Neutron Resonance Structure of Uranium-238

Modifications in the Argonne fast-neutron chopper and its installation at the reactor CP-5 are described. With this system, neutron transmissions of very pure samples of U^238 were measured. Parameters for the resonances observed were obtained by a refined wing shape analysis as well as by the conventional area analysis. A previously unobserved level having a smaller reduced neutron width than any heretofore reported was detected at 10. 2 ev; it is interpreted as being a p-wave resonance. Average parameters of significance to nuclear theory are deduced. For reactor application, the resonance capture integral is calculated from the parameters and is found to be in excellent agreement with the directly measured value.