The LUX-ZEPLIN, or LZ, central detector — a particle detector located at the Sanford Underground Research Facility, or SURF, in South Dakota — has completed its journey almost 5,000 feet below ground.
The detector was launched to ensure the integrity of an experiment testing for mysterious dark matter particles.
The 5,000 pound, nine-foot-tall particle detector was maneuvered underground by a team at SURF. The vessel’s final passage was completed after a series of test moves down a former gold mining shaft at the UC Davis campus.
The LZ project, launched in 2012, is managed by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and involves collaborators from 29 institutions across the United States, Portugal, Russia and the United Kingdom, according to a Berkeley Lab press release.
The project was developed with the goal of expanding researchers’ knowledge of dark matter, a substance comprising about 27% of the universe, but whose detection remains challenging. Dark matter neither emits nor absorbs light, so scientists aim to detect the substance through observation of particle interactions.
“Dark Matter is well motivated by a number of astronomical measurements that provide excellent evidence that (about) 25% of the universe is some exotic form of matter,” said LUX-ZEPLIN spokesperson Kevin Lesko in an email. “It is observed by its gravitational influence on the universe, but so far, this large percentage of the universe has not been detected in the laboratory. “
The vessel contains LZ’s xenon detector, or Time Projection Chamber, according to a Sanford Underground Research Facility press release. The chamber was completed in August as part of the dark matter collaboration. The chamber, which is now contained in the cryostat vessel, was assembled starting in December 2018. Dozens of institutions contributed parts to its assembly.
Major concerns in transporting the detector included maintaining the vessel’s structural integrity and cleanliness, according to a Berkeley Lab press release.
“Between the size of the device, the confines of the space, and the multiple groups involved in the move, the entire process required rigorous attention to both the design and the scheduling,” said Jake Davis, a mechanical engineer at SURF who helped coordinate the vessel’s move, in the Berkeley Lab press release.
The detector and projection chamber, now safely shielded from cosmic waves in its underground home, will be filled with 10 tons of liquid xenon to be cooled to -148 degrees Fahrenheit. Scientists hope to observe dark matter particles interacting with the dense xenon atoms in the vessel.
LZ’s sensitivity is 100 times better than an earlier version of the experiment called LUX.
By going deep underground, the detector is well-shielded from background signals.
“This permits it much greater sensitivity to dark matter signals,” Lesko said in the email. “If the detector were on the surface, it would be swamped with billions of background cosmic ray events.”