MiniBooNE

Like many detectors, this experiment at the Fermi National Accelerator in Batavia, Illinois investigates the oscillation of neutrinos from one type to another. Since 2003, it has observed neutrinos created from protons in Fermilab's particle booster, part of the system that the lab normally employs to accelerate protons to higher energies for other experiments. MiniBooNE is a 40-foot-in-diameter spherical steel tank filled with 800 tons of mineral oil and lined with 1,280 phototubes (some of which are being adjusted in this image) that produce a flash of light when charged particles travel through them. Analyses of these light flashes are already providing tantalizing information about the nonzero status of neutrino mass.

Source: http://www.pbs.org/wgbh/nova/neutrino/dete-05.html