  Suppression of beam losses is essential for successful operation of
high-intensity linac. Historically, the values of the field amplitudes and
phases of the side-coupled, 805-MHz LANSCE linac modules are maintained using a
well-known delta-t tuning procedure. Transverse matching of the beam with
accelerator is performed through adjustments of beam ellipses in 4D phase space
with accelerator lattice using matching quadrupoles. Control of the beam-energy
ramp along the length of a proton linear accelerator is required to improve
tune of accelerator and decrease beam losses. Time-of-flight measurements of
the H- beam energy are now being used to confirm and improve the overall
control of the energy ramp along the linac. The time-of-flight method utilizes
absolute measurements of beam energy using direct signals from beam at an
oscilloscope, as well as the difference in RF phases measured as the beam
passes installed delta-t pickup loops. A newly developed BPPM data acquisition
system is used. Beam energy measurement along accelerator together with phase
scans, klystrons output power control, and delta-t method, allow tuning of
accelerator much more close to original design and reduce losses generated by
linac. Details of the upgraded tuning procedure and results of tuning and
operation are presented.
