Production Public Number: ” SELF Gezhi On the Road Room “( ID: SELFtalks) , author: Chen and Health, Chinese Academy of Sciences, the spallation neutron source Engineering command commander. Cover: Vision China
“About half of the physical and chemical Nobel Prizes are related to large scientific devices. Or the proposed new ideas have been validated on large scientific devices, or large scientific devices provide the most advanced research methods. Found major scientific breakthroughs or get new technology inventions.”
Chinese spallation neutron source
This is a Chinese spallation neutron source located in Dalang, Dongguan, Guangdong. It covers an area of about 400 acres and is a typical large scientific device. In front of it, it is the branch line of the Pearl River Delta Ring Expressway G94 – 9411, connecting Humen and Huizhou.
Why do we build a spallation neutron source? Why did we choose Dongguan in Guangdong? What is the result of our construction? What is the preliminary experimental result?
Twentieth Century: The Century of Physics
The physics of the 20th century has experienced three major leapfrogs, from atomic physics to nuclear physics, and then to particle physics. A hundred years ago, we discovered that atoms are composed of nucleus and electrons. Later we discovered that nucleus is composed of protons and neutrons. Since the 1960s, we have gradually discovered that protons and neutrons that make up the nucleus are composed of quarks.
It should be said that the three leaps of physics in the 20th century have yielded enormous research results and have been transformed into enormous productivity. For example, nuclear power, semiconductors, lasers, computers, GPS, etc., which are widely used nowadays, are inseparable from the progress of physics in the past century.
At the same time, these technologies have had a profound impact on society and politics. On the one hand, nuclear weapons have always been a very serious international political issue. On the other hand, the Internet we use so widely is also invented in the study of physical structure of physics in the last century.
The three leaps of physics not only provide services for the development of physics, but also produce advanced research methods, including large-scale scientific devices such as synchrotron radiation sources and spallation neutron sources.
Why build a large scientific device?
As the study of the structure of matter goes deeper into the nucleus and particle hierarchy, we need more and more energetic particles to study smaller and smaller scales, which requires the use of large scientific devices.
The construction of China’s large scientific equipment originated from the Beijing positive and negative electron collider. This is a major decision of Comrade Deng Xiaoping in the mid-1980s. He says:”We are building a positive and negative electron collider in order to give China’s high technology a place in the world. “It should be said that this strategic goal is gradually being realized.
There are two types of large scientific devices, one is the accelerator for particle physics and nuclear physics, the nuclear fusion device, the large astronomical telescope such as the “Eye of the Sky” in Guizhou, and the other is the synchrotron device, spallation neutron Source, free electron laser, etc.
The large scientific device is called “major scientific infrastructure” and “big science project”. It has become one of the key units of the national science and technology innovation system and a symbol of the country’s comprehensive strength.
For decades, major scientific breakthroughs have been made in research based on large scientific devices. The construction, operation and research of large devices have produced many major scientific and technological innovations, which have effectively promoted the development of high technology.
According to statistics, about half of the Nobel Prize in Physics and Chemistry is related to large scientific devices. The proposed new ideas have been validated on large scientific devices, or large scientific devices have provided the most advanced research methods, and have discovered major scientific breakthroughs or new technological inventions.
What is the spallation neutron source? What is the use?
1994 Nobel Prize in Physics
Neutron scattering is a super microscope that detects matter. Brockhaus in Canada and Shahr in the United States first proposed this innovative idea. Brockhaus suggests that neutron scattering can detect the position of atoms, molecules, and their clusters, and Schal believes that not only can it detect position but also its motion. So they won the Nobel Prize in Physics in 1994.
Why use neutron scattering to study the structure of matter? The means of studying the material structure are now mainly the synchrotron radiation source and the spallation neutron source.
Synchronous radiation is used to detect the distribution of electrons outside the nucleus, while neutron scattering can measure the direction and energy distribution of the neutron and sample nucleus. It can detect the magnetic properties of the material, the position of the nucleus, and large engineering samples. Because of its good penetrability, it also detects dynamic processes in matter.
Compared with the synchrotron radiation source, the spallation neutron source has high cost, complicated technology, and difficult detection, and the experiment is difficult. Therefore, there are only 4 sparse neutron sources in the world, and about 60 synchrotron radiation sources. However, many of the key issues of cutting-edge science and the bottlenecks of the continued development of the national economy and national security can only be solved by sparse neutron sources.
Where does the neutron come from? One way is the reactor. The Molecular Energy Research Institute in Mianyang, Sichuan and Beijing has reactors. It is produced by chain reaction, and there are about 30 in the world.
Another way is spallation neutron source. Particles are used to lift metal targets. They do not use nuclear fuel, they are not nuclear devices, so they have low safety requirements. It is difficult to find a place to build a reactor in the world. Therefore, neutron research is slowly developing towards spallation neutron sources, and its advantages are many.
How does the spallation neutron source work? We use high-energy protons to target, the neutrons we generate will hit the sample, and then we will detect it.
What is the role of neutrons? The first is that it has a magnetic moment, so it can study the magnetic structure. Computer storage is a magnetic material, and superconductivity is also closely related to magnetism, so it is a key technology for studying magnetic materials.
The second is that it distinguishes between light elements and isotopes. As you can see, the reaction cross section of neutrons with various nucleuses varies greatly. Unlike synchrotron radiation, which is proportional to the square of the charge of its nucleus, it is not sensitive to light elements.
For example, lysozyme protein molecules, with synchrotron radiation, you can’t see carbon, oxygen, or nitrogen, but with spallation neutron sources, hydrogen atoms are seen, and the things you get are much richer. Similar high temperature superconductors and other various structures require spallation neutron sources.
For example, everyone is very concerned about combustible ice, which is an energy source that can provide us with clean and sustainable development. But we need to understandSub-source: In-situ measurement of temperature and stress distribution during welding and riveting of A380 wing, optimization process
An interesting example is the British spallation neutron source. Welding and riveting of the Airbus A380 wing. The welding and riveting process is very complicated. For example, the riveting is light and there is no riveting, and the riveting is heavy, which may cause the riveting place to be easily broken in the future. The same is true for welding. Airbus put a section of the A380 wing into the British spallation neutron source, riveting it, welding it, and measuring its temperature and stress changes, resulting in the best process.
There are also Japanese spallation neutron sources, which do very interesting things. The key to electric vehicles lies in the battery. How can the battery capacity be large, charging fast, and safer? On the one hand, we need to find better materials, and more importantly, we must study how to make batteries, depending on the relationship between the macroscopic performance changes of the battery and the changes in the performance of the internal microscopic materials.
The entire battery can be placed in a spallation neutron source, let it charge and discharge hundreds of times, to see the changes in performance and the transport of particles inside, the nature of the electrode. Japan has used this method to achieve a battery capacity of 400 kW/hr per kilogram.
In addition, everyone is very worried about the safety of the battery, such as the appearance of flammable gas during the charging and discharging process, and an explosion. This gas can only be discovered by neutrons, and we can study the conditions under which gas can be generated by spallation neutron sources.
How to build a Chinese spallation neutron source?
This is a Chinese spallation neutron source, consisting of a linear accelerator 80MeV(MeV, energy unit, mega-electron volts), fast loop synchronization Accelerator 1.6GeV, a target station, consisting of three neutron scattering spectrometers. It is jointly established by the Chinese Academy of Sciences and the Guangdong Provincial Government. The legal entity is the Institute of High Energy Physics of the Chinese Academy of Sciences. It has invested a total of 1.86 billion yuan and was completed in March 2018.
Particulation and neutron scattering principles
The generated neutron hits the sample and then hits the component. We detect it, which is the principle of spallation and neutron scattering.
The period of the large scientific installation from idea to completion is very long. In the late 1990s, we were imagining the idea of spalling neutron sources. In 2000, we submitted a report on the development goal of China’s high-energy physics and advanced accelerators to the National Science and Education Leading Group. It was proposed to build a spallation neutron source until last year, after 18 years.
Why is the spallation neutron source to be settled in Dongguan?
In 2000, we had the idea of spalling neutron sources. In 2004, we were approved by the National Science and Education Leading Group. However, there has been no suitable place in Beijing. In February 2006, I attended the meeting organized by the Provincial Development and Reform Commission in Guangzhou, and the leaders of the National Development and Reform Commission talked about the sparse neutron source looking for a construction site.
The then president of the Chinese Academy of Sciences, Lu Yongxiang, put forward an idea. He hopes to combine the strength of the Chinese Academy of Sciences in basic research and applied basic research with the strong economic strength of Guangdong Province and the urgent need to upgrade technological innovation and industrial demand. Get up and build the “third highland” of the Chinese Academy of Sciences in the Pearl River Delta. This is a forward-looking strategic deployment and is now a core scientific device supporting the Science and Technology Innovation Center in Guangdong, Hong Kong and Macau.
In May 2006, the Provincial Development and Reform Commission organized an inspection of Zhuhai, Luogang and Songshan Lake. Songshan Lake is the most suitable, and Dongguan has the strongest support. It is very rare to have such a vision 13 years ago.
The US spallation neutron source used $1.4 billion, Japan’s spallation neutron source used $1.8 billion, and China’s spallation neutron source used 1.8 billion yuan. This spallation neutron source has a series of innovative ideas. Its main performance exceeds the spallation neutron source in the UK, and the localization rate of equipment exceeds 90%.
In the process of construction, we have overcome many difficulties. One of the big difficulties is that the linear accelerator tunnel we built is 19 meters underground. It was seepage in the first rainy season after the completion. It was not the construction unit that cut corners, but they mistakenly referenced the construction experience of Shanghai light source.
The expert of Shanghai Light Source said that the concrete wall of the tunnel is 1 meter thick and the cement is less. The Shanghai light source uses 150 kilograms of cement per cubic meter of concrete. We used 180 kilograms. However, the situation is different. We are underground in the depth of 19 meters. The groundwater in the south is very rich, so there is a serious problem of water seepage in the first rainy season.
Finally, we had to add a tunnel outside the straight tunnel to waterproof, which was a year and a half late. In order to get back in a year and a half, to ensure that we completed the work on time, we took the way of working in parallel, first installed on the ground and installed the equipment that needs to be installed underground, and then the tunnels were repaired, and then they were dismantled and put down, such work The amount is very large.
This is the target station spectrometer hall, linear accelerator equipment building and fast cycle synchrotron.
This is a 200-meter long straight tunnel and a circular accelerator with a ring length of 240 meters.
This is the installation core of the target station. As you can see, this is the case where it is installed step by step.
25Hz AC Magnet
We have a lot of innovations and have overcome many challenges. For example, the current of a magnet reaches kiloamperes, 25 Hz. Older comrades remember that the ballasts of the fluorescent lamps we used in the past will always ring, why? It is because of the 50 Hz AC. Similarly, the current of nearly a thousand amps here produces very severe vibration cracking and eddy current heating, and we have made great efforts to overcome this problem.
Wander Tube Linear Accelerator
There is also a drift tube linear accelerator with 156 drift tubes, each of which is different. The installation error is not more than 30 microns, which is very precise.
Target manufacturing company “going out of the country”
There is also a core target. We have an innovative tungsten-wrapped cladding technology that has reached the international leading level. The manufacturer of the target insert is Beijing Antai Company. We have successfully developed a very critical target. This also enabled them to successfully win the target of the European spallation neutron source.
Spectrometer Construction
This is the first three spectrometers available, including multi-function reflectometers, small angle spectrometers, and general-purpose powder diffraction spectrometers.
A bird’s eye view of China’s spallation neutron source (August 2017)
This is an aerial photograph of August 2017, taken by drones without any modifications.
When we submit a manuscript to a foreign magazine, this photo is used. They always think that we are synthetic, and there is actually no modification. Its construction is so perfect.
The results and applications of Chinese spallation neutron sources
Successful first shot, get neutron beam in advance
In August 2017, our first successful target was successful. Pressing the button gave us a beautiful neutron beam. In July of that year, I visited the English spawning neutron source. Before the button was pressed, the British director repeatedly reminded me that you have to be fully prepared for the first time, hit the target, and press it, there may be nothing.
He said that they couldn’t figure out where the neutron beam ran in more than ten days. However, we have a reasonable design, equipment installation, and high quality of debugging, so we get the beam by pressing the button.
The above is the required acceptance index. Below is the actual indicator we have achieved. Everyone sees that the power achieved is more than twice the acceptance index. All the acceptance indicators have been reached. We successfully passed the national acceptance.
The National Acceptance Committee report believes that the design is scientific and reasonable, the equipment quality is excellent, and it has reached the international advanced level. Through independent innovation and integrated innovation, a series of major technical achievements have been achieved in the high-current proton accelerator and neutron scattering, which has significantly improved. Our country has achieved a major leap in these areas.
Now, we have become the fourth country in the world to have spallation neutron sources after the British spallation neutron source, the US spallation neutron source, and the Japanese spallation neutron source.
The Chinese spallation neutron source has achieved stable and efficient operation. Our power has reached 50 kW, which is half of the design value, providing beam efficiency of over 94%.
After the acceptance, the user’s article was published in the second month. No articles have been published in the first two years of the US spallation neutron source, causing a lot of criticism. Our results are very fast.
Now we have done experimental research in many fields, and there are more than 50 units, including three institutions in Hong Kong and the United Kingdom, to conduct experiments, and eight articles have been published.
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In the future, it is not enough to use only the existing three spectrometers. We are building user spectrometers with research institutes and universities in the Pearl River Delta region. The Guangdong Science and Technology Department also donated two spectrometers. Because of many material residual stresses and metal fatigue problems, the only solution to the problem is to use spallation neutron sources.
We are applying to the National Development and Reform Commission for the second phase of the project to build more spectrometers and to increase its power to 500 kW. It is currently the No. 1 project in the 14th Five-Year Plan of the Academy of Sciences and may even be launched by the end of this year.
There is also a plan to build a southern light source. Because the government of Dawan District of Guangdong, Hong Kong and Macao is eager to establish a synchrotron radiation source, the combination of spallation neutron source and advanced light source is the best match for the big science platform.
Planning a Southern Light Source
We have reserved 600 acres of land in the west of the sparse neutron source. This picture is a vision of the advanced light source in the South. It will be in the Greater Bay Area of Guangdong, Hong Kong and Macau.Construction plays a huge role.
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