In vivo studies of tumor-cell apoptosis induced by nanosecond pulsed electric field require high-voltage nanosecond pulses delivered to the biological tissues. In this paper, a newly developed all-solid-state nanosecond pulse generator based on the Marx generator concept is proposed for this application. The generator comprises four parts: a dc charging power, a solid-state Marx circuit using metal-oxide-semiconductor field-effect transistors, a control circuit using a field-programmable gate array, and the load. This generator has the capability of producing repetitive pulses with a voltage up to 8 kV, pulsewidth of 200-1000 ns, rise time of 35 ns, and repetition rate of 1-1000 Hz with various resistive loads and 1-kV dc input voltage. The all-solid-state design makes the generator compact and reliable. Initial experiments were carried out to verify the performances of the proposed generator.

FPGA-Controlled All-Solid-State Nanosecond Pulse Generator for Biological Applications

A compact and modular pulse forming network (PFN)-Marx generator with output parameters of 5 GW, 500 kV, and 30 Hz repetition is designed and constructed to produce intense electron beams for the purpose of high-power microwave (HPM) generation in the paper. The PFN-Marx is composed by 22 stages of PFN modules, and each module is formed by three mica capacitors (6 nF/50 kV) connected in parallel. Benefiting from the utilization of mica capacitors with high energy density and a mini-trigger source integrated into the magnetic transformer and the magnetic switch, the compactness of the PFN-Marx system is improved significantly. The structure of the PFN module, the gas switch unit, and the connection between PFN modules and switches are well designed for modular realization. Experimental results show that this generator can deliver electrical pulses with the pulse width of 100 ns and amplitude of 500 kV on a 59-ohm water load at a repetition rate of 30 Hz in burst mode. The PFN-Marx generator is fitted into a cuboid stainless steel case with the length of 80 cm. The ratio of storage energy to volume and the ratio of power to weight of the PFN-Marx generator are calculated to be 6.5 J/L and 90 MW/kg, respectively. Furthermore, utilizing the generator to drive the transit time oscillator (TTO) at a voltage level of 450 kV, a 100 MW microwave pulse with the pulse width of 20 ns is generated.

https://www.mdpi.com/2079-9292/10/5/545/pdf

A Compact Modular 5 GW Pulse PFN-Marx Generator for Driving HPM Source

Researchers and manufacturers of lithium-ion batteries (LIBs), electric-double-layer capacitors (EDLCs), and lithium-ion capacitors (LICs) have been able to produce devices with power densities previously thought to be impossible. As a result of their higher power density, these devices are able to source high currents to compact pulsed power loads. Though many pulsed power sources already exist which draw their prime power from electrochemical energy storage devices, the number of systems and their capabilities will increase substantially as energy storage technologies continue to advance. Though manufacturers often list the peak pulsed current capability on the electrochemical cell's datasheet, sometimes the value listed can be limited by the hardware used to test the cells and not always the cells themselves. In order to experimentally validate the pulsed current limitations of newer electrochemical cells, a low impedance test stand, capable of extracting high pulsed current from individual cells has been developed. The impedance of the stand, roughly equal to or less than 1 milli-Ohm, is such that in most cases, the impedance of the cell dominates the discharge current. A description of the test stand, the 100 ms pulsed current limitations of many different cells, and experiments representative of how these devices can function in a pulsed power system will be presented.

Pulsed evaluation of high power electrochemical energy storage devices

This paper discusses the modeling of a peaking switch to study the reduction in rise time for the subnanosecond duration pulses The effect of the various shapes of input pulse, inductance, and interelectrode distance on the output voltage and wave shape is discussed in this paper The modeling has been carried out using the electromagnetic and microwave modeling software of Computer Simulation Technology

Electrodynamic Simulation of High-Voltage Peaking Switch

The lack of turn-off ability makes the spark gap-based Marx generator uncontrollable in terminating the output pulse. In addition, there are some limitations for rise time and voltage gain improvements in the conventional critically-damped Marx design. In this paper, an efficient over-damped design of Marx circuit is proposed, which leads to a shorter rise time as well as a larger voltage gain. A chopping magnetic switch is employed to achieve the desired values of the fall time and full width at half maximum (FWHM). Moreover, adding a DC bias circuit to the magnetic switch provides the ability to adjust the pulse FWHM parameter. Therefore, an output pulse with a shorter rise time, larger voltage gain, and controllable FWHM is achieved. The finite element method is utilized to simulate the structures, and the proposed scheme is evaluated by practical experiments.

A Marx-based generator with adjustable FWHM using a controllable magnetic switch

A new, high-energy-density Marx generator has been developed for High Power Microwave (HPM) applications. The generator (P/N: MG30-3C-100NF) has been shown to deliver 5 GW to a 25 Ohm load with a peak pulse voltage of 300 kV. A modular close-packing geometry combined with mica-film capacitor technology results in a 1.8 kJ energy storage capacity in a 20 in. diameter × 45 in. cylindrical vessel. The compact architecture accomplishes a high energy per pulse, but also facilitates a relatively low inductance of the system which is characterized by a 90 ns voltage risetime when discharged into a matched resistive load. The system includes an EMI-hardened power electronics suite which includes a solid-state trigger generator, compact HVPS, and a digital pressure regulator. The system requires only pressurized dry air for insulation, operates on an internal prime-power battery pack and is controlled via a fiber-optic remote for ease of use on remote platforms. The system design and pulse characteristics are presented in this paper.

Design and performance of an ultra-compact 1.8-kJ, 600-kV pulsed power system

Traditionally, the 1.6-MV Marx generator offered by APELC operates at a charge voltage of 40 kV, an erected voltage of 1.6 MV, a stored energy of 260 J, and an output pulse rise time between 6-8 ns. APELC has developed a pulse conditioning system (PCS) that can be retrofitted into the existing MV Marx generator housing to improve output pulse rise time at a minimal cost of stored energy. The performance characteristics of the newly developed PCS driven by a slightly modified version of APELC's MV Marx generator will be provided. APELC has also retrofitted its staple 15-stage, 33-J, Marx generator with a scaled version of the same PCS. Preliminary results of the scaled version of the PCS are presented as well.

Compact Marx generators modified for fast risetime

Increased interest in deployable High Power Microwave systems has led to demand for compact pulsed power drivers for HPM loads, such as magnetrons, that are sensitive to pulse shape. APELC has developed a 600-J, erected pulsed-forming network capable of delivering a 200-ns square pulse to HPM loads. The generator consists of eight, erected pulse-forming sections charged from a common supply. The resonant sections combine to produce a Fourier-approximated square pulse at the load. Pulse characteristics include a FWHM of 200-ns, risetime of 25 ns, and a decay time of 60 ns. The generator is housed in an 18″ diameter by 60″ long pressure vessel and uses only compressed dry air for insulation. The generator is capable of 50-Hz pulse repetition frequency and features soft-failure modes for continued operation in the event of component failure.

A compact 700-kV erected pulse forming network for HPM applications

The compact, wave-erection, GW-class Marx generator has been previously reported for use in 5 ns to sub-ns risetime pulsed power applications. This generator topology has recently been adapted for high Pulse Repetition Frequency (PRF) applications and is the basis for a new high-PRF pulsed power system. The 33-J generator is capable of delivering a 300-kV pulse into a matched 50-Ohm load, or 600 kV into an open circuit. The high-PRF system includes an 8 kJ/sec TDK-Lambda high-voltage power supply and an APELC trigger and control unit. The APELC trigger unit contains a 150-mJ thyratron-based pulser and facilitates the synchronous pulse charging of the Marx generator. Additionally, the trigger unit provides analog output signals of the thyratron and Marx charging signals and features LED diagnostics and fault indicators on the front panel. Applications of the high-PRF system include sourcing of High Power Antennas. Design considerations, system architecture, and experimental results of the high-PRF pulsed power system are presented in this paper.

Compact 200-Hz pulse repetition GW Marx generator system

A DC-powered, compact source capable of delivering in excess of 300 kV into a matched load is realized driving a 16-stage Marx generator with a 10 kJ/s rapid capacitor charger. The system is capable of delivering 100 J per pulse at a maximum pulse repetition frequency of 100 Hz. The Marx generator and capacitor charger are housed in a cylindrical package with approximate dimensions of 12”X60”. The pair are powered from a 300VDC bus. The unit is controlled remotely via a fiber-optically isolated micro-controller which provides the gate drive signals and user interface for the rapid capacitor charger. Performance data for the Marx generator and the capacitor charger is presented in this paper.

C. Nunnally

Papers

Design and performance of an ultra-compact 1.8-kJ, 600-kV pulsed power system

Compact Marx generators modified for fast risetime

A compact 700-kV erected pulse forming network for HPM applications

Compact 200-Hz pulse repetition GW Marx generator system

Compact, DC-powered 100Hz, 600kv pulsed power source