Operational Performance of New Detection Electronics for Stripline-Type Beam Position Monitors at the SuperKEKB Injector Linac

SuperKEKB injector linac delivers four different beam modes modulated pulse by pulse at 50 Hz, which have 100-times different beam charges, and a pulse may contain two bunches only 96-ns apart. Required low-emittance beams for SuperKEKB rings would need precise beam orbit controls in order to suppress the transverse wakefield in the accelerating structures. A new detection electronics with a wide dynamic range of 40 dB with a high resolution based on a 180-MHz narrow-band detection technique for stripline-type beam position monitors (BPMs) has been developed for the SuperKEKB injector linac. While such measurement condition is challenging, a position resolution of 3 micrometer in one standard deviation was successfully achieved with beam-based tests. The self-calibration system is also installed in order to compensate gain drifts for each input channel with an accuracy down to 0.1%, by using test pulses going through stripline heads between 50-Hz beam pulses. The design concept of the new detection electronics is described in detail, as well as operational performance of synchronized measurement with 100 BPMs for injection beams to four electron/positron storage rings.