Measurement of the $^{239}$Pu(n,f)/$^{235}$U(n,f) Cross-Section Ratio with the NIFFTE fission Time Projection Chamber

TL;DR

This paper reports a precise measurement of the $^{239}$Pu(n,f)/$^{235}$U(n,f) cross-section ratio across a wide neutron energy range using the advanced fissionTPC, improving data accuracy for nuclear physics applications.

Contribution

The study introduces the use of the fissionTPC for high-precision cross-section ratio measurements over a broad energy spectrum, enhancing the reliability of nuclear data.

Findings

Measured the cross-section ratio from 100 keV to 100 MeV.

Provided data to improve nuclear data evaluations.

Compared results with existing ENDF evaluations and previous measurements.

Abstract

The $^{239}$Pu(n,f)/$^{235}$U(n,f) cross-section ratio has been measured with the fission Time Projection Chamber (fissionTPC) from 100 keV to 100 MeV. The fissionTPC provides three-dimensional reconstruction of fission-fragment ionization profiles, allowing for a precise quantification of measurement uncertainties. The measurement was performed at the Los Alamos Neutron Science Center which provides a pulsed white source of neutrons. The data are recommended to be used as a cross-section ratio shape. A discussion of the status of the absolute normalization and comparisons to ENDF evaluations and previous measurements is included.