In numerous pulsed power applications, such as flash X-ray radiography, the voltage pulse shape plays a critical role to guarantee reliable and correct system operation. In particular, for flat-top pulses, the quality of the voltage plateau can be crucial to ensure optimum operating conditions. It can only be obtained if, first, the generator itself delivers a well-shaped pulse and, second, the assembly formed by the transmission line and the load has a matched impedance. However, certain factors, such as high-power levels or high signal frequencies, may introduce variations in the impedance at the load, resulting in a global mismatch. This article puts forward a new approach to mitigate impedance variations that degrade the voltage plateau at the load level. An original solution based on a variable resistor, which is comprised of surface-mount device (SMD) resistors combined with power transistors that operate as on-off switches, is proposed. These enable the device's impedance to be adjusted dynamically. This article elaborates on the conceptual framework and design decisions that led to the development of an experimental prototype. It also presents initial experimental results in which a deliberately degraded voltage plateau, characterized by a peak reaching 1 kV, is corrected. This correction allows the original plateau quality to be restored with an accuracy of approximately2%.

This paper presents a secondary ion mass spectrometry (SIMS) method for the analysis of semiconductor opening switch (SOS) diodes, which are crucial in nanosecond pulsed power systems. The study addresses the gap in experimental measurements of doping concentration in SOS diodes, as the current literature contains mainly theoretical doping profiles. The development of a reliable method for measuring doping concentration is expected to advance SOS technology, given the limited number of manufacturers. The SIMS technique is used to determine the depth distribution and concentration of dopants. The method is adapted to study boron, aluminum, and phosphorus in silicon, with emphasis on detection over several hundred micrometers to clarify the doping profile of SOS diodes. The experimental procedure includes (i) preparation of the SOS diode sample by cutting, polishing, and gold plating; (ii) performing dynamic SIMS analysis using specific conditions for boron/aluminum (O2+/M+) and phosphorus (Cs+/M−) detection; and (iii) using a line scan mode to measure element intensities across the sample, with quantification based on reference samples. The developed SIMS conditions enabled the measurement of the depth distribution of the dopants over a range of 1150 μm with a 2 μm step and providing sufficient lateral resolution. The quantified profiles of boron, aluminum, and phosphorus in the SOS diode are presented. The experimental impurity profiles were in partial agreement with the theoretical doping profiles. This method provides access to the analysis of semiconductor devices with thick structures, which are commonly used in power electronics and solid-state pulsed power.

Non-thermal plasma (NTP) technology offers an innovative solution for converting $\text{CO}_{2}$ into value-added products. Among the various possible reactions, dry reforming of methane (DRM) is particularly attractive as it enables the simultaneous conversion of two greenhouse gases into syngas, a key precursor for synthetic fuel production. Among the existing reactor configurations (dielectric barrier discharges, microwave plasmas, and gliding arcs), nanosecond repetitive pulsed discharges (NRP) have emerged as a promising solution. In this context, a prototype semiconductor opening switch (SOS) generator based on transient-voltage-suppression (TVS) diodes is under development. It provides parameters suitable for NTP-based $\text{CO}_{2}$ conversion: a voltage amplitude up to 15 kV, pulse durations of approximately 10 ns, pulse energy in the tens of mJ, and a pulse repetition frequency (PRF) exceeding 1 kHz in continuous mode and 10 kHz in burst mode. Current work focuses on the comparison of 3 pumping circuits.

This article examines the nanosecond interruption of high current in semiconductor opening switch (SOS) diodes, with the goal of bridging the gap between experimental results and numerical simulations. The experimental results of SOS diodes (0.25 cm2, 0.9 kV) operating as a nanosecond interrupter are presented in a wide range of cut-off current density from 300 A/cm2 to 5 kA/cm2 to analyze the two modes of operation, i.e., drift step recovery diode (DSRD) and SOS. In addition, the numerical simulations of the SOS diode are conducted to investigate the dynamics of the SOS diode in the DSRD and the SOS modes using the Synopsys TCAD. A mixed-mode device with a circuit simulator is utilized to simulate the SOS effect and the dynamic processes occurring during the current cut-off stage. Finally, the experimental and numerical simulation results of the SOS current and load voltage are compared indicating: 1) the accuracy of the TCAD model in the commercially available software, and 2) the possibility of operating the SOS diode in a DSRD mode.

Pulsed Electric Fields (PEF) technique has emerged as a promising approach to extract molecules of interest from different biological material. The present study aimed at optimizing the extraction of C-phycocyanin (C-PC) and other water-soluble biomolecules from Arthrospira platensis cyanobacterium by adjusting PEF process parameters. At a field strength of 5 kV/cm, specific energies comprised between 2.1 and 41.1 MJ/kgDW were applied to the PEF treatment chamber containing an aqueous solution with 1.11 gDW/kgSUS of A. platensis. Experimental results showed that extraction efficiency including C-PC yield and quality are strongly influenced by PEF specific energy. The application of 20.5 MJ/kgDW generated a C-PC yield of 84 mgC-PC/gDW with purity of 0.52 (A620/A280) and selectivity of 3.10 (A620/A680), whereas only 56 % of the cells were disintegrated. Higher specific energies of 30.8 MJ/kgDW improved the disruption of A. platensis cells (85 %) and the C-PC extraction yield (115 mgC-PC/gDW) but at the expense of extracts quality. This study highlights the importance of finding a compromise between PEF energy requirements and extraction performances, which can have significant impact on the overall economic viability of A. platensis downstream processes.

Directed energy applications demand high-voltage pulses with GW peak power and subnanosecond rise times, along with high pulse repetition frequency (PRF) and extended operational lifetimes. Semiconductor Opening Switch (SOS) diodes offer a promising solution, providing kA switching currents, MV withstand voltage, and nanosecond switching capabilities at kHz PRFs. This work focuses on an SOS generator based on modern components with output parameters representative of directed energy applications: 300 kV voltage, 3 kA current, 10-20 ns rise time, and PRF up to 300 Hz. A preliminary circuit design of an all-solid-state nanosecond pulse generator is presented. Furthermore, numerical simulations of the SOS diode are carried out using Synopsys TCAD in order to optimize the doping profile for subsequent fabrication by epitaxy.

The gyromagnetic nonlinear transmission line (GNLTL) is a compact, solid-state source of high-power microwaves (HPMs), consisting of a coaxial transmission line (TL) partially filled with ferrite material. The nonlinearity inherent in the material arises from the interaction between azimuthal and axial magnetic fields. In the present study, the influence of the azimuthal prepolarization field on GNLTL performance is investigated at different levels of axial magnetic field and input pulse amplitudes. It is shown that the azimuthal prepolarization field is not only added to the magnetic field created by the input pulse current but also premagnetizes the ferrite material, thereby altering the initial conditions for RF generation. In our experiments, the generated RF power rises with an increase in prepolarization current. When the axial magnetic field value is low and insufficient for the GNLTL operation, adding the azimuthal magnetic field enables the generation of RF oscillations at the output of the line, thereby expanding its operating mode. A mathematical model based on telegrapher's equations and the Landau-Lifshitz-Gilbert equation for the GNLTL is used to interpret the obtained results. This work describes a new technique for increasing the generated RF power and expanding the operating mode of GNLTL.

This article sets out experimental results of a Marx generator intended for a 2.2 megavolt (MV) electromagnetic pulse (EMP) simulator minimizing SF6 emissions. These results build on previous effort concerning the global design and numerical simulations of the Marx generator. The proposed design allows for direct driving of a peaking stage without the need for an intermediate pulse compression stage, which is present in the current pulse generator design. The results indicate that this simplified architecture can achieve performances comparable to those of the existing generator. Furthermore, the new design significantly reduces greenhouse gas emissions, owing to its compact configuration and for operation up to 70% of its maximum voltage, to the use of dry air insulation in place of SF6. This article presents the development and testing of a five-stage Marx generator prototype (1:3 scale of the 2.2 MV generator), designed to validate the results obtained from our simulation model. Embedded sensors are employed to measure and compared to our simulation’s key parameters of the Marx, including inductance, breakdown delays and dynamic resistance of the spark gaps. Experiments are conducted using both dry air and SF6 insulation to assess and compare the performances and behavior of the generator under each gas. The experimental data obtained are subsequently used to refine the design criteria for a new 2.2 MV pulse generator.

A system based on inductive energy storage and Semiconductor Opening Switch (SOS) diodes offers a promising solution for the development of nanosecond pulse generators. The SOS effect occurs when a silicon p + -p-n-n + structure, containing residua] electron-hole plasma after forward pumping, undergoes a current density of more than 1 kA/cm 2 within the reverse pumping. In this study, the numerical simulations of SOS diodes are conducted to gain insights into the dynamics of the SOS effect using Synopsys TCAD. Initially, the accuracy of the model is validated by comparing static voltage breakdown simulations with experimental results. Subsequently, a mixed-mode device with a circuit simulator is utilized to simulate the SOS effect and the processes occurring during the current cut-off stage. This research contributes to advancing the field of pulse power technology by providing valuable insights into the operation of SOS diodes using commercially available software.

This article investigates the impact-ionization switching mechanism in parallel-connected high-voltage thyristors, aiming to bridge the gap between experimental observations and numerical simulations. A novel experimental setup is designed to study four parallel thyristors triggered in impact-ionization wave mode, marking the first instance of such an arrangement. In addition to the experiment, a numerical simulation is used to assess the impact-ionization switching of high-voltage thyristors in parallel connection. The numerical simulation adopts a quasi-3-D model of the thyristor structure derived from a 2-D model, considering cylindrical symmetry. Three distinct scenarios are explored in the simulation: 1) static voltage breakdown; 2) suppression of unwanted ${d}V/{d}t$ triggering; and 3) delayed impact-ionization breakdown. The article presents a detailed comparison and discussion of the experimental and numerical simulation results related to impact-ionization switching.

This article investigates the use of off-the-shelf (OTS) diodes as opening switches in a 500-kV nanosecond pulsed power generator. A 40-J test bench based on a saturable pulse transformer and a primary thyratron switch is designed to evaluate the performance of the OTS diodes in comparison with standard semiconductor opening switch (SOS) diodes A distinguishing feature of the proposed circuit is the adjustability of the output pulse energy, which is achieved using flat hysteresis loop magnetic cores and variable reset magnetic field. The study confirms the operation of OTS diodes as an opening switch, although highlighting differences in the reverse current conduction that affect the generated voltage pulse characteristics. Based on the successful operation of the OTS diodes, a 500-kV pulsed power generator using an OTS Solid-State Opening Switch (GO-SSOS) is developed. The GO-SSOS provides output voltages of 100–500 kV across resistive loads from 50 $\Omega$ to 1 k $\Omega$ , with a pulse width of about 100 ns and a rise time of less than 40 ns. The generator achieves a peak power of 335 MW and demonstrates an overall energy efficiency in the range of 30%–70% depending on the load. Operation at a pulse repetition rate of 60 Hz is presented, showing a good reproducibility of the pulses with an amplitude and duration deviation of about 2% and 10%, respectively. No degradation of the OTS diodes has been observed after the tests (more than 1000 pulses). As an example of the possible applications of the GO-SSOS, corona discharge in the air is performed, also proving the stability of all the systems under conditions of strong electromagnetic interference.

This article demonstrates the impact-ionization switching of standard thyristors in a series-parallel configuration. The series-parallel triggering of thyristors holds a substantial promise for enhancing both voltage blocking and current capacity of the switch simultaneously. Nevertheless, the key obstacle in this context revolves around acquiring a suitable trigger generator, primarily because this trigger necessitates a combination of high dV/dt and low post-triggering energy to be applied to the thyristor assembly. Thus, a novel trigger circuit is developed to test a setup with two parallel branches, each having two series-connected thyristors (with a wafer diameter of empty set24 mm and a rated blocking voltage of 1.8 kV). These thyristors were tested in the impact-ionization switching mode using a single Marx generator. We conducted experiments in a current flow phase, where energy switching occurred by connecting an RLC discharge circuit. These experiments revealed that the thyristors transitioned from a blocking to a conducting state around similar to 400 ps, enabling the switching of a current pulse with an amplitude of similar to 17.5 kA and a d I/ dt of similar to 8.5 kA/mu s (limited by the circuit). Notably, the current imbalance between the thyristor parallel branches remained under 2%. To the best of our knowledge, this is the first reported instance of successfully triggering high-voltage thyristors connected in series-parallel in the impact-ionization wave mode.

Ultra-wideband (UWB) microwave sources driven by specialised pulsed power generators have experienced a considerable development in the last decade due to their wide domain of new applications such as defence or counter-terrorism activity. The authors present the main findings of a research dedicated to the development of a pulsed power-driven electromagnetic field source for disabling improvised explosive devices (IED). The pulsed power generator driving the source is a 13-stage compact Marx producing voltage pulses reaching an amplitude of 0.5 MV, with a pulse repetition frequency (PRF) of up to 100 Hz. The generator is coupled to a bipolar pulse forming line, providing bipolar pulses with a dV/dt of around 1.6 MV/ns. This pulsed power system feeds an array composed of 16 Koshelev-type UWB antennas through an impedance matching transformer. The resulting electromagnetic source is capable to produce pulsed electric fields (PEFs) having a figure-of-merit (FOM) of 1 MV. First, practical experiments were carried out to study the effects of the PEFs on targets. The targets used in the present study are M2B type flashbulbs, known to have the same susceptibility as the US army M6 detonator. Different configurations of wires (shielded, twisted, etc) with different lengths were used in connecting items inside these targets. The tests were performed by placing the flashbulbs at different distances to determine the essential parameters (i.e., amplitude, duration, and frequency range) of the PEFs required to trigger them. An overview of the experimental campaign and the main findings are also presented followed by conclusions.