Yenan Liu

3-D Internal Charging Simulation on Typical Printed Circuit Board

To obtain more accurate results of internal charging effects, a 3-D computation method of internal charging electric field and potential for arbitrary configuration is developed. In this paper, the charging of a typical printed circuit board partially grounded, which is immersed in high energetic electrons, is simulated to illustrate the 3-D method. It includes two steps: 3-D electron transport simulation and internal electric field calculation. The electron transport is simulated using a self-developed software found on GEANT4. The 3-D calculation of internal electric field at charging equilibrium is conducted by solving a set of electrostatic equations by the software COMSOL Multiphysics. On the basis of the above-said method, the 3-D field and potential distributions within the board are obtained. For the purpose of comparison, a simpler 1-D planar dielectric grounded at the back surface is simulated in the same method. From the simulation results, the following conclusions are drawn: grounding has significant influence on electric field distribution, and the maximum field generally occurs at grounding edges or corners. The electric field computed by the 3-D algorithm is much larger than the 1-D simplified method widely used at present and, hence, the 1-D method may neglect crucial risk.

Model for Rapid-Charging Events for the International Space Station

The rapid-charging events, which were observed by the Floating Potential Measurement Unit on the International Space Station and occurred at its eclipse exit, have attracted a lot of attention recently and are not understood thoroughly yet. Compared with the normal-charging events, which occurred on morning sector, the rapid-charging events are characteristic of rapid rise time (a few seconds) and higher amplitude (−30∼−70  V) and are more dangerous. In this paper, a model for the rapid-charging events is established, with the various current collection mechanisms included and the influence of solar panel excitation taken into account. The calculation results by the model agree well with the typical flight observations. They indicate that both the solar panel switch-on pattern and the cover glass blocking effect play key roles to the features of the rapid charging.

Mechanism for Rapid Charging Events on International Space Station

Rapid charging events, a new spacecraft charging phenomenon first observed on the International Space Station in 2006, have not been thoroughly understood until now. In this paper, a model for the rapid charging based on Ferguson’s theory is described. By model calculations, the fundamental processes and characteristics for the rapid events are investigated to understand the underlying mechanisms. It is elucidated that the rapid charging is a nonequilibrium process driven by the abrupt panel voltage switch-on at eclipse exit, in which case the charging of the cover glasses by the ambient plasma cannot follow the sudden change quickly enough and block the electron collection of the solar panels. As the rapid charging reaches equilibrium, it displays as a normal charging event. The rapid charging amplitude depends on many variables, of which the panel voltage switch-on time, switch-on pattern, and the local plasma density are dominant factors. That is why the rapid charging events data have a lot of scatter...

3-Dimensional Characteristic of Electric Field and Potential Induced by Internal Charging Effects in Typical PCB

To assess satellite internal charging effects more accurately, a 3-D computation method is developed to study the internal charging problems with realistic geometry and grounding configuration. The method includes two steps: 3-D electron transport simulation and internal electric field computation. The transport simulation is carried out by a self-developed software based on GEANT4. And 3-D internal electric field is calculated through solving a set of electrostatic equations by COMSOL Multiphysics. In this work, the 3-D characteristics of electric field and potential in a typical PCB irradiated by an electron beam through an aluminum shield are demonstrated. This PCB is partially grounded by a rectangular circuit and the electron beam uses the GEO space-like spectrum with flux in the worst case. According to these conditions, the 3-D field and potential distributions in charging stationary state can be computed. Finally, the following conclusions are drawn: distributions of dose and charge deposition rate have remarkable edge effects. Severe distortion of electric field can arise around edges of partial grounding, especially at corners. The degree of field distortion decreases significantly with the increase of the distance from the grounding surface.

High voltage breakdown induced by outgassing of space materials

Increasing demand for higher voltage and power levels aboard spacecrafts requires space vacuum as insulator. A concerned issue for this is whether the outgassing of dielectric materials profusely used in spacecrafts can induce breakdown, and what, if it occurs, the mechanism and characteristics are. In this paper, low pressure breakdown induced by outgassing was investigated experimentally. It’s found that vacuum breakdown is significantly facilitated by the outgassing of dielectric materials. Measurements of Paschen’s curves for typical outgassing samples show that significant decrease of breakdown voltage occurs in high vacuum region due to increase of local pressure from outgassed products. Another important mechanism that affects the breakdown voltage is the electrode surface contamination by the outgassed components. Primary models with these mechanisms taken into account are described and the model calculations agree well with the measurements. Both experimental findings and theoretical analysis ind...

A 3-dimensional model of internal charging simulation

To break through the limitation of the traditional 1-dimensional (1-D) method of internal charging computation, a 3-D calculation model of internal electric field and potential for arbitrary configuration dielectric with complex boundary conditions is developed. It includes two steps: 3-D electron transport simulation and internal electric field computation. The transport simulation, which aims for obtaining electron deposition and dose rate distribution, is implemented by a self-developed software founded on GEANT4. And the calculation of 3-D internal electric field, which takes above transport results as input, is conducted through solving a set of electrostatic equations by the software COMSOL Multiphysics. In this paper, this 3-D simulation model applied to a typical printed circuit board grounded on a rectangular circuit and cylindrical pin will be presented. For purpose of comparison, a simpler 1-D planar dielectric wholly grounded on the back surface is simulated in the same method. Finally, the electric field computed by the 3-D algorithm is much larger than the 1-D simplified method widely used at present and hence the 1-D method may neglect crucial risk. Besides, the following conclusions are drawn: grounding has significant influence on electric field distribution, and the maximum field generally occurs at grounding edges or corners. Increasing the curvature radius of the circuit corner can reduce the field and the discharge risk.