Subterranean Dark Matter Detector Starts Listening for Elusive Particles

Buried 2.5 kilometers below the surface, a new dark matter detector in Canada has begun its search for the elusive dark matter, which scientists believe accounts for nearly 90 per cent of all matter in the universe.

Scientists heard their first pops in an experiment that searches for signs of the invisible particles in the form of tiny bubbles. They need further analysis to discern whether dark matter caused any of the COUPP-60 experiment's first bubbles at the SNOLAB underground science laboratory in Ontario, Canada.

Placing the detector so far underground shields it from most of the regular-matter particles that constantly bombard Earth from space. Dark matter, in contrast, is thought to travel through earth and rock undeterred. In addition, researchers submerged the experiment in 25,000 liters of water, which further weeds out neutrons and other “normal” matter.

“The events are so rare, we’re looking for a couple of events per year,” Fermilab postdoc Hugh Lippincott said in a laboratory press release.

Astrophysicists think dark matter accounts for about a quarter of the matter and energy in the universe. But no one has conclusively observed dark-matter particles.

"Our goal is to make the most sensitive detector to see signals of particles that we don't understand," said Hugh Lippincott, a postdoctoral scientist with the Department of Energy's Fermi National Accelerator Laboratory.

The COUPP-60 detector is a jar filled with 60 kilogrammes of purified water and CF3I - an ingredient found in fire extinguishers. The liquid in the detector is kept at a temperature and pressure slightly above the boiling point, but it requires an extra bit of energy to actually form a bubble.

One of the advantages of the detector is that it can be filled with a different liquid, if scientists decide they would like to alter their techniques.