The corona-type spark chamber has been adapted for detection of fission fragments and has been used as the detector for neutron-induced fission cross-section measurements of ${\mathrm{Am}}^{241}$. Measurements were made over the neutron energy range from 0.032 to 80 eV. The ratio of average fission width to spacing is in good agreement with that predicted from the shape of the fast-neutron fission threshold. The number of effective fission channels obtained from an analysis of the distribution of fission widths was found to be 2.9±0.6 channels.

• Received 14 September 1964

DOI:https://doi.org/10.1103/PhysRev.137.B326