Study On Continuous Ion Backflow Suppression Detector Module For Circular Collider

In order to achieve the physics goals at the CEPC,a time projection chamber(TPC)with high point resolution(<100 ?m)and high rate capablity(especially when the ma-chine is operated at the Z pole)is required.To meet the requirements for the CEPC TPC,its ion backflow(IBF)must reduced to a manageable level.IBF is one of the key effects limiting the operation of a TPC at high flux and its point resolution.The back-flowing ions affect the drift of electrons by giving rise to space charge which disturbs the electric field locally.In this thesis the ion backflow of CEPC TPC is analyzed and it is indicated that the traditional gating devices can not be used in our case.A hybrid TPC readout module based on GEM and Micromegas(GEM-MM)is thus proposed.With this module the TPC can be operated in an ungated continuous mode,which is just the demand of CEPC TPC.The main work in this thesis is responsible for the research on the GEM-MM module.Detailed simulations using ANSYS and Garfield++ are carried out to investigate the performance of the GEM-MM module.Simulations on the charge transfer in GEM-MM are presented,including the signal characteristic,electron transparency and gain.The IBF fraction of GEM-MM is calculated as a function of electric field configurations.The detector's operating condition are optimized which provides important reference and necessary complement for the experimental measurement.Simulations show that GEM-MM can suppress ion backflow effectively while maintaining a satisfactory electron transparency.In this thesis,experimental studies on GEM-MM are performed based on the simulation.A GEM-MM prototype detector is built,its energy resolution and gain are measured.The IBF fraction of GEM-MM is also tested with an 55 Fe X-ray source and a Cu X-ray tube.The capability of GEM-MM to continuously suppress ion backflow has been verified.The GEM-MM module can suppress ion backflow more effectively compared with GEM or Micromegas,and its energy resolution is not sacrificed.A relative method is proposed based on the unique energy spectrum of GEM-MM under the irradiation with X-Rays to precisely measure the gain of GEM.The measured gain of GEM have been compared to simulation and the Penning transfer rate is determined.To overcome the limitation of IBF fraction measurents with 55Fe X-ray source and X-ray tube,in this thesis,UV light experimental scheme is designed and some tests are carried out.