Desktop Scanning Electron Microscope High Voltage Control System Design

The development and progress of science and technology, promote the scanning electron microscope (SEM) toward to the multi-function, high resolution, portable miniaturization. In recent years, scanning electron microscopy of our country has got certain development, but compared with other countries, our country in terms of the development of a scanning electron microscope technology is relatively weak, scanning electron microscope manufactured there is still a big gap with foreign countries in the aspect of stability constant, reliability, resolution, especially in the development of desktop scanning electron microscope, is still at the starting stage in our country, therefore the development of desktop scanning electron microscope has a very important significance. Desktop scanning electron microscope with small size, easy operation, large magnification, high resolution, vacuum quickly, don't spray gold measuring non-conductive samples, etc. At present, FEI, the company in the United States launched the Phenom series desktop scanning electron microscope and Japan's Hitachi TM series desktop scanning electron microscope to dominate the world market. Compared with foreign companies, domestic desktop scanning electron microscope research is still blank, has been dependent on imports. Therefore, to speed up the domestic independent brand desktop scanning electron microscope research and development, to break the foreign monopoly, can meet the needs of domestic users, is of great significance.This paper introduces the graduate student workstations in the enterprise, combined with the research project of company's products, focusing on the design of desktop scanning electron microscope high-voltage control system.In this paper, the design of the content is divided into two areas, one is the design of hardware circuit of high voltage control system, mainly introduces the embedded control module, digital to analog conversion module, the electronic beam current detection module, the accelerating voltage control module, the filament voltage control module, boost and voltage doubling circuit module, electron gun filament power supply module design; two is the software design of high voltage control system, mainly introduces the high-voltage control system software architecture, interface design and the main program design, while the main program design includes the program design of generating a voltage signal and the program design of oscillating wave.This design is mainly for small, low-noise desktop scanning electron microscope high voltage system (for office use), high reliability, rapid, automatic control and other characteristics of the design.The innovation of this paper is as follows:(1) Use STM32F103 microcontroller as the main control chip, combined with FPGA technology to complete the control of the whole system.(2) The circuit of the high voltage generator using potting pot, significantly reduced the volume of the circuit board, to ensure that the small, high voltage generator module, solid state.(3) Use the high performance operational amplifier OPA177, and use the closed-loop amplifying circuit to realized the voltage stability.(4) Design the electron beam state anomaly judging module, when the circuit or vacuum is abnormal, the system can accurate judgment and timely closure system.