Temporary Polarisation Insert for a Time-of-Flight Neutron Reflectometer

The suitability of a transportable 3He-spin filter as broadband polariser for a Time-of-Flight neutron reflectometer in combination with a proposed characterisation method for 3He-spin filters is presented. Both, the experimental simplicity and the data treatment procedure for extracting the spin-up and spin-down neutron reflectivity from measurements obtained for a time dependent 3He polarisation, are shown. For benchmarking, the extraction of a very weak magnetic signal from reflectivity data, measured on the magnetic heterostructure Fe(1nm)/Cu(20nm)/Si(substrate) in an externally applied magnetic field of 30 mT is demonstrated and compared to similar measurements on Cu(20nm)/Si(substrate), which show no magnetic signal.