To investigate shock-to-detonation transition (SDT) characteristics of a HNIW-based explosive, a rate law based on the Forest Fire model was calibrated by conducting five wedge tests. In the wedge tests, initial shock pressure at wedge-shaped test explosive charges was varied from 5 to 11 GPa. In each test, the shock trajectory along the wedge-shaped explosive charge was recorded with a streak camera. The streak records showed that sharp SDT occurred in the test explosive. The shock Hugoniot of the test explosive was determined from the free-surface velocity of PMMA attenuators measured with a VISAR instrument and the early shock velocity in the wedges, determined from the shock trajectories. The Pop plot for the test explosive was obtained from run distances to detonation esti-mated based on the shock trajectories. The Forest Fire rate of the test explosive was calibrated from the experimental Hugoniot and the Pop plot. The wedge tests were numerically simulated with the calibrated rate by using a one-dimensional Lagrangian hydrodynamic code. The calculated shock trajectories closely reproduced experimental observations. The rate was further applied to two-dimensional numerical simulations of large-scale gap tests (LSGTs). The estimated critical gap thickness by the LSGT simulations was 43.7 mm, which was in good agreement with experimental data of 46.67 mm. The results of these two types of numerical simulations suggested that the calibrated rate could be used to model most SDT-related applications.

The switched oscillator (SWO) is a quarter-wave oscillator capable of generating mesoband high-power microwave (HPM) pulses. This paper presents a novel high-quality factor (Q) SWO with a capacitive voltage divider (CVD). Unlike conventional SWOs, the transmission line energy of the proposed SWO is gradually coupled with the output load through the CVD. Thus, the proposed SWO can produce a mesoband pulse with a much higher power spectral density within the coupling bandwidth of a target in HPM effect testing. The frequency-domain output-voltage equation of the proposed SWO was obtained through a theoretical analysis of the equivalent circuit of the SWO. Through a numerical analysis, the time-domain output waveform of the proposed SWO was demonstrated to have a high quality factor, and the circuit parameters of the equivalent circuit of the SWO were set to achieve a high quality factor. The circuit parameters selected in the numerical analysis were used in an electromagnetic simulation to determine the design parameters of the parallel-plate transmission line (PPTL)-based SWO with the CVD built on a printed circuit board. The proposed SWO was fabricated and its performance was assessed. For a breakdown voltage of 8.7 kV, the output voltage of the fabricated SWO showed a quality factor of 25, which is more than two times larger than the quality factors of conventional SWOs. Thus, the proposed SWO was demonstrated to produce high-Q mesoband HPM pulses, and it has the potential to be applied in HPM effect testing. Moreover, the proposed SWO improves operator safety by preventing the output load from being charged by a highvoltage power supply. INDEX TERMS High-power microwave, switched oscillator, capacitive voltage divider, mesoband generator.