The Hadron Hose: continuous toroidal focusing for conventional neutrino beams

Abstract We have developed a new focusing system for conventional neutrino beams. The “Hadron Hose” is a wire located in the meson decay volume, downstream of the target and focusing horns. The wire is pulsed with high current to provide a toroidal magnetic field which continuously focuses mesons. The hose increases the neutrino event rate and reduces differences between near- and far-field neutrino spectra for oscillation experiments. We have studied this device as part of the development of the Neutrinos at the Main Injector project, but it might also be of use for other conventional neutrino beams.