From SURF: “Beamline requires precision measurements”

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Sanford Underground levels

Sanford Underground Research facility

August 8, 2016
Constance Walter

From left: Gary Chrutcher, Virgil Bocean , Horst Friedsam, and Charles Wilson, use an instrument called the DMT Gyromat2000 to precisely measure the rotation of the local underground reference system grid with respect to true north.

Scientists with the Deep Underground Neutrino Experiment (DUNE) hope to shed light on the mysteries of the elusive neutrino. So they’ll aim a beam of neutrinos straight through the earth from Fermilab in Batavia, Ill., to detectors on the 4850 Level of Sanford Lab in Lead, S.D. To get the best signal, the center of the beam needs to hit the detectors head on—and that’s where things get a little tricky.


Neutrinos are among the most abundant particles in the universe, but they have no charge so they can’t be steered to the detectors by magnets. And as the beam travels the 800-mile distance between the two points, it will spread out like a flashlight beam, reducing the number by trillions that will reach the target.

“We want the maximum number of neutrinos to reach the detectors, so the correct aiming of the beam is of vital importance,” said Virgil Bocean, senior geodesist with Fermilab.

To properly align the neutrino beam, a team of specialists mapped points underground to coordinates on the surface both at Sanford Lab and Fermilab. The team started with global positioning and global navigation satellite systems.

“The geodetic orientation parameters of the beam were determined with GPS to a high level of accuracy in conjunction with the national Continuously Observed Reference Station (CORS) network—within millimeters,” Bocean said.

But because so much depends on the correct coordinates, including the orientation of the caverns that will hold the detectors, the team needed to match the surface and under¬ground coordinates. And to accomplish that, the team turned to “the ancient technology” of plumb lines, said Randy Deibert of Professional Mapping and Surveying LLC, in Spearfish. Deibert is working with Bocean and geodesist Horst Friedsam, head of the AMD Department at Fermilab.

Three plumb lines were lowered in each of the two shafts: The Yates and Ross. Crews of surveyors on the 1700, 4100 and 4850 levels of Sanford Lab took horizontal measure¬ments between the shafts, while Deibert used a specially designed survey station to capture depth measurements. A Gyroscope at the 4850 level measured the precise orienta¬tion of the underground reference system grid with respect to true north.

“We need to record several readings with each instrument for redundancy and build a larger statistical measurement sample to check for systematic errors,” Bocean said. “It takes all these instrument types to put A and B together and connect the global and local underground information from Fermilab to Sanford Lab.”

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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