On the morning of June 28, the first scientific research equipment of the high-energy synchrotron radiation light source, supported by the National Development and Reform Commission and undertaken by the Institute of High Energy Physics of the Chinese Academy of Sciences, was installed. This marks the fourth-generation synchrotron radiation source with the highest brightness in the world officially entering the equipment installation stage. On the same day, the advanced light source technology research and development and testing platform, which provided technical research and testing support capabilities for this large light source, was transferred to trial operation at the same time.
The high-energy synchrotron radiation light source is one of the major scientific and technological infrastructure projects of the country during the 13th Five-Year Plan period. The core installation of Huairou Science City. The project started construction on June 29, 2019, with a construction period of 6.5 years. When completed, the high-energy synchrotron radiation light source will become China’s first high-energy synchrotron radiation light source, one of the world’s brightest fourth-generation synchrotron radiation light sources, and will provide an important source of original and breakthrough innovative research in the fields of basic science and engineering science. Support platform.
What is a synchrotron radiation light source
According to electrodynamics, when charged particles move at variable speeds, they emit electromagnetic wave radiation. In actual operation, electrons In a circular motion in a magnetic field, the electrons emit X-ray photons along the tangential direction of the circular motion trajectory to obtain synchrotron radiation.
The synchrotron radiation source has excellent characteristics such as high brightness and broad spectrum, and it is the most versatile X-ray source. Since its application in the 1970s, it has become the largest scientific facility with the largest number of operating devices in the world, providing an advanced experimental platform for research in various disciplines.
In the 1940s and 1950s, with the development and needs of particle physics and nuclear physics research, particle accelerators appeared, in order to “store” charged particles conveniently In the experiment, the scientists use a magnetic field to make the electron beam move continuously in a circular motion in the storage ring. Long ago, theoretical physicists predicted that charged particles could emit electromagnetic radiation when deflected, but they have not been observed for a long time.
On a synchrotron of the General Electric Company in the United States, people have seen this kind of radiation for the first time. Because engineers suspected that there might be a short-circuit ignition inside the accelerator, and electron accelerators are all steel structures, if a short-circuit ignition occurs inside, the light emitted is invisible to the outside world, so the engineers specially installed an observation window on the machine. , As a result, as soon as the observation window was installed, there was light coming out. They thought it was a short circuit, but they couldn’t find it no matter how to investigate it. Later, they remembered theoretical physics.The charged particles mentioned by scientists can emit electromagnetic radiation when deflected.
Since this kind of radiation was first observed on a synchrotron, it is called synchrotron radiation, or synchrotron radiation for short.
Both are X-rays. What is the difference between the synchrotron radiation source and the X-rays emitted by CT during physical examination in the hospital?
Conventional medical CT emits X-rays, which use high voltage to accelerate electrons, and then allow the accelerated electrons to bombard metal targets (such as Cu, Mo, Cr, etc.) It produces X-rays, its production cost is low, and it has very good applications in medical imaging. However, because the X-rays obtained in this way are scattered in various directions, and various experiments are often carried out in only one direction, a problem arises. This kind of X-rays are scattered in a large range of angles, and the experiments require fixed directions. Its brightness is not enough.
The synchrotron radiation source is different. Its principle is that X-rays are emitted along the tangent of the circular motion when the electrons move in a circle. The angular range of the synchrotron radiation source is very Small, how small is its angle?
The conventional laboratory X-ray machine emits light at 180 degrees, and its brightness is about 109, while the synchrotron radiation light source has a light-emitting angle of only a few arc seconds (1 degree = 3600 arcseconds), X-rays are emitted at such a small angle, and its brightness can be increased to 1021 by the order of magnitude.
“The light source we are going to build in Huairou, its brightness is higher than 1021, it is close to 1023, so synchrotron radiation should be particularly bright. No. The second is that it has a particularly wide range, from the visible light band to the very high-energy gamma-ray band. Then its particularly wide band means that we can choose, because various experiments may require different wavelengths of light, you You can choose at will, so it brings a lot of convenience to our experiments.” said Dong Yuhui, deputy director of the Institute of High Energy Physics, Chinese Academy of Sciences, and executive vice president of high-energy synchrotron radiation sources.
Electromagnetic radiation is divided into different types according to frequency or wavelength. These types include (wavelength from large to small): electricity, radio waves, microwaves, terahertz radiation (THz) , Infrared radiation, visible light, ultraviolet rays, X-rays and gamma rays. The synchrotron radiation source is currently the only light source that can cover a wide spectrum range from THz to gamma rays and obtain high brightness.
Why is it easy to use
” The spectrum of synchrotron radiation is particularly wide, which means that we can choose what we need for various experiments The light of different wavelengths brings a lot of convenience to our experiments, especially those X-rays with very short wavelengths.” Dong Yuhui said.
Dong Yuhui gave an example of superimposing a 1mm iron sheet behind a 1mm thick iron sheet. If you take X-rays with a photon energy of 10KeV for perspective, this X-rays will be completely absorbed by an iron sheet, and nothing can be seen. If the photon energy is increased ten times to 100 KeV, and the wavelength of this X-ray will be shortened to one tenth, at this time, the shape of the second iron sheet can be seen through the first iron sheet.
“If we want to study the changes of an object in a certain environment, we need a container to simulate the environment, then you have to see the sample inside, you We need X-rays to penetrate the container and shine on the samples inside. Just like when we go to the hospital for examination, we need to see the bones through the muscles. At this time, we need our X-rays to have a relatively high energy and have a comparison. Good penetration ability.” Dong Yuhui said.
In general, the advantages of synchrotron radiation include:
High polarization: derived from the deflection magnet The synchrotron radiation light is completely linearly polarized light on the electron orbit plane. In addition, light of any polarization state can be obtained from a specially designed insert.
High purity: synchrotron radiation light is produced in ultra-high vacuum, there is no pollution caused by impurities, it is very pure light.
High brightness: The synchrotron radiation source is a high-intensity light source with high radiation power and power density. The X-ray brightness of the third-generation synchrotron radiation source is X-ray machine The fourth-generation synchrotron radiation source is 100-1000 times higher than the third-generation.
Narrow pulse: synchrotron radiation is pulsed light, with an excellent pulse time structure, and its width is 10-11～10-8 seconds (tens of picoseconds to several Ten nanoseconds) are adjustable, and the interval between pulses is on the order of tens of nanoseconds to microseconds. This feature is very useful for the study of “change processes”, such as chemical reaction processes, life processes, and material structure changes. And micro-processes of environmental pollution.
can be accurately predicted: the photon flux, angular distribution and energy spectrum of synchrotron radiation can be accurately calculated, so it can be used as a radiation measurement (especially vacuum ultraviolet to X-ray measurement) Standard light source.
In addition, synchrotron radiation also has unique and excellent properties such as high stability, high flux, microbeam diameter, and quasi-coherence.
Where is it used?
The synchrotron radiation source is an ideal multidisciplinary research platform. In all fields related to microstructures, such as physics, chemistry, life sciences and medicine, materials science and engineering, energy science and technology, earth and environmental science, nanotechnology, etc., synchrotron radiation sources have a very wide range of applications.
Using synchrotron radiation, Chen Junyuan, a researcher at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, and Xian Dingchang Institute, Institute of High Energy Physics, Chinese Academy of Sciences, have developed a new development for the entire field of micro-paleontology through cooperation. The direction of the research-the three-dimensional non-destructive imaging research of micro-fossils, has made a series of major discoveries in the field of paleontology.
The Cambrian explosion theory was once considered a serious challenge to Darwin’s theory of evolution, because paleontologists did not find the exact metazoan in the Precambrian strata Fossils prove the source of the Cambrian explosion.
In February 1998, the American “Science” and the British “Nature” magazine almost simultaneously reported on the Late Cambrian (Neoproterozoic Ediacaran) in Guizhou, my country. The discovery of “sponge animals” and “metazoan embryo” fossils from the Doushantuo Formation in Weng’an. The animal fossils in Weng’an are 40 million years earlier than the Cambrian, and are considered to be another great discovery in the paleontology of the 20th century.
If it can be determined that the two-sided symmetrical animals have appeared in the age of the Weng’an biota, we can further determine what stage they are in, which is a significant progress in understanding the development of early life. .
As the animal fossils in Weng’an are mainly animal eggs and embryos, adult fossils are very rare. In order to judge whether the two-sided symmetrical animals have appeared in the age of the Weng’an fauna, and to further determine the evolutionary stage they are in, Chen Junyuan has made unremitting efforts to find 10 “Guizhou Xiaochun insects” in Weng’an with a size of only 0.2mm. “Bilaterally symmetrical adult animal fossils. But this discovery did not convince allscholar. In order to find stronger evidence, Chen Junyuan focused his attention on the vast majority of eggs and embryos in Zhan Weng’an fossils.
Since each of these adult fossils is only 0.2 mm in size, Xian Dingchang puts forward the idea of using synchrotron radiation imaging to conduct three-dimensional non-damage research on paleontological fossils: use The high-intensity and highly penetrating X-rays generated by synchrotron radiation can take stereoscopic photos of fossils, which can prevent traditional fossil research methods from observing only the exterior, or performing destructive slices to observe internal irrecoverable defects. Moreover, the unique phase contrast imaging technology can improve the contrast and clarity of the image and perform high-precision three-dimensional imaging.
Chen Junyuan and Xian Dingchang’s cooperative team made three-dimensional imaging of concentrating leaf embryos on synchrotron radiation facilities in Beijing and Taiwan, and finally achieved an ideal image on the synchrotron radiation facility in Europe. image.
This not only provides new and reliable evidence for the evolutionary history of bilaterally symmetrical animals in the Precambrian, but also proves that organisms have evolved sufficiently complex before the Cambrian. However, due to various reasons, there are not many fossil traces left in certain geological ages, which strongly supports the correctness of Darwin’s theory of evolution.
Dong Yuhui introduced that due to the excellent penetrating ability of high-energy short-wave X-rays, synchrotron radiation sources are widely used in industry. “The synchrotron radiation source is not only used for laboratory research, but is really to solve the real problems facing industrial production.” Dong Yuhui said.
With the support of high-energy light sources, a large number of researches related to industrial development can be carried out smoothly: research on the structure of substances under real working conditions; material research (material genome, industrial component production) Structural changes in the process, structural changes in the service process, etc.); engineering materials (in-situ observation and structural analysis of the growth process of engine blades, real-time structural changes of structural materials, real-time observation of welds, etc.); real-time research on the catalytic process… …
Dong Yuhui introduced that in the research and development of new materials, the previous material research and development is called cooking-style research and development. This element is added a little more, the temperature is raised a little bit, oxygen or Nitrogen changes a little bit, just like changing the heat in cooking, adding some salt and adding some soy sauce, but the efficiency of this blind attempt is very low. With the help of synchrotron radiation light source, high-brightness and high-flux synchrotron radiation light is used for continuous testing. Can speed up the process of research and development of new materials.
Dong Yuhui also introduced the structural change research in the service process: “Whether it is aircraft engine orWhen should they be replaced during the course of their service? This is a very serious matter. When should the aircraft engine be replaced, it will be very expensive if it is replaced too frequently, and accidents will easily occur if it is not replaced. . So we want to see these real artifacts, they are really in service, and their various defects when they are working. For example, how does the crack occur? It needs to see its structural changes in a simulated environment, and a very high-end X-ray is needed to do this. It is impossible for these jobs to be done abroad, and they all involve some industries. The core secret of innovation and transformation can only be done by building our own synchrotron radiation device. ”
How to build to achieve maximum benefit
The size of the synchrotron radiation device is very huge, and the size of the X-ray machine in the general laboratory is about one or two meters. The circumference of the synchrotron radiation device can reach several hundred meters or even more than one kilometer.
The cost of a synchrotron radiation device is as high as several hundred million yuan, or even several billion yuan, and the annual operating cost reaches 10% of the construction cost. The operating life of the synchrotron radiation device It is very long, usually 30-50 years, and the huge construction and operation costs make synchrotron radiation devices often only built with national investment.
In addition to the high cost, another difficulty in the construction of synchrotron radiation devices is technical complexity. Involving accelerator-related magnets, power supplies, microwaves, vacuum, machinery, collimation, etc.; beamline stations related X-ray optics, detectors, precision machinery, weak signal measurement, automation, mass data processing, etc.; as well as air conditioning, water cooling , Compressed gas, low temperature, and even micro-vibration and settlement of infrastructure. Moreover, they are all the most cutting-edge technologies, so that the synchrotron radiation device requires a large team, and close cooperation can be completed and operated efficiently.
“Although this thing is expensive and complicated, it costs money to run, but its use is too wide, so today, synchrotron radiation device is the world’s Large installation with the largest number of operations.” Dong Yuhui said.
Dong Yuhui introduced that the four major synchrotron radiation devices (ESRF, APS, ALS, NSLS) in Europe and the United States have 20,000 users per year and 10,000 related experiments are conducted. Published 5,000 articles and published more than 200 papers in Science, Nature, and PRL every year, which has great support for many users.
The current synchrotron radiation in ChinaSources include: the first generation light source BSRF located in Yuquan Road Park, Beijing, the second generation light source HLS located in Hefei, and the advanced third generation light source SSRF located in Shanghai; the high-energy synchrotron radiation source (HEPS) currently under construction in Huairou, Beijing is one The fourth-generation synchrotron radiation source.
In simple terms, synchrotron radiation sources are divided into four generations: the first generation is a dual-purpose device parasitic on high-energy physical devices; the second generation is specially designed for synchrotron radiation Application dedicated light source; the third generation is a dedicated light source optimized for low emissivity and a large number of inserts; the fourth generation is a new generation of light source with the line radiation limit storage ring as the development direction, which will further improve the emissivity and brightness, and Realize the coherence of the light source.
Dong Yuhui introduced that because Beijing’s scientific research team is concentrated and has the strongest scientific research strength, but there is only one first-generation light source, the fourth-generation light source HEPS currently under construction in Huairou, Beijing, It is to meet the research needs of strong scientific research and industrial innovation teams in Beijing and surrounding areas. After completion, HEPS will be the world’s brightest synchrotron radiation source. It will provide an advanced platform for national and domestic needs and cutting-edge research. The construction process will also promote the development of domestic technology in many fields.
In the selection of construction standards, compared to the storage ring energy of Spring-8 in Japan, which is 8GeV, the APS-U in the United States is 7GeV, and the HEPS under construction in Huairou, Beijing The energy of the storage ring is 6GeV, which is also a choice for optimal economic efficiency.
Dong Yuhui introduced that higher energy means a wider spectral range, and the brightness of commonly used bands can also be improved, but it brings another price. The operating costs of the company have become particularly high.
“The question becomes whether we are worth spending so much money to pursue such a small performance improvement.” Dong Yuhui said, “Now the industry is more recognized The view is that 6 GeVs are a very suitable and reasonable energy zone after weighing the construction difficulty, performance, and price. The US APS will be upgraded, from 7 GeVs to 6 GeVs, and Japan is also preparing to upgrade, from 8 GeVs. Up to 6 GeVs.”
HEPS will be the world’s brightest synchrotron light source after completion. It will provide an advanced platform for national needs and cutting-edge research. The construction process It will also promote the development of domestic technology in many fields.
“In the process of building this light source, improve our country’s design and manufacturing capabilities in the technical fields of precision machinery, optical detectors, etc., This is where our country’s neck gets stuck. We need to use projects to drive the substantive improvement of these high-precision technologies in our country. “Dong Yuhui said.