VARIOUS IMPROVEMENTS TO OPERATE THE 1.5 GeV HDSM AT MAMI

During the last three years at the 1.5 GeV Harmonic Double Sided Microtron (HDSM, [1]) of MAMI a lot of improvements concerning the longitudinal operation of the accelerator were tested and installed. To monitor the rf-power dissipated in the accelerating sections, their cooling water flow and its temperature rise are now continuously logged. Phase calibration measurements of the linacs and the phase/intensity monitors (p/i-monitors) revealed nonlinearities of the high precision step-motor driven waveguide phase shifters. They were recalibrated to deliver precise absolute values. Thereby it is now possible to measure not only the first turn’s phase very exactly, but also to determine the linac’s rf-amplitude within an error of less than 5 % using the well known longitudinal dispersion of the bending system. These results are compared to the thermal load measurements. For parity violation experiments the beam energy has to be stabilised to some 10−6. A dedicated system measuring the time-of-flight through a bending magnet is now used in routine operation and controls the output energy via the linac phases. D ip ol e 1 D iole 4 D ip ol e 3 D iole 2 4.9GHz LINAC ( , ) φ4.9 Emax,4.9 2.45GHz LINAC ( , ) φ2.45 Emax,2.45 4.9G H z M