The 3He polarizing filter on the neutron reflectometer D17

The D17 neutron reflectometer at the Institut Laue-Langevin, Grenoble, can now carry out neutron polarization analysis experiments with a polarized 3He gas filter. The cell containing the gas is housed in the evacuated detector tank. The gas polarization decays with time and must be replenished periodically. A novel method to accomplish this in situ, known as local filling, has been developed to minimize down-time on the instrument. The instrument is now optimized for the rapid collection of off-specular scattering with polarization analysis, complementary to a polarizing supermirror analyser which is used for measurements of specular reflectivity. Cell performance, test and experimental data are presented, along with methods for analysing the data collected using the filter.