Page 113 - Neutrons for Sciences and Society

Chapter 5: The construction of the reactor and the scientific groups
detector, and then VIVALDI and LADI III based on similar technologies. CYCLOPS, the most recent one, is equiped with CCD neutron detectors.]
3. Devices for diffuse scattering
Two instruments were designed for these studies
• The first, D11, was to measure small-angle scattering
to study large structures (e.g. viruses), or large inhomogeneities. The apparatus was designed at Jülich, and installed on one of the cold-source guides by Konrad Ibel, who arrived from Jülich at the beginning of 1970.
A rotating drum velocity selector acts as monochromator. The distances between the monochromator and the sample, and between the sample and detector could be as much
as 40 m. These distances could be reduced by inserting movable guides (before the sample) or moving the detector (after the sample). These huge distances had been proposed initially by Tasso Springer, and were supported by Maier- Leibnitz, since they allowed gains in intensity at the same resolution. I was, wrongly, of the opposite opinion. The detector was a two-dimensional multidetector with side dimensions of 64 cm created in collaboration with the detector group of the CENG. The instrument can also be used for diffraction by systems with a periodicity with a large lattice. This is essential, for example, to study vortex lines in type II superconductors in a magnetic field.
• The second, D7, also on a cold-source guide, was conceived for studying scattering from point defects. The design was refined at Jülich by Günter Bauer and later by Otto Schärpf. It was built by Wilhelm Just who came
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