Apparatus and methodological developments at neutron and synchrotron radiation sources

For structural research with atomic resolution, neutron and synchrotron radiation sources have brought about a surge in evolution. The diffractometers, initially based on conventional X-ray instruments, were soon adapted to the special radiation properties.

An important step for neutron scattering was the construction of the high-flux reactor at the Institut Laue-Langevin in Grenoble. After structural analysis with regard to light atoms, in particular hydrogen isotopes, initially predominated, the use of the continuous neutron spectrum, including shifting its intensity maximum by “hot” and “cold sources”, the time structure of pulsed sources, the magnetic moment (magnetic structures, polarized neutrons) and the easily measured energy transfer by inelastic neutron scattering (dynamics, see Section 8) gained increasing importance. The deficit of neutron sources in Germany that has existed for years has delayed new developments and thus created a backlog. The design of new methods and instruments for spallation neutron sources is another challenge for the coming years.

Crystallography with synchrotron radiation is almost exclusively performed in the medium- to short-wave X-ray region with a particle energy E>2keV, in Germany mainly at HASYLAB at DESY. It requires compatibility of the devices with the special radiation properties and thus is often a departure from traditional instrument types. Synchrotron radiation enables qualitatively new experiments: use of the tunability of primary radiation (e.g. for energy dispersive powder diffraction, anomalous dispersion, EXAFS), its collimation (e.g. high resolution, interferometry, standing waves), its polarization (non-Bragg scattering, atomic anistropies, X-ray crystal optics) and the time structure (kinetics). These branches of research are currently developing rapidly.

For both types of radiation, there is an intensive interaction between the construction of new radiation sources, especially so-called “dedicated sources” (in Europe e.g. the European Synchrotron Radiation Facility, Grenoble), the design of instruments and the development of new methods by physicists and crystallographers.