New material capable of detecting dark matter, scientists say

"It's hard to imagine a better material for searching in this particular mass range," physicist Stephen Derenzo said.
By Brooks Hays  |  March 20, 2018 at 4:18 PM
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March 20 (UPI) -- Scientists believe a new material, known as a scintillator, will expand the search for dark matter.

New analysis suggests the scintillator material is sensitive to dark matter particles with less mass than a proton, which should allow scientists to look for dark matter among a previously unexplored mass range.

Weakly interacting massive particles, or WIMPs, describe dark matter particles with a mass greater than that of a proton. Scientists have tried to directly detect WIMPs using a variety of strategies, but with no success.

What dark matter consists of remains a mystery. Astronomers can only intimate its presence by measuring its gravitational influence. But researchers are hopeful that a search at a lower mass range could yield a breakthrough.

The detection abilities of the new scintillator material, described this week in the Journal of Applied Physics, require temperatures approaching absolute zero, or minus 460 degrees Fahrenheit.

The material is composed of gallium arsenide crystals, or GaAs, enhanced with silicon and boron. Models suggest the unique material should scintillate, or light up, when collisions with dark matter particles knock electrons away.

Researchers at the Lawrence Berkeley National Laboratory in California want to combine the material with a cryogenic photodetector, which can detect tiny amounts of light at extremely low temperatures.

"It's hard to imagine a better material for searching in this particular mass range," Stephen Derenzo, a senior physicist at LBL, said in a news release. "It ticks all of the boxes. We are always worried about a 'Gotcha!' or showstopper. But I have tried to think of some way this detector material can fail and I can't."

Gallium arsenide crystals are fairly easily grown. In recent lab tests, the crystals glowed intensely when electrons were expelled from the crystals' atomic structure. Additionally, the material doesn't suffer from some of the characteristics of other particle-detecting scintillators, such as afterglow, which can lead to a false signal.

Once constructed, the new GaAs scintillator will be positioned deep underground -- protected from interfering cosmic rays -- where scientists hope it will detect dark matter particles.

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