The use of a pseudo-random spin flipper sequence on a polarised neutron scattering instrument

The LONGPOL polarised neutron diffractometer uses a pseudo-random sequence to switch a spin flipper on and off. Cross correlating the data collected with the flipper gating sequence gives a time-of-flight spectrum permitting energy analysis of the scattering. This allows the simultaneous measurement of elastic and inelastic scattering events. For the measurement of quasi-elastic scattering, this energy analysis permits the detection of any inelastic scattering events which would affect our measurements if we had no energy analysis. We describe the instrumental arrangement and give examples of the measurements possible with this technique. (orig.)