The coupling impedance of the RHIC injection kicker system

In this paper, results from impedance measurements on the RHIC injection kickers are reported. The kicker is configured as a “C” cross section magnet with interleaved ferrite and high-permittivity dielectric sections to achieve a travelling wave structure. The impedance was measured using the wire method in which a resistive match provides a smooth transition from the network analyzer to the reference line in the set-up. Accurate results are obtained by interpreting the forward scattering coefficient via the log-formula. The four kickers with their ceramic beam tubes contribute a Z/n=0.22 Ω/ring in the interesting frequency range from 0.1 to 1 GHz, and less above. At frequencies above ~100 MHz, the impedance is ferrite dominated and not affected by the kicker terminations. Below 100 MHz, the Blumlein pulser with the ~75 m feeding cables is visible in the impedance but makes no significant contribution to the results. The measurements show that the kicker coupling impedance is tolerable without the need for impedance reducing measures