The bounder modulators at DESY

The FLASH linac at DESY in Hamburg is a superconducting linear accelerator which provides an electron beam to generate laser light in the nm-regime. Five RF stations provide RF power up to 10 MW to generate and accelerate an electron beam up to lGeV in an RF gun and forty-eight superconducting nine-cell cavities, respectively. Several bouncer type modulators produce HV-pulses up to 130 kV, 140 A at 1.5 ms and up to 10 Hz for the 1.3 GHz klystrons and multi-beam klystrons of the linac. The first modulators have been constructed and delivered several years ago by FNAL to the TESLA Test Facility at DESY, which is now the FLASH linac. Later additional modulators have been assembled at DESY from subsystems, which have been constructed and manufactured by industrial companies. Two additional systems are in operation at PITZ at DESY in Zeuthen. This paper reports on the layout of the modulators, the major changes and improvements and the operation experience.