Baoliang Qian

In this letter, the effect of the trigger optical pulse on the switching performances of a gallium arsenide photoconductive semiconductor switch (GaAs PCSS) under quasi-linear mode is analyzed, both numerically and experimentally. It is found that, under identical optical pulse conditions, the PCSS operates in a unique quasi-linear mode under side incidence, with a 30% reduction in on-state resistance and an 83% reduction in time jitter compared to conventional front incidence. The positive effect of the quasi-linear mode on switching performance is attributed to the uniform illumination and absorption achieved by the device, resulting in a more uniform distribution of photogenerated carriers along the current filament channel.

This paper proposes a novel reverse-design framework for designing resonant structures in relativistic magnetrons (RMs), addressing the limitations of conventional approaches that derive electrical parameters (voltage and magnetic field) from fixed structural parameters. Traditional methods based on Buneman–Hartree and Hull conditions are constrained to forward calculations, whereas our study enables the extraction of key structural parameters (anode radius ra, cathode radius rc) from predetermined operational requirements, including voltage V, magnetic field Bz, resonant frequency fn, and mode number n. By establishing constraints, basic, and additional conditions through monotonicity analysis of value functions, this theory delineates feasible ranges for ra and rc. Case studies involving five distinct RM configurations validate the framework, demonstrating alignment with particle-in-cell simulations from the literature. This method significantly streamlines RM design, reduces empirical trial-and-error, and enhances adaptability to diverse high-power microwave applications.

High voltage pulse generators are widely applied in high power microwave, plasma generation, material processing, and scientific research. Pulse forming lines are widely applied in high voltage pulse generators due to their high energy density and great ability with square waveform modulation. To get a higher energy transfer efficiency and lower characteristic impedance, a novel racetrack Blumlein type pulse forming line (R-BPFL) that is formed by two inner cylinders, two middle cylinders, and one outer cylinder is proposed in this paper. Moreover, repetitive operation is significant for pulse generators. Therefore, this paper proposes a high repetitive primary energy storage system incorporating an energy recovery circuit precisely controlled by three thyristors. A parameter optimization methodology is developed through theoretical analysis to simultaneously satisfy both high-frequency operation requirements and maximum compactness. Finally, a repetitive high voltage pulse generator based on the designed R-BPFL and primary energy storage system is constructed and tested. The experimental results show that the generator designed in this paper had an output power of 10.5 GW on a 40 Ω load, a pulse width of about 115 ns, a repetition rate of 20 Hz, and supported 640 pulses in one run.

The delay time of a gallium arsenide photoconductive semiconductor switch (GaAs PCSS) fundamentally affects its synchronization stability. In this paper, a numerical computational model applicable to the simulation of GaAs PCSS current filaments with opposed-contact electrode structures in nonlinear mode is developed, and the impacts of optical pulse width and optical energy on switching delay are studied. The experimental results demonstrate that both optical pulse width and energy are correlated with switching jitter, and that higher optical energy and narrower pulse width can lead to lower jitter. Based on this result, the multiple avalanche domain theory is employed to analyze the influence of optical pulse width on domain evolution during the switching stage. The results reveal that narrower pulse widths accelerate the formation of avalanche domains, thereby shortening the switching time of the PCSS.

A high voltage pulse power supply based on a Blumlein type pulse forming line (PFL) with a Periodic Slotted Insulation Structure (PSIS) is designed and constructed in this paper. The Blumlein type PFL with PSIS, which inserts PSIS both in the inner line and outer line of the conventional Blumlein type PFL, is able to obtain output waveforms with higher quality and higher energy efficiency compared with the conventional Blumlein type PFL. Meanwhile, the combined insulation structure formed by the media of PSIS and the glycerin filled with the PFL can be used to optimize the electric field strength of the PFL, thereby improving the stability and reliability of the PFL in the repetitive-operation mode. The experimental results show that the high voltage pulse power supply designed in this paper had an output power of about 5 GW at a 50 Ω load, a pulse width longer than 80 ns, a repetition rate of 20 Hz, and supported 100 pulses in one run.

In order to reduce the volume and energy consumption of high-power microwave (HPM) systems, HPM sources with low guiding magnetic fields have become one of the most important trends. However, the beam-wave conversion efficiency of such devices is typically low due to the divergence of the electron beam, which lacks the constraint of a high magnetic field. Here, we investigate a coaxial dual-mode relativistic Cherenkov oscillator (RCO) that exhibits efficient beam-wave interaction at a low guiding magnetic field. On the one hand, the space charge effect of electrons can be reduced by increasing the radius of the device; on the other hand, dual-mode operation can be achieved for efficient beam-wave conversion, while the competition of higher order modes from large radii can be avoided by introducing a coaxial inner conductor to the slow wave structure (SWS). In particle simulations, a guiding magnetic field of only 0.33 T has been demonstrated to confine the electron beam, resulting in an output microwave power of 1.98 GW and a beam-wave conversion efficiency of approximately 43% when the diode voltage and diode current are 510 kV and 9 kA, respectively. Moreover, preliminary validation experiments were conducted, wherein microwaves with a power of 1.71 GW were generated with a beam-wave conversion efficiency of 36%. The experimental results obtained under low magnetic fields provide a high degree of confidence that the size and weight of HPM systems utilizing this device will be significantly reduced.

A solid-state high voltage pulse power supply with three synchronous output voltages is designed and constructed in this paper. The pulse power supply consists of a fractional-turn ratio saturable pulse transformer and three six-stage Marx generators. The FRSPT not only works as step-up pulse transformers but also as magnetic switches of the Marx generators. All magnetic switches are developed based on two communal cores to achieve a perfect multiple-pulse synchronization effect. The experimental results show that the three output voltages have an amplitude of about 168 kV and a rising time of about 102.6 ns with a 2 MΩ dummy load. The pulse power supply can operate stably at frequencies of 1, 5, 10, and 15 Hz with the synchronization jitters less than 1.5 ns.

High power pulse generators are moving in the direction of compact, solid-state, and stable working in a relatively long time. In this paper, a compact pulse forming line-Marx type high power pulse generator, based on a ceramic pulse forming line and a spark gap switch with carbide modified graphite electrodes, is studied numerically and experimentally. Specifically, a ceramic based pulse forming line with high relative permittivity was used to achieve long pulse duration in a limited dimension. A spark gap switch with carbide modified graphite electrodes was proposed to decrease the erosion of the electrodes, which can efficiently prolong the lifetime of the device. The generator was built. With a charging voltage of 34 kV approximately, pulses with peak current over 2.56 kA and a duration of about 86 ns were obtained on a matched dummy load of 50 Ω. The dimensions of the generator are 360 × 280 × 300 mm3. The device can continue working over 6000 pulses with a repetitive rate of 10 Hz, which meets potential applications, including plasma science research.

Realizing the synchronization of multiple gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) is the key for GaAs PCSS in the applications of arrayed pulsed power systems. However, delay jitter makes the synchronization become a challenging task. To improve the delay jitter, we propose a packaging scheme integrating the external shielding electrode (SE) and an illuminating design formed by a light guide plate (LGP) and a bottom reflector (BR). Compared to the conventional PCSS, the PCSS implementing this packaging scheme presents a lower delay jitter and sustains the low-jitter operation of tens of picoseconds within tens of thousands of continuous shots, demonstrating the positive effect of this scheme in improving the delay jitter. Then, the effect is well interpreted with the close correlation between the reduced delay time and the reduced delay jitter and attributed to the increased extrinsic absorption and improved stability of hold-off voltage contributed by the novel package. Furthermore, when this packaging structure is used in the PCSS array, improved synchronization can be found, demonstrating the effect of this novel scheme on minifying the performance difference between each PCSS in the array and making the PCSS with this packaging scheme a promising candidate for the pulsed power systems based on the PCSS array.