Science and Technology Daily reporter Sheng Li
On July 20th, the first major national science and technology infrastructure undertaken by Tsinghua University as an independent legal entity ——“ extremely deep underground low-radiation background frontier physical experiment facility” launching ceremony in Yalongjiang, Sichuan Province The Pingshan Tunnel is held, marking the first and deepest deep underground laboratory in China, jointly established by Tsinghua University and Yalong River Basin Hydropower Development Co., Ltd. ——“China Jinping Underground Laboratory” New stage.
China Jinping Underground Laboratory is located at the entrance of Jinpingshan Tunnel
The extremely deep underground low-radiation background frontier physical experiment facility is a major technological infrastructure that was prioritized by the state during the 13th Five-Year Plan period. The National Development and Reform Commission takes the lead in construction management. The Ministry of Education and the Sichuan Provincial People's Government jointly hold the same. The legal entity is Tsinghua University. The joint construction unit is the Yalong River Basin Hydropower Development Co., Ltd.
This is not only a major responsibility for Sichuan to undertake the national strategy, but also a major event in the process of accelerating innovation-driven development in Sichuan.
After the completion of the project, it will become an important innovation platform for the country. It will lay a solid foundation for the construction of a world-leading deep underground research center, scientific investigation and science education base. It will further consolidate China's science and technology foundation, promote scientific and technological progress, and enhance independent innovation capability and international Influence provides strong support for the high quality development of the economy and society.
CJPL Phase II B2 Laboratory Hall Status
Figure 13 CJPL Phase II C1 laboratory excavation foundation pit renderings
According to the project objectives, the project will use the space conditions of the second phase of Jinping Underground Laboratory to build the underground laboratory with the deepest world, the smallest cosmic flux, the largest available space and complete comprehensive conditions. The cosmic flux is less than every year. 100 square meters, with a volume of more than 300,000 cubic meters.
Large-scale liquid nitrogen low-temperature radiation shielding device, large-scale normal temperature pure water radiation shielding device, extremely low-radiation background measurement and analysis device (minimum detectable activity of about 10 microbecks per kilogram), with full support for direct detection of dark matter in China The ability of frontier physics experiments such as micro-double beta decay experiments and underground nuclear astrophysics experiments.
Explore dark matter:
It is expected to become the world's deep physics experiment center
In cosmology, dark matter refers to substances that do not emit any light or electromagnetic radiation. Modern astronomical studies through gravitational lenses, large-scale structure formation in the universe, and microwave background radiation show that the part we know is only about 4% of the universe, dark matter accounts for 23% of the universe, and 73% is a cause. The dark energy of the universe's accelerated expansion.
In 2009, Tsinghua University cooperated with the Yalong River Basin Hydropower Development Co., Ltd. (formerly Ertan Hydropower Development Co., Ltd.) to construct a deep underground laboratory at 2,400 meters underground in the middle of the Jinpingshan Tunnel.
At the end of 2010, “China Jinping Underground Laboratory” was completed and put into use, becoming China's first and the deepest underground laboratory in the world. In 2014, Tsinghua University and Yalong River Basin Hydropower Development Co., Ltd. signed an agreement to jointly build the second phase of the China Jinping Underground Laboratory, which will increase the underground experimental space from 4,000 cubic meters to 300,000 cubic meters. .
“The ultra-deep underground very low-radiation background frontier physical experiment facility” is aimed at the major fundamental frontier research of new particles and new physics beyond the current particle physics standard model, conducting direct detection of dark matter and no-neutrino double beta decay experiment. And the key scientific research in the field of nuclear astrophysics, such as the key nuclide synthesis process and stellar evolution, to explore new mechanisms, new methods, and new technologies for the development of various basic frontier fields under extremely deep underground near zero cosmic ray background conditions. Radiation background shielding new methods and new technologies provide platform support for the study of major fundamental frontier physical problems in the field of particle physics and nuclear physics in China.
CJPL Phase II C1 Laboratory Status and Foundation Pit Overhead View
After the completion of the project, it will have the internationally advanced comprehensive conditions for deep physics experiments, and it is expected to become the center of the world's deep physics experiments, promote China's international scientific cooperation, attract top scholars at home and abroad to carry out frontier physics experiments, to achieve significant physics. Breakthrough provides infrastructure support.
At the same time, the project will provide an underground radiation measurement platform with a near-zero cosmic line background, which can solve the problem of extremely weak radioactive reference measurement and low dose rate calibration, provide implementation conditions for China's construction of a complete radiation measurement benchmark, and promote marine science. Research in the fields of materials science, environmental science, and biology provides a world-class, extremely low-level cross-innovation platform for these disciplines.
Multiple experimental platforms will be built in 5 years
Major breakthroughs in modern physics often require extreme experimental conditions. Extremely deep underground laboratories are important facilities for conducting physics experiments in the fields of particle physics and nuclear physics, astrophysics and cosmology.
Compared with other underground laboratories in the world, China Jinping Underground Laboratory has the deepest rock coverage, the smallest cosmic flux and the largest available space, and has the advantages of convenient transportation, sufficient power and water resources, and complete infrastructure.
In 2016, since the project entered the 13th Five-Year Plan of the National Major Science and Technology Infrastructure, the National Development and Reform Commission has given strong support from the aspects of overall coordination and funding arrangements, and has included the project in the first batch of simplified approval pilots and officially approved in December last year; Careful guidance and joint efforts. The Sichuan Provincial Party Committee and the Provincial Government attached great importance to it. Provincial Party Secretary Peng Qinghua and Governor Yin Li made important instructions on many occasions. The relevant provincial departments and local party committees and governments at all levels made full efforts to coordinate services. The project undertaker unit Tsinghua University and Yalong River Basin Hydropower Development Co., Ltd. boldly explored and coordinated research, and pragmatically promoted the preliminary work of the project in accordance with national requirements. With the joint support and efforts of all parties, the project officially entered a new stage of accelerated construction.
According to the reporter's inspection, the main construction contents of the project are: construction of underground laboratory comprehensive operation and maintenance support platform, mainly construction of underground experimental support system, underground security support system, underground working condition support system, underground laboratory management information system. Construction of extremely deep underground very low radiation background radiation shielding platform, mainly to construct large liquid nitrogen low temperature shielding device, large normal temperature pure water shielding device, combined solid radiation shielding device. The construction of a very deep and very low background analysis test platform, mainly to build microbeck radiation level background measurement and analysis device, underground radioactivity measurement and analysis system, underground very low radioactive material preparation and test system. Construction of ground-based auxiliary experimental platform, mainly to build ground laboratory, operation and maintenance management center, data storage and material transfer system.
According to the plan, “very deep underground low-radiation background frontier physical experimental facilities”, the project construction period is 5 years.
“ Follow with & rdquo; change & ldquo; and run & rdquo;
Direct detection of dark matter in China & ldquo; leap & rdquo;
Since the completion of the first phase of the Jinping Underground Laboratory in China, the direct detection of dark matter such as the High Purity Direct Detection Cooperation Group (CDEX) led by Tsinghua University and the Direct Detection Cooperation Group (PandaX) led by Shanghai Jiaotong University has been carried out. The experiment and the Jinping neutrino experiment hosted by Tsinghua University have achieved a series of research results. In a relatively short period of time, China's direct detection of dark matter has been carried out from scratch, and the research level has reached international advanced level, from "follow-to-run" to "and run".
In 2013, the CDEX cooperation group led by Tsinghua University published the first independent dark matter research results in China, and the research level reached the international first camp. In 2014, the cooperation team obtained the most sensitive experimental results of similar detectors in the energy zone below 10GeV, and deterministically excluded the dark matter existence areas claimed by the US CoGeNT experimental group for many years. In 2018, the CDEX Cooperative Group published the best international dark matter detection sensitivity test results for the 4-5 GeV energy interval.
Nowadays, the effective experimental data of the CDEX cooperation group has accumulated for more than 4 years. It has carried out physical analysis of multiple channels such as annual modulation, dark matter axis and dark photon. It has not only achieved international advanced level results in dark matter research, but also high purity.核心 Detector independently developed, independent low-temperature low background front-end electronics development and other core technologies have made important breakthroughs.
In 2018, the CDEX team independently developed the world's first low-threshold low-profile configuration of metal oxide integrated circuit preamplifiers for point-electrode high-purity germanium detectors (ASIC-PPCGe) with energy resolutions reaching commercial detector levels. Moreover, the low-energy Ge-68 Yusheng X-ray was measured, demonstrating low background measurement capability.
Dr. Li Yulan, Director of the Department of Radiation Physics and Detection Technology, Department of Engineering Physics, Tsinghua University, introduced the construction of the laboratory
In the future, the cooperation group will build an enriched high-purity tantalum array detector system with a 锗-76 isotope abundance of more than 85% on the order of 100 kg to ton, which will increase the detection sensitivity by two to three orders of magnitude, and simultaneously measure dark matter. And the study of two major frontier scientific issues in the absence of neutrinos and double beta decay.
In terms of international cooperation, the CDEX cooperation team participated in the LEGEND cooperation group composed of hundreds of scientists from more than 40 universities and research institutions in China, the United States, Europe and other regions, independently proposed and promoted the tonnage level based on the LEGEND framework. Pure 锗 no neutrino double beta decay experimental program.Source: Science and Technology Daily The picture in the text is provided by Jinping Underground Laboratory and the network.Editor: Liu Yiyang
Audit: Guan Jingjing