In the upgrade project of Hefei Light Source（HLSⅡ）,a new digital longitudinal bunch-by-bunch feedback system will be developed to suppress the coupled bunch instabilities in the storage ring effectively.We design a new waveguide overloaded cavity longitudinal feedback kicker as the feedback actuator.The beam pipe of the kicker is a racetrack shape so as to avoid a transition part to the octagonal vacuum chamber.The central frequency and the bandwidth of the kicker have been simulated and optimized to achieve design goals by the HFSS code.A higher shunt impedance can be obtained by using a nose cone to reduce the feedback power requirement.Before the kicker cavity was installed in the storage ring,a variety of measurements were carried out to check its performance.All these results of simulation and measurement are presented.
A logarithm processing algorithm to measure beam transverse size and position is proposed and preliminary experimental results in Hefei Light Source II（HLS II） are given. The algorithm is based on only 4 successive channels of 16 anode channels of multianode photomultiplier tube（MAPMT） R5900U-00-L16, which has typical rise time of 0.6 ns and effective area of 0.8×16 mm for a single anode channel. In the paper, we first elaborate the simulation results of the algorithm with and without channel inconsistency. Then we calibrate the channel inconsistency and verify the algorithm using a general current signal processor Libera Photon in a low-speed scheme. Finally we get turn-by-turn beam size and position and calculate the vertical tune in a high-speed scheme. The experimental results show that measured values fit well with simulation results after channel differences are calibrated, and the fractional part of the tune in vertical direction is 0.3628, which is very close to the nominal value 0.3621.
The four electrodes in the stripline beam position monitor(BPM) for Hefei Light Source(HLS II) storage ring are of axially symmetric type. We have derived a new calibration method of electrode gains for this type stripline BPM. The gain fit error of different data grids was analyzed, and the ±5 mm by ±5 mm grid is the best.The electrode gains of two stripline BPMs(HLS II SR-BD-STLB1 and HLS II SR-BD-STLB2) were obtained based on offline calibrated data. The results show that data after fitting gains are improved, with the electrode gains being between 0.94 and 1.15.
