Research On Internal Charging & Discharging Of Typical Structures And Discharging Interference

Deep dielectric charging and discharging effect caused by energetic electrons in space has always been one of the biggest environmental threats to spacecrafts operating in outer radiation belt.So far the existing research achievements still cannot meet the demand of space engineering well.It's still not easy to give an accurate assessment of the deep charging hazard of spacecraft before launch.With the increasingly urgent requirements for high reliability and long life of spacecraft and the continuing application of new materials and devices in space industry,it is of great significance to conduct intensive research on deep dielectric charging to fulfill the requirements of engineering.In this work,the experimental facility and simulation softwares developed by National Space Science Center are utilized to investigate the deep charging and discharging characteristics of typical basic structures of spacecraft component irradiated by energetic electrons.The intrinsic factors and ambient conditions that affect charging&discharging properties of various structures,the characteristics of deep dielectric discharging pulse and the response of typical spacecraft-used device to discharging pulse are also comprehensively studied.The main researches and conclusions of this work are as follows:1)Deep charging and discharging characteristics of typical structures,including dielectric slab and dielectric-conductor adjacent structure,are investigated.For planar dielectric slab,conductivity,thickness and grounding methods are the main influence factors.It's appropriate to choose more conductive material,reduce slab thickness and ground the both sides if possible.For dielectric-conductor adjacent structure,the maximum dielectric surface potential and built-in electric field are positively associated with the width and height(relative to conductor surface)of dielectric.When there is a narrow gap between dielectric and conductor,the electric field inside dielectric will enhance dramatically and may result in internal break-down.The electric field in the gap region can also easily exceed the vacuum break-down threshold value.2)The influence of ambient conditions,including irradiation duration,electron flux,temperature,gas pressure,and orbit variation,are investigated.Continuous irradiation under energetic electrons can reduce the discharging threshold of PTFE material.Discharging tends to be more frequent and has lower intensity in later period.When electron flux gets higher,or temperature goes down,charging potential and discharging risk increases.Dielectrics can be more easily charged in higher vacuum condition,and surface discharging may be triggered when a gas eruption blow across the dielectric.When electron environment changes periodically for certain MEO orbits,the charging evolution often lags behind the electron flux variation.3)The characteristics of discharging pulse are investigated.By statistic analysis of the spontaneous discharging pulse data in experiments,it shows that pulse amplitude increases as discharging interval gets longer.Higher electron flux or lower temperature makes “big” discharging event more likely to happen.Deep dielectric discharging current pulses observed in experiments are usually high-frequency oscillation damping signal and have distinct characteristic peak in frequency domain,which is decided by the impedance of the discharging loop.Dielectric thickness,temperature and electron energy show little effects on the frequency spectrum of discharging current pulse.4)The response of typical space-used device to deep dielectric discharging pulse is investigated.A commonly used integrated operational amplifier is selected to conduct the discharging interference experiment.Results show that opamp may generate anomalous transient output when discharging happens.The characteristics of output transient are related to device configuration,bias condition,discharging voltage and interference coupling path.Subjected to discharging pulse,voltage comparator only generates single polarity transient.Voltage follower and non-inverter behave similarly,nevertheless inverter shows the least sensivity.The noise coupled into the input pin that exceeds the bandwidth of opamp is the cause of output anomalous transient.The amplitude and duration of output transient are strongly associated with input noise amplitude and frequency.