beamline

A beamline is a dedicated optical and experimental facility that guides a particle or photon beam from a primary source to an experimental endstation where measurements are made. In large research facilities, beamlines are attached to accelerator-based sources such as synchrotrons, spallation neutron sources, or free-electron lasers, and are optimized for specific scientific techniques.

A beamline comprises the beam source or its extraction point, a transport system of vacuum pipes and magnetic or electrostatic elements, optical components that shape and condition the beam, diagnostics to monitor intensity and position, and an endstation where instruments and samples are located. The transport system preserves beam quality, while optics control energy, bandwidth, and focus.

Photon beamlines at synchrotrons use bending magnets or insertion devices like undulators and wigglers to produce bright X-ray or ultraviolet radiation. Neutron beamlines at spallation or research reactors deliver neutrons. Free-electron laser beamlines generate ultrafast, highly coherent pulses. Common optical elements include mirrors, monochromators, lenses, phase plates, apertures, and filters.

Endstations host experimental apparatus such as X-ray diffractometers, spectrometers, tomography and microscopy setups, small-angle or wide-angle scattering instruments, and detectors for photons or neutrons. Techniques include crystallography, spectroscopy, imaging, scattering, and diffraction experiments, often with sample environments like temperature control or pressure cells.

Beamline operation requires precise alignment, vacuum integrity, radiation safety, and remote control and data acquisition systems. Beamlines are carefully commissioned and operated by user programs, with proposals, scheduling, and data management. They form a core part of modern facilities enabling high-brightness, time-resolved, and in situ measurements.