Since November 2012, two giant pulsed klystron modulators have been transported from the Ampegon factory in Turgi, Switzerland, to the Deutsche Electronen Synchroton facility in Hamburg, Germany, every month.
At the DESY facility, the European X-ray free electron laser project, which features a 3.4 km long superconducting linear electron accelerator is currently under construction. The project began in 2006 and is expected to be complete by 2015. When finished, XFEL will enable scientists to observe processes on the nanoscale in real time.
The project needs 27 RF stations capable of 10 MW RF power each. Each needs one high voltage modulator that generates pulses up to 12 kV and 2 kA with duration of 1.7 ms and a nominal repetition rate of 10 Hz. To meet this need, DESY ordered the pulsed klystron modulators from Ampegon.
An impedance-matched system is needed for the interconnection between the klystrons and the modulators; this is achieved through four coaxial cables, each with a nominal impedance of 28 ohms in parallel, resulting in an effective cable impedance of 7 ohms.
The modulator is comprised of 24 active modules, but the system is fully operational with just 22. Charging is accomplished through constant power consumption during the pulse pause, using a boost converter.
For the demagnetization of the pulse transformer and for dissipating the inductive stored energy under klystron arcing conditions, four modules are paired with additional switching modules in a two-phase configuration, enabling inverse voltage operation.