MEASUREMENT OF NEUTRON-CAPTURE AND FISSION CROSS-SECTIONS OF PU-239 AND U-235, 0.02 EV TO 200 KEV, NEUTRON-CAPTURE CROSS-SECTIONS OF AU-197, 10-KEV TO 50-KEV, AND NEUTRON FISSION CROSS-SECTIONS OF U-233, 5-KEV TO 200-KEV

The pulsed-neutron beam for these measurements was generated using the Oak Ridge Electron Linear Accelerator. A large liquid scintillator about 40 m from the neutron source was used to detect the prompt gamma-ray cascades resulting from neutron absorption in the sample. In general for **2**3**9Pu and **2**3**5U, these experiments indicated lower neutron fission cross sections than contained in ENDF/B-III for energies above 10 keV. The measured values of the ratio alpha , neutron capture-to-neutron fission, for **2**3**9Pu agree within errors with those derived from ENDF/B-III, Mat 1159. For the present measurements, the uncertainty on alpha for **2**3**9Pu is about 11% at 10 keV and increases to about 30% at 100 keV. The results for **1**9**7Au are about 15% lower than the ENDF/B-III values. The measurements of the ratio of the neutron fission cross section for **2**3**3U to that for **2**3**5U are generally higher than the ENDF/B-III values by about 5%.