Air-Enhanced SGEMP Response - An Experimental and Analytical Investigation

The theoretically-predicted air-enhancement of the external SGEMP response of an object has been measured on a small test body. The replacement currents flowing on the outside of a 20-cm cylinder exposed to Argon puffed-gas x-rays inside a vacuum chamber were seen to increase an order of magnitude above the experiment noise level as the background gas pressure was varied from 10-4 to 0.1 torr. The predicted vacuum response, which was strongly space-charge limited, indicates that the enhanced currents are 30 times the vacuum values at some locations on the object. Parameter variations suggest convincingly that the measured enhancements are not due to any experimental artifact or to IEMP effects. The computer models of the effects agree with the measurements to within a factor of two in the high-pressure collision-dominated electron transport regime, but show greater enhancements at lower pressures than the measurements do.