Photomultiplier tubes dot the 26-ton water tank of ANNIE, the Accelerator Neutrino Neutron Interaction Experiment. Photo: Reidar Hahn, Fermilab

The inside of the ANNIE detector looks like a series of carefully placed Jell-O domes, or perhaps a jeweled Fabergé egg. Its walls are dotted by 137 sensors for detecting packets of light and embrace 26 tons of gadolinium-doped water.

By Catherine N. Steffel. Read the entire article here.