"Super Microscope" takes you to explore the grid
Visit China Spallation Neutron Source
Our reporter Chu Yingjie
Device introduction:
The China Spallation Neutron Source (CSNS) is the first pulsed spallation neutron source in my country and the fourth in the world.
The successful construction of China's spallation neutron source has filled the gap in the domestic pulsed neutron source and application field. Its technology and comprehensive performance have entered the advanced ranks of similar devices in the world, which has significantly improved my country's technical level and independent innovation ability in related fields. It has made a major leap in the field of strong current proton accelerators and neutron scattering, and provided strong support for basic research and high-tech research and development in material science, life science, resources and environment, and new energy.
Dalang Town, Dongguan, Guangdong, Songshan Lake Science City.
It used to be a lychee forest, and now there is a "neutron factory".
The China Spallation Neutron Source (CSNS) is the largest scientific project with the largest single investment in my country so far.
Its completion makes my country the fourth country in the world to have a pulsed spallation neutron source after the United Kingdom, the United States and Japan.
Not long ago, the second-phase project of China Spallation Neutron Source organized a feasibility study report review.
The second phase of the project is expected to start construction in the first half of next year.
What is the spallation neutron source and why is it called "the heavy weapon of the country"?
Chen Yanwei, deputy director of the Institute of High Energy Physics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of High Energy Physics of the Chinese Academy of Sciences) and director of the Dongguan Research Department, made an analogy: "In simple terms, a spallation neutron source is a 'super microscope', which produces neutrons Like a 'probe', it can clearly detect the internal structure of a substance."
According to Chen Yanwei, as a powerful tool for human beings to deeply explore the microscopic world, spallation neutron sources are widely used in popular fields such as new material research and development, performance testing of key components, and are used for materials science and technology, physics, chemistry and chemical engineering, life science, new Energy and other basic research and applied research provide an advanced scientific research platform, which is of great significance for meeting major national strategic needs and solving bottlenecks in many fields of frontier science.
1 Equipment development has reached the international advanced level, and the localization rate of core equipment has reached more than 90%
Neutron, one of the fundamental particles that make up the nucleus of an atom.
Neutrons have many properties.
It is not charged, but has a magnetic moment, which can well help us to study magnetic structures; it has strong penetrating power, is non-destructive, and can study the residual stress and metal fatigue of large engineering components in situ, which is a high-end Manufacturing escort; it is sensitive to elements that are extremely important in the fields of life science and energy, such as carbon, hydrogen, oxygen, nitrogen, etc.; it interacts with atomic nuclei and can distinguish isotopes...
"These characteristics determine the irreplaceability of neutrons in the field of microscopic research." Jin Dapeng, deputy director of the Dongguan Research Department of the Institute of High Energy, Chinese Academy of Sciences, and deputy director of the Spallation Neutron Source Science Center, told reporters.
Studying the microstructure of matter requires a large number of neutrons, which requires the use of spallation neutron sources that can safely and efficiently generate neutrons.
China Spallation Neutron Source is mainly composed of three parts: 2 accelerators, including 1 negative hydrogen ion linear accelerator, 1 fast cycle proton synchrotron; 1 target station; multiple neutron spectrometers.
In addition, there are corresponding supporting facilities.
Chen Yanwei introduced its working principle: the proton is accelerated to 1.6 billion electron volts, and the proton beam with a speed equivalent to 0.92 times the speed of light is used as a "bullet" to bombard a heavy metal target with a high atomic number.
The nuclei of the target are knocked out of protons and neutrons, and scientists use special devices to "collect" the neutrons to carry out various experiments.
The proposal to build China's spallation neutron source began in the late 1990s with research on China's high-energy physics development strategy.
Since then, the China Spallation Neutron Source has been included in the national "Eleventh Five-Year Plan" for the construction of major scientific facilities.
In 2006, China's spallation neutron source was located in Dongguan, Guangdong.
In 2011, the China Spallation Neutron Source began to be officially constructed.
In August 2017, the first proton shot was made and the neutron beam was successfully obtained; in March 2018, it was officially completed; in August 2018, it officially passed the national acceptance and was put into operation.
Spallation neutron source devices are huge, with many equipment parts and complicated processes.
"To build a spallation neutron source, many technologies need to be explored from scratch. It can be built in six and a half years, and it is inseparable from the breakthrough of key core technologies." Jin Dapeng introduced.
The 25 Hz AC magnet used in the fast-circulating proton synchrotron is the first to be developed in my country.
During the development, we encountered technical difficulties beyond imagination.
Core and coil vibration cracking, eddy current heating... How to solve these new problems beyond experience?
Researchers and cooperative units jointly tackled key problems, and finally developed a qualified magnet by their own strength.
The researchers also innovatively proposed a harmonic compensation method for the resonant power supply, which solved the problem of magnetic field synchronization between multiple magnets.
Challenges come one after another—
High-power targets use tungsten material, and tungsten material is not resistant to erosion, and needs to be coated with a layer of tantalum metal.
How to make tantalum thin enough and improve the bonding force of tantalum and tungsten?
The welding of the liquid hydrogen moderator working at a low temperature of about minus 253 degrees Celsius is a very difficult thin-walled welding. How to ensure the reliability?
The construction process of China's spallation neutron source is also the process of independently tackling key problems and mastering core key technologies.
Jin Dapeng introduced that after breakthroughs in a number of key core technologies such as 25 Hz AC magnets, high-power targets, liquid hydrogen moderators, and neutron detectors, the development of other fields has also had a certain impact.
The mass production of various equipment for China's spallation neutron source has been completed by nearly 100 cooperative units across the country.
Through independent innovation and integrated innovation, the research and development of many equipment has reached the international advanced level, and the localization rate of core equipment has reached more than 90%, which not only greatly reduces the cost of equipment, but also greatly improves the technical level and manufacturing capacity of domestic related industries.
Jin Dapeng gave an example: Due to the high level of technology and good product quality, the Chinese spallation neutron source target component manufacturing unit has successfully won the bid for the world's fifth pulsed spallation neutron source-European spallation neutron source The target body part of the source.
2 Technological breakthroughs in the R&D process are expected to bring important technological innovations to tumor treatment
The accelerator tunnel, located 17 meters underground, is lined with complex equipment of various colors and connecting various pipelines.
The researchers used hydrogen to generate negative hydrogen ions and accelerated them in a linear accelerator.
When their energy reaches 80 million electron volts, they "fly" into the fast-cycle proton synchrotron in the ring.
Within one second, 25 waves of negative hydrogen ions came running.
Here, the negative hydrogen ions will be converted into protons, and by continuous "running" and repeated acceleration, the energy will be increased to 1.6 billion electron volts, and the speed will be increased to 0.92 times the speed of light.
A beam of protons near the speed of light is extracted to bombard a tungsten target, thereby producing neutrons.
In the process of research and development of key technologies of accelerators, some new technological achievements have also been produced, and specific applications have been derived and blossomed.
Taking advantage of the breakthrough in the radio frequency quadrupole accelerator technology of China's spallation neutron source, in August 2020, researchers successfully developed my country's first accelerator boron neutron capture therapy (BNCT) experimental device with completely independent intellectual property rights, which can be used for cancer treatment. Research.
This has laid a technical foundation for the localization and industrialization of the complete medical BNCT device in China, and is expected to bring important technological innovations to tumor treatment.
The first clinical equipment has been installed in the hospital, and the installation and commissioning is expected to be completed in May 2023.
After China's spallation neutron source was officially put into operation and opened to domestic and foreign scientists, engineers and technical personnel, and industrial enterprises, the comprehensive effect of large scientific devices has become increasingly apparent.
"China's spallation neutron source has carried out major innovative research in many fields, including residual stress and service performance testing of large engineering components such as deep-sea submersibles, etc., providing a key technology platform for tackling many high-performance structural materials urgently needed by the country. A large number of achievements have also been made in the international frontier scientific and technological research on magnetic materials, nano-functional materials, high-efficiency catalysts, spintronics, organic solar thin-film cells, metallic glasses, high molecular polymers, and biological macromolecules," said Chen Yanwei.
What is residual stress?
It refers to the stress retained in the material, component processing, service, etc., which may lead to deformation or even failure of engineering components.
The shell of the deep-sea submersible is welded with titanium alloy.
The reliability of welding is very important to withstand the huge seawater pressure when diving for 10,000 meters under the sea.
"We tested its welding simulation parts to understand the residual stress parameters of different welding processes, which provided key data support for the prediction of shell life and the selection of welding processes." Jin Dapeng said that large-scale high-speed motion engineering components such as wheels of high-speed rail will also be used in the future. A spallation neutron source is required to verify its residual stress parameters.
As the first major scientific and technological infrastructure in the Guangdong-Hong Kong-Macao Greater Bay Area, the establishment of the China Spallation Neutron Source has brought domestic scientific and technological workers a "sharp weapon" to study materials, especially provided unprecedented convenience for scientists in Hong Kong and Macao.
The super-strong and super-tough "super steel" developed by the team of Professor Huang Mingxin of the University of Hong Kong is to analyze its composition and structure through the Chinese spallation neutron source, and to verify the relevant research results.
3 Provide an advanced research platform for cutting-edge scientific research and major national needs
Orange, purple, blue, light blue, light green... Walking into the experimental hall of the spectrometer at the target station, one after another of spectrometers of different colors, centered on the target station, stretched out like the petals of a seven-colored flower.
After the neutrons are produced, they are moderated and introduced into the spectrometer through the neutron channel.
"The neutron interacts with the nuclei of the sample material in the spectrometer, resulting in scattering, diffraction, and transmission." Jin Dapeng explained that neutrons are like scouts sent in to detect information. The angle, energy, etc. when it comes out are measured and pushed back to study the structure and dynamics of the sample.
Exploring microscopic objects, China's spallation neutron source provides strong support for basic and applied research in materials science and technology, physics, chemistry and chemical engineering, life science, and new energy.
At present, China Spallation Neutron Source has completed 8 rounds of open operation, more than 3,900 registered users worldwide, and completed more than 800 projects.
With the advancement of major national strategic deployments, the development of emerging industries and the needs of international frontier research, the number of users of spallation neutron sources in China has grown rapidly, and the number of projects applying for the use of devices has grown rapidly.
China's spallation neutron source faces "upgrade".
In fact, the first phase of the project design has reserved space for upgrading.
According to the national "14th Five-Year Plan", the second phase of China's spallation neutron source project is about to start.
"China's spallation neutron source has a total of 20 neutron channels planned, and 22 neutron spectrometers can be built." Jin Dapeng told reporters that a total of 5 spectrometers have been put into operation, including the state-invested and constructed phase I project. 3 spectrometers, and 2 user spectrometers built in cooperation with universities and research institutions.
Another 6 different types of cooperative spectrometers are under construction and commissioning, 4 of which are expected to be put into use by the end of this year to meet the different needs of more users.
Different spectrometers have different uses.
The light green general-purpose powder diffractometer, mainly used to study the crystalline and magnetic structure of objects, is now also used for residual stress testing of small parts.
The atmospheric neutron irradiation spectrometer, which has just been put into use, has attracted many high-tech enterprises in China to send their products for testing.
Researchers use high-throughput neutrons to accelerate the process of failing electronic components, thereby driving process iterations and ensuring that electronic components and systems perform with high reliability.
The engineering material stress diffractometer, which will be put into use at the end of this year, can study the residual stress and metal fatigue data of high-speed rail wheels, aerospace engine blades and other equipment without destroying the sample, and on the one hand, provide a reference for improving the process. , on the other hand, it is also possible to evaluate the mileage and time of use of the components to ensure both safety and economy.
Jin Dapeng introduced that most of the spectrometers currently in use are general-purpose spectrometers.
A number of new spectrometers have been specially planned around major national strategic deployments and emerging industry needs.
There are spectrometers under construction, as well as those dedicated to the study of new energy batteries.
After the completion of the second phase of the project, the number of spectrometers in China's spallation neutron source will increase to 20, covering all aspects of research fields for users.
At the same time, the target beam power of the accelerator will be increased from the current 140 kW to 500 kW.
This means that more neutrons can be produced in the same time, which can not only effectively shorten the experimental time, but also make the experimental resolution higher.
"After the completion of the new spectrometer and experimental terminal, the equipment research capabilities of China's spallation neutron source will be greatly improved, the experimental accuracy and speed will be greatly improved, smaller samples can be measured, and faster dynamic processes can be studied. Research, major national needs and national economic development provide a more advanced research platform." Chen Yanwei said.
(China Discipline Inspection and Supervision News)