China digs 2,000 ft to find 'ghost particles': Why it's important

JUNO is set to begin operations in late 2025 to detect around 100,000 neutrinos, including solar, atmospheric, and geoneutrinos over the span of 6 years

The Jiangmen Underground Neutrino Observatory (JUNO), nestled beneath a granite hill in southern China, is nearing completion, ready to probe the enigmatic 'ghost particles', Chinese state media Xinhua recently reported.

 

These ghost particles are known as neutrinos, which are tiny, nearly massless entities that hold the key to some of the universe’s deepest mysteries. Scheduled for full operation by August 2025, JUNO represents a monumental step forward in particle physics.

 

What are ghost particles?

Ghost particles is a nickname often used to describe neutrinos, which are one of the fundamental particles in the universe. This term captures their mysterious and “ghostly” nature – being so numerous yet so hard to detect.

 

Neutrinos interact only through the weak nuclear force and gravity, making them extraordinarily difficult to detect. Unlike charged particles, they do not interact electromagnetically, so they don't leave trails in detectors like most other particles do.

 

Neutrinos are also nearly massless compared to other particles, though recent experiments have confirmed that they do have a very small, but nonzero, mass.

 

Neutrinos are produced in a variety of cosmic and terrestrial processes, including nuclear reactions in stars, like the Sun; supernova explosions, where vast numbers of neutrinos are emitted; nuclear reactors on Earth; and radioactive decay of certain isotopes.

 

Why study neutrinos?

Neutrinos play a crucial role in understanding fundamental physics and the universe's structure such as matter and antimatter imbalance. It can also provide insights into astrophysics and could challenge the existing understanding of particle physics.

 

What is JUNO’s mission?

JUNO’s primary mission is to determine the neutrino mass hierarchy, advancing our understanding of how these ghost particles oscillate between different "flavours" as they travel through space.

 

Insights gained could illuminate fundamental questions about the universe's origins and the imbalance between matter and antimatter. Over six years, JUNO is expected to detect around 100,000 neutrinos, including solar, atmospheric, and geoneutrinos.

 

How can JUNO capture ghost particles?

Despite trillions of them passing through every human body every second, they leave virtually no trace. To capture these elusive particles, JUNO employs a state-of-the-art detector filled with 20,000 tonnes of specially formulated liquid that emits faint flashes of light during rare neutrino interactions.

 

At the heart of JUNO is a colossal, egg-shell-thin acrylic sphere, weighing 600 tonnes and suspended in a 44-meter-deep water tank. This tank, containing 35,000 tonnes of ultra-pure water, acts as a shield against cosmic rays and background noise. Cutting-edge photo-multiplier tubes surround the detector, capable of detecting the faintest flashes with unprecedented efficiency.

 

Additionally, aerospace-grade underwater electronics ensure a failure rate of less than 0.5 per cent over six years.

 

700 scientists from 17 countries involved

With a $300 million budget and contributions from over 700 scientists representing 74 institutions across 17 countries, JUNO is part of a trio of next-generation neutrino observatories, alongside projects in Japan and the United States. Its construction has shattered engineering records, setting a new benchmark in precision and innovation.