The cold neutron transmission through a monolithic polycapillary lens
is studied by scanning a pinhole beam across the entrance cross sectio
n of the lens. The relative transmission as a function of bending radi
us of a tapered channel is obtained. The results are explained in term
s of a reduced critical angle for total reflection for the tapered cha
nnels. A technique for qualitative examination of monolithic lenses is
proposed. (C) 1997 American Institute of Physics.