The MiniBooNE detector
is a 12-meter diameter spherical stell tank, filled with 250,000 gallons of ultra-pure mineral oil. A light-tight
shield just inside the tank wall separates the detector into an spherical inner "signal" region and an outer "veto" shell.
1280 photomultiplier tubes facing inward detect light from particles interacting in the signal region, and 240 veto tubes look for light
from particles in the veto shell. Photomultiplier tubes convert light into electrical signals; these signals are gathered
and interpreted by MiniBooNE's data acquisition computers.