Neutron transmission through pyrolytic graphite monochromators

Thermal neutron transmission measurements have been made as a function of w avelength on a pyrolytic graphite monochromator crystal that has been set t o diffract a horizontal beam at different take-off angles. The major dips i n the transmission caused by the various reflections have been identified. These results can be used for the design of a beamline on which more than o ne instrument is placed. The transmission data show that it is best for the monochromator with the greatest (horizontal) take-off angle to be placed u pstream, with monochromators with decreasing take-off angles progressively further downstream. The order of instruments for which the wavelength is gr eater than 0.43 nm is unimportant.