Neutron Resonance Spectroscopy. X.Th232andU238

Neutron time-of-flight spectroscopy measurements were made for a range of sample thicknesses of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ using the Nevis synchrocyclotron. These included transmission measurements using 200- and 40-m paths, self-indication measurements at 40 m, and Moxon-Rae capture measurements at 33 m. Resonance energies and ${\Gamma }_n$ values were obtained for $n=302\mathrm{}$ levels in ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ to 4.0 keV and 269 levels in ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ to 4.6 keV, with essentially no missed $s$ levels and inclusion of a significant number of $p$ levels. ${\Gamma }_{\gamma }$ values were obtained for 84 levels in ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ and 71 in ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ to 2400 eV, with $〈{\Gamma }_{\gamma }〉=[21.2\mathrm{}\pm 0.3 (\mathrm{stat}.\mathrm{})\pm 0.9 (\mathrm{syst}.\mathrm{}\left)\right] \mathrm{meV} \left({}_{}{}^{232}{}_{}{}^{}\mathrm{Th}\right) \mathrm{and} [22.9\mathrm{}\pm 0.5 (\mathrm{stat}.\mathrm{})\pm 0.9 (\mathrm{syst}.\mathrm{}\left)\right] \mathrm{meV} \left({}_{}{}^{238}{}_{}{}^{}\mathrm{U}\right)$. In both cases a ${\chi }^2$ analysis gives ∼100 degrees of freedom including the effects of measurement errors. The values for the resonance energies were obtained from the data before the analysis was completed for ${\Gamma }_n$ and ${\Gamma }_{\gamma }$ values. The division of the levels into $s$ and $p$ populations, described in detail elsewhere, was made to achieve a "best" fit to many statistical tests relating to the orthogonal-ensemble theory for single level populations, with a resulting good fit to numerous tests. For the chosen $s$ level population,