Measurements of 10Be distributions using a Tandem Van De Graaff accelerator

Abstract 10 Be us a cosmogenically produced radionuclide with a 1.5 × 10 6 y half-life which is useful in the study of geophysical processes. Because of its low production rate (∼ 1.5 × 10 −2 atoms/cm 2 s) and long half-life, it is difficult to determine the quantity of 10 Be in geophysical samples by counting decays. While a limited number of samples have been analyzed this way, it has required large samples, long counting times, careful chemical elimination of all other natural radionuclides from the sample and low background counters. We have been using the Yale MP Tandem as a very sensitive spectrometer to directly measure the ratio of 10 Be. 9 Be atoms in samples of geophysical interest. The procedures used to measure absolute 10 Be content of unknown samples are described, as in the application of these procedures to the determination of the growth rate of a manganese nodule from the Rio Grande Ridge in the South Atlantic Ocean. The geophysical importance of this general procedure is discussed.