDL) are 25 Bq/kg 40K, 4.8 Bq/kg (238U), 2.5 Bq/kg (232Th) for 250–300 g of sample; systematic deviations around the expected values are also shown to be acceptable as the MDL is approached. Finally, we compare the activity concentrations and resulting dry dose rates derived from our NaI-based system with those from routine high resolution gamma spectrometry, and conclude that the new analytical facility is very suitable for accurate and precise dose rate determination.",
keywords = "Dose rate measurement, NaI(Tl) detector, OSL dating, Scintillation gamma spectrometry, Spectrum drift correction",
author = "Minqiang Bu and Murray, {Andrew Sean} and Myungho Kook and Helsted, {Louise Maria} and Jan-Pieter Buylaert and Thomsen, {Kristina J{\o}rkov}",
year = "2018",
doi = "10.1016/j.radmeas.2018.07.003",
language = "English",
volume = "120",
pages = "253--259",
journal = "Radiation Measurements",
issn = "1350-4487",
publisher = "Pergamon Press",

}

Characterisation of scintillator-based gamma spectrometers for determination of sample dose rate in OSL dating applications. / Bu, Minqiang; Murray, Andrew Sean; Kook, Myungho; Helsted, Louise Maria; Buylaert, Jan-Pieter; Thomsen, Kristina Jørkov.

In: Radiation Measurements, Vol. 120, 2018, p. 253-259.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Characterisation of scintillator-based gamma spectrometers for determination of sample dose rate in OSL dating applications

AU - Bu, Minqiang

AU - Murray, Andrew Sean

AU - Kook, Myungho

AU - Helsted, Louise Maria

AU - Buylaert, Jan-Pieter

AU - Thomsen, Kristina Jørkov

PY - 2018

Y1 - 2018

N2 - A recent inter-comparison (Murray et al., 2015) has helped to highlight variability in the measurement of dose rate between luminescence laboratories. Part of this variability probably reflects the difficulties of homogenising and dissolving samples so that the<500 mg used in e.g. ICP-MS and NAA is representative. High resolution gamma spectrometry is the obvious alternative because it can measure samples 100–1000 times larger, but the instrumentation is low-throughput, high capital and running cost, and requires skilled personnel to maintain operation over many years. Here we investigate the potential of traditional low-cost, low maintenance alternatives based on a 3”×3” NaI(Tl) scintillation crystal. The temperature stability is investigated, and a linear (with intercept) correction for spectra drift based on the 1.46 MeV peak from 40K and the ∼100 keV composite X-ray peak from uranium and thorium is shown to minimise this problem. Using a calibration based on wax impregnated standards, the minimum detection limits (MDL) are 25 Bq/kg 40K, 4.8 Bq/kg (238U), 2.5 Bq/kg (232Th) for 250–300 g of sample; systematic deviations around the expected values are also shown to be acceptable as the MDL is approached. Finally, we compare the activity concentrations and resulting dry dose rates derived from our NaI-based system with those from routine high resolution gamma spectrometry, and conclude that the new analytical facility is very suitable for accurate and precise dose rate determination.

AB - A recent inter-comparison (Murray et al., 2015) has helped to highlight variability in the measurement of dose rate between luminescence laboratories. Part of this variability probably reflects the difficulties of homogenising and dissolving samples so that the<500 mg used in e.g. ICP-MS and NAA is representative. High resolution gamma spectrometry is the obvious alternative because it can measure samples 100–1000 times larger, but the instrumentation is low-throughput, high capital and running cost, and requires skilled personnel to maintain operation over many years. Here we investigate the potential of traditional low-cost, low maintenance alternatives based on a 3”×3” NaI(Tl) scintillation crystal. The temperature stability is investigated, and a linear (with intercept) correction for spectra drift based on the 1.46 MeV peak from 40K and the ∼100 keV composite X-ray peak from uranium and thorium is shown to minimise this problem. Using a calibration based on wax impregnated standards, the minimum detection limits (MDL) are 25 Bq/kg 40K, 4.8 Bq/kg (238U), 2.5 Bq/kg (232Th) for 250–300 g of sample; systematic deviations around the expected values are also shown to be acceptable as the MDL is approached. Finally, we compare the activity concentrations and resulting dry dose rates derived from our NaI-based system with those from routine high resolution gamma spectrometry, and conclude that the new analytical facility is very suitable for accurate and precise dose rate determination.

KW - Dose rate measurement

KW - NaI(Tl) detector

KW - OSL dating

KW - Scintillation gamma spectrometry

KW - Spectrum drift correction

U2 - 10.1016/j.radmeas.2018.07.003

DO - 10.1016/j.radmeas.2018.07.003

M3 - Journal article

VL - 120

SP - 253

EP - 259

JO - Radiation Measurements

JF - Radiation Measurements

SN - 1350-4487

ER -