热辐射对行波管阴极温度的影响

Influence of thermal radiation on cathode temperature of traveling wave tubes

由于行波管工作时无法直接测量阴极温度,目前主要通过组件测温和电子枪热仿真确定阴极工作温度。热辐射不仅是电子枪热量传递的主要途径之一,也是产生热损耗的主要因素,因而热辐射是电子枪热分析不可忽略的因素。对热损耗进行了定量分析,考虑了接触热阻和热损耗,建立了全面的热辐射边界,对阴极-热屏组件进行热仿真,通过调整零件表面发射率拟合了阴极-热屏组件测温实验数据曲线,得到了行波管电子枪高温区域零件表面的发射率,分析了热损耗、零件表面发射率对阴极温度的影响,并通过电子枪热平衡实验验证了所得发射率数值的正确性,进而得到了更准确的电子枪温度分布云图。研究表明,阴极温度950~1100℃时其表面发射率为0.65;电子枪零件表面发射率越大,阴极温度越低,阴极筒表面发射率对阴极温度影响最大;温度越高热子热损耗越大,不考虑热损耗仿真得到的阴极表面温度偏高14.4~17.5℃;组件测温得到的阴极表面温度比整管时高42~62℃。

The working temperature of the cathode,as the electron source of traveling wave tubes(TWTs),directly impacts the performance,stability and lifespan of TWTs.Since the cathode’s temperature cannot be directly measured during TWT operation,it is primarily determined through component temperature measurement and electron gun thermal simulation.Thermal radiation is a significant heat transfer mode in the electron gun and a major factor in heat loss.Therefore,it cannot be ignored in the thermal analysis of the electron gun.The heat loss was quantitatively analyzed,the thermal simulation of cathode-thermal shielding assembly was conducted considering contact thermal resistance and heat loss,establishing a comprehensive thermal radiation boundary.The temperature measurement test data curve of the cathode-thermal shielding assembly was fitted by adjusting the surface emissivity of the parts to obtain its value in high-temperature regions of TWT electron guns.The impact of surface emissivity and heat loss on cathode temperature was analyzed,and the accuracy of obtained emissivity value was verified through a heat equilibrium test of electron gun,and then a more precise distribution cloud map of the electron gun was obtained.The research results show that the surface emissivity of cathode is 0.65 when the temperature is between 950 and 1100℃.Besides,the higher the surface emissivity of electron gun components,the lower the cathode temperature,and the surface emissivity of the cathode cylinder has the greatest impact on the cathode temperature;the higher the temperature,the greater the heat loss of the heater.Without considering heat loss,the simulated cathode surface temperature is 14.4−17.5℃higher.The surface temperature of the cathode obtained by component temperature measurement is 42−62℃higher than that of the entire tube.