We present a characterization of the performance of a recently developed gas-fed pulsed plasma thruster (GF-PPT) at low discharge energies (≤5 J). The impulsive thrust measurements were made using EPPDyL's high-accuracy interferometric microthrust stand. The thruster is best suited for small satellite applications and is operated in an unsteady pulsed mode (3 µs/pulse). It is the result of a series of design iterations aimed at achieving the highest thrust efficiencies for unsteady electromagnetic acceleration at low discharge energies. The use of advanced nonlinear magnetic switching technology, which insured a total system inductance of 3-4 nH, combined with an electrode geometry and radial gas injection that favor low profile losses, yielded a total efficiency of 50% at 5 J with argon (at an impulse bit of 32 µNs and a mass bit of .2 µg/shot). This is the highest measured efficiency ever reported for a PPT at this low energy level. Moreover, the low mass utilization efficiency problem that plagued previous gas-fed pulsed

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A new technique was developed to measure the transverse interaction impedance of the DARHT-2 induction cells, designed to accelerate a 2-4 kA, 2 µ sec electron beam pulse. An extensive campaign to minimize the transverse resistive impedance of these massive metglas-filled structures lead to a design with thin ferrite tiles in the form of a ring placed along one wall of the radial line connecting the pulseline feeds to the accelerator gap. This ferrite ring heavily damped all transverse modes. To measure the broadband m=1 impedance, one cell is excited by a matched twinlead on the axis of the beamtube. The ratio of the radial RF magnetic field in the accelerator gap to the azimuthal RF magnetic field at the beamtube wall (far away from the gap) determines the complex impedance, as explained in the paper. This technique is much simpler than the TSD approach for these very large bore systems. It also covers the full frequency band including the reactive impedance at low frequency related to the "image displacement instability". Results with the 10 inch diameter bore "standard cell" indicate a peak resistive impedance of 280 ohms per meter around 575 MHz (Q = 6).

Stored microwave energy has been released using a high-intensity electron beam switch. Experiments using this switch have produced energy compression at room temperature and pulses as short as several nanoseconds. Here we discuss the experimental results and the underlying theory.