High altitude cosmic ray observatory (English: LHAASO,Large High Altitude Air Shower Observatory，Spanish: Observatorio de rayos c ó smicos de gran altitud (nicknamed "Lasso" in Chinese) is the highest, largest and most sensitive cosmic ray detection device in the world, and is China's national major scientific and technological infrastructure.[15]
Gaohaiba Cosmic Ray Observatory is located in Sichuan Province, ChinaDaocheng CountyHaizi MountainIt covers an area of about 1.36 square kilometers.Its core scientific objectives are to explore the origin of high-energy cosmic rays and related cosmic evolution and high-energy celestial activities, and to find dark matter;Widely search for gamma ray sources in the universe, especially in the Milky Way.The observation station includes electromagnetic particle detector array installed on the ground, muon detector array installed underground, water Cherenkov detector array, and wide-angle Cherenkov telescope array, with sensitivity and coverage reaching the international leading level.[26]
In July 2016, the infrastructure construction of Gaohaiba Cosmic Ray Observatory began;On June 19, 2018, the Gaohaiba Cosmic Ray Observatory was officially started.[1]On May 10, 2023, the high altitude cosmic ray observatory (LHAASO, cable), a major national science and technology infrastructure, successfully passed the national acceptance.[7][14]
In March 2024, Gaohaiba Cosmic Ray Observatory was awarded the "National Science Popularization Base for Scientific Research".[25]
Chinese name
High altitude cosmic ray observatory
Foreign name
Large High Altitude Air Shower Observatory（LHAASO）
As material samples outside the solar system, cosmic rays and their origins are important ways for human beings to explore the universe and its evolution.In the 100 years after the discovery of cosmic rays in 1912, the exploration and research related to cosmic rays have produced several Nobel medals, but mankind has never discovered the origin of cosmic rays, thus making the origin of cosmic rays a problem that natural science faces in the 21st century, including dark matterOne of several basic problems, including dark energy, ranks among the top 5 among the 6 or 11 basic scientific problems refined by scientific decision-making bodies in Europe and the United States.The "High Altitude Cosmic Ray Observatory (LHAASO)" was proposed to aim at this major scientific problem.
High altitude cosmic ray observatory
In order to explore the origin of cosmic ray, a charged particle that permeates the whole universe, the gamma astronomy experiment in Europe, America, China and Japan, the Antarctic neutrino experiment in the United States and the giant high-energy cosmic ray experiment cooperated by many countries constitute three pillar research branches.Among them, the gamma celestial literature experiment is particularly mature. In the past 20 years, it has expanded a most active cross field of high-energy physics and astrophysics. More than 150 source objects have been found, among which there are many candidate sources of cosmic rays, which is pregnant with major opportunities for breakthroughs.The international competition in this field is very fierce. After the second generation of MILAGRO experiment, the United States moved from 2700 meters above sea level to the 4100 meters high mountain station site, in order to increase the sensitivity by more than ten times, started the HAWC experiment, completed the construction task, and began observation at the end of 2014.Europe's granderCherenkov Telescope ArrayThe (CTA) plan, which has been included in the just released European Astrophysical Development Roadmap, will spend 200 million euros to upgrade the existing experiments and try to cover a wide energy area with its traditional fixed-point observation devices.
Figure 3: Design sketch of wide-angle Cherenkov telescope array
Alpine experiment is a ground detection method that can minimize the absorption effect of the atmosphere in cosmic ray observation and research. Its scale can be far larger than that of space-based detectors outside the atmosphere, and it has become an indispensable research method for very high and ultra-high energy gamma astronomy and cosmic ray observation.
Figure 2: Design sketch of water Cherenkov detector array
Chinesecosmic rayThrough the long-term cooperation with Japan and Italy, the powerful countries in cosmic ray research for nearly 30 years, the research has made use of the roof of the worldYangbajing Observation StationThanks to its unique natural advantages, it has obtained the successful experience of developing the first generation (AS γ) and second generation (ARGO-YBJ) gamma ray survey telescopes, and is among the international advanced in the field of large field survey.On this basis, we propose to build a high altitude cosmic ray observatory at a site with better comprehensive conditions, use a variety of detection methods to achieve composite and accurate measurement, greatly improve the sensitivity, cover a wider energy spectrum, and build a third-generation gamma astronomical detector, which will reach the world's leading level in the following three aspects:
(1) Ultra high energy gamma ray detection sensitivity.In the energy region higher than 10TeV, the detection ability of the ARGO-YBJ experiment is hundreds of times higher than that of the ARGO-YBJ experiment, and even more than ten times higher than the sensitivity of the CTA plan, occupying the commanding height of the experimental research field for a long time;
(2) Sensitivity of very high energy gamma ray survey.In the energy region of hundreds of GeV, it is 30 times higher than ARGO-YBJ, so it quickly occupies the international leading position with a sensitivity three to four times higher than HAWC;
(3) A device for accurate measurement of cosmic ray energy spectrum and composition with wide energy coverage.The creation of an internationally leading high-altitude cosmic ray research center has a strong impact on solving the mystery of the origin of cosmic rays, one of the major frontier scientific problems in the new century.
Detect target
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High altitude cosmic rayObservation stationThe core scientific objective of the is to explore the origin of high-energy cosmic rays and carry out related basic scientific research on high-energy radiation, celestial evolution and even dark matter distribution.The specific scientific objectives are as follows:
(1) Explore the origin of high-energy cosmic rays.By accurately measuring the wide range energy spectrum of high-energy gamma source, study the characteristics of high-energy radiation source particles, and exploreGalaxyThe evidence of the existence of the internal baryon accelerator has made a breakthrough in the discovery of the cosmic ray source;Accurately measure the energy spectrum and composition of cosmic rays, and study the acceleration and propagation mechanism of cosmic rays.
(2) Carry out scanning and searching of gamma sources throughout the sky, discover a large number of new gamma sources, especially river sources, accumulate statistical samples of various sources, explore their high-energy radiation mechanism, including the mechanism of generating strong time-varying phenomena, study the evolution law of active galactic nuclei centered on supermassive black holes, capture high-energy gamma bursts in the universe, and explore their explosion mechanism.
(3) Exploredark substance、Quantum gravityOr Lorentz invariance destruction and other new physical phenomena, discovering new laws.
Aiming at the above scientific goals, the construction goal of the observation station is to build a gamma ray and cosmic ray detection device with the following design indicators: for the 2TeV gamma ray source, the annual sensitivity will reach<1.3% of the Crab Nebula current intensity;For the 50TeV gamma ray source, the annual sensitivity is also less than 1.2% of the Crab Nebula current intensity;For 100TeV cosmic ray, the effective aperture is>4000msr.The detector array is designed into four parts:
(1) Electromagnetic particle detector array (ED);
(2) Muon detector array (MD);
(3) Water Cerenkov Detector Array (WCDA);
(4) Wide angle Cerenkov Telescope Array (WFCTA).
According to the characteristics and requirements of the detector, the synchronization technology of remote clock in sub nanosecond accuracy is developed, and it is applied to the electronics system scattered over 1.36 square kilometers. At the same time, the front-end signal digitization, data transmission, software case trigger selection assisted by computing clusterAnd real-time online processing under data conditions.
Base composition
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High altitude cosmic ray observatory consists of observation base and measurement and control base.Through extensive site selection and field survey in high-altitude areas in China, the project finally selected the highland of Haizi Mountain in Daocheng County, Sichuan Province, with an average altitude of 4410 meters as the observation base, covering an area of~2040 mu, and established a measurement and control base in the urban area of Daocheng County, which covers an area of~20 mu.Compared with the existing alpine stations in China, this site selection will greatly improve the working conditions of field stations, ensure the life safety of researchers working in the plateau area for a long time, and facilitate the smooth development of international cooperation with convenient transportation and stable social environment.The implementation of this project will be an important layout of China's large scientific facilities in southwest China. The settlement of Gaohaiba cosmic ray observatory in Sichuan will give full play to the advantages of astronomical observation resources in southwest China, build a cosmic ray research and astronomical observation base, build an international leading high-altitude cosmic ray research centerTourism and local economic development have a positive impact.
Overlooking the "cable"
The total investment of Gaohaiba cosmic ray observatory is about 1.2 billion yuan, including about 300 million yuan of Sichuan supporting construction funds.After the project is approved, the construction period is 4 years, and the scientific life is more than 20 years after the project is put into operation.[3]
Following LHAASO's scientific objectives, the overall technical plan is[4]The air shower (EAS) produced by cosmic ray particles and gamma rays in the atmosphere is accurately measured by different technical means in three energy ranges.The implementation scheme is
(1) Construction 1kmtwoElectromagnetic particle detector array and effective area up to 42000mtwoDesign of muon detector array based on dsp（KM2A）。
(2) 78000m with measuring Cherenkov light generated by shower particles in water as the detection technologytwoDesign scheme of detector array（WCDA）。
(3) 18 wide-angle Cherenkov telescope arrays have been built（WFCTA）。
（1）Ground shower particle array (KM2A)
KM2A is designed as a ground particle array with a radius of 575m in the central area. 4901 electromagnetic particle detectors (ED) are evenly arranged in a zigzag shape with a spacing of 15m, and 1171 muon detectors (MD) are evenly arranged in the array in a zigzag shape with a spacing of 30m;The peripheral area is a circular area with a radius between 575m and 635m, and 294 EDs are arranged at an interval of 30m.
ED：It is used to measure secondary electromagnetic particles in EAS.The detection medium is a plastic scintillator, which collects the scintillation light generated by charged particles in the scintillator through wavelength shifted optical fibers and transmits it toPhotomultiplier tube(PMT), which is converted into electrical signals for measurement.
MD：It is used to measure the mussel content in EAS.The basic structure isreinforced concreteThe tank is equipped with a soft water bag, which contains ultrapure water. An 8-10 inch PMT is installed in the center of the top of the water bag to collect the Cherenkov light generated in the water by the muzzle entering the tank and convert it into an electrical signal for measurement.
（2）Water Cerenkov Detector Array (WCDA)
The array area is 78000mtwoIt is composed of two 157.5m × 150m and one 307.5m × 100m large adjacent pools, with a water depth of 4.4m.Each pool is divided into several 5m × 5m unit detectors, each of which is placed with a PMT to observe Cherenkov light generated by secondary particles in EAS in water, and convert it into electrical signals for measurement.
（3）Wide Angle Cherenkov Telescope Array (WFCTA)
Measurement of Cherenkov light or fluorescence generated by high-energy cosmic rays or high-energy gamma rays through showers in the atmosphere.By virtue of the unique movable characteristics of the telescope, phased array layout adjustment, combined with KM2A and WCDA, multi parameter and energy division sections, the energy spectrum of cosmic ray components can be accurately measured.The spherical mirror design scheme composed of multiple lenses is adopted, and the reflected light is collected by the PMT array located in the focal plane.
Constitutive use
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LHAASO aerial photo (taken in 2022)
"Cable" includes 5216Electromagnetic particle detectorAnd 1188Muon detectorIt consists of three major arrays: the 1 square kilometer ground shower particle detector array, the 78000 square meter water Cherenkov detector array, and 18 wide-angle Cherenkov telescopes.This "big guy" can collect the information of secondary particles generated after the atmospheric shower in a large range, deduce the source of the "shower" - the properties of ultra-high energy particles, and measure the gamma rays and cosmic rays from high-energy objects in an all-round and multivariable way.[14]
Management organization
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Chengdu Branch of Chinese Academy of Sciences is the legal entity of LHAASO project.Chengdu Branch has a number of national, ministerial and provincial key laboratories, engineering technology centers and field science stations with domestic leading level and international advanced level.The scope of research includesoptics、electronics、Mechanics、material science 、computer scienceEtc.stayadaptive optics 、microelectronics、laser、Optical electromechanical integration、Instruments and Apparatuses, genetic breeding, fragile ecological restorationenvironmental protectionAnd mountain disaster prevention.In recent years, all units in Chengdu and Chongqing under the CAS have made encouraging achievements in helping China's scientific, technological, economic and social development, and won unanimous recognition from national, local and CAS leaders, closely centering on the national "12th Five Year Plan", the "Leading Action Plan" of the Chinese Academy of Sciences, and the "Innovation 2020" and other major deployments.
The Cosmic Ray Research Center of Chengdu Branch is the main unit responsible for high-altitude cosmic ray observation stations.The staff of the Cosmic Ray Research Center have scientific research and international cooperation experience in the construction and continuous and stable operation of the two major experiments of AS γ and ARGO-YBJ.Through the large-scale installation, commissioning and upgrading of ARGO-YBJ detector and the development, launch and commissioning of the wide-angle Cherenkov telescope, a high-quality scientific research and technical team has been cultivated for the Cosmic Ray Research Center. The team members have acquired the technology and experience in the research, development, production, installation, commissioning and operation of large-scale cosmic ray experiments and related exploration technologies.
Institute of High Energy Physics, Chinese Academy of SciencesIt is the co construction unit of LHAASO project.The Institute of High Energy Physics has the strongest ability to research and develop advanced accelerators such as BEPCII in China, has organized large-scale high-energy physics experiments such as BESIII, and has a high-level interdisciplinary research center covering nuclear chemistry, optics, materials, nano, biology, pharmacy, archaeology, etc,At the same time, it also has an independent high-energy cosmic ray physics research team integrating scientific research and detection technology research and development capabilities.This team was founded in the early 1950s. It is in a leading position in the field of cosmic ray research in China in terms of personnel structure, scientific research ability, basic scientific research resources and conditions, organization and management, and has incomparable advantages.
Value significance
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The Gaohaiba Cosmic Ray Observatory will take advantage of Daocheng's unique high altitude advantage to build an international Gaohaiba Cosmic Ray Research Center with multinational participation in cooperative research, and build a scientific research platform with strong international competitiveness, unique characteristics, and comprehensive opening,It complements the existing three international cosmic ray research centers (the 3000 square kilometer extremely high energy cosmic ray AUGER experiment in South America, the cubic kilometer neutrino ICECUBE experiment in Antarctica, and the European gamma astronomy fixed-point observation CTA device), forming a strong international attraction.We have formed multilateral international cooperation in improving the spatial resolution of gamma ray measurement, extending multi means to low threshold energy, and expanding the ability to observe extremely high energy cosmic rays, and introduced new experiments at home and abroad in a short time.At the same time, it also provides an experimental platform for conducting cutting-edge scientific cross research in the form of atmosphere, meteorology, space environment, etc., and makes important contributions to the relevant national scientific and technological development needs.[5]
Lasso has become the most sensitive ultra high energy gamma ray detector in the world, the most sensitive very high energy gamma ray source survey telescope in the world, and the ultra high energy cosmic ray composite stereo measurement system with the widest energy coverage.
The "cable" put into operation will become an importantparticle astrophysics As one of the pillar experiments, China's research in high-energy gamma ray astronomy has reached the international leading level.
Major events
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On June 19, 2018, Gaohaiba Cosmic Ray Observatory was officially started, with a construction period of 5 years.[1]
From March 22 to 24, 2018, the cooperation group meeting of the High Altitude Cosmic Ray Observatory (LHAASO) was held inSouthwest Jiaotong UniversityHold?About 100 scientific researchers and young students from 24 institutions of the Chinese Academy of Sciences and domestic universities attended the conference.The participants fully exchanged their work from the perspective of theory and experiment through 47 reports on LHAASO's scientific goals and engineering progress.The report includes the origin of cosmic ray acceleration, basic laws of physics, shower physics, solar physics, and progress of LHAASO project inside and outside the Milky Way, including relevant research and construction of various detectors, construction of offline data analysis software and data analysis platform, and construction of data network and computing platform.[11]
On May 17, 2021, Gaohaiba Cosmic Ray Observatory found the first batch of "electron volt accelerator" and the highest energy photon, which opened the era of "ultrahigh energy gamma literature". This achievement was published in the journal NATURE (Nature).[6]
On May 17, 2021, the Institute of High Energy Physics of the Chinese Academy of Sciences and Springer Nature Publishing Agency jointly announced in Beijing that a large number of ultra-high energy cosmic accelerators were found in the Milky Way Galaxy by the "High Altitude Cosmic Ray Observatory", a major national scientific and technological infrastructure, and recorded gamma photons with an energy of 1.4 petaflops of electron volts (petaflops=billions), which is the highest energy photon observed by mankind,It broke through the traditional human cognition of particle acceleration in the Milky Way, and opened the era of ultrahigh energy gamma astronomy.[7]
On July 9, 2021, it was announced that the new achievement of the High Altitude Cosmic Ray Observatory was to measure the brightness of the "standard candle" ultra high energy band.[8]
In October 2021, Gaohaiba Cosmic Ray Observatory passed the environmental protection acceptance of completion.[9]
In October 2022, it was reported that Gaohaiba Cosmic Ray Observatory, High Energy Burst Explorer and Insight Satellite simultaneously detected the brightest gamma ray burst so far, breaking many records of gamma ray burst observation.[10]
In May 2023, the "Lasso" (LHAASO) of Gaohaiba cosmic ray observation station passed the national acceptance on the 10th.[13]
In June 2023,The scientific researchers of the Institute of High Energy Physics of the Chinese Academy of Sciences made a survey of the universe through the high-altitude cosmic ray observatory in Daocheng, SichuanGamma ray burstA complete monitoring was carried out, which is the first time that the whole process of this high-energy explosion phenomenon has been fully recorded by human beings.[17]
On June 9, 2023, Science magazine published the paper of the international cooperation group of the High Altitude Cosmic Ray Observatory (LHAASO, referred to as "Lasso" in Chinese) - Trillion Electron Volts Afterglow of the 221009A Narrow Jet of the Extremely Bright Gamma Ray Burst online.Lasso, located in Sichuan Province, China, recorded the whole process of the trillion electron volts gamma ray explosion at the moment of death of a massive star for the first time, opening the veil of the explosion.[18]
In November 2023, scientists accurately measured the high-energy radiation spectrum of GRB 221009A, the brightest GRB so far, using the Chinese High Altitude Cosmic Ray Observatory "Lasso" (LHAASO), and gained a new understanding of GRB accordingly.[19]
On February 26, 2024, the Institute of High Energy Physics of the Chinese Academy of Sciences announced that Chinese researchers found a giant ultra-high energy gamma ray bubble structure in the Cygnus star forming region through the High Altitude Cosmic Ray Observatory (LHAASO, "Lasso") in Daocheng, Sichuan Province, and for the first time internationally certified the origin of cosmic rays with energy higher than 100 billion electron volts.This achievement was published in the academic journal Science Bulletin in the form of a cover article on February 26, Beijing time.[23]
Honors won
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In February 2024, Gaohaiba Cosmic Ray Observatory - "Lasso" and other deep space major achievements were selectedTop Ten Scientific and Technological Innovation Fields in Sichuan in 2023.[22]
On the morning of February 29, 2024, the National Natural Science Foundation of China (NSFC) released the "Ten Major Advances in Science in China" in 2023, which are mainly distributed in life science and medicine, artificial intelligence, quantum, astronomy, chemical energy and other scientific fields."Lasso found the extremely narrow jet and one trillion electron volts photon of the brightest gamma burst in history" was selected.[24]
In March 2024, Gaohaiba Cosmic Ray Observatory was awarded the "National Science Popularization Base for Scientific Research".[25]
Issue commemorative stamps
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Notice of the Office of the State Post Office on the Contents of the Commemorative Stamps of Scientific and Technological Innovation (IV): the contents of the five commemorative stamps of Scientific and Technological Innovation (IV) in the 2023 special stamp issuance plan, one of which is a high-altitude cosmic ray observatory.The stamps will be issued on November 1, 2023.[16]
