Research On Wide Range And High Precision Electron Gun Control System

The Space Environment Simulation and Research Infrastructure(SESRI)is an important science and technology infrastructure project of Harbin University of Technology and China Aerospace Science and Technology Group Co.LTD in the National Twelfth Five-year Plan.In which a 1.2 MeV/10 mA high-frequency and high-voltage electron accelerator,among other accelerator,will be built.In this thesis,the electron gun and its control of this accelerator are studied.The gun has a ‘triode'design with tungsten wire as its cathode,heated by an electric generator,and a grid electrode added for the fine tuning of the beam currents.Its extraction electrode sits on one interior electrode of the acceleration tube thus its potential is derived from grading resistors.Our original electron gun experimental platform has only provided ways to test ‘diode' style electron gun and it is mainly based on analog circuits and manual control.To test and automatically control the new electron gun,the old platform was modified and improved to provide a wide range and fine tuning of its beam currents so as to meet the requirements of the accelerator.The investigations shows that both optical fiber communication system based on PLC(Programmable Logic Controller)and the infrared communication system of STC12C5A60S2 single chip computer system could offer high voltage isolation thus used in the-15 kV high voltage platform.The electron gun control system employs the LabVIEW based software as the user interface.The communication between the control software and the Siemens series equipment is implemented via the Object Linking and Embedding for Process Control(OLE)interface using of the OPC communication protocol.Which is the main content in this research.The hardware parameter configurations and the corresponding communication programs will be introduced in detail,as well as the operating state of the controlled objects and the feedback datum.The host computer software employs an optimized algorithm for beam current control by using an improved fuzzy incremental PID control algorithmcombining incremental PID and fuzzy theory,through which a fine tuning of electron beam currents of 1 uA-50 mA was achieved.After that,considering the cost reduction and optical fiber communication conversion issue,a hardware system composed of STC12C5A60S2 single chip microcomputer and infrared fiber module was developed for the high voltage platform,which not only offer the high voltage isolation but also enhance personal safety.In conclusion,to test the new triode-style electron gun in the laboratory,two control systems based on PLC and single chip microcomputer were studied,both of which were implemented by combining LabVIEW,incremental PID and fuzzy theory.The algorithm for beam current control was further optimized.The control systems have provided a friendly interface for the test and independent operation of the electron gun,and a precision wide-range of beam currents as well.Such control systems can also be easily integrated into other control system to achieve an automatic control of the whole accelerator.