Neutron Scattering - JUWEL - Forschungszentrum Jülich

HEiDi 17
6 Experiment Procedure
During this practical course not all physical and technical aspects of structure analysis with
neutrons can be discussed in detail. Nevertheless this course is supposed point out the basic
similarities and dissimilarities of x-rays and neutron radiation as well as their specific
advantages and disadvantages in general and referring to single crystal diffraction. The
sample selected for this practical course is most suitable for this purpose because of its special
crystallographic peculiarities.
6.1 The Instrument
Fig. 5 shows the typical setup of a single crystal diffractometer with a single detector.
Outgoing from the radiation source a primary beam defined by primary optics (in our case the
beam tube) reaches the single crystal sample. If one lattice plane (hkl) fulfills Braggs laws, the
scattered beam, called secondary beam, leaves the sample under an angle 2� to the primary
beam. The exact direction of this beam depends only on the relative orientation of the sample
to the primary beam.
For the diffractometer shown in fig. 5 the movement of the neutron detector is limited to a
horizontal rotation around the 2� axis. Thus, only those reflections can be measured, whose
scattering vector Q lies exactly in the plane defined by the source, the sample and detector
circle. This plane is also called scattering plane.
Fig. 5: Scheme of a single crystal diffractometer