BNL, Upton, Long Island, New York
Modes with transverse electric field (TE-modes) in the NSLS-II multipole vacuum chamber can be generated at frequencies above 450 MHz due to its geometric dimensions. Since the NSLS-II BPM system is triggered by the RF at 500 MHz, frequencies of higher-order modes (HOMs) can be generated within the transmission band of the band pass filter. In order to avoid systematic errors in the NSLS-II BPM system, we introduced frequency shift of HOMs by using RF metal shielding located in the antechamber slot.
