Calibration of a polarized neutron reflectometer

In a polarized neutron reflection experiment four reflectivities R-kl are d etermined, where k and l denote the spin state of the incoming and reflecte d neutrons, respectively, either parallel or anti-parallel to the guide fie lds along the incoming and reflected beam. A calibration of the setup is ne eded because the polarizer nor the analyzer are perfect and moreover the ef fective polarizing power of the polarizer and analyzer may depend on the no minal spin state of the incoming and reflected neutrons. It is shown that f our measurements without a sample and four measurements using a magneticall y saturated sample are needed to determine the five instrumental parameters that are relevant to interpret the results of a polarized neutron reflecti on experiment properly. For a time-of-flight reflectometer these parameters are wavelength dependent. (C) 2001 Elsevier Science B.V. All rights reserv ed.