Rendering of the compact HPM system showing PCSS, energy storage, NLTL, diagnostics, and resistive load termination. The total length of the compact switch and NLTL configuration is approximately 90 cm with a 30 cm diameter charging plate and 5 cm diameter NLTL. A zoomed image of the charging plate is shown below the complete system. The charging plates are designed to house two to six 2 nF capacitors. The PCSS is centrally located with an epoxy fill behind the switch (blue block behind). A connecting jack is cut into the PCSS anode for direct connection to the NLTL inner conductor while the ground-side charging plate is threaded to mate with the NLTL outer conductor. Also shown is the beginning of the NLTL with solenoid and ferrites labeled. CVR – current viewing resistor, CVP – capacitive voltage probe.
Circuit schematic for the solid-state, compact microwave generator. The PCSS drops to sub-ohm resistance when illuminated with 3 mJ at 355 nm and has a dark resistance of 44 GΩ at 25 kV charging voltage. Note the fiber optic delay system is not included in this schematic.
Block diagram of the fiber optic delay system utilized for burst-mode operation. Individual beam splitters are polarization sensitive 50/50 splitters. The length difference of each fiber provides a 15.5 ns temporal delay between pulses, resulting in a 65 MHz burst-mode operation. The total optical path length (fiber length and distance traveled in beam splitting/fiber coupling system) for each split path is 2.18 m, 5.26 m, 8.34 m, and 11.43 m, respectively.
In-house machined and constructed beam splitting and fiber coupling system with dimensions 30.5 cm × 24.8 cm × 5.7 cm (width × depth × height).
Temporal waveform of the laser pulses exiting the optical fibers (ripples due to laser cavity modes). The pulses are separated by 15.5 ns resulting in 65 MHz prf.
1.62 cm2 SiC die and cross-section view of the die mounted to the CuW (30%/70%) electrodes. 9 Note that the drawing is not to scale in order to enhance ease of viewing. Not shown in this rendering is the insulating epoxy which encapsulates the die and electrodes.
Minimum on-state resistance of the PCSS (100 μm thick) versus 355 nm pulsed laser energy (7 ns FWHM) at 2 kV charging into a 52 Ω high frequency resistive load. For reference, the minimum on-state resistance of a non-thinned device (357 μm thick) is shown as well. 10
20 kV switching into a 52 Ω high frequency resistive load at 65 MHz. A 0.0495 Ω non-inductive current viewing resistor was used to measure the load current.
Half cross-sectional view of the NLTL showing loaded nonlinear ferrite material. The snug fit along the inner conductor maximizes the magnetic field in the ferrite. Note that the solenoid is left out of the drawing, but is present and wraps around the outer conductor to provide a uniform axial magnetic field in the NLTL.
Vector representation of the magnetization dynamics described by the LLG. The magnetic moment, M, precesses around the effective magnetic field, Heff, before relaxing into alignment with the effective field. The precessional motion is shown by the green dashed-dotted-dotted line and the relaxation is shown by the red dotted line.
Operational center frequency of the NLTL output versus static axial biasing magnetic field. Note the additional data point for the 25 kV series at 42 kA/m compared to the 20 kV series; no measured microwave oscillations were observed at 20 kV incident voltage with 42 kA/m bias.
Measured NLTL input (thin) and output (bold) waveforms plotted versus time for increasing axial biasing field. In the output waveform, increasing bias field moves from right to left and shows decreasing system delay. Also note the signal variation with respect to bias as both frequency and power are affected.
65 MHz burst-mode operation of the NLTL. The waveforms show measured NLTL output with 2.1 GHz oscillations and measured photodiode output of switching laser pulses.
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