Energy Spectrum of Forward Neutrons from p-d Collision at 142 MeV

This work was performed as part of a series of measurements of neutron energy spectra at 0° from different nuclei. In p-d scattering one would expect neutrons which were knocked out at 0° to be approximately monoenergetic, with a spread less than ~ 1 MeV. Previous work was done at 95 MeV by Hofmann and Strauch in 1952 and showed a neutron energy spread of 22 MeV. They attributed this spread to the effect of radial oscillations in the cyclotron, and to multiple traversals of the thin target by incident protons.The time-of-flight system, on the Harwell cyclotron eliminates these sources of energy spread. The internal proton beam was deflected electrostatically on to a thin target at a mean proton radius corresponding to 143 MeV. Protons therefore hit the target at a fixed time, rather than at a fixed radius, so there was little energy spread due to radial oscillations. A proton blocker was placed behind the target so that protons could not make more than one traversal. (author)