Build an astronomical telescope that captures the elementary particles of the universe under the sea at a depth of 3,000 meters? That's right!
Shanghai Jiao Tong University announced on the 17th that the "Hailing Plan" Pathfinder Project Team recently completed various scheduled sea trial tasks and arrived in Shanghai safely, and the scientific expedition laid a solid foundation for the follow-up promotion of the "Hailing Plan". The voyage was led by Xu Donglian, a scholar of Li Zhengdao of Shanghai Jiaotong University, and Tian Xinliang, a scholar of marine engineering, and more than 30 researchers and technicians from Shanghai Jiao Tong University, Peking University, Tsinghua University, University of Science and Technology of China, and the Second Institute of Oceanography of the Ministry of Natural Resources participated together.
The Jiefang Daily Shangguan News reporter learned that the "Hailing Project" explores the construction of China's first deep-sea neutrino telescope, explores the extreme universe by capturing high-energy celestial particles - neutrinos, builds China's complete multi-messenger astronomical network, promotes cutting-edge cross-cutting research in particle physics, astrophysics, geophysics, marine geography, marine life, etc., has the great potential to breed a number of original scientific discoveries, aiming to "deploy a number of forward-looking, strategic, and basic cutting-edge technology research and development projects" "in the deep sea, deep space, deep ground, Deep blue and other fields actively seize the commanding heights of science and technology." The project is led by the Li Zhengdao Research Institute of Shanghai Jiaotong University, and the project team leader is Jing Yipeng, an academician of the Chinese Academy of Sciences, and invites academicians and top scientists of the Chinese Academy of Sciences with rich experience in various fields of science and engineering as project consultants.
The "bottoming system" and the "four-season submarine marker" are deployed in the South China Sea
[Neutrino astronomy is emerging, and the small particles contain great mysteries]
Neutrinos are one of the basic units that make up the universe and the most numerous particles in the universe. It is not charged and interacts with matter extremely weakly, like a ghost, and extremely difficult to catch. Neutrinos were first predicted theoretically in 1930, but were not experimentally observed until 1956. Scientists' research on its properties has repeatedly refreshed human understanding of the basic laws of physics and won the favor of 4 Nobel Prizes.
There are currently 3 types of neutrinos known to exist, electron neutrinos, miu neutrinos, and pottery neutrinos. Due to the quantum effect, they can be converted to each other in the process of space-time propagation, similar to the face-changing performance of Sichuan opera, which can change its appearance at the moment of space-time transformation, which is the famous neutrino oscillation phenomenon. By building different detectors to study the oscillatory behavior of neutrinos, humans were able to get a partial glimpse of the basic laws of matter formation in the universe. However, neutrinos themselves still have many unsolved mysteries, such as the absolute mass geometry of neutrinos, whether they are antiparticles of their own, and so on.
There are many sources of neutrinos in the universe, such as the Big Bang, supernova explosions, binary neutron star mergers, black hole explosions and other extreme astrophysical processes. At the same time, if dark matter is an elementary particle, it is also possible to produce neutrinos by annihilating each other or decaying spontaneously. Because of its ghostly nature, neutrinos have strong penetration, can easily escape the extreme, dense celestial environment, carrying the information of the violent physical processes in it, and are the ideal for studying the extreme universe.
As early as 1912, physicists found that the Earth's atmosphere was continuously bombarded by space-intensive ions, that is, "cosmic rays", which produced a large amount of secondary radiation that could reach the ground, or was closely related to the origin and evolution of life on Earth. However, because cosmic rays are deflected by magnetic fields in interstellar propagation, their origin is still a mystery. Once these neutrinos produced by cosmic ray reactions are detected, they can be traced back to the source, so that they can solve the century-old mystery of the origin of cosmic rays by detecting the neutrino sources of high-energy celestial bodies.
The idea of neutrino astronomy originated in 1960 when Markov proposed to build an array of Cherenkov light detection elements in the deep sea or in a lake. At present, related projects in the Mediterranean Sea and Lake Baikal are planned, but it is difficult to build a neutrino telescope in the seawater, and the most well-known neutrino telescope in the world, Ice Cube (Ice Cube), has chosen to build the detector array in the Antarctic ice layer at a depth of 2500 meters.
The picture shows the Ice Surface Laboratory of the Ice Cube Neutrino Telescope in Antarctica
【"Ice Cube" failed, "Sea Bell" sailed to explore the sea for 3500 meters】
Built in 2010, Ice Cube remains the world's largest neutrino detector. In 2013, Ice Cube detected for the first time a diffuse stream of high-energy neutrinos from beyond the earth, knocking on the door to high-energy neutrino astronomy.
Unfortunately, this neutrino stream shows no signs of agglomeration or explicitly points back to any known celestial source, suggesting that there is no celestial source of intensely radiating high-energy neutrinos in the universe near Earth. To effectively find celestial sources of high-energy neutrinos, it is still necessary to improve the detection sensitivity of the next generation of neutrino telescopes. At present, Europe and the United States are actively preparing to build a second-generation neutrino telescope with greatly optimized performance, which is expected to be built around 2030, when the field of neutrino astronomy may achieve a major breakthrough.
Xu Donglian, chief scientist of the "Sea Bell" project, has studied and worked in the Ice Cube Cooperation Group for many years and has been active in the field of neutrino astronomy in recent years. Through the accumulation of time in the international cooperation group, she gradually germinated a "dream" - china-led construction of neutrino telescopes in the waters of the South China Sea.
In September 2018, Xu Donglian returned to China to join the Li Zhengdao Research Institute, and in November of the same year, its "Neutrino Astronomy Research" project received support from the "Overseas High-level Young Talents Special Project", mainly to carry out the site selection of neutrino telescopes and the research and development of prototype prototypes of detectors, and attracted a large number of like-minded scientists and engineering and technical experts from Shanghai Jiaotong University and other universities and scientific research institutions. In August 2020, Xu Donglian, on behalf of the "Hailing Project" team, formally proposed the construction planning and action plan of the South China Sea Neutrino Telescope - "Hailing Project" at the National High Energy Physics Development Strategy Seminar (Qingdao).
In the past two or three years, after careful demonstration and the development of related instruments and equipment, as a pre-research demonstration project of the "Sea Bell Project", the "Sea Bell Pathfinder" sea test team has recently successfully deployed several sets of self-developed experimental instruments in the predetermined sea area, not only collecting in situ precious data of more than 1TB of capacity at a depth of 3500 meters, but also scanning and testing the related properties of all-water deep seawater. After preliminary analysis, the feasibility of pre-selected sea area as a candidate site for neutrino telescopes is verified. In addition, the team also successfully deployed a set of submarine markers that can monitor the submarine flow field, biological activity, sediment and test telescope components for a long time, providing a basis for the design and long-term operation and maintenance of subsequent telescope arrays.
Column Editor-in-Chief: Xu Ruizhe Text Editor: Xu Ruizhe
Source: Author: Xu Ruizhe