Compensation for Beam Loading in the 400-GeV Fermilab Main Accelerator

At the design ramp slope of 125 GeV per second and 5 × 1013 protons per pulse, the RF System in the Fermilab main accelerator must deliver 1 megawatt of power to the proton beam. RF amplitude and phase changes resulting from beam loading during acceleration are compensated for by separate somewhat slow feedback systems. Phase shifts resulting from transient beam loading during injection are compensated for by a third feedback system of broader bandwidth. The feedback systems are described and performance details are discussed.