"Magnifying glass" for studying the atomic world


"Magnifying glass" for studying the atomic world

The Multiphysics Spectrometer rises.

Photos in this column:

Nanfang Daily reporter Wu Qinhu

"Magnifying glass" for studying the atomic world

Vacuum chamber (top).

"Magnifying glass" for studying the atomic world

Workers conduct experiments.

The China Spallation Neutron Source multiphysics spectrometer has recently passed acceptance testing by a panel of experts and will be open to the public in October. This is the world's fourth multiphysics total neutron scattering spectrometer and the first domestic multiphysics total neutron scattering spectrometer, its flux exceeds that of a similar spectrometer on the British splitting neutron source of the same power, and the resolution reaches the advanced world level.

This multiphysics spectrometer is jointly developed by Dongguan Institute of Technology, City University of Hong Kong and the Spallation Neutron Source Research Centre. The collaboration has become iconic.

Nanfang Daily interviewed Yin Wen, Deputy Director of the Neutron Research Department of the Dongguan Research Department of the Institute of High Energy Physics of the Chinese Academy of Sciences and responsible for the multiphysics spectrometer system, about the development process and the value of China's first multiphysics spectrometer.

Southern Daily reporter Chen Qiliang Wu Qinhu

What is a multiphysics spectrometer?

Like a magnifying glass that allows you to see the wings of a bee, the multiphysics spectrometer is a "magnifying glass" for observing the atomic world.

The Chinese multiphysics spectrometer with a neutron splitting source is located in a building about one floor high, inside which various precision instruments are located. In the R&D demonstration, the reporter saw that the samples processed by the glove box first entered the vacuum chamber with the sample rod and lifting equipment. Then, a series of material structure data will gradually appear next to it on the monitoring screen.

What is a multiphysics spectrometer? Yin Wen drew an analogy: just as a magnifying glass can clearly see the wings of a bee, the multiphysics spectrometer is a "magnifying glass" to observe the atomic world, "can open another window so that people can understand the world."

The creation of this multiphysics spectrometer began in September 2018 and was successfully launched at the end of January this year. For more than two years, researchers have overcome many difficulties.

“Our physical design started in 2017. We constantly optimized the parameters, invited international experts for verification, and repeatedly revised many versions.” Yin Wen said that the design of the spectrometer is not optimal, but only better.

By 2019, the institute began ordering various equipment. After the epidemic, factory production suffered, and some of the equipment was difficult to deliver. For example, in the vacuum chamber for the experiment, in order to ensure a high degree of chamber vacuum, it was decided to use electron beam welding of the main chamber made of aluminum alloy with a thickness of 100 mm, which is extremely difficult. For this reason, Chen Yanwei, deputy director of the Institute of High Energy Physics of the Chinese Academy of Sciences and director of the Science Center of Spallation Neutron Sources, went to Nanjing to personally communicate with the manufacturing company, and finally "won" the equipment after more than 20 test weldings.< /p>

In order for the spectrometer to be completed as soon as possible, overtime has become the norm for the design team. According to Yin Wen, the spectrometer's detector is very expensive, and a small module costs more than 1 million yuan, so it must be installed with great care. The day before New Year's Eve at Gengzi, the professional detector electronics team was still busy installing detectors on site. On the fifth day of the Lunar New Year, many research scientists returned to Dongguan to continue the installation and commissioning of equipment.

The spectrometer has a neutron tube 30 meters long, it is an imported device, the installation accuracy is very strict, and it must be controlled within the range of plus or minus 25 microns. Due to the epidemic, foreign engineers could not come to install, so the project team and the professional commissioning team decided to do it themselves. “In the wind, once the hall door is opened, the laser tracker data will drift. If there is a deviation in the installation position, it will affect the flow of the spectrometer. The collimation group and we took a big risk together.” Yin Wen said that at that time it was expected that the neutron flux on the sample could reach 2.0×10 to the seventh power, but after installation, the measured result was 3.01×10 to the seventh power. which was well above the original expectations.

"In addition to self-installation of equipment, we also insist on independent research and development, and the localization rate of multiphysics spectrometric equipment exceeds 90%," said Yin Wen.

One typical device is the radial collimator, which needs to be covered with a layer of neutron-absorbing material on an organic film to reduce noise during the measurement. In the past, this kind of equipment depended on imports. This time, the design team decided to develop on its own, and the team researched on its own. Although it did some workarounds, it finally realized the domestic replacement of radial collimators, and the performance was not inferior to foreign products.

"The biggest advantage of independent R&D is that once equipment is damaged, we can replace it immediately and we are no longer under the control of others." Yin Wen said that only by reducing dependence on imports can we truly achieve technological self-sufficiency.

It is worth noting that the single sample rod, protective material, test platform and many other equipment of the multiphysics spectrometer are manufacturedlocal businesses in Dongguan. Yin Wen said that a few years ago, the ability of local enterprises to support large scientific installations was relatively low, but now this support ability has increased significantly.

What can this spectrometer do?

Multiphysics spectrometers are expected to provide a deeper understanding of the atomic structure and how materials work, and to play an important role in the fields of materials science, condensed matter physics and life sciences.

January 26 this year is the most memorable day for Yin Wen. On the same day, the multiphysics spectrometer will receive the first neutron beam and check various technical parameters. Chen Hesheng, an academician of the Chinese Academy of Sciences, and many senior experts from the Dongguan Institute of Technology, the Spallation Neutron Source, and the City University of Hong Kong attended the testimony together.

"Many of us couldn't sleep the night before," said Yin Wen, since many types of equipment are self-developed, and neutron tubes are also self-installed, if there is a problem with one equipment, it will affect the neutron beam.

When the neutron switch was turned on, Yin Wen said quietly in her heart, "It must be! It must be!" The final result surprised everyone. Using various methods, continuous measurements and multiple checks, the test results are better than the acceptance index.

Bandwidth and resolution are two key indicators of the technical level of a spectrometer. Bandwidth determines the efficiency of the spectrometer, and resolution affects the clarity of the spectrometer. The initial acceptance index was 2% resolution and 10 at the 6th power of flux, and finally reached a resolution of 0.4% and 3.01×10 at the 7th power of flux.

Compared with three other multiphysics spectrometers in the world, the calculated flux of this spectrometer is 4-5 times that of the British neutron spallation source spectrometer with the same power, ranking first in the world; resolution and megawatt level. The splitting neutron source spectrometer is comparable and has reached the advanced world level.

This effect is not easy to achieve, and there is a problem. "If you use a neutron tube, the resolution will drop. But if you don't use a neutron tube, the flux will drop again. This is a dilemma in research," Yin Wen said. that can be used During subduplexing, make sure that the resolution is not degraded.

Yin Wen visualized that neutrons are like a group of particles moving in the process of flight. Some of them run fast and some run slowly. They are more obvious and easier to observe and catch. The development team increased the particle range from 17 meters to 30 meters, separated the wavelengths, and effectively solved the problem of insufficient resolution of scientific research.

What is a multiphysics spectrometer used for? Yin Wensaid that the multiphysics spectrometer is mainly used for structural studies of long-range ordered but locally disordered materials and long-range disordered materials, and will play an important role in my country's materials science, condensed matter physics, life sciences, nanotechnology. and other disciplines.

For example, an expert from the City University of Hong Kong came here to study the properties of medium-entropy alloys. This alloy can still maintain structural stability at minus 240 degrees Celsius. With multiphysics spectrometers, experts can better understand the atomic structure and how materials work.

In the field of new energy, the Chinese Academy of Sciences has developed a new energy battery with the highest energy density at the time, but the principle of its operation is not clear. Later, by studying neutron scattering, it was found that the interatomic distance in batteries of this type changes during charging and discharging. It is expected that batteries with fast charging, long battery life and high energy density will be developed using multiphysics spectrometers.

In the field of condensed matter physics, the reason a small USB drive can have a large capacity is due to its special local structure. Studying this localized structure using neutron scattering could lead to new discoveries.

In the field of life sciences, multiphysics spectrometers can be used to study some drugs. Which structure of the drug is better absorbed by the human body and promotes the action of the catalyst? The multiphysics spectrometer will bring a new research method to the life sciences.

This is expected to update the source code

There is a strong demand for domestic scientific research, but in the past, Chinese scientists could only turn to foreign countries for help. With the creation of more spectrometers, a number of original innovative breakthroughs are expected in the future.

I heard that the multiphysics spectrometer was successfully launched, and many specialists from universities and institutes specially came here. At present, the multiphysics spectrometer is implementing projects from users such as the Dongguan Institute of Technology, the City University of Hong Kong, the Chinese University of Hong Kong, the Shenzhen Graduate School of Peking University, and the Songshan Lake Materials Laboratory.

Multiphysics spectrometers started accepting applications from users in early July, and have been well received by domestic and foreign users.households, especially the research staff of the Dongguan Institute of Technology. At present, users are mainly focused on two areas of high performance batteries and alloys. This is expected to lead to a number of innovative breakthroughs in the future.ov in studies of performance mechanisms.

According to the statistics of authoritative organizations, over the past few years, Chinese users of the spallation neutron source have published more than 60 user articles in leading journals such as Science, and scientific results in the first three years far exceed this figure. source of spallation neutrons in the US and Japan.

What is the reason? Yin Wen said that after the reform and opening up, Chinese scientists have entered the field of neutron scattering research, but the number of published articles has increased dramatically. If we take 2017 as an example, the results of research by Chinese scientists in the field of neutron scattering accounted for 14% of the world results.

The domestic scientific research is strong and the demand for scientific research is high, but at that time, the Chinese spallation neutron source had not been built, and Chinese scientists could only turn to foreign countries for help. "We found that in recent years, it has become increasingly difficult for Chinese scientists to apply for experimental equipment for foreign fission neutron sources." New users. Adding to the difficulty, "leaving Chinese scientists to use their own source of fission neutrons is a responsibility on our shoulders."

Earlier, the Chinese Spallation Neutron Source opened three spectrometers: a conventional powder diffractometer, a multifunctional reflectometer, and a small-angle scattering instrument. The adoption of the multiphysics spectrometer has expanded the scope of the spallation neutron source for microcosm studies from a few angstroms to 0.1 angstroms.

Over the next three years, China Spallation Neutron Source will build 7 spectrometers in succession. China Spallation Neutron Source (Phase II) will build 9 more spectrometers. These spectrometers will provide powerful support for the independence of science and technology.

Planning: Zhang Zhichao