Angle-dispersive time-of-flight diffraction in a pulsed beam: an efficient technology to exploit the thermal-neutron spectrum - design of a JULIOS diffractometer and experimental tests

The time- and position-resolving scintillation detector JULIOS was used for diffraction experiments in a pulsed neutron beam at the ISIS spallation source at the Rutherford Appleton Laboratory. Angle-dispersive time-of-flight measurements with samples positioned in the primary white beam were performed on standard materials and on zinc-containing spinel oxides; cation distributions of these compounds were determined by least-squares intensity refinements. The experimental setup was used for a comparison of results obtained using white-beam diffractometry at a pulsed spallation source and results obtained using conventional diffractometry with monochromatic neutrons at a continuous reactor beam. A gain by a factor of about 50 in intensity in favour of the white-beam technology was obtained when results were extrapolated for an equal time-averaged mean neutron flux. A JULIOS-type diffractometer was designed to take full advantage of the time structure of the ISIS frame.