In the plans of the Chinese mega-collider that will deny the LHC

Physicists at the Institute of High Energy Physics (IHEP) in Beijing are designing the world's largest particle breaker. If constructed, the 100 km circumference facility will be larger than the 27-kilometer Large Hadron Collider (LHC) at CERN, the European particle physics laboratory near Geneva, Switzerland – and would cost about half of the price.

This ambitious 30 billion yuan ($ 4.3 billion) complex, known as the Circular Electron-Positron Collector (CEPC), was designed by IHEP director Wang Yifang. . He has been leading the project since the discovery of the elementary particle called the Higgs boson at the LHC in 2012.

The CEPC will produce Higgs bosons by crushing electrons and their counterparts of antimatter, positrons. Because they are fundamental particles, their collisions are sharper and easier to decipher than the LHC proton-proton collisions. Thus, as soon as the Chinese site is open, it will allow physicists to study the mysterious particle and its weakening exquisitely. detail.

Last week, IHEP released a progress report outlining the collider blueprint. The initial funding for research and development was provided by the Chinese government, but its design is the result of an international collaboration of physicists and the team hopes to raise funds from around the world. (Researchers behind rival plant Higgs, one of the long-time competitors, known as the International Linear Collider, expect to know by the end of the year whether Japan will invest money to host it.)

The plans reveal that the Chinese collider would circulate in a circle located 100 meters underground, at a place still undetermined, and would host two detectors. By the end of its ten-year life, the electron-positron machine could be upgraded to collide protons at energies seven times higher than the LHC at its peak. Before the publication of the report, Nature spoke to Wang about the project.

After six years of design work, an international panel of experts said the collider was ready for operation. Construction could begin as early as 2022. What's going on now?

We are currently working on research and technology development (R & D). Nobody had ever built such a large machine before, and we want to minimize costs. Its specifications are different from any other machine in the world in the past and we have to prove that this is achievable.

Two years ago, the International Collider Advisory Committee stated that the project lacked international participation. Has progress been made on this front?

This has not changed much, as international participation is still limited by the financial commitment of international partners. They are all interested, but they must get the endorsement of their funding agencies. They are waiting to hear the Chinese government's position on its funding, and this decision depends on the outcome of R & D. But CERN is working on a new European strategy for particle physics, so we hope that this time the CEPC will be able to be included. A similar process will take place in the United States, probably over the next year or until 2020. We hope that it will be included in both.

A Chinese collider operating in the 2030s would be in direct competition with CERN's own projects to build a successor to the LHC. Do you think that there is a need for more than one mega-collider?

It is too early to say that it is a competition. I think it is good to have different proposals and to explore in depth the advantages and disadvantages of each proposal. Then we can see which is the most feasible and the community will decide.

Do you think that the international community would accept China becoming the world's center of high energy physics, given that the country does not have free Internet access and has significant government controls?

Such a center would help China to internationalize and open more to the world. And that will bring more resources to the scientific community. At the very beginning, people may think that it is not as practical compared to Switzerland. But we hope that the collider would be a good thing, at least for the Chinese. Moreover, I do not think it will be the only center in the world. Historically, we have always had many centers of particle physics, even though we have fewer and fewer. But I really hope we will not be the only ones. If you have no competition in one area, you will die at some point.

China is currently experiencing an explosion of accelerator facilities. Tell me about some of these plans.

The spallation neutron source in Dongguan is now operational. It's small but pretty good. IHEP also plans to build a 1.4-kilometer light source in Huairou, North Beijing, at a cost of 4.8 billion yuan. It is a circular electron accelerator capable of generating synchrotron radiation – extremely intense X-rays. These are useful for almost all research disciplines, including materials science, chemistry, biology, environmental science, geology and medicine. We think that the government will definitely approve the project by the beginning of next year, and then we can start construction. We think it would be a world leading machine. Most light sources are upgrades to existing machines, so they are limited. We can use the best configurations, the best technologies, without constraints.

The institute also plans to launch an experiment – a detector measuring highly energetic particles known as cosmic rays – on the Chinese space station with crew, which is expected to be launched in 2020. What will it do and how will it improve? there existing experiences?

We want to know where the cosmic rays come from and how they get so high energy. The answers to these questions will help us understand the Universe. We would also like to use it to search for new particles, such as dark matter, that can not yet be generated by the accelerators of the Earth. One of today's best experiences in this regard is the International Space Station's Alpha Magnetic Spectrometer (AMS), which has yet to show any obvious signs of dark matter. This means that we need experiments that can detect more particles and at higher energies. The high energy cosmic radiation detection experiment will study about ten times more powerful particles than the AMS and measure their energies with better resolution. We have almost completed our design and we are now trying to get support from the Chinese government. We are probably talking about 200 to 300 million US dollars for the detector. He is on the list of candidates for possible projects for the future Chinese space station. We have to wait, but I am optimistic.

Do you think that funding for science in China will continue to be high?

The government is certainly interested in supporting science. They hope that every penny invested will be worth something, and sometimes in high energy physics we will disappoint them – we are not able to generate immediate results.

Did the political situation between the United States and China have an impact on the relations between the scientists of the two countries?

It's difficult at the moment. If we hold a conference in China, US academics can come freely, but those who work in US national labs say they can not get permission. In addition, it is very difficult for Chinese scientists to obtain a letter of invitation to these laboratories in the United States. I really hope that it is only temporary and that politicians can realize that the exchange of science and collaboration in science are mutually beneficial.

This interview has been modified for clarity and length.