【作者】 彭浩；

【导师】 王又青； 唐霞辉；

【作者基本信息】 华中科技大学 ， 物理电子学， 2012， 博士

【摘要】 高功率射频板条CO2激光器是工业应用CO2激光器非常重要的一种类型,已经成为激光焊接和切割的主力光源和重要发展方向。本文针对高功率板条CO2激光器的射频放电特性,系统分析并实验研究了射频激励气体放电特性、大功率射频电源及传输匹配、大面积射频放电的平板电极、激光器功率控制及抗干扰措施。论文主要内容包括以下几个方面：(1)根据射频放电气体理论模型,指出射频激励板条激光器需工作在a放电模式,给出了一维射频放电模型。通过实验分析激励频率对放电特性的影响,主要包括频率对击穿电压的影响、频率对射频辉光放电区结构的影响,在此基础上总结了一些选择放电频率的规律。在大量实验数据的基础上给出了气体配比和气压选择的方法。(2)针对高功率射频板条CO2激光器的射频功率源的要求,设计了基于电子管的大功率自激式射频电源,包括直流高压回路、灯丝加热电路、栅极调制电路以及产生射频功率的振荡放大电路。在振荡和功放电路部分,计算了电子管的工作模型和元件参数。确定了射频电源和放电负载直流的阻抗匹配方案,并给出了计算匹配参数的方法。提出了纵向采用并联谐振电感的均压方式,当电极纵向和横向分别为中间馈入和侧面馈入方式时,在电极侧面电感不对称分布条件下通过计算,得到了整个电极的二维均压模型,并通过实验进行了验证。(3)针对扩散冷却平板电极的结构和热环境,设计了蛇形和改进的蛇形等电极的冷却水流道方案,通过仿真得到电极的温度场分布并进行比较,得知最理想的流道方案为改进的蛇形方案。通过对不同流道设计的电极进行放电出光实验,改进蛇形水道电极在高占空比时,激光功率增益饱和的现象没有出现,可以认为该流道设计满足了在最大占空比条件下冷却气体温度的要求。(4)通过对激光器功率控制方式的研究,设计了基于透过率0.5%的球面取样镜和热电偶堆的功率取样单元,采用改变脉冲宽度对注入的射频功率进行调节,考虑到产生PWM波的稳定性和实时反馈的要求,设计了专用的功率控制电路板,通过上位机PLC和下位机CPLD的通讯,完成了优化的激光功率反馈控制,提高了激光功率的稳定性,功率波动<±1.5%。(5)采用“简易点测法”对板条激光器进行电磁辐射强度检测,通过屏蔽及接地措施将整机电磁辐射值降为0.04W/m2。根据屏极高压供电电路、灯丝大电流供电电路、栅极脉冲调制信号驱动电路三个电路的传导干扰路径,分别设计了衰减抑制比达55dB、40dB、30dB的LC低通滤波器,解决了射频传导干扰。更多还原

【Abstract】 High power radio-frequency (RF) slab CO2laser is a very important type of industrial CO2laser. It becomes one of the main industrial laser sources, and an important trend for laser welding and cutting. To investigate the discharging behavior in the RF slab CO2laser in this paper, the RF excited gas discharge characteristics, the RF high power supply and the transmission matching, the discharge plate electrodes with large area, the laser power control and the anti-jamming measures are analyzed theoretically and experimentally. The main contents include the following aspects:(1) According to the theoretical model of RF discharge gas, it points out that the RF-excited slab laser needs to work in the a-discharge mode. A one-dimensional RF discharge model is given. Experimental researches mainly discuss the effects of excited frequency to the discharging quality. It contains the relationship between the breakdown voltage and the excited frequency, and the effect of exited frequency to the property of plasma in the discharge area. Furthermore, several rules for selecting the excited frequency are obtained. Through a series of experiments, the optimal scheme to choose the air mixture and the atmospheric pressure are obtained.(2) RF power sources for high power RF slab CO2laser requirements is designed based on high-power self-excited RF power which include amplifier circuit including the DC high voltage circuit, the filament heating circuit, the gate modulation circuit and a RF power oscillation. Oscillation and amplifier circuit section has calculated the tube model and component parameters. Determine the RF power and dc discharge load impedance matching, and calculate the matching parameters. Pressure longitudinal parallel resonant inductor, when the electrode vertical and horizontal, respectively, for intermediate feed and side feed into, by calculating the electrode side inductance asymmetric distribution, get the entire electrode two-dimensional pressure model and verified through experiments.(3) According to the structure and thermal environment of the electrode, the heat exchanger for the electrodes has been calculated and analyzed. The finite element theory of temperature field is discussed. By designing different flowing channels, a series of discharging and lasing experiments have been taken. When improving the serpentine waterways at high duty cycle, the laser power gain saturation phenomenon will not appear. It proves that the flowing channel design meets the cooling gas temperature requirements at the maximum RF power injection.(4) RF slab CO2laser power control, power sampling unit sampling based on the transmittance of0.5%of the spherical mirror and thermocouple heap, changing the pulse width adjustment of the injected RF power, taking into account generate PWM wave stability and the requirements of real-time feedback, the design of a dedicated power control circuit board, through the host computer, PLC and lower machine CPLD communication, the optimized laser power feedback control, to improve the stability of the laser power, the power fluctuations<±1.5%.(5) The simple point measure on the slab laser electromagnetic radiation detection, shielding and grounding the whole electromagnetic radiation is reduced to0.04W/m2. According to the conductive interference paths of anode high voltage power supply circuit, the filament current supply circuit and gate pulse modulation signal drive circuit, LC low-pass filter for attenuation of suppression ratio up to55dB,40dB,30dB are designed to solve the conducted RF interference.更多还原