Effect of a metallized chamber upon the field response of a kicker magnet: simulations results and analytical calculations

Metallized racetrack vacuum chambers will be used in the pulsed magnets of the Austrian cancer therapy and research facility, MedAustron. It is important that the metallization does not unduly degrade field rise and fall times or the flattop of the field pulse in the kicker magnets. This was of particular concern for a tune kicker magnet, which has a specified rise and fall time of 100 ns. The impact of the metallization, upon the transient field response, has been studied using Finite Element Method (FEM) simulations: the dependency of the field response to the metallization thickness and resistivity are presented in this paper and formulae for the field response, for a ramped transient excitation current, are given. An equivalent circuit for the metallization allows the effect of an arbitrary excitation to be studied, with a circuit simulator, and the circuit optimized. Furthermore, results of simulations of the effect of a magnetic brazing collar, located between the ceramic vacuum chamber and flange, of the tune kicker magnet, are reported.