The Stawell Underground Dark Matter Lab Nears Completion

Australia is shortly to join the search for a theorised but as yet unseen dark matter particle, in a laboratory built 1-kilometre underground in an active gold mine. Having withstood every challenge thrown at it so far, including a global pandemic, the lab is on track to be completed by the end of this year and to begin operations in 2022.

We here at SpaceAustralia.com have been keenly following the development of the lab over the last year or so. Our first article about the lab from January 2020 detailed the reasons for building it in Stawell and the various collaborations that exist with Australian and international institutions. Back then, we were hopeful that the lab would be operational within the year, but the global pandemic has caused inevitable delays in its construction.

But now we’re happy to report that despite the challenges posed by COVID-19, the construction of structural steel and partitions is underway at the Stawell Underground Physics Laboratory (SUPL), and the installation of plumbing and electrical services has begun.

Director of the ARC Centre of Excellence for Dark Matter Particle Physics, Professor Elisabetta Barberio, confirmed that researchers are anticipating starting work in SUPL in 2022.

“The pandemic has caused a lot of unexpected challenges, but it is pleasing to see that the works on the Stawell Underground Physics Laboratory are on track to be completed by the end of the year,” she said. 

In fact, the scientists that will be hands-on with the dark matter experiment once it is installed in the lab are currently in training – and it’s not white lab coats that they are wearing, but safety harnesses and hard hats.

The dark matter experiment is known as SABRE – Sodium Iodide with Active Background REjection – is a vessel standing 2-m high and containing highly sensitive detectors and specialised equipment. The researchers need to be able to make changes on the fly, and that can involve climbing into the vessel to adjustment the detectors or even alter the wiring.

Right now, 6 post-graduate students and researchers from the University of Melbourne are taking part in confined spaces training and learning the safety and procedural aspects that will allow them to work with the SABRE vessel once it is installed in SUPL. 

“We are looking forward to taking our equipment down into the laboratory and starting to collect data that we hope will help us understand the nature of dark matter. It is incredible to think that what was once a cavern will be a fully functioning physics laboratory in just a few months,” said Professor Barberio.

Equipment will start being delivered to the lab around November, with construction expected to have been completed by December. Being so far underground and surrounded by about 100-ton of steel means that other sources of earthly and cosmic radiation can be mostly eliminated, but working in such a unique location will not be without its challenges.

For starters, there’s the mine car ride through long, winding tunnels just to get to work. And then, with the mine still active, the lab will need to be vacated every eight hours or so when blasting is taking place. Our progress update on the lab’s construction from August 2021 talked about some of the unique challenges posed by working 1-km underground.

But the potential payoffs in operating SUPL are huge. 

“If we manage to find [dark matter], that’s a guaranteed Nobel Prize,” said ANSTO strategic projects senior advisor Dr Richard Garrett. “It’s like [gravitational] waves. That’s another thing they were looking for 30 to 40 years until, finally, these enormous experiments [like LIGO and Virgo] found it.”

Complicating the search for dark matter though is the fact that scientists don’t yet know exactly what they are searching for. It could be anything from unseen black holes, down to tiny, almost massless, particles like photons of light.

We discussed these different ‘dark matter candidates’ in an article from December 2020, and talked about how SABRE will be able to detect Weakly Interacting Massive Particles, or WIMPs, if they exist.

But exist they might, with some controversial detections already having been made under a mountain in Italy’s Gran Sasso National Laboratory, and more recently by the PandaX-II particle detector in China. At this point, astronomers are not prepared to say that they’ve discovered dark matter, though the unique location of SUPL in the Southern Hemisphere will help to provide confirmatory evidence if they have. Or, if those results cannot be replicated even with SUPL's brand new extremely sensitive detectors, it might be a clue that we need to focus on other dark matter candidates.

No matter what happens at SUPL, whether there are detections of WIMPs or not, we are going to learn something. And with the science starting next year, we might not have much longer to wait until we do.