Ratio of the ternary to binary fission induced by thermal and resonance neutrons in ²³⁹Pu

Measurements were performed of the ratio of ternary to binary fission (T/B) in ²³⁹Pu by neutrons in the energy region from 0.020 eV to 50 eV. The ternary and binary fission time-of-flight spectra were recorded at a 8.1 m flightpath at the Geel Linac with large gold-silicon surface-barrier detectors on both sides of a 1 mg/cm² double-faced ²³⁹Pu target. From these time-of-flight spectra the ratios of the areas of the strongest isolated resonances in ternary and in binary fission were calculated; moreover in the region 0.02-1 eV ratios were calculated for about 40 zones throughout the spectrum. The T/B ratio does not vary significantly in the energy region below 1 eV; this is not the case in the region 1-50 eV, where the T/B value for the 15.5 eV resonance is significantly larger than for the other resonances. These T/B values seem to be correlated with the resonance spin J and with some other fission characteristics.