Level densities of Al28, Si29, and Ca41 inferred from fluctuation measurements

Neutron total cross sections for Al-27, Si-28, and Ca-40 have been measured with good statistics (approximately 1%) and good energy resolution over the energy range 4 less-than-or-equal-to E(n) less-than-or-equal-to 20 MeV. Two techniques have been used to infer the level density of the compound nuclei. The first is the conventional procedure of deducing an average level width and relating this to the level density. An alternative method is to deduce the level density from the magnitude of the variance of the cross section. A previous study of these two techniques suggested that the two yielded results which were not completely consistent. Our examination of the discrepancies indicates that they are reduced but not eliminated with better data. It seems likely that a part of the problem is the uncertainty in input parameters.