Measuring the ²³⁵U(n,f)/⁶Li(n,t) cross section ratio in the NIFFTE fissionTPC

Neutron-induced reactions are important to our understanding of fundamental nuclear physics as well as nuclear applications. Due to their impact on a wide range of nuclear physics applications, it has become important to better understand the probability such reactions occur and try to minimize their uncertainties. In particular, there is a need for precision neutron-induced fission cross section measurements on actinides. Neutron-induced fission cross sections are typically measured as ratios, relative to a well-known cross section standard. The ²³⁵U(n,f) is a well measured standard, often used as a reference on cross section ratio measurements of other actinides. However, some light particle reactions are also well-known and their use as reference can provide information to remove shared systematic uncertainties that are present in an actinide-only ratio measurement. The NIFFTE collaboration's fission time projection chamber (fissionTPC) is a charged particle tracker designed for precision measurements of neutron-induced fission reactions. Detailed 3D track reconstruction of the reaction products enables evaluation of systematic effects and corresponding uncertainties which are less directly accessible by other measurement techniques. This work focuses on the recent measurement of the ²³⁵U(n,f) using as a reference the light-ion standard ⁶Li(n,t) reaction. Preliminary data of the ²³⁵U(n,f)/⁶Li(n,t) measurement conducted at the Los Alamos Neutron Science Center will be presented.

LLNL-ABS-836692: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.