Angular distribution of ultracold neutrons produced by scattering of cold neutrons in superfluid 4He
Lamoreaux S. K., Golub R.
The angular distribution of ultracold neutrons (UCN) produced by the inelastic scattering of cold (8.9 A) neutrons in superfluid 4He has been calculated. These calculations have shown that this distribution is isotropic at zero UCN energy, while at the limiting velocity of UCN (8m/s) there is a 6% asymmetry in the forward-versus-backward directed UCN production rate. Although this is a relatively weak effect, it should be taken into account in accurate Monte Carlo simulations of proposed superfluid 4He UCN sources and in those that exist now.