D7 diffuse scattering

Pleced on guide H15 a monochromator sent a beam towards the sample passing through a disk chopper. The elastic scattering resulting from magnetic and structural effects were measured in four sets of detectors placed around the sample. Data were initially sent to the NICOLE system, subsequently the PDP11/34 replacements. The instrument was later developed to include polarisation analysis increasing its versatility.

IN4 thermal beam TOF spectrometer

Neutrons from the reactor passed through two crystals, one of which at least was rotating (120Hz), to the sample, then a vertical plane secondary flight path of 4 m to the detectors. There were 67 position for the 48 boxes of 6 detectors. Data were sent to the NICOLE system, and later a PDP11/34 computer. Unlike IN5, which typically used wavelengths beyond the Bragg cutoff wavelength for aluminium, shorter wavelengths on IN4 gave rise to an unavoidable background from window scattering from the cryostats and reflections around the sample. As an example the scattering from a 10% vanadium scatterer was comparable to this unwanted wall-scattering, which was, of course, sample dependent. Spectroscopy up to 150 meV covered an interesting range for chemists, and physicists. A major experiment was the measurement of the structure factor of liquid rubidium (Egelstaff, Copley et al).
The instrument was later rebuilt in a horizontal detector plane and 2 m flight path, using a fixed crystal and fermi chopper.

IN7 statistical chopper

This instrument, with a single arm for detectors at 4m used a psuedo-statistical chopper to measure crystal fields. The cross-correlation was performed on a NOVA minicomputer. Any signal over the mean level was enhanced by the technique, which was hence useful for peaks arising from induced crystal field transitions.
The instrument was shut down when, with D5, the beam tube was reallocated to other instruments .