Recoil Type Neutron Spectrometer for 0.05 to 1 Mev

A neutron energy spectrometer is described, suitable for the region 50 kev to 1 Mev. Hydrogen recoils from CH₄ in a proportional counter are collimated and enter a second counter. The sum of the pulse heights is analyzed whenever a coincidence occurs. A third counter in anticoincidence discriminates against cases in which all the energy is not lost in the first two. With the collimation used the energy spread is $\text{∼10\%}$ and the efficiency an approximately linear function of energy, being 10⁻⁵ at 180 kev.