We present a first experimental demonstration of a new method to extract a well-collimated beam of ultra-cold neutrons (UCN) from a storage vessel. Neutrons with too large divergence are not removed from the beam by an absorbing collimation, but a diffuse or semidiffuse channel with high Fermi potential reflects them back into the vessel. This avoids unnecessary losses and keeps the storage time high, which may be beneficial when the vessel is part of a UCN source with long buildup time of a high UCN density.
@article{arxiv.physics/0703079,
title = {Efficient extraction of a collimated ultra-cold neutron beam using diffusive channels},
author = {P. Schmidt-Wellenburg and J. Barnard and P. Geltenbort and V. V. Nesvizhevsky and C. Plonka and T. Soldner and O. Zimmer},
journal= {arXiv preprint arXiv:physics/0703079},
year = {2009}
}