Sharp Laboratories Measurements I

Abstract

Radiocarbon measurements were begun at Sharp Laboratories in the spring of 1962 with the construction of a complete C14 dating laboratory. This first system used the method described by Fairhall, Schell, and Takashima (1961) for the conversion of CO2 to methane via ruthenium catalyst. This system proved to be fast and reliable, giving overall yields of solid sample to counting gas of better than 90% for the total conversion and purification (the conversion yield of CO2 to methane is quantitative). The detector in present use is 2 L, with construction materials consisting solely of O.F.H.C. copper, teflon, and epoxy resin. The shield consists of 4 in. of high purity lead (specially prepared), 4 in. of borated hydrogenous neutron moderator, a guard counter (cosmic ray detector), and 1 in. of ultra pure mercury. The gross to net ratio obtained with this system averages about 53. The background, for P in cm methane pressure, is:Background = 3.95 ± .008 + .00705P