Energy Distribution of Ternary a-Particles in 252Cf(sf)

摘要

We have dedicated a new experiment to remeasuring the ternary a-particle energy spectrum in 252Cf spontaneous fission using an array ofunshielded silicon detectors and unambiguously discriminating a-particlesfrom neighboring isotopes by time-of-flight techniques using fission frag-ments as the start. Compared to many previous experiments, which en-tailed detection thresholds of 6 to 9 MeV a-particle energy due to theAE-E method applied and use of protection foils on detectors, the energydistribution of ternary a-particles could, for the first time, be measureddown to 1 MeV. Furthermore, the energy spectrum of 6He could be anal-ysed, albeit with weak statistics, and the yield ratio 6He/4He was deduced.For 4He, an excess in the yield as compared to a Gaussian shape is observedat energies below 9 MeV whose magnitude is in close agreement with datapresented by Tishchenko et al. in 2002. On the other hand, the data for-merly published by Loveland in 1974 exceed the low-energy yield of ternarya particles by up to a factor of two. We present our results on the ternarya-particle spectrum, and also the data on 6He, and discuss prospects forfuture measurements.