Monday, May 2, 2016
Constance Walter, Communications Director, SURF
Amid streamers, a piñata and paper unicorns, LUX researchers celebrated the 300-live-day run of their dark matter detector.
“I would describe the mood as exciting, joyous and electric,” said Mark Hanhardt, Sanford Lab support scientist. Why unicorns? For LUX researchers, they symbolize thesearch for the elusive WIMP, or weakly interacting massive particle, the leading contender in the dark matter search.
But don’t kid yourselves, in the search for dark matter, these researchers remain focused and motivated.
LUX consists of one third-of-a-ton of liquid xenon inside a titanium vessel.
Researchers hope to identify the very rare occasions when a dark matter particle collides with a xenon atom inside the detector. When that happens, the xenon atom will recoil and emit a tiny flash of light, which will be detected by sensitive light detectors.
In October 2013, after a 90-live-day run, LUX announced it was the most sensitive dark matter detector in the world. “LUX was so much larger than existing detectors that within a few weeks of starting its first run in 2013, it had surpassed all previous direct detection experiments,” said Richard Gaitskell, co-spokesperson for LUX.
And the trend continues. In December, LUX released a reanalysis of the 2013 data, which discussed new calibration techniques that allowed for even greater sensitivity. Those techniques, which included the use of tritiated methane, krypton-83 and a neutron generator, were used in the most recent run; however, results willnot be available before the end of 2016.
The 300-day run began in November 2014 and the detector has been in WIMP search mode or calibration mode since. But it has not been without its challenges, Gaitskell said. “During any dark matter search, we must ensure the detector is taking data in a completely stable mode in which the operating conditions are clearly understood,” he said. “This means we monitor the detector health continually and occasionally we have to react to any apparent issues that have developed.”
At regular intervals throughout the new run, calibrations were carried out for two weeks every four months to ensure a high level of accuracy in measuring responses to backgrounds and potential dark matter signals, he added.
After 19 months, the run officially ended today at 1 p.m. “That’s a long time to to operate a detector without a significant break,” said Simon Fiorucci, LUX science operationsmanager. “But it was critical to demonstrate our ability to do so as we prepare to run LZ for more than three years.”
Later this year, LUX will be decommissioned to make way for a new, much larger xenon detector, known as LUX-ZEPLIN, or LZ. This second generation dark matter detector will have a 10-ton liquid xenon target and be up to 100 times more sensitive.
“The tremendous success of LUX paved the way for LZ,” said Murdock Gilchriese, LBNL (Lawrence Berkeley National Laboratory) operations manager for LUX and LZ project director. LZ will be located inside the same 72,000-gallon water tank that currently shields LUX.
“Sanford Lab will continue to play a global role in the search for dark matter,” said Jaret Heise, science director at Sanford Lab. “We’re looking
forward to working with the expanded collaboration, which will include 31 institutions and about 200 scientists.”
In the meantime, LUX researchers are continuing their work, including testing several new calibration techniques that will be used in LZ. The team has come a long way and made significant progress. “We are all proud to have made it this far,” Fiorucci said.
See the full article here .
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. 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.