Excitation And Detection Of The Transverse Quadrupole Mode Beam Oscillation In The HLS Ⅱ Storage Ring And Related Research

In order to study the influence of transverse quadrupole oscillation on beam parameters and enhance understanding of higher-order transverse wakefield generated by the beam, excitation and detection of the transverse quadrupole mode beam oscillation in the single-bunch mode and multi-bunch mode are respectively operated in the HLS Ⅱ storage ring. The effect of short-range transverse quadrupole wakefield on transverse quadrupole oscillation frequency under single bunch is analyzed. Related experimental researches are also performed based on stripline beam position monitor(BPM).Firstly, research status at home and abroad is investigated. Different exciting and measuring methods of the beam transverse quadrupole oscillation are described. After a comprehensive comparison, experimental scheme for excitation and detection of the transverse quadrupole mode beam oscillation in the HLS Ⅱ storage ring is determined. The stripline transverse quadrupole kicker and stripline BPM are choosen to be exciter and detector.The related theories for excitation and detection of the transverse quadrupole mode beam oscillation are introduced. The beam movement theory is firstly introduced. The exciting principle, exciting methods and measuring methods for the beam transverse quadrupole oscillation are highlighted. The effect of short-range transverse quadrupole wakefield on transverse quadrupole oscillation frequency is analyzed. Signal analysis principles in time domain and frequency domain are also briefly introduced.Structural parameters are optimized and designed for the stripline transverse quadrupole kicker in order to match characteristic impedance of electrode with characteristic impedance of external transmission line. The stripline transverse quadrupole kicker is modeled and electrode port reflection parameters are calculated. Function simulation for the stripline transverse quadrupole kicker is performed, the result shows that it can excite the beam transverse quadrupole oscillation. The stripline transverse quadrupole kicker is machined. The characteristic impedance of electrode and electrode port reflection parameters are measured.Refer to design method for the stripline transverse quadrupole kicker, structural parameters are similarly optimized and designed for the stripline BPM. The stripline BPM is modeled by Microwave Studio(CST). Coupling influence between electrodes is analyzed. Using boundary element method stripline BPM is modeled by Matlab code and some parameters of position sensitivities, transverse quadrupole signal, etc are simulated.Off-line calibration platform is built and the stripline BPM is off-line calibrated. According to difference/sum ratio(△/∑) and log-ratio methods, position sensitivities are calculated and errors do not exceed3%compared with simulation results. Mapping figures and empirical polynomial fitting formulas are obtained. Normalized sum signal is off-line calibrated and it’s no more than6%in the interval (Omm,0mm) to (5mm,5mm), which is consistent with simulation result. Transverse quadrupole signal and electrode gains are also off-line calibrated.Excitation and detection of the transverse quadrupole mode beam oscillation are operated in the HLS Ⅱ storage ring. Experimental platform is performed. Experiment is done in the multi-bunch and single bunch condition respectively. The effect of short-range transverse quadrupole wakefield on transverse quadrupole oscillation frequency under single bunch is analyzed. The transverse quadrupole oscillation is measured when beam is injected. In addition, some online experiments are done based on the stripline BPM, including measurement for beam position and electrode gains, etc.This work is supported by the Natural Science Foundation of China (10875117,11175173and11105141) and the HLS major maintenance and reconstruction project.