Reasearch On Far Ultraviolet Photon-counting Imaging Detector Based On Induced Charge Wedge Strip Anode And Vernier Anode

As we all know,the ionosphere around the earth has an important influence on human communication and navigation,aerospace,military activities and so on.At present,UV spectral imaging technology is one of the most commonly used methods in the study of the ionosphere,and the photon counting imaging detector based on micro-channel plate?MCP?and the position sensitive anode is an essential tool to achieve this technology.According to the requirement of the detector used in the far ultraviolet?FUV?limb imaging spectrometer,a FUV sealed tube photon counting detector based on MCP and wedge-strip anode?WSA?was developed.The detector was composed of a sealed tube,a WSA outside the tube,a position readout circuit,a real time data acquisition and processing software.Among them,the sealed tube was a vacuum tube composed of Magnesium fluoride?MgF₂?window,Cesium iodide?CsI?photocathode,MCP stacks and resistive anode.At the same time,the induced charge photon counting imaging detector based on Vernier anode with higher spatial resolution was been studied.Compared with the photon counting detector with a metal anode located in the inner of the vacuum tube,the electron cloud coming from the MCP reacts with the resistance anode first and then generates induced charge on the metal position sensitive anode in the induced mode,so it avoids the negative effects of the electron cloud directly with the metal anode.As a result,it not only greatly reduces the image position nonlinearity and instability,but also can improve the spatial resolution of the image of the detector.The specific research has the following several points.?1?Optimization and development of the sealed tube photon counting detector based on MCP and WSA in the FUV band.A new method for calculating the WSA inter-electrode capacitance has been proposed based on the Schwarz-Christoffel transformation theory.This method makes up the defect that the electrode width can not be fully considered and the capacitance between any two electrodes can not be realized in the existing method.The calculation precision of this method is about9-15.Based on this model,the optimization scheme of the WSA was proposed and a optimized WSA was designed with the pitch of 1.5 and the effective area of 48.According to the requirement of the WSA to the electronic cloud,the structure of the detector was optimized by the electronic cloud model.The photon counting detector was developed with MgF2 as the window material,CsI as the photocathode,Ge with the resistance of 200M?/?was selected as the charge induced layer and the ceramic with a thickness of 1mm as the insulating substrate.?2?Testing of the image performance of the detector.Experimental platform was set up to test the image performance of the detector that designed.The main testing performances include the detective quantum efficiency of the detector,gain of the detector,dark counts of the detector,spatial resolution of the detector,maximum count rate and the image linearity of the detector.The test results show that the various performance indexes of the detector can meet the requirements of the FUV limb imaging spectrometer.?3?The theoretical optimization and development of the Vernier anode.The optimization theories include the imaging linearity theory and the spatial resolution theory.The decoding algorithm of Vernier anode was modified based on the principle of anode design,as a result,the imaging linearity of the Vernier anode has been effectively reduced.At the same time,the influence of the electronic cloud size and the Vernier anode design parameters on the imaging linearity was studied by the Vernier anode detector imaging simulation software that developed;The theories of the partition noise and electronic noise of the Vernier anode was developed;Based on these theories,the optimization scheme of the Vernier anode was proposed and a optimized Vernier anode was designed with the pitch of 0.891,the effective area of 48 and the theoretical resolution of 2.3.The main innovations of this paper are as followings.?1?A new method for calculating the WSA inter-electrode capacitance has been proposed.This method makes up for the defect that the electrode width can not be fully considered and the capacitance between any two electrodes can not be realized in the existing method.It can guide the optimization of the WSA design.?2?A Vernier anode imaging simulation software has been complied by Matlab.Comparing to commonly used Labview software simulation,this method can not only quantificationally study the infulcence of anode design parameter on the imaging linearity of Vernier anode,but also improve the simulation speed.?3?The noise theory of Verneir anode has been developed.It can be used as a theoretical foundation for the optimization design of Verneir anode.At the same time,it is a supplement of existing Verneir theory system.