Statistical properties of $^{243}$Pu, and $^{242}$Pu(n,$\gamma$) cross section calculation

TL;DR

This study measures the level density and gamma-ray strength function of 243Pu using the Oslo method, and uses these data to calculate the 242Pu(n,gamma) cross section in previously unmeasured neutron energy ranges.

Contribution

It provides new experimental data on 243Pu's level density and gammaSF, and applies these to accurately compute the 242Pu(n,gamma) cross section.

Findings

Level density follows constant-temperature model above pairing gap.

Gamma-ray strength function shows a scissors resonance at 2.42 MeV.

Calculated cross sections match previously unmeasured neutron energy data.

Abstract

The level density and gamma-ray strength function (gammaSF) of 243Pu have been measured in the quasi-continuum using the Oslo method. Excited states in 243Pu were populated using the 242Pu(d,p) reaction. The level density closely follows the constant-temperature level density formula for excitation energies above the pairing gap. The gammaSF displays a double-humped resonance at low energy as also seen in previous investigations of actinide isotopes. The structure is interpreted as the scissors resonance and has a centroid of omega_{SR}=2.42(5)MeV and a total strength of B_{SR}=10.1(15)mu_N^2, which is in excellent agreement with sum-rule estimates. The measured level density and gammaSF were used to calculate the 242Pu(n,gamma) cross section in a neutron energy range for which there were previously no measured data.