A theoretical model for the microsecond-conduction-time plasma opening switch (POS) based on magnetohydrodynamics is presented. The operating processes are associated with the magnetic field transport in the switch. The concept of the freezing-in of magnetic field in fluids is used to analyse the dynamics of this field in the plasma. One-dimensional and two-dimensional numerical simulations lead to the identification of two operating regimes, related to the Hall and the snowplow effects. The transition between these two regimes is determined by the plasma density. Scaling relations are developed from this model. In particular the electrical charge Q, conducted by the POS during the conduction time, provides a useful tool for comparisons between theory and experiments; it is shown to be the essential parameter for the switch design.
High-power-microwave (HPM) emission has been observed in S-band with a compact magnetically insulated line oscillator (MILO). The device is driven by a low-impedance Marx generator which was designed and built at Commissariat à l'Energie Atomique, Centre d'Etudes Scientifiques et Techniques d'Aquitaine for HPM experiments. Measurements with fast and sensitive I-dot probes, installed inside the slow-wave structure (SWS), have given the evidence of the MILO oscillation. The main frequency at 2.40 GHz is confirmed by measuring the emitted radiation by using both an in-vacuum antenna and a horn placed in the far-field region. The frequency response of the MILO SWS is compared to a 3-D simulation performed with MAGIC, an electromagnetic particle-in-cell code. In the first configuration, a microwave output power of 1 GW has been obtained, which is in good agreement with the simulations. Then, an optimization of the cathode geometry has led to an increase of the pulse duration and to a better stability of the emission frequency. Finally, based on the fair agreement between the experimental results and the corresponding simulations, a novel design is presented, which should give a higher emitted power at 2.34 GHz.
This paper presents the design, fabrication, and characterization of a compact wideband antenna for high-power microwave applications. The antennas proposed are array of high-power wideband patches with high compactness and less than λ/10 thick. The concept developed can be fed by highvoltage signals (up to 60 kV) in repetitive operation. Two designs are produced at central frequencies of 350 MHz and 1 GHz. Their relative bandwidth is larger than 40% at 350 MHz and 25% at 1 GHz for S11 < −10 dB, respectively. The arrays studied produce a gain of more than 14 dB.Index Terms-Broad-band antennas, high-power microwave (HPM) antennas, patch antennas.
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