Study Of The Surface Electron Source For The Micro Channel Plate Electron Scrubbing And The Gated Power Supply For The Image Intensifier

Image intensifier which consists of three parts:photocathode,MCP(Micro Channel Plate)and phosphor screen,is a key component in a low light night vision device.This paper focus on the two key parts of image intensifier,MCP electron scrubbing and gated power supply for photocathode.MCP is an electron multiplying device made of glass,with a large number of microporous,which will absorb a lot of gas in production process.So the outgassing by baking and electron scrubbing is necessary in MCP production.In order to perform uniform electron scrubbing for all micro pores of MCP,a uniform surface electron source to provide input electron is essential.Thermionic emission is used as an electron generating method and can be used to generate a surface electron source.In this paper,according to the filament thermionic emission theory,combined with the existing structure of electron gun,we choose the plane spiral structure as the electron gun filament.The installation structure of the electron gun is also designed.The simulation results provide a reference voltage for each component of the electron gun.Electronic uniformity of the electron gun output surface is more than 70%by experiments.The simulation voltage values agree with experimental results well.The results show that voltage of filament needs to be usually-200V,when the electron gun opening diameter are 40mm,in this situation,the focus potential is greater than 500V,MCP input surface potential is greater than the focus potential about 200V.In order to extend the dynamic range of image intensifier,especially in strong light environment,it is necessary to set a gated power supply for the image intensifier photocathode.In this paper,a new gated power supply is designed for image intensifier photocathode.According to the gated power supply requirements,the combination of two circuits is designed to achieve from narrow pulse 8.7ns to wide pulse close to DC output,with output pulse repetition frequency 1 kHz,duty cycle adjustment range from 0.0008%to close to 100%,high voltage level 250V,low voltage level 0V.The design also meets the requirements of low cost,low power,and small size.For an image intensifier,in order to achieve automatic gating,it is necessary to obtain an external feedback signal to adjust the pulse width.In order to obtain a quick feedback response,this paper presents a new sampling method of feedback according to the brightness of phosphor screen.The brightness of phosphor screen sampling feedback circuit is designed,which can avoid weak current sampling in high voltage circuit,thus achieving a simple,fast feedback signal acquisition.