A high-resolution multi-parametric study of 239Pu(n th, f) with the Cosi-Fan-Tutte spectrometer

Abstract

The Cosi-Fan-Tutte spectrometer has been used to measure for the first time in one go the mass-nuclear charge-energy correlations of well-resolved light group masses for 239Pu(n th, f). About 2 × 10 6 events were collected and analysed. The global mass distribution is consistent with the Lohengrin data. The mean proton odd-even effects in yields and energy are δ p=(11.8±0.3)% and δE K o−e=0.49±0.15 MeV respectively. The δ p( E L) varies from ≈7% to ≈25% for E L=90 to 116 MeV. The present analysis consists of 21 values of E L compared to only 5 values for Lohengrin. The apparent mean neutron odd-even effect δ n=(3.5±0.1)% is much lower than the δ n= (6.5±0.7)% for Lohengrin. The mean value of conditional variance 〈 σ z 2( Z| A)〉=(0.42±0.02); the 〈 σ z 2( Z| A)〉 increases from 230Th to 250Cf and this behaviour turns out to be important for understanding the dynamics of the fission process.