Throughout history, people have studied nature using visible light, that is, they have used the light that we can see with our eyes. However, the light we see is part of a much wider spectrum. Electromagnetic waves (EM) ranging from radio waves to gamma rays make up this spectrum, different wave types have different wavelengths as seen in Figure 1. Visible light is a very small part of that spectrum. The smaller the wavelength of the radiation we use when examining nature, the smaller the details we have of the material we are examining.

The introduction of synchrotron radiation (SI) sources has revolutionized the range of EM radiation we can use in research.

Types of electromagnetic waves

Figure 1. Types of electromagnetic waves, the scales on which wavelengths coincide, and the radiation region provided by synchrotron radiation sources

As we can see from this figure, synchrotron laboratories provide photons (radiation) in the wavelength range of 10 -5 -10 -11 m, making it possible for us to investigate the detailed structure of any material. In this way, the fields in which SI is used exhibit a wide spectrum from medicine to archaeology, from materials science to art, from environmental sciences to energy. There are more than 50 SI sources on Earth .

What is synchrotron radiation?

SI is electromagnetic (EM) radiation emitted by rapidly moving charged particles approaching the speed of light in a circular orbit with high intensity and wide energy range tangentially to the orbit. We can compare SI sources to giant microscopes. We can show the structure of this giant microscope with a diagram like Figure 2.

synchrotron radiation sources
Figure 2. Scheme showing the main elements in synchrotron radiation sources

Electrons from an electron gun are boosted to an energy level of about 100 MeV by a linear accelerator, where they are transferred to the voltage-amplifying amplifier ring and from there to the storage ring, where they are placed in a circular orbit to obtain synchrotron radiation. The energy of the electron beam in the storage ring can vary between 1 and 8 GeV, depending on the designs of the rings in different laboratories. Motion in a circular orbit is achieved by lattices of electromagnet groups around the storage ring, and the energy lost by SI is supplemented by radio frequency (RF) cavities. Electrons moving at a speed close to the speed of light propagate tangentially to the orbit in a narrow conical volume in the SI direction of motion. The intensity of radiation is proportional to the fourth power of the energy of the electron beam. In other words, the higher the electron energy, the stronger the radiation we get. Since the energy of the electron is directly proportional to the radius of the orbit, the energy increases as the radius increases. As can be seen from Figure 3, SI sources all over the world are placed in large round buildings.

Figure 3: Examples of SI laboratories around the world. (a) Spring8 Japan Harima, Japan. Storage ring energy 8 GeV, ring circumference 1.4 km (Wikipedia) (b) Diamond Radiation Source , Oxford, England. Storage ring energy 3 GeV, ring circumference 561.6 m (c) ALS Berkeley , USA. The energy of the storage ring is 1.9 GeV, the circumference of the ring is 198 m.

Various beamlines and test stations are set up on the storage ring in order to be able to perform experiments/measurements in different areas and to benefit from the different features of SI (Figure 2). Optical systems in the beamlines allow us to choose the wavelength to be used or to scan the wavelength. These assemblies are installed in radiant-proof lead-walled chambers, where users do not have access. According to optical setups, it is possible to use techniques such as X-ray diffraction, absorption, scattering, fluorescence absorption spectroscopy, infrared spectroscopy and microscopy, photo emission spectroscopy in beam lines. At the experimental stations where the samples meet the radiation, the temperature we want the sample to be in, There are structures where we can control environmental conditions such as pressure, etc., and detectors that collect signals from the sample. The walls of these chambers are also lead and the users leave here before the experiment starts and the sample is irradiated and they have no access to it during the experiment.

When we look at the research areas and the types of experiments that can be done, we see that the synchrotron laboratories create a colorful environment suitable for interdisciplinary studies, where users can share their experiences in different fields of expertise.

Synchrotron radiation properties

About 10 synchrotron laboratories in the laboratory from a tool main reason for the very common throughout the world 18 in order more powerful X-ray (X-ray radiation) producing. Since its discovery by Wilhelm Rontgen in 1895, X-rays have been used as an important tool to examine the structure of all types of organic (bone, lung, cell, etc.) and inorganic (metal, glass, gas, etc.) materials. In fact, as we can see from Table 1, if we examine the Nobel Prizes, we observe that the number of studies using X-rays originating from the laboratory and SI* in the following years is high.

As for SI, although it has been conceptually defined since the end of the 19th century, it was first observed experimentally in 1947 at the General Electric Research Laboratory (NY, USA) during the development of a closed-loop strong X-ray source [2] . Although this radiation was considered as an undesirable energy loss in ring accelerators, which were considered as X-ray sources at first, the broad spectrum and application potential of SI was realized after a while.

The multi-purpose use of synchrotron laboratories is due to the unique properties of the obtained radiation.

  1. High beam intensity directed across wide energy range: Focused propagation of SI from the source causes a high number of photons in a small volume to be collected by the optical elements and a large number of photons to be incident on the sample. Its high photon density enables systematic data collection in a short time, even from materials with weak beam diffraction. For example, with a laboratory device, it is possible to make measurements that take hours from biological samples in seconds in the synchrotron. Its wide energy range enables the examination of different properties of materials by utilizing radiation of different wavelengths. For example, with infrared spectroscopy, it can be determined which elements the material consists of, the molecular structure of the material can be examined by X-ray diffraction, or the bond structures between molecules can be determined by X-ray absorption.
  2. Pulsed radiation: Since electrons pass through the experimental stations where the radiation is collected, at nano/picosecond intervals, it is possible to examine the reactions taking place in this time scale.
  3. Polarized radiation:   When we look at the electron orbit, the radiation shows linear polarization in the orbital plane and elliptical polarization outside this plane. By making use of this property of radiation, we can obtain information about the bonds and molecular structure in molecules.

Examples of usage areas of synchrotrons

Applications in different fields require different designs and arrangements for placing samples in the SI path and collecting data at experimental stations. For example, a frequently used application in molecular biology research is to determine the protein structure and to design drugs suitable for this structure. In this case, the protein crystals are frozen to protect them from radiation damage, and the data is collected at low temperature under a stream of liquid nitrogen using a complex system. In order to quickly collect data from large numbers of crystals, samples are placed in X-rays with robotic systems, data collection takes only seconds, and the first stages of data analysis are automated.

Another example of the use of Synchrotron radiation is the study of catalyst reactions, which have come to the fore in recent years due to bottlenecks in the environment and energy. In researches on the structures of zeolite heterogeneous catalysts used to separate crude oil more efficiently and quickly, rapid progress has been made with the data obtained from Synchrotron radiation sources. In these studies, time-dependent measurements are made by using X-ray fluorescence, reflection, diffraction and emission methods in a complementary way, and it is possible to understand the effects of different sized voids in the catalyst structure on the reactions [4] .

a Patch of Grass by Vincent van Gogh Paris Apr June 1887 oil on canvas 30 cm 40 W640
Figure 5. Finding the lost painting of Vincent Van Gogh (a) Piece of Grass, Paris, April-June 1887, oil painting, 30-40cm, Kröller-Müller Museum, Otterlo, The Netherlands. (b) Portrait of woman hidden in the background of Piece of Grass CC-BY-ND (Source: Looking over the artist’s shoulder )

Another application is the ability to examine works of art and archaeological objects without destroying them. With these applications, which are a bit like detective work, it is possible to make visible what we cannot see with the naked eye. Non-destructive imaging was already done using conventional X-rays in museums, but it was not possible to obtain a detailed image by distinguishing the different pigments of the paint on the painting. Working together, art historians and synchrotron physicists (with synchrotron resources in the USA, Germany, and France) broke new ground in methods for imaging substrates. A good example is Vincent van Gogh’s painting “Patch of Grass” in Figure 5(a). It is known that the artist painted different paintings on the same canvas in the early periods, and it is estimated that 1/3 of his first paintings were in this situation. In this image, it was predicted from images obtained by conventional X-ray scanning that another image might be hidden behind the grass. Examining the region using infrared radiation imaging at the synchrotron, element-specific fluorescence mapping for pigments, and X-ray microscopy, combining the results revealed the animation seen in Figure 5(b). Thus, the missing link in a series of portraits of peasant women by Van Gogh was found. Combining the results for the pigments by examining the element using specific fluorescence radiation mapping and X-ray microscopy revealed the animation seen in Figure 5(b). Thus, the missing link in a series of portraits of peasant women by Van Gogh was found. Combining the results for the pigments by examining the element using specific fluorescence radiation mapping and X-ray microscopy revealed the animation seen in Figure 5(b). Thus, the missing link in a series of portraits of peasant women by Van Gogh was found.[5] .

Our last example is BC. It is about the lost document containing the writings of the 3rd century Greek mathematician Archimedes on the concept of infinity, floating bodies, intersecting planes, and other topics. Parchment documents written by Archimedes using iron-containing ink, MS. It was compiled into a book in 530 BC in Constantinople and AD. A copy of this book was prepared in 950, again as a manuscript.

Archimedes Palimpsest
Figure 6. A page showing Archimedes’ writings on floating bodies. ( Wikimedia Commons )

Records show that the copy went to Jerusalem in the 1200s, where the skin was damaged and the pages were separated, cleaned with a weak acid, and used as a prayer book, this time again with iron-containing ink on it. The adventures of these pages are then quite complex, but eventually, in 1998, an unnamed millionaire loaned them to the Walters Art Museum in Baltimore. Then archeologists, philologists, physicists and material scientists come together in the above-mentioned Van Gogh painting methods that we various synchrotron radiation light using Archimedes’s work day took out .

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