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

The NIFFTE collaboration's fission time projection chamber (fissionTPC) is a $2\times2\pi$ charged particle tracker designed for measuring neutron-induced fission. The fissionTPC provides three-dimensional reconstruction of fission-fragment ionization profile enabling evaluation of systematic effects and corresponding uncertainties which are less directly accessible by other measurement techniques. Preliminary results of $^{239}$Pu(n,f)$/^{235}$U(n,f) cross-section ratio, for incident neutron energies from 100 KeV to 100 MeV will be discussed. The measurement was performed at the Los Alamos Neutron Science Center which provides a pulsed white source of neutrons.