Alan Bromborsky

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.

Intense microwave radiation from a repetitive backward‐wave oscillator driven by a relativistic electron beam

High‐power microwaves (20–50 MW, 8.8 GHz) have been produced in repetitive pulses at a rate of 10 Hz in a joint experiment by Harry Diamond Laboratories and Sandia National Laboratories. These microwaves were produced with Harry Diamond Laboratories’ backward‐wave oscillator (BWO), driven by a 600 to 800‐kV, 2‐kA electron beam, which was guided by a magnetic field of variable strength from 0.75 to 1.05 T. The beam was produced with Sandia National Laboratories’ repetitive high‐voltage pulser, RAVEN. Microwave diagnostic instrumentation included a directional coupler, heterodyne receiver, dispersive waveguide delay line, and calorimeter. In a train of 10 pulses, the shape, duration, and amplitude of the injection voltage and beam current remained unchanged for each individual pulse. The intensity of the final microwave pulse was 40% of the first pulse, and the final pulse was 80% as long as the first. The basic pulse shape remained unchanged. More intense microwave radiation should be obtained with a highe...

Reflex triode with unidirectional ion flow

Experimental results are reported which show that the ion beam generated by a simple reflex triode can be made almost totally unidirectional toward the virtual cathode. This ion flow is accomplished by constructing the triode so that a controlled surface flashover generates plasma on only one side of the dielectric anode foil.

Unidirectional Ion Generation and Geometric Focussing of Ions in a Reflex Triode

Experiments studying the phenomenology of the reflex triode ion accelerator have led to a simple anode design that produces an intense (5 kA average current, 1.7 MeV beam energy, 25 ns current pulse) pulsed ion beam in which greater than 95% of the ions generated are extracted through the virtual cathode. Subsequent experiments have also shown that a simple concentric-spherical anode-cathode geometry can be used to focus the ion beam and increase by an order of magnitude the on-axis ion flux to 1.1 kA/cm2.