  A neutron optical transport system is proposed which comprises nested short
elliptical mirrors located halfway between two common focal points M and M'. It
images cold neutrons from a diverging beam or a source with finite size at M by
single reflections onto a spot of similar size at M'. Direct view onto the
neutron source is blocked by a central absorber with little impact on the
transported solid angle. Geometric neutron losses due to source size can be
kept small using modern supermirrors and distances M-M' of a few tens of
metres. Very short flat mirrors can be used in practical implementations.
Transport with a minimum of reflections remedies losses due to multiple
reflections that are common in long elliptical neutron guides. Moreover,
well-defined reflection angles lead to new possibilities for enhancing the
spectral quality of primary beams, such as clear-cut discrimination of short
neutron wavelengths or beam monochromation using bandpass supermirrors.
Multi-mirror imaging systems may thus complement or even replace ordinary
neutron guides, in particular at the European Spallation Source.
