Measurement of the Longitudinal and Transverse Coupling Impedances of the Higher-Order Modes of the Re-Entrant Accelerating Cavity

摘要

Higher-order modes were studied in a model cavity (re-entrant single cell cavity) which was designed for the KEK Photon Factory electron storage ring. Fifteen resonances were observed up to 1,300 MHz, and mode assignments were made for all of the resonances. The longitudinal electric field and the transverse electric and magnetic fields were measured near the beam axis to determine the coupling impedance of each mode. The observed parameters of the TMO-mode resonances were in reasonable agreement with the SUPERFISH calculation. The transverse coupling impedances of the HEM1 modes at 829.3 MHz (TM110-like) and 1070.8 MHz (TM111-like) were 12 M omega /m and 27 M omega /m, respectively. The observed parameters are discussed in view of the beam instabilities. (Atomindex citation 13:659552)