  The NeXus format allows the storage of measured data next to a description of
sample and instrument setup in a standardized manner. The NeXus standard itself
gives only general rules how an instrument setup is described. A so called
instrument definition contains a minimal set of information and the location of
that information within a file. In this paper instrument definitions for
neutron triple-axis and time-of-flight reactor machines are suggested.
Furthermore a structure for the storage of instrument logbook information is
presented.
