From SURF: “Surface lab cleanroom paves way for LZ assembly”

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Sanford Underground levels

Sanford Underground Research facility

July 31, 2017
Christel Peters

The surface laboratory cleanroom. Matt Kapust.

After years of planning, building and installing systems, Sanford Lab’s cleanroom is, well, really clean, paving the way for the LUX-ZEPLIN collaboration to begin assembling the second-generation dark matter experiment.

Lux Zeplin project at SURF

“Now that construction is complete and we have done a first round of extensive cleaning of all surfaces, we are taking careful measurements of the degree of cleanliness and radon concentration in the air,” said Simon Fiorucci, a member of the LZ collaboration. “This will take several more weeks until we are convinced of the room’s performance. We expect to receive the first LZ detector parts to start assembly by the end of the year.”

At the same time the cleanroom was under construction, Sanford Lab was building a new radon-reduction facility. That building was completed and equipped earlier this summer. Radon, a naturally occurring radioactive gas, significantly increases background noise in sensitive physics projects. The radon reduction system pressurizes, dehumidifies and cools air to minus 60 degrees Celsius before sending it through two columns, each filled with 1600 kg of activated charcoal, which remove the radon. The pressure is released, warmed and humidified before flowing into the cleanroom.

“That’s the magic part of this cleanroom,” said John Keefner, underground operations engineer and project manager for the cleanroom construction.. “The room will be positively pressured so radon can’t get in.”

Creating a clean space for scientists requires more than dust rags and vacuum cleaners. Robyn Varland, custodian for the Davis Campus, and Melissa Barker, a contract custodian from The CleanerZ, worked diligently to remove the visible—and unseen—particles that lingered on the surfaces of the room. The other systems that maintain a clean environment are also in place and functioning; the radon-reduction, water purification and air filtration systems.

“It took about 80 hours to clean and we worked at it hard,” Varland said. “It just takes time, you can’t ‘go clean’ fast.”

Varland uses the same system that is in place for the Majorana Demonstrator cleanroom.

U Washington Majorana Demonstrator Experiment at SURF

In the Surface Lab cleanroom, Varland and Barker spent seven hours just on the grating. “That was the hardest part,” Varland said. “Each bar was vacuumed and washed thoroughly with a wet rag and scrubbing tool to lift the particulates. Spray, wipe with a rag, rinse it out three times.”

And it’s all done moving only half-an-arm-length at a time—all while suited up in cleanroom garb to prevent any contamination.

“Once the initial cleaning happens, you then become the source of dust,” said David Taylor, experiment review engineer for LZ. “That requires special PPE and procedures to keep it clean. Now, the particle counts are really low. That means the dust is gone and it’s ready to use.”

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About us.
The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

Fermilab LBNE