Air Pressure Effects on Internal SGEMP: A Benchmark Experiment for Computer Code Validation

The effects of air ionization on the internal system-generated electromagnetic pulse have been examined parametrically in an electron-beam experiment performed as a benchmark for a computer-code validation program. A right circular cylinder containing a distribution of field and wall-current sensors was injected with a pulsed electron beam. Air pressure in the cylinder was varied between 1 mTorr and 3 Torr. Sensor responses are presented that show space-charge limiting of cavity current at the lowest pressures, space-charge barrier breakdown at intermediate pressures, and current pinch, current neutralization and the development of plasma tails at the higher pressures. Comparisons are made between representative measurements and the corresponding computer-code predictions.