Constant-Power Power Supplies for the TESLA Modulators

For the TESLA Test Facility at DESY modulators, which generate high voltage, pulses of 130 kV with an electrical power of up to 16.8 MW are used. The pulses have a repetition rate of up to 10 Hz and a width of 1.7 ms. Since it is not possible to take the pulsed energy directly from the mains the required energy is stored in capacitor banks to be released during the pulse. Power supplies are needed to recharge the capacitor banks of the modulators without disturbing the mains. In particular the low repetition rate of the pulses has to be suppressed. Tobe independent from the repetition rate the power supplies have to operate in a constant power mode. The DC charging current into the capacitors decreases during the loading with the same factor with which the voltage increases. In this way the current taken from the threephase mains is constant. Different types of power supplies have been investigated at DESY and are described here. These types are antiductors with secondary diode bridges, switched mode power supplies, diode bridges plus series switched mode supplies, diode bridges with SCR bridges in sequential phase control

A MHz-repetition-rate hard X-ray free-electron laser driven by a superconducting linear accelerator

International audienceThe European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created