Total Neutron Cross Sections of U²³³ and U²³⁵ from 0.02 to 0.08 ev

Neutron transmission measurements of U²³³ and U²³⁵ have been obtained from 0.02 to 0.08 ev. The 2200 m/sec total neutron cross section values have been calculated from a linear least-squares fit to the data in this region and found to be 587 ± 6 and 690 ±10 barns, respectively. The data were taken with the Materials Testing Reactor (MTR) fast chopper with an instrument resolution of 2 µsec/m. Experimental techniques, involving the use of a 1024-channel time-of-flight analyzer for measuring total cross sections at low energies, are described.