Characterization of the wavelength spectrum of guided neutron beams

A simple method is introduced for the determination of the effective temperature of neutron beams. It is mathematically derived that the thermal equivalent neutron flux measured with a thin foil made from a 1/ν-nuclide is proportional to the product of the real flux and the average wavelength. The real flux can be determined using fully absorbent materials. From the ratio of the two fluxes the average wavelength and the effective temperature can be determined. The method has been tested in thermal and cold neutron beams. (author)