Bunch‐by‐bunch position measurement and analysis at PLS‐II

A bunch‐by‐bunch measurement system has been developed at Pohang Light Source II. The system consists of a four‐channel button pick‐up, 20 GHz sampling oscilloscope and an 800 MHz low‐pass digital filter. Upon measuring a bunch‐by‐bunch spatio‐temporal beam motion matrix over many turns, singular‐value decomposition analysis is used to reveal the dominant coupled‐bunch modes. The system can diagnose injection oscillations due to kicker errors and the effect of resistive‐wall impedance that gives rise to instability during operation. A bunch‐by‐bunch measurement system has been developed at Pohang Light Source II, consisting of a four‐channel button pick‐up, 20 GHz sampling oscilloscope and an 800 MHz low‐pass digital filter.