A Long-Awaited Arrival
Tiny clear crystals that could unlock the secrets of the universe sit in a tightly-sealed box, safe from a hostile world that threatens to instantly destroy them. For Australian researchers, anxiously waiting for this precious cargo to arrive from Shanghai, the journey has been anything but ordinary.
The crystals, which have taken more than a decade to produce, will be at the heart of a world-leading project to detect dark matter particles in the depths of a mine shaft in Stawell, western Victoria. Dark matter is a highly elusive, invisible material thought to make up about 80 per cent of the universe and hold galaxies together.
A team of physicists has been working in a lab one kilometre underground at the Stawell Gold Mine, building on international research. The highly-purified crystals will be installed in the lab and are expected to flash with a burst of light when they interact with dark matter particles.
"This has taken a lot of research and development because this is the most pure sodium iodide crystal ever made," University of Melbourne physicist and project director Elisabetta Barberio told AAP.
A Fragile Cargo
Before the experiment can commence, the crystals have to survive the fraught weeks-long sea journey from China. Their sensitivity is extreme: "As soon as there's a little bit of humidity, they melt," Professor Barberio said.
It's been a long road to both grow and transport them. American scientists began producing the powder to make the crystals about a decade ago, far from agricultural zones where potassium in the air from fertiliser could contaminate it. The crystals were then grown in a lab in Shanghai, carefully kept sterile and dry for years.
Now, they have been packed in a dark, dry, vacuum-sealed and padded box to come to Melbourne, where they will be collected and driven to Stawell. Once at the mine, the box will be carefully monitored by an accelerometer to minimise vibration while it is slowly lowered into the underground lab.
Protecting Against False Signals
Scientists will decontaminate the box before opening it and store it in a nitrogen-filled tank to keep it pure and dry, before installing the crystals into the detector. Professor Barberio said the extreme measures would keep the crystals safe from radioactivity — a critical concern because radiation can mimic the very signals they seek.
"Dark matter interacts very, very rarely, like maybe a couple of times a day," she explained. "But if you have radioactivity around you, radioactivity like a neutron can mimic dark matter ... and there will be a lot of false positives."
The Investigator's Stakes
The potential payoff is immense. "If we see something, that's huge," Professor Barberio said. "But if we don't see anything, we can rule out a lot of hypotheses."
She summed up the scientific quest with a simple analogy: "It's a little bit like being an investigator."
As the crystals make their way to the Australian lab, the researchers are watching closely — aware that a single misstep could undo years of meticulous work. The journey, they know, is far from over.