The first dark matter detector in the Southern Hemisphere officially became operational on August 19.
SUPL located in an abandoned gold mine. Photo: SUPL
The Stawell Underground Physics Laboratory (SUPL) is built within an abandoned gold mine in Australia. The facility aims to utilize its unique location to detect signals from mysterious matter believed to exist throughout the universe.
Astronomical observations over decades indicate the existence of a type of matter that we cannot see. This dark matter does not emit or interact with light, and it rarely interacts with ordinary matter. Occasionally, dark matter particles may collide with atoms of ordinary matter, producing detectable signals. SUPL is constructed 1 kilometer underground to block cosmic rays from reaching the equipment. Surrounding the detector is a shield made of steel and polymer weighing approximately 100 tons, along with a liquid scintillator system that helps eliminate false alarms.
The SUPL detector contains 50 kg of ultra-pure sodium iodide crystals, which can emit flashes of light when struck by a passing particle. This extremely sensitive light detector continuously monitors the tank for signals. Other particles, such as neutrinos, may also produce similar light flashes, coinciding with signals in the liquid scintillator. Any light flashes occurring solely in the sodium iodide tank are believed to originate from dark matter.
This design is common among dark matter detectors like XENON1T and LUX, which use liquid xenon, superfluid helium, or supercooled water. However, the advantage of SUPL lies in its location. Previous dark matter detectors have been concentrated in the Northern Hemisphere, so building a detector in the opposite half of the world will help confirm or rule out some intriguing signals reported by earlier experiments.
For instance, the facility that preceded SUPL, the Gran Sasso Laboratory in Italy, identified a potential dark matter signal last June. Researchers suggested that this result corresponded to Earth’s position in its orbit as the planet passed through a “wind” of dark matter. However, this could also be influenced by other seasonal factors such as humidity fluctuations.
SUPL could provide more accurate conclusions. If the system detects a spike in signals in June, it would serve as solid evidence for the dark matter wind hypothesis. Conversely, if the signal peaks around December, it would reveal the impact of summer weather.
