Critical design issues of the novel multi-beam LANSCE front end

The proposed novel 100 MeV injector for the modernization of the LANSCE Accelerator Facility* is aimed to replace the existing injector based on 750-keV Cockcroft-Walton columns. The specific feature of the LANSCE accelerator is the simultaneous delivery of beams with multiple beam flavors to several targets. Acceleration of various beams in a single RFQ provides less flexibility for optimal adjustment of acceleration and focusing parameters concerning the existing LANSCE setup caused by differences in beam current, charge per bunch, and beam emittances. An important issue in the low-energy beam transport of the proposed injector is the different levels of space charge neutralization of the multi-component beam. Coupling between degrees of freedom in the presence of strong space charge forces of the beams results in unavoidable beam mismatch in the Front End and requires careful six-dimensional matching of beams with accelerator structures. The paper discusses key issues in the planned Front End and suggests ways to mitigate them.