Glasgow University Radiocarbon Measurements I

Abstract

Two radiocarbon counting systems have been established in the Chemistry Department, University of Glasgow, since late 1967. The counting gas is methane, at pressures up to 10 atm, and 2 alternative procedures are followed for methane production, (a) high pressure synthesis in a stainless steel 4.5 1 reactor and (b) low pressure synthesis in an all glass flow-reactor. Both systems employ 0.5% ruthenium on alumina pellets as catalyst (Engelhard Industries Ltd.). Early samples synthesized with Air Products' hydrogen showed evidence of tritium contamination. This gas supply was later replaced with tritium-free hydrogen supplied by Messrs. Griesheim, Düsseldorf, Germany. Both detectors used for routine measurements are 0.5 1 internal gas counters supplied by Beckman Instruments Inc., California. The detectors are surrounded by a concentric-wall multiple anode anticoincidence counter. The entire counter assembly is encased within a 4-in.-thick lead shield manufactured from aged lead by J. Girdler and Co., London. Counter electronics, anticoincidence system and power supply are of Beckman design (Sharp and Ellis, 1965).