Focusing beams

This is the beam-exit end of one of two NuMI horns. The horn creates a magnetic field that focuses charged particles into a beam as they pass through it (into the plane of the picture). Some of the particles from the resulting, now-focused beam then decay into neutrinos, which travel in a straight line through the earth to a distant detector for scientists to study. Read about how to make a neutrino beam in symmetry. Photo: Reidar Hahn