SD Mines Helps Keep Two of the World’s Most Sensitive Dark Matter Experiments Clean

Radon reduction researchers pictured with the machine they designed are (from left to right) SD Mines physics graduate student Joseph Street, Richard Schnee, Ph.D., along with lab technicians David Molash and Christine Hjelmfelt.

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 instutitions 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.

Last edited 5/17/2018 3:54:35 PM

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