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The Ring Positron Collider Is Controversial. What Is Wang Yifang Sticking To?

2019/11/8 9:53:00 0

Ring Positron ColliderControversy

"For CEPC, we are continuing to design and carry out preliminary research on key equipment. The original plan was built in 2022, but according to the present situation, it is absolutely impossible to get ahead of schedule, and there is great possibility of being pushed back. " On the morning of November 3rd, Wang Yifang, a member of the Chinese Academy of Sciences and a high-energy physicist, said in an interview with the media, such as the twenty-first Century economic report.

CEPC, the Ring Electron Positron Collider, is a world class high energy particle accelerator project proposed by Chinese high energy physicists in 2012, and Wang Yifang is the main promoter of the project.

Wang Yifang focused on the field of high-energy physics and led the completion of the design, development, operation and physical research of the Beijing spectrometer (BESIII) on the Beijing electron positron collider. At the same time, he also pioneered the experimental study of neutrinos in China, proposed the Dayawan neutrino experimental scheme and led the team to complete the design, development, operation and physical research of the experiment.

In 2012, the Wang Yifang team discovered a new neutrino oscillation mode through the Dayawan neutrino experiment. The results were selected in the ten major scientific breakthroughs of the US in 2012, and won the first prize of National Natural Science in 2016.

At present, the Jiangmen neutrino experiment proposed by Wang Yifang is in the construction stage and plans to complete the construction around 2021. This is also the second large-scale neutrino experiment conducted by China. In addition, promoting the construction of CEPC is also an important task for Wang Yifang.

For the possible situation behind the project, Wang Yifang told reporters that the promotion of a project depended on many aspects. When it was proposed in 2012, the plan was launched in 2022, leaving the preparation time for about 10 years.

"So far, we are basically pushing forward according to the plan. At that time, the 10 year task is now 3 years away from 2022, and there is still a lot of preparatory work to be done, so we still need more time. This also depends on the implementation of the national" 14th Five-Year plan "and other major plans. Wang Yifang said.

Compared with the previous Dayawan neutrino experiment and the construction of Jiangmen neutrino experiment, CEPC is much larger in scale and capital investment. Because of this, CEPC's project has caused a lot of controversy. Many people have raised opposition and doubt about the project. The most familiar objection is Chen Ning Yang.

So in the past years, whenever Wang Yifang talked about the CEPC project in public, the most frequently asked question was "is CEPC useful? What's the use? " For these questions, Wang Yifang has answered many times, but he still says every time that he hopes to get more people to understand the value of CEPC through his constant science popularization.

What are the practical benefits of CEP in addition to basic scientific research? Wang Yifang answered many years ago that he believed that CEPC could enable China to achieve localization in at least the following technologies: 1. High performance superconducting high frequency cavity can be applied to almost all accelerators. 2, high efficiency and high-power microwave power source can be applied to radar, broadcasting, communication, accelerator, etc. 3, large cryocooler can be applied to scientific research facilities, rocket engines, medical equipment, and so on. 4, high-speed, radiation resistant silicon detectors, electronic circuits and chips.

In addition, Wang Yifang also believes that CEPC can help China lead the world in precision machinery, microwave, vacuum, automatic control, data acquisition and processing, computer and network communications, etc., and can train thousands of top physicists and engineers, and introduce thousands of top international scientists and engineers to form an international scientific center.

The way to explore neutrinos

At the 2019 Tencent science WE conference held in the afternoon of November 3rd, Wang Yifang said neutrinos play a very important role in the whole physics. Neutrinos account for three of the 12 most basic particles in the physical world, so neutrinos constitute the most basic unit of the physical world.

In 1930, the famous scientist Wolfgang Pauli put forward the concept of neutrino in order to solve the problem of energy and momentum inconservation in the microcosm. After 26 years or 1956, American scientist Reines discovered neutrinos in experiments and won the Nobel prize. In 1987, supernova neutrinos were observed in Japan's Shen Gang experiment and us IMB experiment.

After the discovery of three neutrinos, in 1988, the atmospheric superneutrino oscillations were discovered in the Japanese superego experiment. In 2002, the solar neutrino oscillation was discovered in SNO experiments in Canada, and the two experiments were awarded the Nobel prize for discovering neutrino oscillations.

Wang Yifang said that by 2002, scientists had discovered two neutrino oscillations, but from the physical point of view, three neutrinos should have three oscillations. So they put forward experiments in 2003 and began to promote the construction of neutrino experiment in Dayawan. Finally, in 2012, we found third neutrino oscillations.

The Jiangmen neutrino experiment is being built before Wang Yifang completed the experiment in Dayawan in 2008. The purpose of the experiment is to study the quality order of neutrinos and accurately measure the oscillation parameters of neutrinos, and also to study neutrino, solar neutrino, supernova neutrino and earth neutrino.

Wang Yifang said that in the Jiangmen neutrino experiment, he also hoped to find a new decay called "double neutrons without neutrinos". It would be able to determine whether the neutrino is neutrino itself or neutrino and anti neutrino are different particles. This is a very important research goal in particle physics.

For this reason, the construction of neutrino experiment in Jiangmen has also been greatly improved. According to Wang Yifang, in order to achieve these scientific goals, we need to build a large detector, which requires 20 thousand tons of liquid scintillator.

"The liquid scintillator in the Dayawan experiment just mentioned is only 20 tons, which is nearly 1000 times worse. The 20 thousand ton detector is 20 times larger than the world's largest liquid scintillation detector. " Wang Yifang said.

At the same time, the experiment also needs to increase the light collection of the detector by 5 times, which is a great improvement over the past. For this reason, the Wang Yifang team needs to increase the transparency of the detector liquid by nearly 2 times, and at the same time, the detection efficiency of photomultiplier tubes for detecting photons will be increased by 2 times.

Wang Yifang said that in the process of promoting the construction of neutrino experiment in Jiangmen, various difficulties encountered, such as photomultiplier tube, took 8 years for their team to get the standard sample tube.

But for now, the whole Jiangmen neutrino experiment is progresses very smoothly. Wang Yifang told reporters, "after the completion of the construction of the neutrino experiment in Jiangmen, we believe that we will achieve very important results. It will also become a very important research base in the development of the international neutrino."

Dayawan neutrino experiment has been carried out, and the neutrino experiment in Jiangmen is being built. But Wang Yifang still feels inadequate. He admitted that the overall development of high-energy physics in China is still quite different from that of other countries. The core is still reflected in the lack of infrastructure.

At the same time, the whole industry has completed the establishment of the standard model of particle physics, and all the particles have been found, which means that even if China wants to build large-scale infrastructure, it also needs to find a new physical system beyond the standard model.

It is against this background that Wang Yifang proposed the construction of a large loop electron positron collider.

Why do we do CEPC?

Wang Yifang said that the idea of CEPC has been well recognized internationally, and is also regarded as the first choice for the future development of particle physics. For China, this is also an ideal choice. It is the best opportunity for China to lead the world in basic physics research.

Wang Yifang also gave four reasons for this:

First, Higgs particle is the most important window in the study of particle physics.

Second, the quality of the Higgs particle is not particularly heavy. The ring collider is an ideal Higgs particle factory, which is a more efficient design than the linear collider.

Third, many of the international competitors, such as Europe, the United States and Japan, have other projects on hand, and they can't afford to make the ring Higgs particle factory temporarily.

Fourth, the ring electron positron collider is exactly what China will do. The Beijing electron positron collider has accumulated 30 years of research experience.

From the scale of the project, once the CEPC is implemented, it will be a major leap in China's basic scientific research. It can be compared that the circumference of the Beijing Electron Positron Collider is 240 meters, and the circumference of CEPC will reach 100 kilometers.

This huge scale span has also brought huge capital investment, and the issue of investment is also an important focus of CEPC.

In response to project funds, Wang Yifang stressed in the interview, "I saw many reports that this project needs hundreds of billions of dollars. I need to clarify again. After two estimates, this project only needs 36 billion yuan."

"As for how 100 billion came, maybe some people took the second stage of the project into account," Wang Yifang continued. "After the completion of the ring Positron Collider, it has a 100 kilometer tunnel. We don't want this tunnel to be wasted, so there are other possibilities. For example, this tunnel can be used for proton collider or heavy ion collider."

However, only the ring-electron Positron Collider is being planned, and the plan for the completion of the CEPC mentioned above is not yet necessary. Wang Yifang said that if we want to make these follow-up plans, we need to meet two important prerequisites: first, the device has significant scientific discoveries; second, there must be breakthroughs in key technologies.

"These two conditions are indispensable. There will be no second phase if one is missing. And if there are significant technological breakthroughs in meeting these two conditions, such as high temperature superconductivity, its contribution to society is not billions or billions, but more than trillions. Wang Yifang said.

Wang Yifang also said that the development of science from the early hand eye to the microscope on the experimental table, to the large space telescope and the large ground accelerator, is an inevitable trend. "The object of our research is either getting bigger or smaller, which is very difficult for our manpower to touch, so we need to use the instrument. Future development, who has the ability to build these devices, who will eventually become the leader of the world.

In his view, the core question that Chinese scientific circles need to answer now is whether Chinese scientists have the courage, ability, and social and public support to make the most important and core issue of future scientific development.

"CEPC is the core and the most difficult problem. If we dare to do it, we will decide whether China's future scientific development can go to the center of the stage." Wang Yifang said.

 

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