Measurement of the transverse range of (n,2n) recoils in Au

The lateral spread of approx.100 keV recoils in Au foils has been determined by a radioactive counting technique. A uniform distribution of recoils initially moving nearly parallel to the foil surfaces was generated by (n,2n) reactions with a high-energy neutron beam from a cyclotron. The fraction of (n,2n) activity which escapes the transverse surface is a measure of the transverse spreading of the recoils. Projected ranges were measured by orienting some of the foils perpendicular to the incident neutron beam. The experimental results are in excellent agreement with the predictions of the MARLOWE binary collision code, and indicate that the transverse range < x of approx.100 keV self-ions in Au is approximately one-sixth of the projected range