Collimation of H− beam transverse halo by triplets and foil scrapers

Transverse beam halo from a high current linac is an important source of beam losses in a ring as the next stage accelerator. A method is introduced that uses periodic triplet cells and foil scrapers to collimate the beam halo in the beam transport line from the linac to the ring and transports the collimated particles to a beam dump. It has good properties such as being low beam loss in the beam line and avoiding local collimators. Comparisons are made with doublet cells and FODO cells as well as with other collimation methods. In the paper, applying the method to the Chinese Spallation Neutron Source (CSNS) is also presented, together with the simulation results, using macro-particles and taking into account nuclear elastic scattering effect and foil stripping efficiency.