Deep Dielectric Charging Research Articles

Deep Dielectric Breakdown of Silicates: Microstructural Damage and Implications for Lunar Space Weathering

Solar energetic particle events electrically charge the lunar surface and may produce electric fields sufficient to induce dielectric breakdown in regolith grains. We irradiated series of silicate minerals with electrons to determine their physical and chemical response to deep dielectric charging and subsequent breakdown. Two electrical phenomena, flashovers and subsurface dielectric breakdown, produced damage including erosional and eruptive channels, surface pits, comminuted grains, and melt and vapor deposits. Iron abundances strongly affected the scale of damage and the minimum fluence required to reach dielectric breakdown; higher iron abundances required higher fluences to reach the breakdown threshold and produced more areally dense damage with each event. If dielectric breakdown is a prominent space-weathering process on the Moon, it should contribute to differential weathering signatures across the lunar surface as a function of target composition.

Synergistic Effect of Temperature and Operating Voltage on Deep Charging of PEEK in the Space Solar Power Station

When the Space Solar Power Station operates in its geostationary orbit, deep dielectric charging may occur due to the implantation of the space electrons into the dielectrics and destroy the electronic devices. In this work, during the high-energy electron storms event, the deep dielectric charging characteristics of the poly-ether-ether-ketone flat plate have been studied by the Geant4 simulation as a function of temperature. It is found that the maximum electric field strength decreases when the temperature of the space environment increases, which is due to the increasing dark conductivity. When the front plate of the poly-ether-ether-ketone is biased at 10,000 V, and the back plate is grounded, the electrostatic discharge is the most likely to occur, while the case of 10,000 V on the front plate with the back plate suspended (ungrounded) is the safest. It is well analyzed through the influence of the initial electric field generated by the bias voltage on the electric field induced by the electron deposition.

Spacecraft charging with EMA3D Charge

Spacecraft are exposed to harsh radiation environments. These dynamic radiation environments present significant threat to mission performance when charge accumulation and dissipation is not adequately mitigated. EMA3D Charge is a new simulation platform tailored to the study of surface charging, deep dielectric charging, and radiation hardening of spacecraft and their components. Charge implements multiple solvers capable of co-simulating: finite element electromagnetics, boundary element method surface charging, particle transport and particle-in-cell. The multiple solvers facilitate model reuse and enable powerful physical analysis not possible with separate, individual solvers. The solvers include a three-dimensional particle transport tool, a surface charge balance solver, and a finite-element-method electromagnetic solver that supports both quasi-static and full-wave (or fully electrodynamic) solutions. This article summarizes the solvers, example applications, and validation compared to accepted numerical solutions for spacecraft in the space plasma environment.

Comparison of Pulsed Electroacoustic Measurements and AF-NUMIT3 Modeling of Polymers Irradiated with Monoenergetic Electrons

Successful spacecraft design and charging mitigation techniques require precise and accurate knowledge of charge deposition profiles. This paper compares models of charge deposition and transport using a venerable deep dielectric charging code, AF-NUMIT3, with direct measurements of charge profiles via pulsed electroacoustic (PEA) measurements. Eight different simulations were performed for comparison to PEA experiments of samples irradiated by 50 or 80 keV monoenergetic electrons in vacuum and at room temperature. Two materials, polyether-ether ketone (PEEK) and polytetrafluoroethylene (PTFE), were chosen for their very low conductivities so that minimal charge migration would occur between irradiation and PEA measurements. PEEK was found to have low acoustic attenuation, while PTFE has high acoustic attenuation through the sample thicknesses of 125 and for each material. The measurements were directly compared to AF-NUMIT3 simulations to validate aspects of the code and to investigate the importance of various simulation options, as well as to characterize the PEA instrumentation, measurement methods, and signal processing used. The measurement and simulation values for magnitude of charge deposition, penetration depth, and charge deposition spatial profiles are largely in agreement, though spatial and temporal distributions in incident electron flux and effects of radiation-induced conductivity (RIC) and delayed RIC during the deposition process complicate the process. This work provides an experimental validation of the AF-NUMIT3 deep dielectric charging code and insight into the accuracy and precision of the PEA method.

Reduction of Deep Dielectric Charging of Polyimide by Incorporation of Glass Microsphere or Glass Fiber Reinforcement

In outer space’s extreme electron radiation environment, the insulating medium will experience a deep dielectric charging effect. As an excellent insulating medium, polyimide is widely used in spacecraft. In practical use, glass microspheres and glass fibers are often added to increase its mechanical strength. However, the influence of glass microspheres and glass fibers on deep dielectric charging effects has often been ignored in previous studies. Therefore, the work in this article established a 3-D deep dielectric charging model of glass microsphere and glass fiber reinforced polyimide. Using the model, the effects of glass microsphere and glass fiber volume fraction, glass microsphere spacing, glass fiber orientation, and 3-D glass fiber structure were investigated. The results show that the larger the volume fraction of glass fiber or glass microsphere, the more obvious the decrease of polyimide composite media’s average electric field strength. Under the same volume fraction, glass fibers are more favorable to reduce the average electric field strength than glass microspheres. The surface of glass microspheres will form charge accumulation, increasing local maximum electric field intensity, which is greater than the maximum electric field value of pure polyimide under electron radiation. When the spacing of glass microspheres decreases, the degree of electric field distortion increases, but the electric field value decreases when the microspheres contact each other. When the glass fiber orientation is perpendicular to the ground plane, it can better provide the electronic release channel, thereby reducing the deep dielectric charging effect. Using 3-D glass fiber structures can reduce the polyimide’s average electric field value and reduce the maximum local electric field distortion.

Optimized Design of Slip Ring Assembly for Aerospace to Reduce Deep Dielectric Charging

The deep dielectric charging of the slip ring assembly caused by high-energy electron radiation leads to the failure of the solar array drive assembly (SADA), which accelerates the failure of the whole satellite. It is necessary to optimize the structure of the slip ring assembly according to the deep dielectric charging characteristics to reduce the risk of discharge accidents. In this article, based on the law of current conservation, a 3-D simulation model for deep charging of slip ring assembly is established by combining Geant4 with COMSOL. Under the FLUMIC3 electron radiation environment, the essential characteristics of the electric field and potential distributions in the slip ring assembly are studied. Based on these, optimization schemes for aluminum shielding structures, insulation baffles, and ground structures are proposed. The simulation results show that the simultaneous use of the three proposed optimization schemes can significantly reduce the electric field distortion caused by high-energy electron radiation, and the maximum reduction is about 70%. At the same time, the overall quality of the aluminum shield and the basic structure of the slip ring assembly can be maintained. It provides specific references for the actual design of slip ring assembly in SADA.

Coupling Effect of Electron Irradiation and Operating Voltage on the Deep Dielectric Charging Characteristics of Solar Array Drive Assembly

A deep dielectric charging model of a solar array drive assembly (SADA) under the coupling effect of electron irradiation and operating voltage is established based on the bipolar charge transport process. The distribution of space charge, potential and electric field in SADA are simulated and analyzed under three different operating conditions, i.e., flux model for internal charging (FLUMIC) spectrum electron irradiation acting alone; operating voltage acting alone; electron irradiation and operating voltage coupled. The effects of electron flux enhancement, electron direction, and operating voltage on charging properties are studied. Based on these investigations, discharge risk and location are pointed out. In the case of electrons incident from the end surface acting alone, much more space charge will accumulate than that from the columnar surface, and the maximum electric field will be above 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> V/m when the flux enhancement exceeds 100. When the operating voltage acts alone, the maximum electric field will not exceed 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> V/m as long as the operating voltage is below 8772 V. Under typical spectrum, the maximum electric field under coupling effect increases linearly as the operating voltage increases. When the electron flux enhancement increases to 100 and 1000, the electron irradiation dominates the deep charging characteristic. This provides theoretical guidance for the methods of discharge containment in SADAs.

Grounding Method and Working Voltage Influence on Deep Dielectric Charging of Polyimide in GEO Environment

In order to guide the design of effective shielding layer to reduce the risk of dielectric electrostatic discharge in high-power and high-voltage spacecraft under GEO environment, it is necessary to explore the influence of grounding method and the joint action of high working voltage and deposited charge on the deep dielectric charging characteristics. In this article, based on the FLUMIC3 model, the electron flux of GEO environment is calculated, and an assessment method for the dielectric electrostatic discharge risk is established by combining Geant4 and a finite element method. Then, this method is used to calculate and analyze the influence of the grounding method and operating voltage on the electric field distribution of the polyimide under different shielding thicknesses. The results show that increasing the shielding thickness and grounding area can effectively reduce the polyimide internal electric field, and the aluminum shielding safety threshold required under the worst conditions is 2.920 mm; the influence of the working voltage mainly depends on the application method and the voltage value. During the working voltage increase from 100 to 5000 V, assume the working voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) is applied to one side of the polyimide sample, when the other side is suspended, namely, not grounded (B, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> -S; C, S- V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ), the maximum electric field depends on the deposited charge and it does not change with the working voltage; when the other side of the sample is grounded (A, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> -G; D, G- V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ), the maximum electric field and its distribution are determined by the working voltage and the deposited charge. Within this voltage range, the safety threshold of the aluminum shielding layer needs to reach 4-5 mm. In summary, under high working voltage, the grounding area of the sample can be increased, and the appropriate working conditions can be selected to determine the optimal shielding thickness that can suppress dielectric electrostatic discharge.

Energetic electron detection packages on board Chinese navigation satellites in MEO

Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

Monitoring Deep Dielectric Charging Effects in Space

A deep dielectric charging effects monitor was proposed for providing in situ measurements of deep dielectric charging effects on satellites via measurements of the surface leakage currents and the internal charging potential of the dielectric. The detailed design and the first flight results onboard a medium Earth orbit (MEO) navigation satellite were discussed. Large temporal variations of the leakage currents were observed in the outer zone. The first flight data showed that the maximum charging electric field of the FR4 dielectric was less than 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> V/m, the incident internal flux was less than 100 pA/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and no charging risk was determined in this period. The calculated conductivity of the FR4 dielectric was about 1.4-3.7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> S/m. These results showed that conductivity obtained by the traditional method overestimated the true value, whereas that obtained by the charge decay method underestimated the true value.

Effect of Electron Irradiation and Operating Voltage on the Deep Dielectric Charging Characteristics of Polyimide

Space Solar Power Station (SSPS) will operate in geosynchronous orbit. Its operating environment is rather complicated, including space plasma, energetic particles radiation, extreme temperature, and cosmic rays. To reduce power loss, SSPS has to apply high-voltage (HV) power generation and transmission technique. Deep dielectric charging will be a major problem in the design of insulation structure in SSPS. In this paper, the hopping conductivity of polyimide was studied. Hopping distance and hopping barrier height were obtained from surface potential decay analysis. Second, a deep dielectric charging model of polyimide under FLUMIC spectrum electron irradiation was established, in which the hopping conductivity parameters were applied. The effects of electron flux enhancement and operating voltage on the charging characteristics were discussed in four cases, i.e., A) suspended-HV; B) HV-suspended; C) grounded-HV; and D) HV-grounded. When the electron flux enhancement increases, the influence on case A is much larger than the other three cases. When the operating voltage increases, the influence on cases A and B is small, whereas the influence on cases C and D increases fast. Thus, when designing the SSPS, the effect of operating voltage and electron flux enhancement on the insulation system must be carefully considered.

The Compact Environmental Anomaly Sensor Risk Reduction: A Pathfinder for Operational Energetic Charged Particle Sensors

Compact environmental anomaly sensor risk reduction (CEASE-RR) is a new sensor designed for anomaly attribution due to the space radiation environment. It does this using two solid-state particle telescopes that have been designed to measure proton and electron fluxes that are the drivers for three of the four primary space environment effects (event total dose, deep-dielectric charging, and single event effects). These telescopes are integrated into a compact package along with space reserved for a planned electrostatic analyzer being developed for the final CEASE 3 design (covering the fourth primary space environment effect—surface charging). The sensors themselves will measure a wider dynamic range in particle flux, provide higher energy resolution, have better out-of-band contamination rejection, and improved diagnostic capability compared to previous CEASE instruments. The CEASE-RR instrument is planned to be launched in 2018 to geostationary orbit as part of an Air Force Research Laboratory flight experiment. The sensor design, calibration, and planned flight experiment objectives are described in this paper.

A new charging model for exposed dielectric of spacecraft

In order to consider comprehensively the effects of high-energy electron radiation and space plasma on the exposed dielectrics outside a spacecraft, in this paper, a model named surface and internal coupling charging model for the exposed dielectric of spacecraft is proposed, and its numerical solution is obtained. It is based on the deep dielectric charging model, with considering the interaction between the exposed dielectric surface and the ambient plasma by adding an incident charging current into the boundary in the proposed model, and the potential of infinite plasma is regarded as the referential potential (zero potential). The determinate solution of the model is analyzed and a numerical solution in one-dimensional case is provided by using an iterative algorithm to overcome the coupling between electric field and conductivity. The solution includes the potential of spacecraft body, the distribution of dielectric potential, and the electric field. Moreover, the new model is compared with surface charging model and internal charging model. The results show that the new model has an advatage of depicting the electric field exactly with respect to the surface charging model; if the internal deposition current is equal to zero, the new model degenerates into the one depicting the surface charging. It considers the effect of surface potential on charging results compared with the internal charging model. The three kinds of currents, namely the surface incident current, the internal deposition current and the leakage current, are considered comprehensively in the new model. Among them, the leakage current is the most complicated, which is determined by the potential and the dielectric conductivity affected by the electric field, radiation dose rate, and temperature. Using this new model, the surface and internal coupling charging simulation of the exposed dielectric can be performed. Therefore, the new model can provide a more comprehensive assessment for the charging of exposed dielectric of spacecraft.

Mitigating Deep Dielectric Charging Effects in Space

Mitigating Deep Dielectric Charging Effects in Space

Electrostatic Discharge of Plasma Created by Hypervelocity Impact 2A12 Aluminum Targets With Gradient Potential

Based on the objective reality of gradient potential existence in spacecraft surface caused by charging particles in space-plasma environment or solar wind activities, electrostatic discharge of spacecraft with surface charging or deep dielectric charging would be induced by debris or meteoroids impact. To simulate the gradient potential on the spacecraft surface in the laboratory, spacecraft surface was segmented into different parts, which different spacing reserved in two adjacent surfaces was added resistance to create different potential surfaces, and the highest potential surface as a target in the segmented surface. Circuit system realizing different gradient potential, discharge test system, as well as ultrahigh-speed camera acquired system was built by ourselves; combining with two-stage light gas gun loading system, four set experiments have been performed about hypervelocity impact on 2A12 aluminum target with gradient potential. In the experiments, spacings of 2A12 aluminum target were the same among different potential parts in every experiment, and the spacings of four set experiments were 2, 5, 10, and 15 mm, and high-potential 2A12 aluminum as the target, respectively. The experiments were performed at the impact velocity of about 3 km/s and the incidence angles of 60° (between projectile flying trajectory and target plane). Voltage probes and current probes were used to acquire discharge voltages and currents during the process of the impact. The experimental results showed that the discharge induced by impact plasma was generated between high- and low-potential targets by forming a plasma discharge channel, the gaps with 2–15 mm can evoke discharge among different targets, and the variations of the discharge current along the high- and low-potential targets did not obviously. However, the discharge duration decreased with an increasing of distance between high- and low-potential targets at the near collision velocities and the same incidence angle of the projectile. The whole physical process of discharge had experienced four stages in general, which created by hypervelocity impact 2A12 aluminum targets with gradient potential. The first stage was plasma generated by hypervelocity impact, the second stage was complex mixed plasma including plasma generated by hypervelocity impact and discharge plasma induced by split targets with gradient potential, the third stage was discharge plasma induced by hypervelocity impact, and the fourth stage was the discharge between charging particles due to the reciprocating motion of charging particles in the electromagnetic field.

Fast Measurement of Dielectric Conductivity for Space Application by Surface Potential Decay Method**Supported by the Fundamental Research Funds for the Central Universities in Nanjing University of Aeronautics and Astronautics under Grant No NS2014089.

Surface potential decay of polymers for electrical insulation can help to determine the dark conductivity for spacecraft charging analysis. Due to the existence of radiation-induced conductivity, it decays fast in the first few hours after irradiation and exponentially slowly for the remaining time. The measurement of dark conductivity with this method usually takes the slow part and needs a couple of days. Integrating the Fowler formula into the deep dielectric charging equations, we obtain a new expression for the fast decay part. The experimental data of different materials, dose rates and temperatures are fitted by the new expression. Both the dark conductivity and the radiation-induced conductivity are derived and compared with other methods. The result shows a good estimation of dark conductivity and radiation-induced conductivity in high-resistivity polymers, which enables a fast measurement of dielectric conductivity within about 600 min after irradiation.

Dielectric charging research status and prospect

Dielectric charging phenomenon, caused by the interaction effect between space environment and spacecraft material, has a severe threat to the normal operation of spacecraft. Especially, the problem becomes more serious with the improvement of spacecraft operation voltage. An overview of dielectric charging research status, exsiting problems and prospect are reviewed. Firstly, dielectric charging phenomenon, hazards, research history and new challenges are introduced. There have five development stages: the initial attention, the focus of surface dielectric charging, the focus of deep dielectric charging, the rapid development of dielectric charging and new challenges and demands. The development demands of spacecraft dielectric in China are analysed. There have several insulation positions, which are easy to occur fault in practice. They include surface flashover on insulation material bewteen solar cells of solar array, surface flashover on insulation material between electrodes of solay array drive assembly, the insulation material in cables and pulse discharge of circuit board. Secondly, the specific research status and exsiting problems of surface dielectric charging and deep dielectric charging are summarized from the following aspects: dielectric charging mechanism, dielectric charging mitigation and numerical simulation. Next, the top issues about dielectric charging experiments and material characteristics are introduced. They include in-situ surface potential decay measurement and characteristics of dielectric radiated by electrons, in-situ space charge measurement and material characteristics under electron radiation, surface flashover characteristics of dielectric radiated by electrons in vacuum. Two kinds of space charge in-situ measurement, short-circuit PEA (Pulsed Electro-Acoustic) and open PEA are introduced. At present, there do not have the mature in-situ space charge measurement setup under electron radiation in China, the difficult points in design and debugging are analysed. It is interesting of the surface flashover of dielectric under electron radiation. The latest experimental results indicated that the flashover voltage shows a distinctly different variation tendency under the two cases (after electron radiation and during electron radiation). The first case of after electron radiation, flashover voltage becomes higher than that without electron radiation. Because of the effect of deposited electrons in dielectric surface layer and the changes of trap distribution inside material. The trap distributions of polyimide after electron radiation are calculated based on surface potential decay measurement and Simmons theory. The results show that the shallow trap level increases slightly with the increase of electron energy (3–11 keV), ranging from 0.81–0.85 eV, while the deep trap level remains unchanged about 0.94 eV; the second case of during electron radiation, flashover voltage exhibited a dramatic drop from 26.9 kV (energy: 5 keV) to 10.5 kV (energy: 30 keV), due to the combined effect of incident kinetic electrons flowing to dielectric surface and deposited electrons in dielectric surface layer. Finally, the key scientific issues in the filed of space dielectric charging are put forward and prospected based on the present research status.

Transient Analysis of Spacecraft Exposed Dielectric Charging Using SICCE

Spacecraft exposed dielectric interacts directly with the ambient plasma and may be faced with energetic electron irradiation. Using the charging model surface and internal coupling charging model for spacecraft exposed dielectric (SICCE), it is possible to investigate this special charging process, including both surface charging (SC) and deep dielectric charging. Based on the finite-difference time-domain method, a transient solution of the SICCE in the 1-D case is proposed in this paper with adequate verifications. An important improvement is made to the SICCE by employing secondary electron yield formula in Katz form, which is the same with Spacecraft Plasma Interaction Software (SPIS) and NASA Charging Analyzer Program (NASCAP) $-2k$ . The typical charging environment for exposed dielectric is assumed Geosynchronous Earth Orbit (GEO) worst plasma environment combined with Flumic3 energetic electron irradiation. The charging characteristics of a 3-mm polyimide board with front surface exposed to this typical environment and back surface connected to the spacecraft body is investigated. The total charging process in time-domain can be divided into three stages: the first is dominated by fast SC of spacecraft body with the typical time less than 1 s determined by spacecraft capacitance, the following stage lasts until the dielectric surface potential reaches equilibrium with the charging time of several hundred seconds determined by dielectric board capacitance, and the deep dielectric charging dominates in the third part with the charging time more than 2 h. If the magnitude of the body potential is larger than the dielectric surface potential in equilibrium, overcharge and feedback appear in the surface potential evolution. Peak electric field appears on the point connecting spacecraft body and reaches a maximum value in charging equilibrium. In the case of multiple roots of SC equation, transient solution has the advantage of avoiding unstable charging potential. This investigation can further enrich engineers’ understanding of spacecraft exposed dielectric charging.

Discussion on Non-Linear Conductivity Characteristics With Space Charge Behavior of Modified Epoxy for Spacecraft

High-energy electrons in space can penetrate into dielectric materials on spacecraft and cause deep dielectric charging which is often harmful. The level of charging is determined not only by the incoming flux but also by the rates of electron accumulation and electron leaking. It is desirable to enable faster leaking of the accumulated charge. This paper discusses the nonlinear conductivities with space charge behavior of two samples of modified epoxy. They were obtained respectively by adding zinc oxide (ZnO) particles of two different sizes ( $2~\mu \text {m}$ , $10~\mu \text {m}$ ) to pure epoxy (EP). We studied the conductivities of the samples and the space charge effects in strong electrical fields. Our results showed that the nonlinear conductivity threshold of $2~\mu \text {m}$ modified EP (ME2) was $1.7\times 10^{7}$ V/m whereas that of $10~\mu \text {m}$ modified EP (ME10) was $1.4\times 10^{7}\text {V}$ /m. These values are 50% and 40% higher than that of EP respectively. These results suggest that the modified epoxy materials (ME2 and ME10), if used on spacecraft, are better than pure EP for leaking away the accumulated charge, thus reducing the dielectric charging level. Meanwhile, space charge distribution tests indicated that $10~\mu \text {m}$ modified EP (ME10) had a nice charge dissipation performance, while $2~\mu \text {m}$ modified EP (ME2) did not have space charge accumulation. Finally we make the conclusion that nonlinear conductivity performance can affect space charge distribution for dielectric to a certain degree.

Leakage Current of Grounded Dielectrics in Electron Radiation as a Diagnostic Method to Evaluate the Deep Charging Hazards in Space

Deep dielectric charging, which is a coupling process of charge deposition and charge relief, is a significant factor in spacecraft anomalies and failures. With the aim of developing a method for evaluating the deep dielectric charging hazards, this study investigated the leakage current and charging electric field of grounded dielectrics in space usage by a method combining Monte Carlo simulation and a model of radiation-induced conductivity. The analysis adopts multiple cases of electron spectra and various thicknesses of the shielding layer and dielectric. The analysis results show that the leakage current, which can be easily measured, is strongly related to the charging electric field in various situations. Therefore, monitoring the leakage current can be a more effective approach for evaluating deep dielectric charging hazards than monitoring electron flux.