This report documents work conducted in FY13 on electrical discharge experiments performed to develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Further, experiments were conducted to determine if free carrier electrons could be excited into the conduction band thus lowering the effective breakdown voltage when UV photons (4.66 eV) from a high energy pulsed laser were incident on the rutile sample. This report documents the numerical approach, the experimental setup, and summarizes the data and simulations. Lastly, it describes the path forward and challenges that must be overcome in order to improve future experiments for characterizing the breakdown behavior for rutile.
A lightning flash consists of multiple, high-amplitude but short duration return strokes. Between the return strokes is a lower amplitude, continuing current which flows for longer duration. If the walls of a Faraday cage are made of thin enough metal, the continuing current can melt a hole through the metal in a process called burnthrough. A subsequent return stroke can couple energy through this newly-formed hole. This LDRD is a study of the protection provided by a Faraday cage when it has been compromised by burnthrough. We initially repeated some previous experiments and expanded on them in terms of scope and diagnostics to form a knowledge baseline of the coupling phenomena. We then used a combination of experiment, analysis and numerical modeling to study four coupling mechanisms: indirect electric field coupling, indirect magnetic field coupling, conduction through plasma and breakdown through the hole. We discovered voltages higher than those encountered in the previous set of experiments (on the order of several hundreds of volts).
This report documents calculations conducted to determine if 42 low-power transmitters located within a metallic enclosure can initiate electro-explosive devices (EED) located within the same enclosure. This analysis was performed for a generic EED no-fire power level of 250 mW. The calculations show that if the transmitters are incoherent, the power available is 32 mW - approximately one-eighth of the assumed level even with several worst-case assumptions in place.