Neutron scattering determination of local order in amorphous and liquid systems using a position sensitive detector

This paper consists of a description of the two axis spectrometer 7C2 on the hot source of the reactor Orphee at Saclay. Our main purpose will be to emphasize the problems due to the association of the position sensitive detector with various types of the sample environment. In order to determine the local order on disordered systems we need to use containers for the liquid state, furnaces for high melting point systems, etc... Even for amorphous materials, the use of a cryostat is often necessary to get rid of paramagnetic scattering or to reduce thermal excitations broadening the structure. We shall give some examples of experiments which have already been realized on this spectrometer and we shall try to point out some future possible developments