MEASUREMENT OF ALPHA TO FISSION BRANCHING RATIOS OF HEAVY ACTINIDES BY SEQUENTIAL ETCHING OF ALPHA AND FISSION TRACKS IN CR-39

A sequential etching method for revelation of alpha and fission tracks in CR-39 was developed and optimized. Using this technique alpha and fission tracks can be differentiated unambiguously because of signific ant differences in their sizes and appearance times. This registration and revelation procedure for alpha and fission tracks may be used for studies of half lives, alpha to fission branching ratios and identifi cation of radionuclides based on their decay schemes. It has the added advantage that both alpha emissions and fission events can be studied using one detector and hence uncertainties related to efficiency regi stration geometry, registration times, amount of radionuclides etc. ca n be eliminated or minimised. The sequential etching procedure was use d to measure the alpha/S.F. branching ratio of Cf-252 and Cm-244 and c ompared with published data in which other techniques were used. These two radionuclides were chosen because in 252 Cf both alpha and sponta neous fission rates are comparable and in Cm-244 alpha events are much more than spontaneous fission events and hence form two extremes. The results indicate that the present method gives very precise and accur ate values for alpha/S.F. branching ratio for Cf-252 and Cm-244 and ca n be considered as reference nuclides for this technique of measuremen t.