Design and fabrication of button-style beam position monitors for the HEPS synchrotron light facility

At the High Energy Photon Source (HEPS),a high orbital stability of typically 10% of the beam size and angular divergence must be achieved.The beam size at the insertion devices is 10μm horizontally and 1μm vertically,which implies that the beam orbit must be stabilized to the sub-micrometer level.This results in stringent tolerance and quality control requirements for the series production of beam position monitor (BPM) pickups.In this study,analytical formulas were used and CST simulations were performed to analyze the effects of the mechanical tolerances of BPM pickups on beam position measurement.The results of electromagnetic?eld simulations revealed how various mechanical errors,such as button size and location accuracy,as well as the related button capacitance,exert different in?uences on the beam position measurement.The performance of an actual BPM pickup was measured,along with an assessment of the error on the beam position measurement.Additionally,a wake?eld analysis,including an investigation of trapped resonant modes and related thermal deformation,was conducted.

A high sensitivity tune measurement system for BEPCII

Background The tune is one of the most important parameters of the storage ring which play a crucial role in the brightness optimization.The synchrotron radiation will suppress the oscillation and make the detection unusual difficulty without any kicker excitation.Purpose A new high sensitivity tune measurement system is developed to show the real-time tune during the colliding.Method Peak diode detectors are used to convert short beam pulses from a button BPM into slowly varying signals.Their DC components,constituting a large background related to beam offsets,are suppressed by series capacitors,while the small signals related to beam oscillations are passed to the subsequent stages for amplification and filtering.Conclusion A direct diode detection technique based on the diode peak hold circuit could increase the sensitivity by hundreds time which gets a clearly tune peak even with synchrotron radiation and bunch-by-bunch feedback damping.

A scintillator detector for beam tuning of low-energy single electron accelerator

Purpose Nine scintillator detectors were developed for beam tuning of low-energy single electron accelerator instead of the picoammeter and Faraday cup,both of which will be insensitive to the weak-current beam lower than picoampere.Methods The detectors are based on plastic scintillator and photomultiplier tube(PMT)and the beam is 100 Hz pulsed electrons in the energy range of 0.1 to 50MeV.The beam flux was tuned from about 107 to quasi-single electron for each bunch according to the measurement results of these detectors installed along the beam pipe and after slits.In order to determine the number of electrons in a bunch,the gains of each PMT were finely calibrated,and the energy response of each detector was calibrated with 207Bi radioactive source.Moreover,the deposited energy in the plastic scintillator,the electron detection efficiency and light collection efficiency,as a function of electron incident energy,were also simulated in detail by Geant4.Results Nine detectors worked well at a gain of 0.6×10^(6) after installation in the beam pipe,and the number of electrons in a bunch could be measured at each detector position.The single electron peak was seen when the beam reached the final detector.Conclusion The commissioning result shows that the beam was tuned to quasi-single electron level successfully and the scintillator detector is an effective method to measure the weak-current beam lower than picoampere.