Disciplines
Physics, Astronomy (100%)
Abstract
Neutron optics has developed into an important research field for its great potential applications. Neutron
diffraction is a well-known and widely applied neutron-optical effect. For cold neutron diffraction perfect single
crystals are not suitable because of the too small lattice periodicity. Recently, Prof. R. A. Rupp and his co-workers
proposed that the neutron photorefractive effect, i.e. a light-induced change of the neutron-refractive-index, can be
used as an effective technique to obtain phase gratings for cold neutrons. Recently ionic gratings caused by light-
induced ionic charge transport were obtained in the first one-dimensional ionic conductors (a -LiIO 3 crystals) and
thermally fixed. These gratings are very promising for cold neutron diffraction. In order to study the phase grating
for cold neutron diffraction in the a -LiIO 3 crystals, we will study the neutron photorefractive effect in details. The
following investigations will be carried out:
(1) Ultraviolet photorefraction and the superionic phase transition of a -LiIO 3 crystals. In order to clarify the
relationship between the two effects, I will study the temperature dependence of physical quantities (e.g. the
dielectric permeability of a -LiIO 3 crystals) and their inter-relation.
(2) Doping of a -LiIO 3 crystal with transitional metals (Mn, Fe, Cr, Cu, etc.). By repeating the holographic
recording experiments in different crystals with different dopants and dopant concentrations, it is expected to
determine the optimum dopant and its optimum concentration in a -LilO 3 crystal for efficient holographic
recording.
(3) Recording and fixing of phase gratings for cold neutron diffraction. In order to achieve homogeneous gratings
with large sizes (several cm2 ), large reflectivity (in the percentage range) and small grating periods to obtain
strong cold neutron diffraction, I will apply special holographic recording techniques and thermal fixing techniques
to get a long-time stable phase grating.
(4) Cold neutron diffraction The phase gratings will be tested in diffraction experiments with cold neutrons. The
results will help us to understand the mechanism of the neutron photorefractive effect in a -LilO 3 crystals.