A Single Electron Beam Tuning Detector Based On Plastic Scintillator

This paper is based on the requirements of "Electromagnetic Condition Assurance Program-Accelerator Beam Commission and Position Monitoring" by Institute of High Energy Physics,Chinese Academy of Sciences.In order to obtain weak current and the low energy electron beam that hit the target chamber,a single electron beam detector is designed and fabricated.Usually the weak beam current of accelerator need to be measured by picoammeters,Faraday cup and other equipments.However,when the beam intensity is lower than the sensitivity of the microampere-order,so the normal current measurement method is no longer applicable.In this paper,a single particle sensitive low-current beam detector based on a plastic scintillator(Saint-Gobain BC 408)and a photoelectric multiplier tube(XP1912)was developed to measure the 100Hz pulsed electron beam from 0.1 to 50 MeV.In each pulse there are 107 electrons to quasi-single electrons.Using the linear relationship between the scintillation intensity and the electron number in the low energy range,the scintillation intensity measured by detector,then the actual electron number can be derived.Based on Geant4 simulation to energy deposition of different energy incident electrons in the plastic scintillator,electron detection efficiency and light collection efficiency,the measurement results can be scaled and corrected.The simulation results show that the energy of smaller than 3MeV is almost completely deposited in the scintillator,while the energy that is larger than the energy of 3MeV electrons deposited in the scintillation body gradually tends to 1.8MeV flat area with the increase of the incident electron energy.Plastic scintillator's electron detection efficiency is 100%,light collection efficiency is up to 27.8%.A total of nine detectors were developed for actual beam position monitoring and measuring the number of electrons passing through each detector.A gain test was performed on all the detectors and energy calibration was done using a 207Bi single electron radioactive source.Slit experiments show that the adjustable slit can reduce the beam intensity to one twentieth of the original.The results show that the low energy electron beam monitor system can meet the requirements of monitoring single electron beam.