Development Of Detection System For Direct Nuclear Radioactive Ion Beam Experiment In Everal Times Coulomb Barrier Energy Region

The elastic scattering and breakup experiments of ⁸B+9)(6Pb,^9,10,11Be+²⁰⁸Pb and⁸B/⁹C+²⁰⁸Pb around 3times the Coulomb barrier have been successfully conducted on the Radioactive Ion Beam Line in Lanzhou（RIBLL）at Heavy Ion Research Facility in Lanzhou（HIRFL）.The statistics around the grazing angle are especially important in these experiments.Different reaction systems or energies usually lead to different grazing angles.Therefore,in this paper,based on the main features of the RIBLL1 beamline,a charged particle detection system is designed to meet the requirements of complete kinematic measurement for the products of singular nuclear reactions,the detection system is a set of high-efficiency detector system consists of six sets of telescopes,each composed of a three-layer structure Double-Sided Silicon Strip Detector（DSSD）+Pixel Silicon Detector（PSD）+CSI（Tl）.The main work carried out in this paper is as follows:（1）The design scheme of the detector array meeting the experimental requirements is given:the detector array is composed of six sets ofΔE-E telescope detection system,and the six sets of telescopes are compactly arranged to cover the angles of 3°-35°,covering a large stereo angle in the range of 10°-25°（θ）.Each telescope consists of three layers.The first layer is a DSSD with a thickness of 150μm,the second layer is a PSD with a thickness of 1500μm,and the third layer is a Cs I（Tl）detector with a thickness of 20 mm.The geometric efficiency of the detector system can reach up to 90%.（2）Geant4 simulations were used to evaluate the effect of rotation of each telescope detection system toward the center of the detection system with the center of the effective detection area as the pivot point on the geometric efficiency.The optimal rotation angles for Tel1,Tel2,and Tel3,Tel4,Tel5,and Tel6 were calculated to be 6°and 19°,respectively,with geometric efficiencies of 20.1%and 6%in the overall range of（3°-35°）×2π,respectively.（3）The elastic scattering and breakup reaction experiments of ⁷Be on a ²⁰⁸Pb target at an incident energy of E_lab=125 Me V were simulated and completed on this detection system using Geant4.The breakup events were obtained by analyzing the data,and simulations of empty target experiments were performed to obtain the effect of the reaction of ⁷Be occurring on the target front detector on the elastic scattering cross section and its effect on the fragmentation reaction cross section.It is obtained that for the effect of the reaction of ⁷Be occurring on the target front detector on the fragmentation reaction cross section,the percentage is about 10%,which is not negligible.From the simulation results,it can be seen that the new generation of high-efficiency charged particle detector equipment developed in this paper has greatly improved in terms of geometric efficiency,coverage angle range,and detector modularization.