Design And Study Of Control And Protection System For Excimer Laser

Excimer laser has largest pulsed laser energy in the ultraviolet band and has many unique applications in the industrial micro-processing,physical and material research,medicine and other fields.And these applications require high performance of excimer laser,especially stable operation,convenient control and reliable protection.The study on control and protection system for discharging pumped excimer is carried on in this thesis.Firstly,the basic structure of excimer laser,the functional modules design and anti-interference design of control system are briefly introduced.The control system realizes effective and reliable control of the laser machine.Then,the protection circuit of high voltage discharge system realized the abnormal protection control of the thyratron.The optimization of analog transmission made that the entire working state of laser machine can be monitored effectively.Finally,this thesis pays much attention on energy nondestructive measuring and closed-loop control.The detection system takes PIN photodiode to detect the light outside main optical path,which realizes the nondestructive testing.Also,high-speed and high-precision integral circuit was designed to process accurate detecting.Combined with closed-loop control scheme to adjust the voltage to compensate for the attenuation of laser,the systerm achieved a stable laser pulse energy output.The system designed in this thesis includes a multi-closed-loop control of analog detection,discharge high-voltage detection and protection,laser pulse energy detection.Analog detection module measures the V-F converted frequency value directly,whitch improves the conversion speed and accuracy.The response time is about 6ms and the average error is less than 0.5%.The program realized the high-precision analog transmission and control under the strong electromagnetic interference environment and can meet the requirments of precise gas replacement and temperature dynamic balance.The thyratron protection circuit can respond to abnormalities of each pulse,whitch realized the closed-loop control and effective abnormal protection of the high-voltage module.The laser energy detection system was tested on 248 ArF and 308 XeCl excimer laser.Circuit response time is about 10us,which meets the requirements of kHz high repetitions.The measuring datas were statistically in accordance with the results of the external energy meter.The laser system combines laser pulse energy detection and high-voltage control to achieve an efficient constant energy mode operation.Energy mean and energy volatility both kept constant,which can meet the application requirements.