The UK Dark Matter Collaboration
The UKDMC was an experimental consortium formed in 1987 to conduct searches for galactic WIMPs.
It followed the first such effort which started in the west coast of the United States in the previous year. The UKDMC included UK astrophysicists and particle physicists from the Rutherford Appleton Laboratory, Imperial College London and Sheffield University.
Detectors were set up 1,100 m underground in a halite seam at the Boulby Mine in the North East of England. The mine operators, Cleveland Potash Ltd., provided access to several disused tunnels and caverns in low background salt rock for the UK underground physics programme.
Boulby Underground Laboratory.
The UKDMC deployed multiple dark matter experiments, developing WIMP search techniques using scintillator crystals, gaseous detectors, and liquid xenon detectors. First results were published in 1996 from room temperature NaI(Tl) crystals. NAIAD was an array of such crystals that operated in 2001-2003. The early experiments were built and operated in a challenging environment, until a new laboratory was built in 2003 to accommodate the expanding ZEPLIN and DRIFT programmes.
DRIFT is a gaseous Time Projection Chamber (TPC) designed to detect the directionality of dark matter interactions (a powerful way to reject most backgrounds). The ZEPLIN programme developed liquid xenon detectors, based on the excellent prospects for high sensitivity and scalability offered by a noble liquid target. The UKDMC continued until 2007, when the collaborating institutions separated to pursue the ZEPLIN-III and DRIFT-II projects independently.
“Detectors were set up 1,100 m underground in a halite seam at the Boulby Mine in the North East of England”
View of the Palmer Laboratory at Boulby where the ZEPLIN-II, ZEPLIN-III and DRIFT-II experiments operated.
The ZEPLIN Programme
The foundations for the two-phase noble element detector technology were laid in 1970, when the possibility of particle detection in a two-phase argon chamber was demonstrated by Russian scientists.
The ZEPLIN programme at Boulby dates back to the late 1990s; it featured a sequence of experiments of increasing complexity aimed at applying this technique to dark matter detection.
ZEPLIN-I was a single-phase liquid xenon experiment which published final results in 2005; it featured at its core a PTFE-lined 5-kg chamber with three 8-cm diameter photomultipliers viewing the liquid xenon scintillation.
ZEPLIN-II and ZEPLIN-III were the first two-phase systems designed dark matter searches, and were essentially developed in parallel and exploiting different technological solutions. Groups from the University of California, Los Angeles, LIP-Coimbra in Portugal, and ITEP-Moscow joined the UK groups at various stages of the programme.
ZEPLIN-II became the first such system to search for dark matter in the world, completing in 2007; it utilized a deep, high-reflectance PTFE chamber containing 31 kg of liquid xenon with readout from seven 13-cm diameter PMTs in the gas phase. ZEPLIN-III concluded the liquid xenon programme at Boulby, with science runs in 2008 and, following an upgrade phase, in 2010/11; its design featured 31 2-inch PMTs immersed in the liquid, viewing a thin disc geometry of 12 kg of liquid xenon under high electric field.
The ZEPLIN-III experiment.
After conclusion of ZEPLIN-III in 2012, the UK groups joined the LUX experiment then being deployed at SURF, as the LUX-ZEPLIN collaboration was being formed. The series of sodium iodide and xenon detectors at Boulby covered several orders of magnitude in spin-independent WIMP scattering cross-section, producing some world-leading results along the way. The DRIFT programme was equally pioneering, seeding a significant worldwide effort in directional detection for dark matter.
More technical detail and relevant references can be found in Section 6.1 of Chepel & Araujo, JINST 8, 2013.
Progress in WIMP cross-section sensitivity from the UKDMC programme at Boulby.
The LUX Experiment
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Other projects with UK participation
DEAP-3600, DM-TPC, DM-ICE
Surface facility and Yates shaft headframe, Lead, SD.
Water tank containing presently the LUX experiment in the Davis cavern, 4850-ft underground level, SURF. LZ will be installed within the same water tank.