Studies Of The Optical Readout Imaging Detector Based On THGEM And CCD Camera

In recent years,great progress has been made in the fabrication process and performance of domestic THGEM,and THGEM has also been developed in particle physics experiments and imaging applications.As far as the charge readout method of the detector is concerned,in order to achieve fine imaging,the detector itself is required to have higher position resolution,and readout electronics is also required to have high density multiplexed readout capability.However,the domestic research on MPGD readout chip is just beginning,and it is still the bottleneck and shortcoming of MPGD application.The avalanche effect of electrons in THGEM microspores produces a large number of avalanche electrons,which is accompanied by a large number of avalanche luminescence.Therefore,in addition to charge induction readout,avalanche luminescence may also be used for readout.The purpose of this paper is to develop a position resolution imaging detector based on domestic THGEM and general scientific CCD camera with the optical readout method.And its position resolution is better than 0.5mm.An X-ray imaging detector model with a sensitive area of 60 × 60mm2 has been developed,and a number of imaging examples have been obtained by successfully completing the two-dimensional imaging of the object samples based on optical readout.The relative light yield curve of the detector with gain is measured.The position resolution of the detector is measured by double slit and blade method,and the result is better than 275μm.The above results show that the detector has good optical readout ability and has great potential in large area imaging.In order to obtain stable THGEM with high gain and increase the avalanche light yield,THGEMs with eight kinds of FR-4(epoxy resin and glass fiber composite)substrate have been developed based on the domestic PCB manufacturers in China.All the structures of THGEMs are the same except the substrate.Their performance in voltage resistance,gas gain and energy resolution are tested and compared.Finally,a new FR-4 substrate,THGEM,which has the best comprehensive performance,is selected.Using this new FR4 substrate,multi-layer THGEM(M-THGEM)were developed.The gain of a single 2-layer M-THGEM film in the gas Ar+C02 = 90:10 can easily reach 1.0 × 104,and can work stably for a long time,and can be used in optical readout.In addition,the rapid test system for THGEMs is developed in this paper.The gas replacement mode of the THGEM performance test was improved,and the rapid gas replacement system was built.The system can realize the quick replace gas for the THGEM detectors with effective area of 100 × 100mm2 and smaller.Compared with the conventional method which needs 2～10 hours(which is determined by the size of the detector chamber)to replace gas,it takes only about 10 minutes to replace the gas by using the system,and the result of gas replace is better than that of the traditional method.