Resonant spin depolarization at the test facility KARA: overview of recent efforts

The Karlsruhe research accelerator KARA offers a setup to measure the beam energy with resonant spin depolarization. The depolarization is excited by the stripline kickers of the bunch-by-bunch feedback system and the resonant frequency is measured via change in Touschek lifetime. Energy measurements with resonant spin depolarization are implemented as a standard routine in the control system and are used regularly to measure both the beam energy and the momentum compaction factor for different energies and optics regimes.
Long-time experience with the setup, short polarization time, and variation options of beam energy in combination with much available beam time qualify KARA as a test facility for systematic studies. Such studies are of particular interest for future colliders designed for precision studies like FCC-ee, as resonant spin depolarization is known for its high accuracy. This contribution presents the resonant spin depolarization setup at KARA and selected results of recent measurement campaigns.