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Glasgow University Radiocarbon Measurements VIII

Published online by Cambridge University Press:  18 July 2016

M J Stenhouse  and
M S Baxter
M J Stenhouse
Affiliation:
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ
M S Baxter
Affiliation:
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ
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The analytical facilities at Glasgow have been extended to include gas proportional (CO2 and CH4) and liquid scintillation (C6H6) counting laboratories. The results presented here were obtained during 1972-1974 using the CO2 gas counting system only. In brief, organic samples, after pretreatment as described in the text, are burned in a tube combustion unit and the evolved CO2 absorbed in KOH solution. BaCO3 is precipitated and acid-hydrolyzed in vacuo using H3PO4. Evolved CO2 is purified via adsorption/desorption on CaO and is stored prior to counting. The 2.6L proportional counter is surrounded by a gas-flow Geiger anticoincidence guard and 10cm thick Pb shielding to reduce background count rates to ca 4.9 cpm at 1 atm filling and barometric pressures. A barometric sensitivity in background of −0.01cpm/mbar is observed. Constant gas gain is ensured by monitoring the coincidence meson spectrum and normalizing the detector operating voltage. All sample activities are related to the NBS oxalic acid standard count rate which averages 14.71 cpm at 1 atm filling pressure and 15°C. Mass spectrometric assay of CO2 after counting is performed on a VG Micromass 602B instrument to a precision of 0.05% (±1σ). Since uncertainties quoted on all results represent 1σ counting errors alone, they are related to precision of measurement rather than accuracy. The bulk of data quoted here are connected with a long-term study of the medical aspects of artificial 14C from nuclear weapon tests. These results should therefore be assessed in conjunction with those pub previously (Harkness and Walton, 1972; Farmer et al, 1972).

Type
Research Article
Information
Radiocarbon , Volume 18 , Issue 2 , 1976 , pp. 161 - 171
Copyright
Copyright © The American Journal of Science 

References

Farmer, J G, Stenhouse, M J and Baxter, M S, 1972, Glasgow University radiocarbon measurements VI: Radiocarbon, v 14, p 326–330.Google Scholar
Harkness, D D and Walton, A, 1972, Glasgow University radiocarbon measurements IV: Radiocarbon, v 14, p 111–113.Google Scholar
Stenhouse, M J, 1974, Artificial production of 14C from nuclear weapon tests and its uptake by man: PhD thesis, Univ Glasgow.Google Scholar