Preparation of Sources for Alpha Spectrometry

Abstract

Summary A simple method is presented for the preparation of alpha sources to be analyzed by an alpha spectrometer equipped with a semi-conductor detector. The procedure consists of evaporating to dryness an aqueous solution of the alpha-emitter, redissolving the residue in situ with 0.1 Ν HNO3, precipitating with 3Ν NH4OH and drying. The residual NH4NO3 is redissolved in 3 N NH4OH, dried again, and sublimed at a higher temperature. The deposit is washed with distilled water, after which the plate is dried and ignited at red heat. Dramatic improvement is illustrated with several alpha emitters of different chemical properties, including 208/209Po, 230Th, 231Pa, 232/234U, and 238/239Pu. By providing better distribution of the alpha-emitting nuclides and by removing alpha-absorbing impurities, the same procedure significantly increases the gross alpha counting rate and is recommended for use in improving the accuracy and reproducibility of routine alpha counting.