The world's largest! The glass ball in the Greater Bay Area that explores the beginning of the universe is fully built!

Author: Li Chuanfu Shi Xiangqi

On October 11, 2024, in Jiangmen, Guangdong, a world-class scientific project, the Jiangmen Neutrino Experiment (JUNO), has entered the final stage of construction. This experimental device, located 700 meters underground, has attracted global attention with its core detector, the world's largest single organic glass ball. This huge "glass ball" is not only a masterpiece of engineering technology, but also a light of hope for mankind to explore the mysteries of the universe.

The core scientific goal of the Jiangmen Neutrino Experiment is to measure the neutrino mass order, which is a key unsolved mystery in particle physics. Neutrinos are one of the most basic particles in the universe. They hardly interact with any matter, so they are also called "ghost particles." Despite this, neutrinos play a vital role in the evolution of the universe, the formation of stars, and supernova explosions. By accurately measuring the mass order of neutrinos, scientists hope to unlock the secret of the asymmetry of matter and antimatter in the universe, which is of great significance to our understanding of the origin and structure of the universe.

The detector of the Jiangmen Neutrino Experiment consists of a stainless steel mesh shell with a diameter of 41 meters, a plexiglass ball with a diameter of 35.4 meters, 20,000 tons of liquid scintillator and 45,000 photomultiplier tubes and other key components. This huge plexiglass ball has an inner diameter of 35.4 meters and is made of 263 12-centimeter-thick curved ball panels and upper and lower chimneys. It weighs about 600 tons and is currently the largest single plexiglass ball in the world. Its completion marks a major breakthrough in the technology of the Jiangmen Neutrino Experiment and also demonstrates China's R&D and innovation capabilities in the field of high-energy physics.

During the construction of the Jiangmen Neutrino Experiment, the scientific research team overcame many technical difficulties, including the successful development of the photomultiplier tube with the highest photon detection efficiency in the world with independent intellectual property rights, breaking the international monopoly in this field, and obtaining patent authorizations from the European Union, the United States, Japan, etc. In addition, a high-strength, high-precision, high-transmittance photomultiplier tube underwater explosion-proof system was developed, a high-cleanliness, high-sealing, high-efficiency liquid scintillator purification system was developed, and an innovative design of underwater electronics was adopted to achieve aerospace-level reliability with civilian devices.

The international cooperation of the Jiangmen Neutrino Experiment has also reached a new height. Since the establishment of the international cooperation group in July 2014, it has now developed into a large international cooperation group consisting of 750 researchers from 74 research institutions in 17 countries and regions. This international cooperation model not only promotes the sharing of scientific research resources, but also provides a platform for scientists around the world to jointly explore the mysteries of the universe.

With the completion and operation of the Jiangmen Neutrino Experiment, it is expected that this large scientific facility will officially start taking data in August 2025 and will operate for about 30 years. Its successful operation will further consolidate China's international leading position in the field of neutrino research, and form a tripartite trend with Japan's top Kamioka Neutrino Experiment and the United States' Deep Underground Neutrino Experiment, jointly promoting the in-depth development of global neutrino research.

The Jiangmen Neutrino Experiment is not only a demonstration of China's scientific and technological strength, but also a great attempt by mankind to explore the origin of the universe and the basic laws of physics. With the completion of this huge "glass ball", we have reason to believe that it will reveal more mysteries of the universe for us in future scientific explorations.