China’s JUNO Observatory Prepares for Neutrino Research with Final Facility Stage Completion: Unlocking the Mysteries of Ghost Particles
China has reached a major milestone in its quest to decode one of the most elusive phenomena in particle physics. The Jiangmen Underground Neutrino Observatory (JUNO), located in Guangdong province, has entered its final phase as it begins filling its detector with ultrapure water. This cutting-edge facility is designed to study neutrinos, often referred to as “ghost particles” due to their near-undetectable nature.
A Mega Facility with a Singular Mission
The JUNO project, costing $376 million, is a collaborative effort involving 750 scientists from 74 institutions across 17 countries. The centerpiece of the observatory is a massive subterranean spherical detector, 35 meters in diameter, housed 700 meters underground. This detector is supported by a 41.1-meter stainless steel frame and will eventually contain 20,000 tonnes of a special liquid scintillator, suspended in 35,000 tonnes of ultrapure water.
Ultrapure water, filtered through multiple stages, began filling the detector this week at a rate of 100 tonnes per hour. This process marks a crucial step toward preparing JUNO for its groundbreaking research. The filling process will occur in two stages over eight months. Initially, ultrapure water will occupy both the interior and exterior of the detector for two months. Following this, the water inside the detector will be replaced by the liquid scintillator over six months.
The Quest to Measure Neutrinos
Neutrinos are among the smallest and lightest of the 12 elementary particles that compose the universe. These particles, produced in abundance by stars and nuclear reactions, have no electrical charge and travel at nearly the speed of light. Despite their omnipresence, neutrinos are notoriously hard to detect as they interact very weakly with matter.
The JUNO detector aims to measure the mass hierarchy of neutrinos by capturing interactions from those produced by two nearby nuclear power plants. When a neutrino interacts with the liquid scintillator, it will create two flashes of light, which are recorded by an array of 20,000 photomultiplier tubes surrounding the detector. This data will help scientists uncover the mass differences between the three known types of neutrinos—a critical puzzle in understanding the universe’s building blocks.
JUNO’s Global Significance
JUNO is one of the most advanced neutrino observatories in the world, positioned to lead a new generation of experiments in this field. It will begin data collection in August 2025, ahead of comparable international facilities like the Deep Underground Neutrino Experiment (DUNE) in the United States and Japan’s Hyper-Kamiokande, both set to commence in 2027-28.
The project also highlights China's growing leadership in high-energy physics. Wang Yifang, director of the Institute of High Energy Physics (IHEP), noted that JUNO’s completion would consolidate China's global standing in neutrino research.
A Collaborative Effort
JUNO's success is a testament to international scientific cooperation. Nearly 300 researchers from European countries like Italy, Germany, and France are involved in the project, showcasing its global appeal and importance.
This facility not only represents a leap forward in neutrino detection technology but also serves as a beacon for collaborative scientific endeavors. Its findings are expected to answer fundamental questions about the nature of the universe and the forces that govern it.
