Total kinetic energy release in ${}^{239}\mathrm{Pu}(n,f)$ post-neutron emission from 0.5 to 50 MeV incident neutron energy

The average total kinetic energy $\left(\overline{TKE}\right)$ in ${}^{239}\mathrm{Pu}(n,f)$ has been measured for incident neutron energies between 0.5 and 50 MeV. The experiment was performed at the Los Alamos Neutron Science Center (LANSCE) using the neutron time-of-flight technique, and the kinetic energy of fission fragments post-neutron emission was measured in a double Frisch-gridded ionization chamber. This represents the first experimental study of the energy dependence of $\overline{TKE}$ in ${}^{239}\mathrm{Pu}$ above neutron energies of 6 MeV.

Figure 1

Representative anode waveform signal. Baseline and decay regions for signal processing are indicated by arrows between two vertical lines. The original baseline and decay regions are label A and B while the modified regions are labeled ${\mathrm{A}}^{\prime }$ and ${\mathrm{B}}^{\prime }$, respectively.

Figure 2

Raw digitized waveforms from the anode plate signal for (a) a fission fragment without $\alpha$ particles and (b) a fission fragment and one $\alpha$ contamination in the signal decay.

Figure 3

Raw anode spectra for a subset of fission fragments (a) before and (b) after $\alpha$ contamination correction to raw waveforms.

Figure 4

Anode spectra for a subset of fission fragments (a) before and (b) after energy loss corrections in target backing material and gain matching of the backing side anode to the non-backing-side anode.

Figure 5

Calibrated neutron time-of-flight distribution.

Figure 6

Average total kinetic energy for fission products post-neutron emission for ${}^{239}\mathrm{Pu}(n,f)$. Modeling predictions by Madland and Lestone and current ENDF/B-VII cross section of ${}^{239}\mathrm{Pu}(n,f)$ are also plotted.