WIMP detector. Technicians with a Weakly Interact- ing Massive Particle (WIMP) detector 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. This scintillation detector has a 6-kilogram sodium iodide crystal in a central section with a tube on each end that holds light amplification devices (photo-multiplier). The detector observes the light given off after a normal nucleus recoils after being hit by a WIMP, a rare event due to the WIMP's weak interactions with other matter. The detector is shielded from cosmic rays by 1100 metres of overlying rock.