What is a beamline?

After its production in the accelerators, the synchrotron light is guided to the experimental stations, called Beamlines, installed around the Storage Ring. It is in the beamlines that the radiation passes through the samples to be analyzed.

Synchrotron Light Sources can accommodate several beamlines, and experiments are carried out using different techniques, such as Spectroscopy (from Infrared to X-rays), X-ray scattering, crystallography, tomography and others.

The technical requirements of a beamline depend on the characteristics of the light beam that will be needed to illuminate the samples in the analysis to be performed (such as energy resolution, size and divergence), as well as their interaction with the detection system.

Each beamline is composed of four main systems: the radiation source, the front end, the optics and the experimental station (with its detectors and sample holders), as well as a set of infrastructure elements.

Radiation Sources and front-end

The source of radiation is the component that accelerates electrons using intense magnetic fields in order to make them produce electromagnetic radiation. This component may be a magnetic dipole of the magnetic lattice of the storage ring or an insertion device: a wiggler or an undulator.

The front end is the first set of components, still inside the accelerator shield, which separates the vacuum chamber from the storage ring from the rest of the beamline. The synchrotron radiation produced by the radiation source goes through on the front end, and its main function is to limit the range of synchrotron radiation according to the range of energy used in the beamline.

Optics

Before reaching the sample, the synchrotron radiation has its electromagnetic spectrum “filtered” according to the experimental technique used. The optical portion of the beamline “molds” the light beam to deliver it in the form required by the experiment, by collimation and focusing of the beam and selection of energy. These components are housed in radiological protection huts and are subject to precise control of temperature, humidity and particulates.

Monochromators: This element filters a range of wavelengths of the source spectrum, and operates based on the principle of diffraction of electromagnetic radiation. They allow selection of the desired wavelength, be it infrared, ultraviolet or X-ray radiation.

Mirrors: This are optical elements used throughout the beamline to geometrically shape the synchrotron light beam for the conditions required in the experiment (such as size and divergence of focus).

Experimental Station

The experimental station is the section of the beamline where the samples are analyzed. It is an isolated environment, equipped with radiological protection and precise control of temperature, humidity and particulates. It is the most dynamic part of a beamline, since each new experiment defines specific conditions for the conditioning of the samples (which may be in different physical states) and for the detection systems, aiming at the observation of different aspects of the interaction of the Synchrotron light with matter.

Positioning Systems and Sample Environments: These systems are used to position the samples in front of the light beam, often with submicron resolution. Such systems include furnaces and cryostats for temperature conditioning, devices for deformation or application of high pressure and electric and/or magnetic fields for in situ or in operando experiments.

Detectors: These devices quantitatively analyze the result of the interaction between the Synchrotron Light and the atoms of the material, by either diffraction, absorption or fluorescence. They include CCD-type area detectors or photon counters; diffractometers for positioning detectors; multi-channel scintillators, photodiodes, ionization chambers, etc.

The set of all these equipment allows a quantitative description of the types of atoms and molecules that constitute a given material, their chemical states, spatial organization, magnetic properties, etc.