A tank of water and a fire extinguisher over 2.4 kilometres (1.5 miles) beneath the surface aims to find dark matter.
COUPP-60 is an underground dark matter experiment consisting of apparatus that includes a large jar containing purified water and CF3I, a chemical found in fire extinguishers. The aim of the detector is to search for signs of dark matter particles. When a particle passes through the detector its energy will produce tiny bubbles in the clear liquid.
“It’s an underground observatory,” explained Fermilab’s Hugh Lippincott, who oversaw the installation of the detector. “So it’s looking for the same thing in a different way. The only reason why we know about dark matter is from telescopes and satellites, but we don’t know what it is. Now we’re trying to follow it up, by going underground.”
Running since early May, it’s already started detecting particles, however, it’s yet to find any dark matter. Although COUPP-60 is buried deep in an underground laboratory, the advantage it has over orbital and terrestrial instruments that are searching for dark matter is that it’s shielded from the noise of other particles: dark matter passes effortlessly through the Earth, whereas most other particles don’t. “We turned it on and saw what we think are alpha particles,” Lippincott told All About Space, “It’s a radiation detector so we can see dark matter but we can also see neutrons and alphas.”
Scientists have been testing COUPP-60 over the last few weeks for its sensitivity and accuracy, and one of the plans is to increase shielding against other particles around the detector by submersing it in over 26,000 litres (7,000 gallons) of water.
It may not have detected any dark matter yet, but the experiment has gone smoothly so far and Lippincott is hopeful that they will be able to confirm a signal from COUPP-60 in the near future. “It would be lovely to detect some signal that was dark matter. Within six months to a year we would not expect to see anything and then after that, who knows?”