Construction is nearing completion on the SABRE South dark matter experiment, housed one kilometre underground in the Stawell Gold Mine in regional Victoria. Australian researchers anticipate beginning data collection next year to test unresolved particle physics results first detected in Italy in 1998.
Deep beneath the surface of regional Victoria, a decade of planning and engineering is culminating in a facility designed to tackle one of astrophysics’ most enduring puzzles. Construction of the SABRE South experiment inside the Stawell Gold Mine places Australia at the forefront of a global race to detect and verify dark matter, an invisible substance thought to make up the vast majority of the universe.
Shielding the Stawell Underground Physics Laboratory From Cosmic Noise
Hunting for a substance that does not emit, absorb, or reflect light requires extreme environmental controls. To eliminate interference from cosmic rays and background noise, the SABRE South experiment is housed under a kilometre of rock in the Stawell Gold Mine, where the rock overburden provides nearly three kilometres of water-equivalent shielding.
Before installing sensitive equipment, researchers from the ARC Centre of Excellence for Dark Matter Particle Physics measured muon levels both inside and outside the Stawell Underground Physics Laboratory over a full year. They detected 30,000 muons inside the facility, contrasted with the 8.4 billion muons expected on the Earth’s surface—a reduction that confirms the site is sufficiently quiet for rare-event searches.
Beyond cosmic radiation, researchers faced the meticulous task of mitigating natural radioactivity. Every component placed near the detector’s core must undergo strict screening to eliminate trace radioactive contaminants that could otherwise swamp faint signals.
Replicating the DAMA/LIBRA Result With Sodium-Iodide Crystals
At the center of the SABRE South detector are several sodium-iodide crystals intended to interact with hypothesised dark matter particles known as WIMPs, or Weakly Interacting Massive Particles, producing faint flashes of light.
This setup directly mirrors the long-standing DAMA/LIBRA experiment in Italy, which reported an annual modulation in its event rate—a yearly rise and fall consistent with the Earth moving through the galaxy’s dark matter halo. While that Italian experiment generated considerable debate, other research groups using different target materials have struggled to resolve the findings. SABRE South offers a distinct methodological advantage by using the exact same target material.
“What sets SABRE apart is that we use the same target as DAMA, sodium iodide, so it is a genuine like-for-like test rather than a comparison across different technologies.”
Professor Phillip Urquijo, Innovationnewsnetwork
Researchers worldwide are pursuing similar verifications. Professor Urquijo noted that three major overseas groups are currently racing to replicate the original Italian findings in Spain, South Korea, and Italy.
What the Research Means for Our Understanding of the Universe
While the Standard Model explains visible matter and forces, it fails to account for the invisible material holding galaxies together. University of Melbourne theoretical physicist Nicole Bell described the initiative as the ultimate quest to understand the world in which we live
.
“About 75 to 80 per cent [of the universe] is this dark matter that we don’t know, so [this research] will tell us what the majority of the universe is made of.”
Elisabetta Barberio, Director of the ARC Centre of Excellence for Dark Matter Particle Physics, abc.net.au
When data collection begins next year, verifying any potential signal will require patience. Because the experiment searches for seasonal fluctuations tied to Earth’s orbit, researchers emphasize that a single year of data will not suffice to confirm a discovery.
“We’re looking for the seasonal effects, so if we just saw it one year, we might say that’s a fluke. You need five years to see it — you need to make sure that it’s not a mistake.”
Professor Phillip Urquijo, abc.net.au
Related reading
