What is the purpose of the HZB research reactor?

Neutron beams – prospects for research

The research reactor generates neutron beams for a wide range of scientific investigations. Just as X rays opened up new fields for observation in medicine, engineering, and science after their discovery at the turn of the twentieth century, neutron beams too present new prospects for research.

Model of the atomic arrangement in a lattice structure (silver iodide)

Application fields

The work on the Berlin research reactor ranges from pure research to application-oriented investigations. All material is made up of atoms. In the various materials their arrangement presents characteristic patterns. In addition they move and vibrate. The configuration of atoms is decisive for the properties of the substances they make up, and their movements give rise to heat effects. In order to understand better the properties of materials and these heat effects we must study the configurations and movements of their atoms. To do so science makes use not only of X rays and electron beams, but also of neutrons, which so to speak function as probes when they penetrate the inside of materials.

Neutron scattering

When neutrons and atoms collide the neutrons scatter – they “rebound” in a characteristic fashion. Scientists can then analyse the type of scattering to obtain information on the arrangement of atoms and their behaviour in the various materials. In a typical scattering experiment neutrons coming from the reactor core pass through a beam hole to a so called monochromator. This reflects neutrons with a particular speed to the test specimen, where they are scattered. The distribution of scattered neutrons is measured with detectors. The scattering curves thus obtained can be analysed to determine the atomic arrangement in the test piece.

Neutrons from the reactor core collide with atoms in the test piece. The neutrons scatter and are registered in detectors. The type of scattering allows insights into the atomic and molecular structure of various substances.

Schematic of the scattering experiment


Neutrons alone are sufficient to verify light atoms, e.g. hydrogen, in an atomic structure. Neutrons alone are sufficient to differentiate between similar metal atoms and to determine the magnetism of individual atoms. Neutron scattering therefore affords contributions to chemistry, biology, metal sciences, and solid state physics that cannot be obtained in any other manner.

The cold source

When installed a so called cold source that greatly reduces the speed of neutrons also allows users to:

  • study the movements of atoms,
  • determine the structure of highly complex atomic configurations, e.g. the thread molecules of plastics or the macromolecules of biological substances,
  • explain structural defects in atomic arrangements as they occur in solid bodies at high temperatures or under irradiation.

The research reactor however does not serve the development or testing of nuclear technology.

International research groups

The research reactor is used by various scientific disciplines and to a considerable extent by research groups from abroad. Accordingly the array of scientific instruments at the HZB should not only cover the needs of these work groups, but also meet the wishes of universities and institutes abroad.

The research reactor generates neutrons. These neutrons serve science so to speak as a probe for the inside of materials. Neutron scattering cannot be replaced with any other method in chemistry, metal science, or solid state physics.

How does a nuclear reactor work?