South
Dakota School of Mines & Technology is helping to ensure highly
sensitive underground dark matter experiments are free of radon that could contaminate
the results. SD Mines researchers are building a radon mitigation system at SNOLAB in Canada and at the Sanford Underground Research Facility (SURF)
in Lead, S.D.
The team, led by Richard Schnee,
Ph.D., professor and head of the physics department at SD Mines, is building
machines that filter out radon particles to produce ultra-pure air needed for
the SuperCDMS
experiment in SNOLAB and for the LZ (LUX-ZEPLIN) experiment
in SURF. The team is also helping
ensure the parts used to build the experiments are relatively free of radon.
“Our detectors need very low levels
of radon,” Schnee says. While the radon levels at the 4850 Level at SURF are
safe for humans, they are too high for sensitive experiments like LZ, which go
deep underground to escape cosmic radiation, Schnee explains. “We will take
regular air from the facility and the systems will reduce the levels by 1,000
times or more.”
The system in SURF will be
installed in the coming months while the system at SNOLAB will go in next year.
“The real problem for these super
sensitive dark matter detectors are the radon daughters that are radioactive,”
says Schnee. Even miniscule amounts of radioactive particles could contaminate
and throw off the experiments - so the work of Schnee and his team helps ensure
the cleanest possible environment for the best overall results.
The two experiments, SuperCDMS and
LZ, are in a race to determine
the nature of dark matter in the universe. But, Schnee says, the
experiments are also complementary to each other as they are searching for dark
matter in different areas. To use a metaphor, if dark matter were a lost child
in a large cornfield, LZ would be looking in one part of the field and
SuperCDMS would be looking in another. The U.S. Department of Energy (DOE) gave
approval for the construction of LZ in 2016, and the DOE recently approved
funding and start of construction for the SuperCDMS SNOLAB experiment. Both projects will begin
operations in the early 2020s to hunt for suspected dark matter particles called weakly
interacting massive particles, or WIMPs. SD Mines is one of 26
institutions working on the SuperCDMS and one of 37 institutions on LZ.
SuperCDMS will be at least 50 times
more sensitive than its predecessor, exploring WIMP properties that can’t be
probed by other experiments and giving researchers a powerful new tool to
understand one of the biggest mysteries of modern physics. The experiment will
be assembled and operated at the Canadian laboratory SNOLAB, located 6,800
feet underground inside a nickel mine near the city of Sudbury, Ontario. It’s
the deepest underground laboratory in North America. There it will be protected
from high-energy particles, called cosmic radiation, which can create unwanted
background signals.
LZ is going into SURF, 4,850 feet
below ground in Lead, SD, where it will also be protected from cosmic radiation.
LZ will be 30 times larger and 100 times more sensitive than its predecessor,
the Large
Underground Xenon experiment.
For more information on the
SuperCDMS SNOLAB project and the SuperCDMS collaboration, check out this website.
For more information on LZ click here.