Conceptual Design of a Longitudinal Halo Collimator for J-PARC Linac

A longitudinal halo collimator has been designed for J-PARC linac. We plan to adopt a “successive collimation scheme” taking advantage of the three-fold symmetry of our arc section. Adopting this scheme, smaller momentum aperture of around 0.5 % can be achieved with larger physical horizontal aperture of the collimator. We are also expecting that this collimator system is effective in beam diagnosis in the beam commissioning.