Neutronenarme

Neutronenarme are components of neutron facilities that generate, transport, and shape neutron beams from the source to experiments. They form the neutron-optical section between the reactor or spallation target and the experimental station, guiding neutrons while preserving flux and beam quality.

Most neutronenarme consist of long evacuated tubes (neutron guides) whose inner walls are coated with neutron-reflective materials. Neutrons reflect at grazing incidence, so guides use supermirror coatings (multilayers such as Ni/Ti) to extend the critical angle. Guides can be straight or curved to suppress direct line of sight to the source, reducing background. Assemblies of guides deliver beams to multiple instruments. Performance depends on neutron wavelength, coating quality, surface roughness, and losses from absorption and scattering.

Applications include neutron diffraction, inelastic scattering, reflectometry, and imaging (neutron radiography and tomography). Neutronenarme enable higher flux and controlled divergence, allowing detailed studies of crystal structures, surfaces, polymers, biology, and materials under extreme conditions.

Construction and safety involve shielding against fast neutrons and gamma radiation, activation management, and appropriate ventilation and monitoring. Guides operate in vacuum or inert gas to minimize scattering. Alignment, calibration, and maintenance are essential for stable performance.

Notable facilities with extensive neutron-guide networks include the European Spallation Source (ESS) and the Institut Laue-Langevin (ILL), as well as national reactors and spallation sources.