Pulsed Power Technology Research Articles

Double enhancement of energy storage density in relaxor ferroelectric 0.8BaTiO3-0.2BiScO3 by Li defect-regulated strategy

To meet the ever-increasing demands for pulsed power technologies, the development of lead-free dielectric ceramics with a large energy storage density (Wrec) and high energy storage efficiency (η) is crucial for enhancing the electrical performance of power capacitive devices. The conventional solid-solution, while effective in suppressing long-range order and improving energy storage performances, often results in a reduction of maximum polarization. This reduction necessitates the application of a larger electric field to obtain a relatively high Wrec. Herein, an effective strategy to enhance Wrec again via inducing Li-related defect dipoles is proposed. By introducing (Bi0.5Li0.5)TiO3 into 0.8BaTiO3-0.2BiScO3 matrix, the polarization contribution from defect dipoles together with intrinsic polarization induces an at least two-time enhancement in Pmax. Our findings indicate ∼62.9 % enhancement in the Wrec of 0.8BT-0.2BS, elevating from 2.56 J cm−3 to 4.17 J cm−3 at electrical field of 300 kV cm−1, while preserving an energy storage efficiency of 90.35 %. Furthermore, it also exhibits good thermal stability with the variations of ΔWrec < 3 % and η< 5 %. This research introduces a novel strategy for defect regulation strategy in the design of high-performance dielectric materials, which is expected to expedite the optimization of the advanced energy storage capacitors.

Enhanced energy storage performance of lead-free Sr0.7Bi0.2TiO3 ceramics via tape casting

Abstract The development of pulsed power technology demands high energy storage density dielectric materials. In this study, Sr0.7Bi0.2TiO3 relaxor ferroelectric (rFE) ceramic thick films were prepared using a tape-casting process. The ceramics exhibit a dense structure and typical rFE hysteresis curves, achieving an energy storage density of 4.77 J cm−3 and efficiency of 94.4%, attributed to the high polarization intensity, low remnant polarization, and low hysteresis loss of rFE. Additionally, the material demonstrates good temperature stability. Moreover, the Sr0.7Bi0.2TiO3 ceramic thick films show advantages in charge-discharge performance, capable of discharging within hundreds of nanoseconds and achieving a power density of 137 MW cm−3. Overall, the Sr0.7Bi0.2TiO3 ceramic thick film exhibits a comprehensive performance advantage in terms of energy storage density, efficiency, and power density. Additionally, the material was fabricated using the tape-casting process, which is compatible with subsequent multilayer ceramic capacitor production, indicating potential for further performance enhancement.

Guest Editorial Special Issue on Pulsed Power Science and Technology

Guest Editorial Special Issue on Pulsed Power Science and Technology

Micro-plasma jet improves triggering in pulsed power technology

Micro-plasma jet improves triggering in pulsed power technology

High energy-storage properties of Sr0.7Bi0.2-xLaxTiO3 lead-free relaxor ferroelectric ceramics for pulsed power capacitors

Ceramic capacitors are very promising to be commercialize with ease for high pulse power technology owing to their fast charging/discharging rate, high bending strength and as well as their high energy density. Small, fine, and compacted grains in conjunction with slim P-E loops, and high breakdown electric field strength (Eb) play crucial role in the improvement of recoverable energy storage density. In this work, the microstructure and electrical properties of La2O3 modified Sr0.7Bi0.2-xLaxTiO3 ceramics (SBLTO, x = 0, 0.01, 0.02, and 0.05, and short for SBTO, SBLTO-0.01, SBLTO-0.02, and SBLTO-0.05, respectively) were investigated in details. Furthermore, introducing La2O3 into SBTO ceramics not only refined grains and increased insulation resistance, but also resulted in significantly better energy-storage characteristics, as compared with the pure SBTO ceramics. Recoverable energy-storage density (Wrec) was obtained up to 5.8 J/cm3 in SBLTO-0.01 lead-free ceramic, which is better than that of other reported SBTO-based ceramics. Moreover, the Wrec of the SBLTO-0.01 ceramic also presents good frequency (2–500 Hz) and thermal (25–120 °C) stabilities under an electric field strength of 150 kV/cm. Furthermore, the charge-discharge results demonstrated a high power density∼92 MW/cm3 and a short discharging speed time∼39 ns. As a result, our work offers SBTO-based ceramics with a feasible method for enhancing the energy-storage characteristic.

Giant overall energy density performances via introducing aliovalent cations in BNT-based ferroelectric ceramics

The strategy of introducing aliovalent cations in the ferroelectric perovskites is the most promising for obtaining excellent overall energy storage density performances, simultaneously with good efficiency and thermal stability in dielectric ceramics for high pulse power technologies. Aliovalent cations could greatly enhance the short-range ferroelectric order (Polar nanoregions, PNRs), and local random field caused by vacancies, mismatch between size, electronic configuration, and other physical and chemical properties of aliovalent cations with the host perovskite. PNRs and local random field make the ceramic relaxor like with excellent overall energy storage density results such as total energy storage density (WT = 10.55 J/cm3, recoverable energy storage density Wrec = 7.82 J/cm3), power density (PD = 197 MW/cm3), current density (CD = 1312 A/cm2), and ultra-fast discharge rate (t = 24 ns) simultaneously with good working efficiency of 74 % by introducing 14 mol% of Bi(Zn1/3Nb2/3) aliovalent cations in the morphotropic phase boundary (MPB) (Bi0.47Na0.47)TiO3–0.06BaTiO3 composition. In addition, the same optimum sample also showed good thermal stability up to 240 °C, with <10–13 % variation in recoverable energy storage density and working efficiency respectively. The reason of excellent overall energy storage density, and their thermal stability in a broad temperature range might be due to short-range ferroelectric order, local random field, relaxor ferroelectric polymorphic phases, highly dense microstructure with small and uniform grains, as well as large band gape. Our study provides a good clue to obtain giant overall energy density results with good working efficiency and thermal stability in relaxor ferroelectric ceramics for high pulse power technology.

Nano-Pulse Treatment Overcomes the Immunosuppressive Tumor Microenvironment to Elicit In Situ Vaccination Protection against Breast Cancer.

We previously reported that nano-pulse treatment (NPT), a pulsed power technology, resulted in 4T1-luc mammary tumor elimination and a strong in situ vaccination, thereby completely protecting tumor-free animals against a second live tumor challenge. The mechanism whereby NPT mounts effective antitumor immune responses in the 4T1 breast cancer predominantly immunosuppressive tumor microenvironment (TME) remains unanswered. In this study, orthotopic 4T1 mouse breast tumors were treated with NPT (100 ns, 50 kV/cm, 1000 pulses, 3 Hz). Blood, spleen, draining lymph nodes, and tumors were harvested at 4-h, 8-h, 1-day, 3-day, 7-day, and 3-month post-treatment intervals for the analysis of frequencies, death, and functional markers of various immune cells in addition to the suppressor function of regulatory T cells (Tregs). NPT was verified to elicit strong in situ vaccination (ISV) against breast cancer and promote both acute and long-term T cell memory. NPT abolished immunosuppressive dominance systemically and in the TME by substantially reducing Tregs, myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs). NPT induced apoptosis in Tregs and TAMs. It also functionally diminished the Treg suppression capacity, explained by the downregulation of activation markers, particularly 4-1BB and TGFβ, and a phenotypic shift from predominantly activated (CD44+CD62L-) to naïve (CD44-CD62L+) Tregs. Importantly, NPT selectively induced apoptosis in activated Tregs and spared effector CD4+ and CD8+ T cells. These changes were followed by a concomitant rise in CD8+CD103+ tissue-resident memory T cells and TAM M1 polarization. These findings indicate that NPT effectively switches the TME and secondary lymphatic systems from an immunosuppressive to an immunostimulatory state, allowing cytotoxic T cell function and immune memory formation to eliminate cancer cells and account for the NPT in situ vaccination.

Micro-particle injection experiments in ADITYA-U tokamak using an inductively driven pellet injector

A first-of-its-kind, inductively driven micro-particle (Pellet) accelerator and injector have been developed and operated successfully in ADITYA-U circular plasma operations, which may ably address the critical need for a suitable disruption control mechanism in ITER and future tokamak. The device combines the principles of electromagnetic induction, pulse power technology, impact, and fracture dynamics. It is designed to operate in a variety of environments, including atmospheric pressure and ultra-high vacuum. It can also accommodate a wide range of pellet quantities, sizes, and materials and can adjust the pellets’ velocities over a coarse and fine range. The device has a modular design such that the maximum velocity can be increased by increasing the number of modules. A cluster of lithium titanate/carbonate (Li2TiO3/Li2CO3) impurity particles with variable particle sizes, weighing ∼50–200 mg are injected with velocities of the order of ∼200 m s−1 during the current plateau in ADITYA-U tokamak. This leads to a complete collapse of the plasma current within ∼5–6 ms of triggering the injector. The current quench time is dependent on the amount of impurity injected as well as the compound, with Li2TiO3 injection causing a faster current quench than Li2CO3 injection, as more power is radiated in the case of Li2TiO3. The increase in radiation due to the macro-particle injection starts in the plasma core, while the soft x-ray emission indicates that the entire plasma core collapses at once.

Comparative Study of Different High Voltage Switches Used in Pulsed High Voltage Application

High-voltage switches play a crucial role in pulsed power applications, where the efficient and reliable control of highvoltage pulses is required. This study aims to compare different types of high-voltage switches commonly used in pulsed power systems including electromechanical switches, vacuum switches, gas-filled switches, triggered spark gaps and solidstate switches. The comparison study focuses on key performance parameters such as voltage handling capability, current carrying capacity, turn-on time, and repetition rates are considered to provide a comprehensive study and analysis of the switch’s suitability for different pulsed power applications. Gas-filled switches such as spark gaps, thyratrons and ignitrons have been used in pulsed power systems due to their high voltage handling capability and low switching losses. However, they suffer from a limited lifetime and require maintenance and periodic replacement. Solid-state switches, i.e. Silicon-Controlled Rectifiers (SCRs), Insulated Gate Bipolar Transistors (IGBTs) and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) offer advantages in terms of longevity, reliability, and reduced maintenance. However, they have limitations in high-voltage applications and exhibit higher switching losses. The findings of this comparison study will assist researchers, engineers, and system designers in selecting the most appropriate high-voltage switch for pulsed power applications, considering the specific requirements and constraints of the system. This will ultimately contribute to the advancement and optimization of pulsed power technologies across a wide range of scientific, industrial, and strategic applications.

An annular pulse forming line based on coaxial transmission lines.

The miniaturization, lightweight, and solidification of pulse forming lines (PFLs) are of prime significance during the evolution of pulsed power technology. In this paper, an all-solid-state annular pulse forming line (APFL) based on film-insulated coaxial transmission lines is developed to generate fast-rise time quasi-square pulses. First, a coiled coaxial transmission line (CCTL) comprised of multilayer polypropylene films with outstanding insulating properties is constructed. It can withstand direct current voltages up to 200kV, with a cross section diameter of 7.4mm. In addition, in order to turn the pulse transmission direction from circumferential to axial, a compact insulated terminal with a 90° bend structure is designed for CCTL. Although single terminal inductance can slow down the rising edge of the output pulse, their parallel connection in an APFL can weaken such an effect. The APFL, with a characteristic impedance of 2.95Ω and a transmission time of 13ns, is composed of three CCTLs with six terminals, which can run over 100 thousand times under the pulse voltage of 75kV. Finally, 15 series APFL modules are employed to assemble a multi-stage PFL for the Tesla-type pulse generator. When charged to a voltage of 1 MV, the mixed PFL consisting of a coaxial line and the multi-stage PFL outputs quasi-square pulses with a voltage amplitude, rise time, and width of 510kV, 4ns, and 41.5ns, respectively, and the fluctuation of the flat top is about 6%.

High Energy Density Achieved in Novel Lead-Free BiFeO3-CaTiO3 Ferroelectric Ceramics for High-Temperature Energy Storage Applications.

The development of high-performance electrostatic energy storage dielectrics is essential for various applications such as pulsed-power technologies, electric vehicles (EVs), electronic devices, and the high-temperature aviation sector. However, the usage of lead as a crucial component in conventional high-performance dielectric materials has raised severe environmental concerns. As a result of this, there is an urgent need to explore lead-free alternatives. Ferroelectric ceramics offer high energy density but lack stability at high temperatures. Here we present a lead-free (1 - x)BiFeO3-xCaTiO3 (x = 0.6, 0.7, and 0.8; BFO-CTO) ceramic capacitor with low dielectric loss, high thermal stability, and high energy density up to ∼200 °C. The introduction of CTO (x = 0.7) to the BFO matrix triggers a transition from the normal ferroelectrics to the relaxor ferroelectrics state, resulting in a high recoverable energy density of 1.18 J cm-3 at 190 °C with an ultrafast dielectric relaxation time of 44 μs. These results offer a promising, environmentally friendly, high-capacity ceramic capacitor material for high-frequency and high-temperature applications.

A repetitive frequency square wave generator based on Blumlein pulse forming network and pseudospark switch.

The Blumlein pulse forming network (PFN) has widely beenused in pulsed power technology to generate square waves with short pulse widths. In this paper, we developed a repetitive frequency square wave generator based on Blumlein PFN and pseudospark switch (PSS). A Blumlein PFN with unequal capacitances has been proposed, and the PFN parameters have been optimized for better output waveforms. A single-gap PSS with a withstand voltage of 40kV and a repetitive frequency of 100Hz has been designed to switch the Blumlein PFN. The experiment results show that the square wave generator can output pulses with a voltage of 26kV, a rise time of 25ns, and a pulse width of 90ns on a matched load of 11Ω. It has operated steadily for 10h with a repetitive frequency of 100Hz, and the jitter remains at around 1ns after 1.05 × 106 shots.

Simulation of effect of metal particles on breakdown process of three-electrode gas spark switches

Compared with two-electrode gas spark switch, three-electrode gas spark switch has the advantages of lower operating voltage, higher reliability and less discharge jitter, so it has been widely used in pulse power systems. However, due to the characteristics of pulse power technology, the gas spark switch is easy to cause ablation on the electrode surface during use, and the metal particles generated by ablation will significantly affect the stability and reliability of the switch. In this work the discharge process of the three-electrode gas spark switch under atmospheric pressure nitrogen environment is simulated first. In this model, the ionization coefficient near the trigger electrode is modified to compensate for the shortcomings of the local field approximation, and the relevant mathematical derivation process is given. The formation of the initial electrons is described by the field electron emission phenomenon, and the development process of electron collapse into the streamer is obtained. The physical mechanism of switch on is investigated, and the development process of each stage of switch discharge is described in detail. Then, the discharge process of the switch is studied when there are metal particles near the trigger. The study shows that the presence of metal particles enhances the electric field near the trigger and accelerates the formation of the initial electron cloud. In addition, in the presence of metal particles, the metal particles and the trigger will first break down, forming a high-density plasma channel after the breakdown, and becoming the source of the subsequent flow development. At the same time, because the metal particles on the channel have an obstructing effect on the streamer development, the streamer generates a discharge branch after contacting metal particles. In the end, the influences of metal particles of different shapes and sizes on the discharge process are discussed. The results show that metal particles with sharp shapes have stronger electric field distortion, when the electric field intensity is large enough, it may cause field emission on the surface of metal particle. And it is also made clear that the size of metal particle is small, the obstruction of the development path of streamer is small, and the streamers quickly converge behind the particles.

Improved energy storage properties achieved in NaNbO3-based relaxor antiferroelectric ceramics via anti-parallel polar nanoregion design

With the increase in environment protection requirements and the development of pulse-power technology, environmentally friendly antiferroelectric materials with superior energy storage performance have received increasing attention.

Impact-Ionization Switching of High-Voltage Thyristors Connected in Parallel

Thyristors triggered in the impact-ionization wave mode is a promising switching method in pulsed power technology. This triggering approach enhances the current capability of standard thyristors, allowing switching a current pulse with an amplitude of 200 kA and a current rise time rate-of-change (dI/dt) of 58 kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> s. Thyristor wafer area can be considered as one of the factors that are limiting the peak current amplitude and dI/dt. Switching thyristors in parallel is a possible solution to overcome these limitations. However, no evidence was found in the literature for successful parallel switching of standard thyristors in the impact-ionization wave mode. In this research, the possibility of parallel switching of two standard thyristors rated for 2.2 kV with a wafer diameter of 32 mm was investigated. A Marx generator equipped with a peaking module was used to charge the thyristor equivalent capacitance (1 nF) up to double its static breakdown voltage with a voltage rise time rate-of-change (dV/dt) of more than 1 kV/ns, as required for impact-ionization triggering. The diagnostic system includes two wideband voltage probes (VPs) with a subnanosecond time response, which allows simultaneous measurement of a voltage drop across each thyristor connected in parallel. Two stages of thyristor operation were investigated: 1) a triggering stage, without energy switching, when a dc bias voltage is applied; and 2) a current flow stage, with energy switching, when an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$RLC$</tex-math> </inline-formula> discharge circuit is connected. In these experiments, thyristors change from blocking to conducting state within 400 ps, switching a current pulse with an amplitude of 11 kA and a dI/dt of 6 kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> s (circuit limits). The current imbalance between the thyristors was less than 10%. To the best of the authors’ knowledge, it is the first time reported that high-voltage thyristors connected in parallel have been successfully triggered in the impact-ionization wave mode.

A Novel Variant of Marx Generator Circuit Using Hybrid Energy Storage

With the development of pulsed power technology and the expansion of its application areas, the requirements for pulsed high-voltage supplies are getting sophisticated. Many researchers are exploring new circuits or trying to improve the performance of the existing circuits. In this study, we introduce a variant circuit of the Marx generator based on hybrid energy storage (HES). This circuit topology, referred to as the LCL circuit in this article, allows two inductors and one capacitor to discharge simultaneously to obtain a higher output voltage. By observing the simulation results, we compared the performance of this proposed circuit with circuits based on other energy-storage methods, including capacitive energy storage (CES), inductive energy storage (IES), and the previously studied HES. After confirming the operation process of an LCL module, a two-stage experimental circuit has been built using power MOSFET switches for carrying out the verification experiments. With a charging voltage of 800 V, the output voltage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 8.4 kV with a rise time of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 30 ns has been obtained on a 200- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> load. The voltage addition of two modules has indicated the potential of a Marx circuit for a much higher output voltage.

Development of a nanosecond high voltage pulser based on Semiconductor Opening Switch

Nanosecond pulser is widely used in beam injection and extraction. Semiconductor Opening Switch (SOS) is a type of high voltage diode with P+-P-N-N+ semiconductor structure, which has a great application prospect in pulse power technology for its notably short switching-off time, high repetition rate and large working current. The cutoff time of the SOS is dependent on the duration and amplitude of the pumping current, which may reach thousands of amperes. A two-stage magnetic compression pumping circuit without external demagnetization cicuits is proposed to meet the operational requirements of SOS. The circuit was simulated by Pspice, which confirmed the principle of the circuit. A prototype of the pulser was constructed based on the simulation analysis. The experiments indicated that the reverse pumping current with amplitude of 460 A and duration of 18 ns, and a 16 kV, duration of 14 ns pulse was generated on the load of 50 Ω. The design, simulation and the test results of the nanosecond high voltage pulser are presented in the paper.

Study of Bipolar Inductively Isolated High-Voltage Pulse Source

To meet the application requirements of pulsed power technology in wastewater treatment and other aspects (for example, a scenario that requires a high-voltage pulse source that can output a pulse with a rising edge in the nanosecond range and a device that can stabilize the pulse under high-frequency conditions), this paper designed an inductively isolated bipolar high-voltage pulse source. It consists of three parts: the primary charging power supply, the isolated driver circuit, and the pulse-forming circuit. By using inductance instead of traditional resistance isolation, using the inductance for charging and isolation, the inductance can increase the charging voltage of the capacitor, so the circuit can achieve a higher voltage output. The dual-Marx generator parallel connection design of the pulsed power supply topology, using a primary charging power supply for positive and negative polarity charging, can simultaneously output the reverse polarity and size of high-voltage pulses to achieve a bipolar output, so the load has an effect on the pulse. The equipment was selected on the basis of the design of the isolated driver circuit, primary charging power supply circuit, and pulse-forming circuit for the corresponding simulation, and in the experiment to build a principle model, the tests showed that the pulse source output pulse amplitude range was 0~10 kV (the positive pulse voltage was 5 kV, and the negative pulse voltage was −5 kV), the pulse rising edge was approximately 200 ns, the pulse width was 1 μs, and the frequency range was 0~1 kHz for the pulse source frequency. The power supply was designed to be used in applications such as wastewater treatment.

Nanosecond Pulsed Electric Fields (nsPEFs) Modulate Electron Transport in the Plasma Membrane and the Mitochondria

Nanosecond pulsed electric fields (nsPEFs) are a pulsed power technology known for ablating tumors, but they also modulate diverse biological mechanisms. Here we show that nsPEFs regulate trans-plasma membrane electron transport (tPMET) rates in the plasma membrane redox system (PMRS) shown as a reduction of the cell-impermeable, WST-8 tetrazolium dye. At lower charging conditions, nsPEFs enhance, and at higher charging conditions inhibit tPMET in H9c2 non-cancerous cardiac myoblasts and 4T1-luc breast cancer cells. This biphasic nsPEF-induced modulation of tPMET is typical of a hormetic stimulus that is beneficial and stress-adaptive at lower levels and damaging at higher levels. NsPEFs also attenuated mitochondrial electron transport system (ETS) activity (O2 consumption) at Complex I when coupled and uncoupled to oxidative phosphorylation. NsPEFs generated more reactive oxygen species (ROS) in mitochondria (mROS) than in the cytosol (cROS) in non-cancer H9c2 heart cells but more cROS than mROS in 4T1-luc cancer cells. Under lower charging conditions, nsPEFs support glycolysis while under higher charging conditions, nsPEFs inhibit electron transport in the PMRS and the mitochondrial ETS producing ROS, ultimately causing cell death. The impact of nsPEF on ETS presents a new paradigm for considering nsPEF modulation of redox functions, including redox homeostasis and metabolism.

Comparison of conventional crushing and high-voltage pulsed power technology as techniques for disaggregating different types of spent magnesia-carbon refractory bricks during recycling

Three different types of spent magnesia-carbon (MgO–C) bricks were chosen to evaluate the liberation of magnesia particles through high-voltage pulsed power technology (HVPPT) and conventional comminution (jaw and cone crushing). The primary objective was to determine how the different types of MgO–C bricks comminute and whether magnesia particles could be restored to their original raw material particle size distribution (PSD).Analytical results revealed that the bricks contained varying amounts of graphite and resin binder, indicating differences in their compositions and therefore comminution properties. The HVPP technique demonstrated its ability to liberate magnesia particles within the +1700 μm fraction, whereas conventional crushing predominantly formed composite particles (containing MgO and carbon) within this size range, with over 63% particles falling in this category. This finding suggests that MgO particles were not adequately liberated during the conventional crushing process, indicating the need for an additional comminution step to achieve the desired liberation.