Beam dynamics in LANSCE accelerator facility with lower energy

In operation of the LANSCE accelerator facility, occasionally it is required to provide beam at a lower beam energy than the nominal energy of 800 MeV. In this paper we examine the regime when the last sector of the LANSCE linear accelerator is off, so that the beam energy becomes 700 MeV. The purpose of our study is to evaluate beam quality and required changes in the accelerator setup. Simulations of lower energy beam dynamics were performed starting from the beginning of Coupled-Cavity Linac through Switchyard and beamlines to Proton Storage Ring (PSR), followed by the process of beam accumulation in PSR. The original design of injection beamline to the Proton Storage Ring at nominal energy of 800 MeV assumes elimination of cross-terms in beam 6D sigma-matrix at the point of injection to PSR; however, these terms are amplified when 700-MeV beam is injected. Comparison of beam dynamics with nominal and lower energy operation is presented.