Transmission-line impedance measurements for an advanced hadron facility

Abstract

High-intensity synchrotrons such as the proposed Advanced Hadron Facility (AHF) [1] and the Los Alamos Proton Storage Ring (PSR) [2] must have a low beam-coupling impedance for stability. The conflicting requirement of low eddy-current effects in the rapid cycling AHF makes the AHF beam-pipe design a particularly difficult problem. A ceramic pipe deposited with conducting stripes has been proposed for AHF. It can have adequately small eddy currents, but it may have an unexpectedly large coupling impedance. Therefore, a facility for measuring transmission-line impedances has been established and is described in this paper. Measurements of transverse and longitudinal coupling impedances for ceramic/metal and other beam-pipe segments are reported; a ceramic/metal chamber can have adequately small impedance. Results of impedance measurements for other AHF and PSR devices, such as a PSR beam pickup and bumper magnet, are also reported. © 1989.