KAIPING, China — Beneath a granite elevation in southern China, a monumental neutrino detector is nearing completion, set to unravel the secrets of enigmatic subatomic particles known as neutrinos. The Jiangmen Underground Neutrino Observatory (JUNO) is poised to embark on the intricate task of detecting these extraordinarily light cosmic entities.
This facility is one of three major detectors being constructed worldwide, with its counterparts located in the United States and Japan still in the process of development. The endeavor to identify neutrinos is a significant undertaking to deepen our understanding of the universe, and experts believe that the technology employed in this Chinese project could set new benchmarks in the field. Andre de Gouvea, a theoretical physicist not connected to the project, expressed excitement about its potential implications, stating, “If they can pull that off, it would be amazing.”
Neutrinos are particles that have existed since the Big Bang, and trillions pass through our bodies each second. They are produced in substantial quantities by stars like the sun, as well as during collisions of atomic particles in accelerators. While the scientific community has been aware of neutrinos for nearly a century, comprehensive understanding of their properties remains elusive. “It’s the least understood particle in our world,” remarked Cao Jun, a manager for the JUNO project, emphasizing the necessity for further investigation.
Detecting neutrinos poses a unique challenge due to their elusive nature; they hardly interact with other matter. As a result, scientists rely on observing the byproducts of neutrino collisions, which generate flashes of light or charged particles. To enhance the chances of these rare interactions, physicists advocate for the construction of significantly large detectors. “The solution for how we measure these neutrinos is to build very, very big detectors,” de Gouvea explained.
The Kaiping facility represents a $300 million investment and took over nine years to develop. Positioned 2,297 feet (700 meters) underground, it is safeguarded against cosmic rays and radiation that could disrupt its neutrino detection capabilities. As of Wednesday, workers have commenced the final phase of construction, which involves filling the spherical detector with a special liquid that emits light upon the passage of neutrinos, and encasing it in purified water.
The focus of JUNO will be on measuring antineutrinos, the counterpart of neutrinos that provide essential insights into their behaviors, being generated by two nuclear power plants located more than 31 miles (50 kilometers) away. These antineutrinos will produce observable flashes when interacting with particles in the detector. The facility is uniquely equipped to tackle a major scientific question regarding the three variants of neutrinos that oscillate in transit, and researchers aim to categorize them by mass.
Identifying these delicate variations in such an elusive particle will prove to be a formidable task, as Kate Scholberg, a physicist at Duke University, noted, “It’s actually a very daring thing to even go after it.” The establishment is anticipated to commence operations by the latter half of next year, and the journey to collect and analyze the ensuing data will extend the time frame before the broader mysteries of neutrinos can be fully illuminated.
To complement the efforts of the Chinese detector, Japan’s Hyper-Kamiokande and the Deep Underground Neutrino Experiment (DUNE) in the United States are also under construction, aiming for completion around 2027 and 2031 respectively. These facilities will cross-validate the findings of JUNO through distinct methodologies. “In the end, we have a better understanding of the nature of physics,” stated Wang Yifang, the chief scientist and project manager for the Chinese initiative.
While neutrinos may interact minimally with their surroundings, their presence since the universe’s inception makes them critical to comprehending cosmic evolution. Researchers hope that by studying these Big Bang remnants, they can decipher the fundamental characteristics of the universe’s formation and expansion billions of years ago. “They’re part of the big picture,” Scholberg affirmed, noting that understanding the predominance of matter over antimatter in the universe may hinge on insights gained from neutrinos — a pursuit that ultimately requires capturing these elusive particles to unlock their secrets.
