Crystal-GRID: Current status and prospects for experimental studies of atomic collisions in solids.

The Doppler effect of electromagnetic radiation represents a very direct indicator to study the motion of emitting particles. In the Crystal-GRID technique one uses the ultra high resolution power of the crystal spectrometers GAMS4 and GAMS5 to measure the Doppler broadening of $\gamma$ radiation emitted from excited nuclei. Thus it represents a new nuclear probe for the direct study of atomic motion in solids at kinetic energies of several hundreds of eV.

A detailed description of the experimental technique will be given together with an overview on already performed experiments using massive single crystals
of TiO2, NaCl, Ni and Cr. In these experiments the comparison of experimental data to predictions deduced from Molecular Dynamics simulations has allowed to obtain new repulsive interatomic potentials.

The currently used double flat crystal geometry of the spectrometers has allowed to use only massive targets. Recent technical improvements of the GAMS5 spectrometer towards a double bent crystal geometry
will allow to extend the technique to studies of crystalline layers as they may result from ion implantation. The current status of the spectrometer and the expected capabilities will be presented.