Recently, the national large-scale science project in Dongguan, Guangdong Province, China's successful spallation neutron source targeting neutron beams, marked the successful completion of the CSNS main project and entered the trial operation phase. What is its use? Security is not safe? Reporter went to the scene, as you announced one by one.
What is it?
Like a 'super microscope', you can study the microscopic structure of matter
'When a bunch of neutrons is incident on a research sample, it interacts with its nucleus or moment to produce scattering, and by measuring changes in the energy and momentum of the scattered neutrons, it is possible to study the effects of various neutrons at the atomic and molecular scales The microscopic structure and movement of matter tell people the position of atoms and molecules and their motion state, which is called neutron scattering technique. "Chen He-sheng, commander and project manager of China's spallation neutron source project said.
In 1932, when British physicist Chadwick discovered neutrons, people began to realize that the nuclei are made up of positively charged protons and uncharged neutrons, which are the most important science and technology of the 20th century One of the successes is the fact that neutrons are non-devastating because they are uncharged, have a magnetic moment, and have strong penetrating power, enabling the resolution of light, isotopic, and neighbors, making neutron scattering a matter of study of both physical and dynamical properties One of the ideal probes, like X-rays, is a powerful tool in multidisciplinary research to probe the microstructure and motion of matter.
Chen Hesheng further explained: 'For example, suppose there is an invisible net in front of us. We keep throwing many glass marbles. Some marbles go through the net and others hit the net and play different angles If we record the movements of these marbles, we can roughly deduce the shape of the net; if the marbles are enough, dense and strong, we can accurately portray this net and even deduce its material '
However, for neutron scattering studies, which require neutron probes, an appropriate neutron source must be available and advanced neutron sources are the basis of neutron science research.How can we obtain neutron-producing neutrons The neutron source has always been the goal that scientists are constantly striving for.
High-flux neutron sources include the reactor neutron source and the spallation neutron source.Nuclear reactors are a kind of stable and continuous neutron source, which play a great role in the neutron science research.But due to the limitation of reactor cooling technology, The neutron flux of reactors reached saturation in the sixties and seventies of the last century.With the progress of science and technology, corresponding research systems such as thin films, nanoclusters, biological macromolecules and proteins have larger scale distributions, Therefore, the fast, high-resolution neutron scattering measurement of small samples urgently needs a new generation of higher flux, wider band neutron sources, spallation neutron sources came into being.
'It is a heavy ion target bombarded with energetic protons from a large accelerator, causing spallation reactions of metal atoms, releasing large amounts of neutrons that form very strong neutron beams, neutron moderation (neutrons and media Nuclear collision, causing neutrons to reduce energy and reduce the deceleration phenomenon) and the sample scattering, and finally received by the neutron scattering spectrometer, our researchers based on these neutron scattering data analysis of the microscopic characteristics of the observed object. Saying that a spallation neutron source is like a 'super-microscope' can study the microstructure of materials such as DNA, crystalline materials, and polymers, Chen said.
Second question: What kind of long?
Very large, built in 13 meters to 18 meters deep underground
Due to these unique properties of spallation neutron sources, as well as the increasingly stringent safety assessment requirements of the international community, neutron scattering studies by spallation neutron sources are commonly used in developed countries.Nowadays, pulsed neutron spreaders The main countries of origin are the United Kingdom, the United States and Japan.China's spallation neutron source will become the first spallation neutron source in developing countries and become one of the four largest spallation neutron sources in the world, thus greatly enhancing China's Basic research and high-tech level.
Although neutrons are so tiny, the spallation neutron source that produces a strong neutron beam is an exceptionally bulky device and is a unit of various high, sophisticated, and sharp equipment.
Reporters on the scene saw the CSNS tunnel built within 13 meters to 18 meters deep underground.The main construction includes a beam energy of 80 mega-electron hydrogen negative ion linear accelerator, a beam energy of 1.6 billion Electron volt fast proton proton synchrotron, two beam transport lines, a target station and three spectrometers, as well as the corresponding facilities and civil works.
Chen Hesheng said: "CSNS Phase I neutron spectrometer number 3, the future can be built up to 20. Current beam power of 100 kW, we have also set aside to further improve the beam power to 500 kW and additional Second target station upgrade space.
The first three spectrometers built for the universal powder diffraction instrument, multi-function reflector, small angle scatterometer.
'Universal powder diffractometer is mainly used to study the crystal structure and magnetic structure of materials; multi-functional reflectometer to study the surface and interface structure of the material by analyzing the reflected neutrons from the sample; small angle scattering instrument is used to detect the material system in 1-100 Microscopic and mesoscopic (a system of macroscopic and microscopic) structures within the nanometer scale, Chen said.
Third question: What use?
Can make high-speed rail and aircraft safer and more comfortable, can be used for cancer radiotherapy research
Spallation neutron source can produce strong pulsed neutron, and by measuring the neutron beam in the sample scattering reaction process, to detect the position and movement of the sample nucleus position, therefore, in materials science and technology, life sciences, physics, chemistry and chemical industry, Resources and environment, new energy and many other fields have a wide range of applications.
An example was given by Chen He-sheng: "In June 1998, an inter-city express in Germany was accidentally derailed and the culprit turned out to be an aging wheel, which was detected on a British spallation neutron source and found to have internal cracks '
In fact, both the wheel and rail of the high-speed rail and the turbine and the wing of the aircraft have stress, which determines the service life and safety of the high-speed rail and the aircraft. However, this stress can not be seen or touched, Has become the key to avoiding a disaster.Now scientists have been able to measure the residual stress on the sprocket and wing on the spallation neutron source, optimizing the machining process, so that high-speed rail and aircraft become more safe and comfortable.
Chen Hesheng said: 'Spallation neutron source technology also plays an irreplaceable role in the fields of biology, life, medicine and other research fields and is complemented by synchrotron radiation sources, becoming the most important platform for basic scientific research and new material research and development For example, the proton and neutron spallation neutron source can be used for tumor radiotherapy research, has been applied in many developed countries.In addition, the development and utilization of new clean energy combustible ice, spallation neutron source The neutron diffraction technique under high pressure can be used to study the formation mechanism and stability conditions of combustible gas methane hydrate. The research results will provide a scientific basis for the safe and efficient exploitation and utilization of combustible ice.
The construction of the CSNS device will also greatly enhance the international exchange and cooperation in the domestic science and application of neutron scattering and provide good opportunities for China's neutron scattering technology and applications to occupy a place in the international frontier.
'The construction of proton accelerators, target stations and neutron spectrometers in the construction of CSNS involves a large number of strategically high-tech needs, and these technological difficulties require the joint efforts of China's top scientific research forces. Therefore, the construction of this project will attract A large number of world-class scientists come to carry out scientific research activities and will attract more than 600 experts and scholars from home and abroad to come together for a study in Dongguan after the project is completed, "said Sun Mu, party secretary of the Institute of Physics, Chinese Academy of Sciences.
Q4: Is it safe?
Living in the vicinity for a year, the amount of radiation received is only equivalent to take a long-haul aircraft
Such a large scientific device, its safety is how it will not pollute the surrounding environment?
Chen Hesheng said: 'CSNS is based on a new generation of accelerators, does not require nuclear materials, the power comes from electrical energy, radiation strict control in the environmental safety and security.We have done calculations in the vicinity of the spallation neutron source to live for 1 year, the radiation exposure to residents only Equivalent to taking a long-haul plane.
According to reports, there is a monitoring station near CSNS to monitor the radiation situation at any time. "Scattered neutron source project environmental impact report" also proposed accident emergency plan. As spallation neutron source is a ray device, as long as the power down, Sub-source of the main radiation immediately disappeared.
In addition, the spallation neutron source and reactor nuclear device completely different, does not require nuclear raw materials, there is no chain reaction, the accelerator operation will be a small amount of particles lost to produce secondary particles, such as: X-ray, gamma rays and Children, etc., all of which are radioactive, commonly known as instantaneous radiation.
"These radioactive materials, which are 5-6 orders of magnitude lower than the reactor's neutron source, have much less environmental impact and will be stored in a nationally designated waste repository." China's Spallation Neutron Source Project Manager Chen Yuan Bai said.
As soon as the accelerator is shut down, the main source of environmental damage disappears and can be said to be as reliable as a faucet. The accelerator is automatically controlled by electronics to shut down the accelerator. In the event of a failure, the accelerator can be shut down in milliseconds. And other natural disasters, spallation neutron source machine will stop functioning, the radiation field disappear immediately after repeated demonstration studies, spallation neutron source is a relatively clean beam device.
