Images Dated 10th September 1997

Worker looks at a WIMP detector in a pool of water

WIMP detector. Technician looks at the Weakly Interacting Massive Particle (WIMP) detector in a water tank at the UK Dark Matter Collaboration (UKDMC) project site at Boulby Mine, Britain. About 90% of the universe's mass may be invisible dark matter such as WIMPs. The detector is 1100 metres underground to shield it from cosmic rays which could affect the results. The water & white plastic cladding around the detector shield it from natural radioactivity in the mine's walls. The detector contains a scintillation device which measures the recoil energies of normal nuclei aft- er they have been hit by a WIMP, a rare event due to the WIMPs weak interactions with other matter

© DAVID PARKER/SCIENCE PHOTO LIBRARY