Measurement of the Average Neutron Yield per Fission forAm242m

The average number of neutrons per thermal neutron fission, $\overline{\nu }$, was measured for ${\mathrm{Am}}^{242m}$ with the use of a spark-chamber fission detector and a paraffin-moderated neutron detector. The value obtained is 3.24±0.12 neutrons per fission. To check the method, measurements also were made on ${\mathrm{U}}^{235}$ and ${\mathrm{U}}^{233}$, which gave 2.43±0.08 and 2.54±0.04 neutrons per fission, respectively.