Neutral beam line to study KL0→π0νν¯ decay at the KEK 12-GeV proton synchrotron

A neutral beam line was constructed at the 12-GeV proton synchrotron of KEK for an experiment to study KL0→π0νν¯ decay. It was designed to make a well-collimated KL0 beam with small γ and neutron halos. In a series of beam-survey experiments, beam profiles and energy spectra of γ's and neutrons were measured. It was confirmed that the beam was sharply collimated with a halo-to-core flux ratio lower than 10-4. These experimental results were well reproduced by a Monte-Carlo simulation based on the GEANT-3 program.