  Incremental upgrades of the legacy low level RF (LLRF) equipment-50 years for
the Los Alamos Neutron Science Center (LANSCE)-involves challenges and problems
not seen with new and total replacement opportunities. The digital LLRF upgrade
at LANSCE has deployed 30 of the 53 required systems as of September 2022. This
paper describes the performance of the digital upgrade, current status, and
future installations along with the technical challenges, including unexpected
challenges, associated with deploying new digital systems in conjunction with
legacy analog equipment. In addition, this paper discusses the operational
details of simultaneous multi-energy beam operations using high energy
re-bunching, beam-type specific set points and simultaneous multi-beam
operations at LANSCE. The adaptability of the digital LLRF systems is essential
as the design is able to accommodate new control and beam parameters associated
with future systems without significant hardware modifications such as the
expected LANSCE Modernization Program. This adaptability of the digital LLRF
technology was recently demonstrated with the Module 1, 201.25-MHz high-power
RF upgrade completed in 2021.
