Improvements of a Branch Module for an Inductive Voltage Adder Based on Measurements and Circuit Simulations

For future upgrades of some CERN kicker systems, doubling of the driving current by replacing a matched impedance by a short circuit termination is of interest, because it allows a doubling of the kick strength, without an increase in magnet length or generator voltage. Therefore, for driving kicker magnets featuring a short-circuit termination, a novel approach for a pulse generator architecture based on an inductive voltage adder is currently being investigated. So far, a branch module for an inductive voltage adder has been designed and built. To account for the reflection at the short circuit, the branch module has a topology comprising two independently controlled semiconductor switches. This allows energy to first be injected into the kicker magnet, then to circulate the resulting current in a freewheeling-interval, and the energy to be reabsorbed at the end of the pulse. To validate the operation of the module, it has been tested with a resistive load of $10 \Omega$. This test revealed undesired oscillations of the pulse shape. In order to investigate these issues and to improve the circuit, a circuit simulation model has been developed including relevant parasitic parameters of the circuit elements. The simulation showed good agreement with the measurements. Hence, it was possible to identify and implement measures to damp the oscillations, both in the simulation and the real circuit as required for the application. The contribution describes in detail the measurements and simulation results as well as the implemented improvements to the circuit.