Improved analytical model of the transverse coupling impedance of ferrite kicker magnets

Abstract

A transformer model of ferrite kicker magnets is presented in this paper. Based on this model, an equivalent circuit is derived for which the elements can be obtained by bench measurements or by estimates from the magnet geometry. Improved formulas for the transverse coupling impedance of lumped and traveling wave kicker magnets are derived from the model and the equivalent circuit. The formulas differ from the corresponding handbook results in their dependence on the external termination or aperture aspect, respectively. The effect of ferrite properties on the transverse coupling impedance is analyzed. The model was confirmed by bench measurements with the twin-wire technique made on the full-size and half-size prototypes of the extraction kicker of the SNS accumulator ring. The application of this model to the design of the kickers allowed a significant reduction of the SNS transverse coupling impedance budget.

Impedance measurements of the Spallation Neutron Source extraction kicker system

“…This provided the renewed motivation to investigate the wireless direct impedance measurement as a complementary method. Coupling impedance measurements without wires have been reported in the literature [13] and preliminary results for the SNS extraction kicker were obtained with this method [7,11]. PRST-AB 7…”

Longitudinal and transverse impedance of a ferrite kicker for non-ultrarelativistic beams

“…Based on Nassibian and Sacherer's theory, improved formula was developed in Ref. [3] for transverse impedance calculation and the result is confirmed by bench measurement. In Refs.…”

Interpretation of coupling impedance bench measurements

“…The R&D and design work for the construction of the Spallation Neutron Source (SNS) required detailed impedance studies of various components [13,14]. The transverse impedance of the extraction kickers was judged to be critical to the performance of the accumulator ring and received special attention [15]. The measured data is obtained from the network analyzer as a normalized ratio S DUT 21 =S REF 21 S 21N which is translated via a model to the Z DUT .…”