Bpecii Test Beam E3 Line ¦Ð Meson Target And The Magnetic Spectrum Proposed System Design

The test beam is located at the end of BEPCII (Beijing Electron-Positron Collider)-LINAC (Linear Accelerator), which consists of three beam lines: E1, E2 and E3. The E1 beam is a primary particle beam to be used for intense slow-positron facility. The E2 is a mixed high energy particle beam to be used for irradiated experiments. The E3 provides single secondary particle beam: electron, pion and proton, which is selected by detectors and magnetic spectrometer for detector prototype beam test.As part of overall advancement of BEPCII, the multiple particles events will increase in E3 beam line. In order to enhance resolving capability for multiple particles events and improve momentum resolution of single particle, the magnetic spectrometry system of E3 beam line in test beam is needed to be designed again. The scintillation fibers detectors and GEM-based TPC were used to replace the original MWPC detector, and the positions of detectors in E3 beam line were adjusted too. In this paper, the designed magnetic spectrometer system and detectors of E3 beam line were described. Their performances and operating principle were described detailed too. In addition, the paper presents that the methods of reconstructing track and momentum of particles in DM2 based on positions information from three position detectors, which will be used to calculate the theoretic momentum resolution of magnetic spectrometer.In order to increase the single particle events ofπ, an inbuilt compound target was designed by geant4 simulation based on theory of single pion photo-production. In addition, to test the momentum resolution, detection efficiency for single particle and resolving capability for double-particle of the new magnetic spectrometer system, we did MC simulation by Geant4 code. The test results show that momentum resolution of single particle is better than 0.5%, track separating of double-particle is less than 3 mm, which satisfy the design parameters of the magnetic spectrometer. Therefore, the new designed magnetic spectrometer could give accurately momentum of single particle and separate double-particle, which provide the test detectors with known momentum, kinds, position and the incidence angle on the prototype of particle events.