A deep mine shaft at MMG Mining’s Rosebery site in Tasmania could become the new home of internationally renowned research into the mysteries of dark matter.
Melbourne University experimental physicist Professor Elisabetta Barberio has been looking at the Rosebery mine as a possible replacement for her underground laboratory in Victoria.
Professor Barberio said her team was looking for a place to continue her experiments into dark matter.
“We had (a laboratory) in Victoria’s Stawell Gold Mine, then they closed the mine and we didn’t know what was going to happen.
“We looked for an option where we could move the experiment.
We don’t know what dark matter is. It is one of the biggest mysteries.Elisabetta Barberio, Melbourne University Professor of High Energy Physics
“The mine at Rosebery is very deep. We did some measurements and the environment has the right parameters. It is very low radioactivity.”
Professor Barberio said her first choice was still the Stawell Gold Mine, where the laboratory was already built, but the University of Melbourne was very keen to go on with the work if the mine was ruled out.
Should the project move to Rosebery, Professor Barberio said it could generate a lot of opportunity for the area.
“There is a lot of potential with a visitor centre. If we build a laboratory there, there would be jobs and it would help education. There are a lot of visitors coming to the (Stawell) mine.”
Her impressions of the Rosebery mine were favourable. “I was quite impressed - it was very good safety and the people were very welcoming.”
DARK MATTER DOWN A MINE
Professor Barberio is a member of the Centre of Excellence for Particle Physics at Terascale (CoEPP) at Melbourne University. As an experimental physicist, she helped start Australia’s first dark matter direct detection experiment.
She heads the SABRE project, which is searching for evidence of dark matter. The project has two sites, one in the Southern Hemisphere, currently at Stawell, and the other at the Laboratori Nazionali del Gran Sasso in L’Aquila, Italy.
Professor Barberio said dark matter made up most of the matter of the universe, but scientists did not know what it was.
“It’s one of the biggest mysteries,” she said.
Dark matter is by its nature, extremely hard to detect. The big prize is to record the fact that it actually exists.
One of the most important features of the research is to screen out all the background ‘noise’ from cosmic radiation and other particles that could interfere with the signals from dark matter.
Because it is so elusive, the machines that detect it have to be extremely well buffered from all other types of particle zooming around the planet, such as radioactive waves from the sun and beyond (called cosmic radiation).
The deep underground space is ideal because the earth’s crust forms a natural shield.
Professor Barberio has assessed the 1.8 kilometre deep mine at Rosebery as being suitable for what is called an ultra-low background project.
THE HUNTERS CAN SENSE THE PRIZE
Scientists estimate that the amount of non-light matter is about four times larger than light matter, which is what we can currently detect.
Although they have reasoned that dark matter exists, they have never confirmed it physically.
They believe it comprises 80 per cent of the matter in the universe, that it holds most galaxies together and that it has had a basic role in structuring matter.
They are close to confirming that it exists. An experiment in Italy has detected a signal that scientists believe could be dark matter, but they need a similar one in the Southern Hemisphere before they can confirm it.
Hence Professor Barberio’s research at the Stawell Gold Mine in Victoria. If the Italian research and the Stawell (or Rosebery) experiments have the same results, then Professor Barberio can confirm she has detected dark matter.
Such a discovery would be a world first.
BURYING THE CRYSTAL DEEP
The SABRE machine is very different from most machines operating in mines.
In the centre is a very pure crystal of sodium iodide, which sits suspended in one and a half tons of special liquid.
The crystal and tubes attached are inside a very pure, air-tight copper casing which in turn is inside a stainless steel vessel filled with the special liquid.
Cocooning that is another shield made of lead, polyethylene and water.
The first challenge is to build a crystal pure enough for the experiments.
Once its purity is proven, Professor Barberio can move to the second stage of the research, which is to place a 50 kilogram crystal in the shielded chamber.
The experiment consists of recording every time a particle of dark matter hits the crystal.
Each time that happens, the crystal emits a light. The light is then captured in a tube attached to the crystal, enhanced, and recorded.
If Professor Barberio opts for the Rosebery mine, building on the specialised machine for the research would start.
Depending on the mine, the rock and what excavation was needed, she estimated the laboratory would cost around $5 to $7 million.
And as for when that would happen?
“We will know something in the next month to a month and half,” she said.