  The Los Alamos Neutron Science Center (LANSCE) accelerator at Los Alamos
National Laboratory (LANL) has been in service for over 50 years. Efforts to
update and modernize crucial systems, many of which are origi-nal, are ongoing.
This paper reports on the refurbishment of the Low-Level Radio Frequency (LLRF)
Resonance Control Water System (RCWS) for the half-mile long Cavity-Coupled
LINAC (CCL). The RCWS controls the resonance frequency of the cavities by
controlling the temperature of the cooling water delivered to each of 44
accelerator modules. Of the 44 modules making up the CCL, 20 now have an
upgraded RCWS. Upgrading in-cludes removing the old hardware and installing new
components including: water pumps, mix tanks, valves, temperature switches,
flow switches and plumbing. This paper describes the design of the new system,
material and component selection, installation, and technical challenges.
