The Quaternary Isotope Laboratory Thermal Diffusion Enrichment System: Description and Performance

Abstract

The thermal diffusion enrichment system of the Quaternary Isotope Laboratory consists of 23 hot wire columns of 3m effective length combined to 2 separate systems of 3 and 3 separate systems of 4 columns at the top, each system in series with 1 bottom column. From ≈ 130 L NTP of CO (∼ 65g of carbon) it produces ≈ 8 L NTP of CO (~ 4g of carbon) enriched in 12 C 18 O by a factor 6 to 7 and in 14 C 16 O by a factor 7 to 8 in about 5 weeks. For 12 C 18 O the system has a theoretical equilibrium separation factor of about 250 and a theoretical equilibrium enrichment of about 15. For 14 C 16 O these values are 1300 and 16, respectively. The dependence of thermal diffusion transport on gas exchange between top and bottom section and between columns and reservoirs and on wire temperature is given. Forced gas exchange and a higher wire temperature gave a more rapidly increasing enrichment without substantially increasing its final value of 6 to 7 for 12 C 18 O. A comparison with the Groningen enrichment system shows that the two systems behave very similarly and that not the system geometry but individual column parameters and the ratio total sample mass/enriched sample mass are the dominant factors determining the enrichment.