考虑温度梯度的卫星外露介质深层充电

Deep Dielectric Charging of Exposed Dielectric of Satellite Considering Temperature Gradient

卫星外露介质因热导率低而在光照面与背光面之间存在温度梯度,这将影响介质电导率继而影响深层充电过程。为此,建立了考虑温度场的介质深层充电模型,针对1维模型给出了数值求解方法并进行了验证。模型的温度梯度效应是通过介质电导率对温度的依赖关系而体现的。以聚酰亚胺介质为代表,通过试验测试和数值拟合得到了253~353 K温度范围内的介质本征电导率,并根据经验公式从Geant 4计算的辐射剂量率获取了辐射诱导电导率。计算结果表明：温度梯度会对深层充电产生显著影响;在地球同步轨道恶劣电子辐射环境下,对于3 mm厚背面接地聚酰亚胺平板,当最低温度263 K出现在背面时,电场强度峰值超过10 MV/m,表面电位超过-10 kV,且随着温度梯度增加,电场强度畸变加剧,且随温度梯度而近似呈线性增长。相关结论可为介质深层充电评估提供有益参考。

Because of the poor heat conductivity, there exists a temperature gradient between the front surface with sunshine and the shadowed surface of a dielectric board outside the satellite coating. This temperature gradient will affect the deep dielectric charging（DDC） by changing the material conductivity. We put forward a mathematic model in which the temperature gradient in DDC is taken into account. An efficient numerical solution was given for the one-dimensional charging model with corresponding verification. In this model, the effect of temperature gradient was taken into account by correlating with material conductivity. Selecting polyimide（Kapton） as the typical satellite dielectric, we carried out measurement and made data fitting to obtain a temperature spectrum of conductivity within the range of 253~353 K. For radiation induced conductivity（RIC）,Geant 4 simulation was adopted to get the radiation dose rate and then RIC was calculated using an empirical formula. The computation results show that temperature gradient has a notable influence on DDC. Under the energetic electron flux of GEO serious radiation, a back grounded Kapton board, with the thickness of 3 mm and the grounding boundary temperature 263 K, will charge to more than-10 k V with the electric field in magnitude of 10 MV/m. The distortion of electric field increases linearly as the temperature gradient turns up.