L. K. Felker

Quantitative determination of 252Cf

Abstract Sealed 252 Cf sources in the microCurie to milliCurie range are routinely used in industry and research. At present, no reliable analytical method is available for precise determination of the activity. Very strong sources can be analyzed by neutron counting but the error is large. We propose to use γ-ray spectroscopy for such analysis. In particular, high-energy γ rays (above 1 MeV ) of fission fragments in equilibrium with the source are very convenient because they have little absorption in materials surrounding the source. It is found that the 1435.8-keV γ-ray of 138 Cs and the 1596.5-keV γ-ray of 140 La are well isolated and sufficiently above the background under these peaks. We have measured the γ/α ratio for the 252 Cf with an uncertainty of better than 5%. The experiment involved the preparation of several thin 252 Cf sources, alpha pulse height analysis, determination of α decay rate, and the measurement of γ singles spectrum with a well-shielded germanium spectrometer. The measured ratio and the γ-ray spectroscopy of unknown samples can provide the activity of 252 Cf in these samples.

Proton Single-Particle States In The Heaviest Actinide Nuclei

The level structure of 249Bk has been investigated by measuring the γ‐ray spectra following the α decay of a chemically and isotopically pure 253Es sample. Alpha‐gamma coincidence measurement was performed using a Si detector for α particles and a 25% Ge detector for γ rays. A gamma‐gamma coincidence measurement was performed with the Gammasphere spectrometer. The Es sample was obtained by extracting the 253Es which grew in a 253Cf source material produced in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Additional information on the 249Bk levels was obtained from the study of γ rays produced in the β− decay of 249Cm. The 249Cm sample was produced by neutron irradiation of 248Cm. Using the results of the present study and the results of previous 248Cm(α,t) and 248Cm(3He,d) reaction spectra, the following single‐particle states have been identified in 249Bk: 7/2+[633], 0.0 keV; 3/2−[521], 8.78 keV; 1/2+[400], 377.55 keV: 5/2+[642], 389.17 keV; 1/2−[530], 569.19 keV; 1/2−[521], 643....