A Neutrino Factory works by using an intense beam of protons that interact in a target to make lots of charged pions. These are unstable particles that decay into another type of unstable particle, the muon. The muons live for two-millionths of a second, which is just long enough to collect them, form them into a beam, accelerate them to higher energy, and inject them into a ring of magnets in which they circulate until they decay. When they decay they produce a muon-type (flavored) neutrino, and electro-type antineutrino, and an electron. If the ring is shaped like a race-track, with two long straight sections, then the muons that decay whilst travelling down the straight sections produce a beam of neutrinos and antineutrinos traveling in the direction of the straight section. This is the beam we want.