Design And Implementation Of Plasma Probe Electronics System

With the progress of science and technology,low-temperature plasma has been more and more widely used in semiconductor doping and etching process,military aircraft stealth design and metal welding processing.Accurate diagnosis of the plasma physical state is the premise of rational utilization.Langmuir probe diagnosis method has attracted much attention because of its simplicity and efficiency.However,the temperature and density of plasma span multiple orders of magnitude.This poses a challenge to the probe diagnostic electronics system.Through the investigation of the relevant literature,this paper makes a theoretical analysis of the plasma probe,and gives clear performance indicators,such as voltage,current scanning range,sampling rate and resolution and so on.In order to meet the above measurement requirements,a set of software and hardware system solutions are proposed.The designed analog front end board includes circuit modules such as test waveform,voltage amplification,power amplification and instrument operational amplifier sampling,while the data acquisition board includes FPGA device selection,DAC waveform circuit,ADC and analog conditioning circuit,DDR2 read and write storage circuit and USB interface modules.These circuits provide reconfigurable and reliable hardware support for the system.In addition,a visual upper host with software platform is developed for data processing,storage and visualizing.We separately test the hardware and software functional modules,and jointly test the electronics system to determine the overall performance,including DDR2 read and write performance test,ADC dynamic and static performance test,DAC output test and USB transmission test and so on.After a long time test,the whole system runs stably and can be flexibly controlled by users.The test results show that the electronics system achieves the expected goal and meets the performance requirements,which proves the feasibility of the design scheme.The innovations of this thesis are as follows:1)According to the measurement requirements of plasma probe diagnosis,a set of electronic software and hardware system with perfect function is designed and implemented.The joint test results show that the operation of the system is stable and the data acquisition result is reliable.2)The type,amplitude and frequency of the plasma scanning waveform can be flexibly controlled by the host computer.The waveform is generated by direct digital synthesis and applied to the plasma probe after voltage amplification and power amplification.