Quantitative Radioisotope Measurements with the NSF-Arizona Regional Accelerator Facility

Results of tests on the tandem accelerator mass spectrometer (TAMS) at the University of Arizona are presented. These results demonstrate: (a) measurements of 14C/13C ratios with precisions of a few percent can be made in a period of one to several hours; (b) measurements with precisions of 0.5% have been made in which the uncertainties were mainly statistical and in which contributions to the uncertainty of machine fluctuations were negligible; (c) precise measurements of the ratio of 14C/13C in samples of N.B.S. oxalic acid and of 1890 wood are consistent with the accepted value of that ratio; (d) the real signal from a 44,000 year old sample is equal to the background rate produced from a dead carbon sample. In addition, results of some measurements on archaeological samples are presented.