Radiocarbon Dating With the Quantulus in an Underground Counting Laboratory: Performance and Background Sources

Kalin, Robert M.; Long, Austin

doi:10.1017/s0033822200011917

Cited by 17 publications

(9 citation statements)

References 5 publications

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“…Count rates were recorded every 50 min for statistical analysis. See Kahn and Long (1989) for more complete description of the counting system.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, both counter background and chemical blank must be minimized, and their values and variabilities must be well known and statistically well behaved. Kahn and Long (1989) previously discussed counter background; we discuss below the measures taken in this study to minimize environmental contamination and chemical blank for dating old wood.…”

Section: Methodsmentioning

confidence: 99%

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High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

Long

Kalin

1992

Radiocarbon

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Calculations show the possibility of detecting 14C remaining after 10 or 11 decay half-lives in natural materials, such as wood, using commercially available liquid scintillation (LS) detectors. Assuming in-situ 14C production has contributed insignificantly to the measured 14C, one can calculate finite ages approaching 70 ka. In practice, defensible finite age determinations involve careful considerations of several critical elements in the procedure. These critical elements are: 1) the integrity of the sample itself, in terms of younger contaminants and of in situ-produced 14C; 2) the availability of "dead" background material; 3) chemical blank in laboratory preparation of, in this case, benzene; and 4) stability of background and efficiency of the LS counting system. High-sensitivity 14C dating reveals a low level of memory effect 14C in benzene synthesized in the laboratory from anthracite or marble. This level of 14C activity is equivalent to that found in 53 ka old wood, and thus, is not distinguishable from petrochemical benzene used in routine dating. If careful control of laboratory conditions can maintain this 14C blank constant, reproducible dating beyond 53 ka would be possible. Although we have not completed a systematic analysis of the origins of memory effect, lithium reactors used in acetylene production and organic solvents in wood pretreatment are likely sources.1Present address

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“…Count rates were recorded every 50 min for statistical analysis. See Kahn and Long (1989) for more complete description of the counting system.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

Long

Kalin

1992

Radiocarbon

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“…SOC isotopic analysis for δ 13 C values and radiocarbon dates ( 14 C) were determined by the University of Arizona Laboratory of Isotope Geochemistry (Kalin & Long 1989;Donahue et al 1990) after soil sample preparation to remove roots, particulate organic matter, and carbonates. Roots (> 2 mm diameter) were removed from bulk soil with a 2-mm sieve.…”

Section: Isotopic Analysismentioning

confidence: 99%

Can soil organic carbon isotopes be used to describe grass‐tree dynamics at a savanna‐grassland ecotone and within the savanna?

McClaran

McPherson

1995

J Vegetation Science

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Abstract. We evaluated the use of soil organic carbon (SOC) isotopes to describe grass‐tree dynamics at locations at the savanna‐C4 grassland ecotone and within a temperate semiarid Quercus savanna in southeastern Arizona, USA. SOC will not describe grass‐tree dynamics at locations within the savanna because isotope composition near the soil surface does not correspond with the overlying vegetation and recent C3 carbon has been deposited at deep soil depths with no C4analog. In contrast, SOC can describe grass‐tree dynamics at the savanna‐grassland ecotone because isotope composition near the soil surface corresponds with overlying vegetation and significant deep soil deposition of C3 carbon was not apparent. At the ecotone, trees became established in the last 700–1700 years. There is no evidence to suggest an unstable grass‐tree mixture at the ecotone since that time.

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“…The room is a Faraday cage and in overpressure of filtered air to remove radon. The University of Arizona Radiocarbon Laboratory in Tucson, Arizona, has an underground laboratory with 5 Quantuluses which have a 10-m overburden at 15 °C (Kalin and Long 1989). The instrument temperatures for 14 C dating are kept close to the benzene freezing point at 7 °C.…”

Section: Low-background Laboratories For Liquid Scintillation Countingmentioning

confidence: 99%

“…Quantulus™ (PerkinElmer, Inc.) is an ultra low-level liquid scintillation spectrometer used in numerous radiocarbon laboratories for radiometric 14 C age determinations. Sample sizes down to a few hundred mg of carbon have been measured with various sample holder configurations (Haas 1979;Kalin and Long 1989;Hogg 1992;Kaihola et al 1992;Buzinny and Skripkin 1995) which give lower backgrounds than larger vials.…”

Section: Introductionmentioning

confidence: 99%

Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry

Plastino

Kaihola

2004

Radiocarbon

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Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus™ has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.

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Radiocarbon Dating With the Quantulus in an Underground Counting Laboratory: Performance and Background Sources

Cited by 17 publications

References 5 publications

High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

Can soil organic carbon isotopes be used to describe grass‐tree dynamics at a savanna‐grassland ecotone and within the savanna?

Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry

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