Measuring reaction probability ratios to simulate neutron-induced cross-sections of short-lived nuclei

Measuring the neutron-induced fission cross-sections of short-lived nuclei represents an experimental challenge due to target activity and the low intensity of neutron beams. One way to alleviate the problems inherent in the direct measurement is to use the surrogate method, where one measures the decay probability of the same compound nucleus formed using a charged beam and a stable target. The decay probability of the compound nucleus is then used to estimate the neutron-induced cross-section. As an extension to the surrogate method, we introduce a new method of reporting the fission probabilities of two compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. The ratio method was checked in a known case, the ²³⁶U(n, f)/²³⁸U(n, f) cross-section ratio, which turned out to be the same as the probability ratio of P(²³⁶U(d, pf))/P( ²³⁸U(d, pf)). As an application, the ²³⁷U(n, f)/ ²³⁵U(n, f) cross-section ratio was inferred, on the basis of the measured P(²³⁸U(d, d′f))/P(²³⁶U(d, d′f)) probability ratio.