"A New Era of Neutrino Physics" World's Largest Neutrino Detector Completed in China

Related Vendors

TU München

Wuxi InfiMotion Technology Co., Ltd.

After more than ten years of construction, the Jiangmen Underground Neutrino Observatory (JUNO), developed with the involvement of the Technical University of Munich, is now completed. The core element is the neutrino detector, which is 20 times larger than previous facilities of its kind. Its purpose: to learn more about neutrinos, such as their mass hierarchy.

Neutrinos pose great mysteries to particle physicists. Their properties appear enigmatic and point to as-yet-undiscovered physics beyond the established Standard Model of particle physics. The Jiangmen Underground Neutrino Observatory (JUNO) in China, now operational after ten years of construction, aims to provide more clarity in this area.

Technical specifications of the neutrino detector

The JUNO features a neutrino detector that is approximately 20 times larger than other detectors of its kind. It consists of the largest acrylic glass sphere ever manufactured by humans, with a diameter of 34.5 meters. This sphere has now been filled with 20,000 tons of highly pure organic scintillation liquid. When elementary particles like neutrinos interact with this liquid, faint blue flashes of light are produced, which are detected by 43,000 photosensors. This will enable JUNO to investigate one of the central questions in particle physics today: the hierarchy of neutrino masses, and whether the third neutrino mass state is heavier than the second.

To shield against cosmic radiation, JUNO is located 700 meters underground in a pool filled with 35,000 tons of high-purity water. This also dampens the natural radioactivity of the surrounding rock. JUNO is equidistant from eight nuclear reactors at the power plants in Taishan and Yangjiang, enabling the measurement of the neutrino mass hierarchy. For this, researchers detect the light produced by reactor neutrinos interacting with the scintillator with unprecedented precision. Around 45 such events are expected per day. Over time, this will create a detailed spectrum containing information about the neutrino mass hierarchy as a fine structure.

The spokesperson for the JUNO collaboration, Prof. Yifang Wang from the Chinese Academy of Sciences, emphasizes: "The completion of the filling phase of the JUNO detector and the start of data collection represent a historic milestone. For the first time, a detector of this scale and precision, dedicated solely to neutrinos, is in operation. JUNO will help us answer fundamental questions about the nature of matter and the universe."

"We are entering a new era of neutrino physics and opening the door to new discoveries. In the coming years, we will finally be able to answer key questions in neutrino physics and gain clues about new physics," says Dr. Hans Steiger, who leads TUM's contributions to JUNO. "In numerous precision experiments in laboratories and at particle accelerators worldwide, we have conducted precision measurements of the fundamental properties of this ultra-high-performance scintillator. These results now enable the interpretation of the measurement data from the JUNO detector."

International collaboration in fundamental research

JUNO is operated by the Chinese Academy of Sciences and involves more than 700 researchers from 74 institutions in 17 countries and regions. In Germany, participants include the TUM, the universities of Tübingen, Aachen, Mainz, and Hamburg, as well as the GSI Helmholtz Centre in Darmstadt.

JUNO is designed for a scientific lifespan of up to 30 years. Looking ahead, the detector also offers the potential for an upgrade to search for neutrinoless double-beta decay with unprecedented sensitivity. Currently, TUM is already developing the significantly more complex chemistry of the future liquid scintillator. "In the coming years, this technology is expected to open new avenues in the search for these rare decays and provide the world's best sensitivity," emphasizes Steiger. (sg)