Methods for High Resistivity Measurements Related to Spacecraft-Charging

Abstract

A key parameter in modeling differential spacecraft charging is the resistivity of insulating materials. This parameter determines how charge will accumulate and redistribute across the spacecraft, as well as the time scale for charge transport and dissipation. ASTM constant voltage methods are shown to provide inaccurate resistivity measurements for materials with resistivities greater than ~10 17 Ω-cm or with long polarization decay times such as are found in many polymers. These data have been shown to often be inappropriate for spacecraft charging applications, and have been found to underestimate charging effects by one to four orders of magnitude for many materials. The charge storage decay method is shown to be the preferred method to determine the resistivities of such highly insulating materials. A review is presented of methods to measure the resistivity of highly insulating materials-including the electrometerresistance method, the electrometer-constant voltage method, and the charge storage method. The different methods are found to be appropriate for different resistivity ranges and for different charging circumstances. A simple, macroscopic, physics-based model of these methods allows separation of the polarization current and dark current components from long duration measurements of resistivity over day-to month-long time scales. Model parameters are directly related to the magnitude of charge transfer and storage and the rate of charge transport. The model largely explains the observed differences in resistivity found using the different methods and provides a framework for recommendations for the appropriate test method for spacecraft materials with different resistivities and applications..

Investigation Into Surface Potential Decay of Polyimide by Unipolar Charge Transport Model

“…The free electron densities are ∼ 3.38 × 10 −2 C·m −3 and 3.93 × 10 −2 C·m −3 at the initial surface potentials of −1093 and −2056 V at t = 94.5 h, respectively. Then, we can obtain the resistivity of polyimide, which is ∼ 8.08 × 10 16 -9.40 × 10 16 · m. The results are in good agreement with that measured by charge storage decay resistivity test [9], [58] and SPD methods [12], [13]. The resistivity of polyimide shows that it is too high to be measured by the ASTM method [10], [11].…”

“…Electrons will be injected into and migrate in the upper half energy band [28]. In the meantime, the surface potential will decay in time [9], [11]. The SPD curves can be divided into different parts, which are resulted by different physical processes, respectively.…”

“…Frederickson et al [9]- [11] developed a charge storage decay resistivity test method to study the ohmic resistivity of highly insulating materials. Fitting the SPD curves by the charge depolarization and conduction model, they found that the ohmic resistivity of polyimide is several order higher than the results obtained by the ASTM method.…”

Degradation of polyimide under exposure to 90 keV electrons

“…This region is fit by Eq. (2), from which a decay time and the dark resistivity of the material may be derived [33]:…”

Study of discharge after electron irradiation in sapphires and polycrystalline alumina

“…4,5 In essence and in the case of oxides, it has been shown that breakdown could be delayed by introducing impurities, whose nature and concentrations meet specific requirements, or by achieving a microstructure that favors to some degree the spreading of charges. [6][7][8][9][10][11][12] Indeed, it contributes to the improvement of component reliability of industrial devices, for instance in thin insulating systems as those used in plasma display panels, 13 spacecraft insulating, 14 alumina rf-window, 15 power electronic capacitors, 16 high-k materials of metal-oxidesemiconductor structures, 17 and field emission display spacers. [6][7][8][9][10][11][12] Indeed, it contributes to the improvement of component reliability of industrial devices, for instance in thin insulating systems as those used in plasma display panels, 13 spacecraft insulating, 14 alumina rf-window, 15 power electronic capacitors, 16 high-k materials of metal-oxidesemiconductor structures, 17 and field emission display spacers.…”