Calculation of the radiation-induced conduction current in dielectrics irradiated with high-energy electrons and protons having a two-component maxwellian distribution

Abstract

A method is considered for calculating the distributions of the space-chargefield and of the radiation-induced conduction current over the thickness of dielectric coatings, and of the potential of their open surface corrected for the space-charge field, during interactions with electrons and protons. This method is used to consider these quantities for a two-component MaxweUian distribution of the charged particles. The optimal thickness of coatings on artificial satellites is also determined.During the period when an artificial satellite is in orbit, its surface becomes negatively charged relative to the surrounding space plasma as a result of interactions with radiation. Depending on the geomagnetic situation and on the electrophysical properties of the surface coatings, the surface potential can reach tens of kilovolts or more, and this produces the negative consequences of electron-stimulated discharges, degradation of the coatings, malfunctioning of the on-board apparatus and, consequently, a shortening of the apparatus service life in orbit [1][2][3][4][5].It was established experimentally that the greatest danger results from the electron-stimulated discharges which can develop at quite high potentials of the dielectric coatings, -6 kV, but not at -(10--20) kV [6]. The energy for such a discharges is stored in the dielectric coatings during the buildup of a prebreakdown charge which enters (or leaves) the dielectric due to radiation-induced conduction currents. It is therefore important to study the role of such currents in the process of charge buildup in order to prevent the development of electron-stimulated discharges. For this purpose the author has developed a method for calculating the distributions of the space-charge field, of the radiation-induced conduction current over the thickness of the dielectric coatings, corrected for the space-charge field, and of the potential of their open surface during interaction with high-energy electrons and protons.Since the greatest number of failures in the operation of on-board systems and assemblies in a satellite occurs during periods of geomagnetic perturbations at high altitudes (particularly in a geostationary orbit) in the shadow of the Earth [8], it is for this case that the method developed by the author is intended [7]. One of the key problems of the method is to determine the form of the energy distribution function and of the boundary of the energy spectrum of the charged particles interacting with the satellite. The analysis presented below of the geomagnetic conditions at the height of the geostationary orbit enables this problem to be solved.During periods of geomagnetic perturbations in the shadow of the Earth a geostationary satellite (L = 6.6, where L is the geomagnetic shell parameter) intersects the ring current region and sometimes (one case in six) also the plasma layer region and (or) the boundary of the outer radiation belt [9]. This period is characterized by a displacement of the plasma sphere to lower-altitude regions (L --4-5) [10, 1...

Electric Polarization of Low-Orbit Spacecraft

“…In processes (1), (2), and (4) vacancies for a neutral particle on the surface are denoted as X , while M represents the Earth's atmosphere constituents O, N 2 , O 2 , N , and ON.…”

“…-k ea n e n A + k cd n A + J d , where ᑣ is the rate of production of electrons in the ionosphere; 2 k ei = 1/τ e is the rate of electron-ion recombination 2 Electrons are produced under the action of electromagnetic radiation of the Sun (the main source of production) and under bombardment by charged particles (so-called corpuscular ionization), the latter mechanism being essential only at high latitudes due to screening effect of the geomagnetic field. Therefore, in further calculations it is assumed ᑣ = 0.…”

“…In [1][2][3][4][5], the results of our numerical calculations of basic characteristics of volume charging of non-metallic coating of satellite constructions are presented together with some recommendations for decreasing the above effects. However, these calculations were performed for high-altitude satellites, and in recent years, after research programs SCATHA and CRRES, there is some loss of interest in such satellites.…”