At the GSF, an irradiation facility has been established which allows
one to test and calibrate neutron measuring devices under realistic ne
utron field conditions. It consists of an accelerator neutron source,
an irradiation cavity, and a variable moderating assembly. As a first
approach to spectra observed in reactor environments, a simple set-up
of heavy water, polyethylene and iron shields was installed. The spect
ral neutron fluences were measured with a Bonner spectrometer and part
ly verified by Monte Carlo calculation.