A capacitor discharge, quasi-trapezoidal pulse generator for particle extraction

In the CERN SPS accelerator, two methods for particle extraction are used. One of these methods, called slow extraction, delivers extracted beams with a duration of up to several seconds to the majority of experiments. The other, fast resonant extraction, providing particle bursts with a duration of a few milliseconds, is used for neutrino experiments. For the latter kind of extraction, a quadrupole magnet is installed, which is connected to a high voltage pulsed power generator delivering quasi-trapezoidal current pulses. The pulsed power generator is a capacitor discharge system generating current pulses, with a rising slope having 2 different gradients, of which the second one is approximately zero. The falling slope is obtained through natural decay in a freewheel circuit. The use of modern GTO switches has resulted in a much simpler circuit than the use of standard thyristors would have permitted.