Bench measurements and beam tests of a prototype stripline kicker for swap-out injection in the ALS-U

The ALS upgrade to a diffraction-limited light source (ALS-U Project) relies on a swap-out injection scheme, where the circulating current is maintained constant by injecting on-axis fresh bunch trains replacing old trains, which are simultaneously extracted. The realization of a stripline kicker to perform such an operation presents several challenges in terms of optimal matching to the pulser, contributions to the beam coupling impedance, and dissipation of the power deposited by the stored beam. To test our design choices for the ALS-U kicker, we have built and installed on the ALS a test kicker with characteristics similar to the design for the ALS-U, as the more challenging aspects of the project are concerned. In particular, while the small distance between stripline electrodes reduces the required pulser voltage, the extreme proximity of the circulating beam requires a careful evaluation of the interaction between beam and kicker. In this paper we present the measurement techniques used to improve the alignment of the stripline electrodes during assembly and monitor their status after installation on the ALS.