Voltage Pulse Research Articles

An 8 mm endoscopic histotripsy array with integrated high-resolution ultrasound imaging

An 8 mm diameter, image-guided, annular array histotripsy transducer was fabricated and characterized. The array was laser etched on a 5 MHz, 1–3 dice and fill, PZT-5H/epoxy composite with a 45 % volume fraction. Flexible PCBs were used to electrically connect to the array elements using wirebonds. The array was backed with a low acoustic impedance epoxy mixture. A 3.6 by 3.8 mm, 64-element, 30 MHz phased array imaging probe was positioned in the center hole, to co-align the imaging plane with the bubble cloud produced by the therapy array. A custom 16-channel high voltage pulse generator was used to test the annular array for focal lengths ranging from 3- to 8-mm. An aluminum lens-focussed transducer with a 7 mm focal length was fabricated using the same piezocomposite and backing material and tested along with the histotripsy array. Simulated results from COMSOL FEM models were compared to measured results for low voltage characterization of the array and lens-focussed transducer. The measured transmit sensitivity of the array ranged from 0.113 to 0.167 MPa/V, while the lens-focussed transducer was 0.192 MPa/V. Simulated values were 0.160 to 0.174 MPa/V and 0.169 MPa/V, respectively. The measured acoustic fields showed a significantly increased depth-of-field compared the lens-focussed transducer, while the beamwidths of the array focus were comparable to the lens. The measured cavitation voltage in water was between 254 V and 498 V depending on the focal length, and 336 V for the lens-focussed transducer. The array had a lower cavitation voltage than the lens-focussed transducer for a comparable operating depth. The histotripsy array was tested in a tissue phantom and an in vivo rat brain. It was used to produce an elongated lesion in the brain by electronically steering the focal length from 3- to 8-mm axially. Real time ultrasound imaging with a Doppler overlay was used to target the tissue and monitor ablation progress, and histology confirmed the targeted tissue was fully homogenized.

Ultra-fast switching memristors based on two-dimensional materials

The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.

Si/SiGe QuBus for single electron information-processing devices with memory and micron-scale connectivity function

The connectivity within single carrier information-processing devices requires transport and storage of single charge quanta. Single electrons have been adiabatically transported while confined to a moving quantum dot in short, all-electrical Si/SiGe shuttle device, called quantum bus (QuBus). Here we show a QuBus spanning a length of 10 μm and operated by only six simply-tunable voltage pulses. We introduce a characterization method, called shuttle-tomography, to benchmark the potential imperfections and local shuttle-fidelity of the QuBus. The fidelity of the single-electron shuttle across the full device and back (a total distance of 19 μm) is (99.7 ± 0.3) %. Using the QuBus, we position and detect up to 34 electrons and initialize a register of 34 quantum dots with arbitrarily chosen patterns of zero and single-electrons. The simple operation signals, compatibility with industry fabrication and low spin-environment-interaction in 28Si/SiGe, promises long-range spin-conserving transport of spin qubits for quantum connectivity in quantum computing architectures.

ANALYSIS OF THE MAGAMP POWER CONVERTER STABILITY TAKING INTO ACCOUNT OF THE INTERVAL UNCERTAINTY OF THE MAGAMP CORES PARAMETERS

To ensure the functioning of radio electronic equipment (RAE), semiconductor power converters (NPEs) are used, which perform the functions of converting and adjusting the parameters of electrical energy. The modern consumer needs NPEs with a rigid set of operational characteristics - ensuring functional parameters in a wide range of changes in all disturbing factors. The existing principles of NPE construction do not always allow such a set of characteristics to be realized. The article analyzes the stability of the pulse voltage stabilizer based on high-frequency magnetic amplifiers, taking into account the technological spread of their core parameters. The circuit of the voltage stabilizer is presented, its operation is described, the principle of operation of the high-frequency magnetic amplifier is disclosed, and its transfer function in the frequency domain is found. The study is based on the use of interval analysis theory. The conducted analysis of the stability of the NPE, taking into account the interval uncertainty of the parameters of the cores of high-frequency magnetic amplifiers, confirmed their performance both with technological dispersion of the parameters of the cores and with a wide range of changes in all disturbing factors, including the parallel operation of voltage stabilizers on a common load.

Power Scavenging Microsystem for Smart Contact Lenses.

On-the-eye microsystems such as smart contacts for vision correction, health monitoring, drug delivery, and displaying information represent a new emerging class of low-profile (≤ 1mm) wireless microsystems that conform to the curvature of the eyeball surface. The implementation of suitable low-profile power sources for eye-based microsystems on curved substrates is a major technical challenge addressed in this paper. The fabrication and characterization of a hybrid energy generation unit composed of a flexible silicon solar cell and eye-blinking activated Mg-O2 metal-air harvester capable of sustainably supplying electrical power to smart ocular devices are reported. The encapsulated photovoltaic device provides a DC output with a power density of 42.4 µW cm-2 and 2.5mW cm-2 under indoor and outdoor lighting conditions, respectively. The eye-blinking activated Mg-air harvester delivers pulsed power output with a maximum power density of 1.3mW cm-2. A power management circuit with an integrated 11 mF supercapacitor is used to convert the harvesters' pulsed voltages to DC, boost up the voltages, and continuously deliver ≈150 µW at a stable 3.3V DC output. Uniquely, in contrast to wireless power transfer, the power pack continuously generates electric power and does not require any type of external accessories for operation.

High-Performance Memristive Synapse Composed of Ferroelectric ZnVO-Based Schottky Junction.

In pursuit of realizing neuromorphic computing devices, we demonstrated the high-performance synaptic functions on the top-to-bottom Au/ZnVO/Pt two-terminal ferroelectric Schottky junction (FSJ) device architecture. The active layer of ZnVO exhibited the ferroelectric characteristics because of the broken lattice-translational symmetry, arising from the incorporation of smaller V5+ ions into smaller Zn2+ host lattice sites. The fabricated FSJ devices displayed an asymmetric hysteresis behavior attributed to the ferroelectric polarization-dependent Schottky field-emission rate difference in between positive and negative bias voltage regions. Additionally, it was observed that the magnitude of the on-state current could be systematically controlled by changing either the amplitude or the width of the applied voltage pulses. Owing to these voltage pulse-tunable multi-state memory characteristics, the device revealed diverse synaptic functions such as short-term memory, dynamic range-tunable long-term memory, and versatile rules in spike time-dependent synaptic plasticity. For the pattern-recognition simulation, furthermore, more than 95% accuracy was recorded when using the optimized experimental device parameters. These findings suggest the ZnVO-based FSJ device holds significant promise for application in next-generation brain-inspired neuromorphic computing systems.

Design and fabrication of a coupled high-Q photonic nanocavity system with large coupling coefficients.

In a previous work, we demonstrated a coupled cavity system where photons in one storage cavity can be transferred to another storage cavity at an arbitrary time by applying a voltage pulse to a third cavity placed in a p-i-n junction. In this work, we demonstrate methods to improve the transfer efficiency and photon lifetimes of such a coupled system. Firstly, we designed a photonic-crystal structure that achieves a large coupling coefficient without reducing the radiation quality factor compared to the previously proposed structure: The photonic-crystal design was changed to a more symmetric configuration to suppress radiation losses and then optimized using an automatic structure tuning method based on the Covariance Matrix Adaptive Evolutional Strategy (CMAES). Here we added two improvements to achieve an evolution toward the desired direction in the two-dimensional target parameter space (spanned by the coupling coefficient and the inverse radiation loss). Secondly, to improve the experimental cavity quality factors, we developed a fabrication process that reduces the surface contamination associated with the fabrication of the p-i-n junction: We covered the photonic structure with a SiO2 mask to avoid the contamination and the electrode material was changed from Al to Au/Cr to enable cleaning by a weak acid. Owing to these improvements of the cavity design and the fabrication process, the obtained system provides coupling strengths that are about three times stronger and photon lifetimes that are about two times longer, compared to the previously reported system.

Electrically‐Reconfigurable Extremely‐High Density Physical Unclonable Cryptographic Keys Based on Aurivillius Ferroelectrics

AbstractIn the era of information, emerging hardware security primitives, i.e., hardware random number generators and physically unclonable functions, hold profound promise for the establishment of exceptionally secure network information systems. Nonetheless, these potential solutions are constrained by inherent drawbacks, including the need for additional error correction circuits or algorithms, heightened susceptibility to environmental interference, and limited data density. This paper demonstrates the extremely high‐density, physical‐unclonable cryptographic keys by harnessing stochastically ferroelectric domain polarizations in Aurivillius ferroelectric material CaBi2Nb2O9 (CBNO). Ferroelectric polarization of CBNO nanodomains can serve as a robust source of physical unclonable entropy. Through the application of high‐speed voltage pulses, the inherent randomness of ferroelectric polarizations can be enhanced, thereby yielding cryptographic keys characterized by remarkable uniformity, uniqueness, and negligible environmental sensitivity. More importantly, the voltage pulse operations facilitate the configurability of the ferroelectric cryptographic keys with no correlation. An unprecedented data density of 435 Gbit µm−2 is therefore achievable with a miniaturized CBNO of less than 1 um2. Notably, the reconfigured keys successfully pass the National Institute of Standards and Technology random number tests without requiring additional post‐processing steps. Emanating from the inherent attributes of the material, these high‐density ferroelectric keys confer intrinsic advantages to information security, evincing substantial resistance to duplication or cloning.

Switching Converters Dynamics Considering Non-Ideality of the Error Amplifier within the Analogue Control System

The paper discusses a pulse voltage converter with a high switching frequency of a switch with an analog control system capable of providing the required conversion frequencies. The pulsed voltage converter under study has a control system with a proportional-integral regulator, implemented on the basis of a general-purpose operational amplifier. Operational amplifiers with such parameters are widely used as part of modern control microcircuits for pulse-width converters. In this work, the influence of the technological spread of the gain of the operational amplifier on the dynamics of the converter is studied. The studies were carried out both using the developed nonlinear dynamic model of the system, and using a small-signal open-loop dynamic model. A technique has been developed for selecting the parameters of the controller, taking into account the technological spread of the gain of the operational amplifier based on a nonlinear dynamic model. An analysis of the results obtained using a nonlinear dynamic model showed a significant influence of the specified spread on the dynamics of the system, even when the cutoff frequency of the open-loop control system is significantly removed from the frequency of the high-frequency pole of the operational amplifier. This must be taken into account when designing pulse voltage converters with analog control systems, namely, when choosing the parameters of regulators. It is shown that with the optimal values of the controller, selected according to the proposed method, the effect of technological gain spread on the frequency characteristics of an open circuit in the low-mid frequency regions is minimal, which indicates the effectiveness of the method.

Autonomous Light Intensity Adaptation in an Energy‐Efficient Retinomorphic Organic Ferroelectric Neuristor

Autonomous Light Intensity Adaptation in an Energy‐Efficient Retinomorphic Organic Ferroelectric Neuristor

Research on the surface characteristics of 42CrMo alloy steel pulse electrochemical machining

Electrochemical processing, due to its unique material removal mechanism compared to mechanical processing, often results in significantly different micro-morphologies. It is widely used in areas such as aerospace component processing, surface finishing, passivation, micro-structure mold processing, etc. The complexity of alloy steel composition makes uniform etching difficult to achieve, and the post-etch micro-morphology is also complex, making it challenging to describe and analyze. Therefore, it is difficult to analyze the surface morphology of electrochemical etching under different parameters. In this study, a self-developed electrochemical etching device with adjustable DC voltage, pulse width voltage, and pulse width positive and negative voltage output was used. Different parameters of pulse voltage were used to etch the surface of 42CrMo alloy steel. Due to the strong relationship between surface roughness parameters and the chosen measurement scale, as well as the surface morphology and waviness errors introduced by specimen preparation and etching processes, a wavelet filtering method was used to remove the low frequency components in the surface morphology, and only the surface roughness part was retained for fractal parameter calculation and analysis. The research showed that fractal analysis can also be applied to analyze the surface morphology after electrochemical etching. Pulse voltages with characteristic voltages, characteristic pulse frequencies, and duty ratios can achieve better surface quality during positive pulse etching. Positive and negative pulse etching can obtain better surface morphology than positive pulse etching, but the etching amount is lower, making it suitable for precision finishing.

Universal Continuous Model of Active Power Factor Correctors

The purpose of the work is to develop continuous mathematical models of power factor correctors for switch-mode power supplies. The models are designed to solve optimization problems aimed at increasing the energy efficiency of these devices. This goal was achieved by developing a universal continuous averaged model of switch-mode voltage converters, which are an integral part of any active power factor corrector. State-space averaging method was proposed for constructing such a universal model. It has been shown that such a model adequately reproduces the processes in any of the main types of DC-DC voltage converters. The possibility of constructing a mathematical model of an active power factor corrector based on the proposed universal model of a DC-DC voltage converter is substantiated. The features of the structures of active power factor correctors for switching power supplies are considered and the problems that arise when studying their energy efficiency are shown. By simulation in the time domain with using the constructed model, diagrams of transients of the power factor corrector during load and primary network voltage disturbances are obtained. The most important result is the creation of a universal continuous mathematical model of switching voltage regulators. This model, unlike previously proposed models, is suitable for use in the analysis, modeling and design of any power factor correctors without the need to modify it in each specific case. The significance of the results obtained lies in accelerating the design process of active power factor correctors built on the basis of any type of pulsed DC-DC voltage converters. The developed model is intended for use in the Micro-Cap electronic circuit analysis program. However, since it is ultimately a software module in the SPICE language, this model can be used in many circuit analysis programs that support this language.

Experimental study of liquid aluminum droplet breakup characteristics based on a Drop-on-demand (DOD) magnetohydrodynamic actuation

In magnetohydrodynamic (MHD) drop-on-demand (DOD) actuation, Lorentz force generated in different excitation stages are exerted on the liquid metal jet to form a "push-pull" mechanism, which is crucial for generating accurate and repeatable metal droplets. In this study, the important parameters of the excitation current waveform in the magnetohydrodynamic (MHD) process, including the influence of the excitation voltage pulse width ratio and current amplitude on the velocity, energy, volume, and breakup length of aluminum droplets are studied. The conversion process of surface energy and kinetic energy during the formation and fall stage of liquid droplets is analyzed. The results show that the negative and positive excitation voltage pulse width ratio of the MHD pump has a significant effect on the droplet velocity, breakup time, size, and sphericity. The amplitude of the excitation current and Hartmann number has a significant impact on the generation of stable droplets. The results show that the single droplet ejection state can be achieved within the Ha number between 319.5 and 391.1. As the Ha number increases, the volume, length, kinetic energy and surface energy of the droplets at breakup time also increase. The size of droplets can be adjusted by changing the amplitude of excitation waveform.

Challenges in Measurement of Low-Value ESL and ESR of High-Performance PFN Capacitors for Klystron Modulator

In the high voltage line type pulse modulators, Pulse Forming Network (PFN) capacitors are one of the important components. These capacitors operate at peak kilo ampere current range and at repetition rate in the range of a few hundred hertz. The performance of these capacitors is critical w.r.t. overall system performance, and they are required to operate at high power density and low losses with high reliability. The Equivalent Series Inductance (ESL) and Equivalent Series Resistance (ESR) are two critical parameters that affect the performance of these capacitors. PFN modulator demands a capacitor of very low ESL and ESR for reliable operation and generation of high-voltage pulses. Higher ESR value adversely affects the performance of the capacitor by raising its temperature and thus deteriorating its life. ESL value does not directly affect life, but it affects the quality of high voltage pulse. In RRCAT, the PFN capacitors purchased from Indian manufacturers were showing high-temperature rise and failures. Therefore, new capacitors were designed to have lower ESL and ESR values. Measurement of ESL and ESR is important to evaluate the performance of the capacitors. The low value of these parameters makes their measurement a challenging task and requires special techniques. For low values of ESL and ESR (less than 100 mΩ) measurement, a differential measurement technique was used in which modification and different layouts were explored to improve the repetitive accuracy of the measurements. The differential ESR and ESL measurement techniques with more emphasis on the low-value ESR measurement will be discussed in the paper.

A two-stage insulation method for suppressing thermal crosstalk in microarray sensitive units

Thermal crosstalk between array structures is a key factor in limiting the sensitivity of micro-nano array sensors. We propose a two-stage thermally isolated structure with thermal holes and heat dissipation layer and pulsed voltage heating to reduce thermal crosstalk. Through finite element thermal simulation analysis as well as thermal interference test, the results show that the thermal crosstalk of the two-stage structure is reduced by 12.89% and 39.67%, respectively, in the steady state compared to the structure with no thermal isolation, and pulsed voltage heating leads to the thermal crosstalk of the two-stage structure to be <10%.

Numerical simulation of streamer, pressure wave, and vortex induced by nanosecond pulsed surface dielectric barrier discharges

In this study, a two-dimensional fluid model is employed to simulate the streamer, pressure wave, and vortex in surface dielectric barrier discharge driven by nanosecond pulse voltage (ns-SDBD). It comprises a numerical model with two interconnected modules: discharge dynamics and gas flow dynamics. These modules are coupled through the physical variables including ‘EHD force’, ‘thermal source’, ‘velocity field’, ‘gas temperature’, and ‘gas pressure’. Our research primarily focuses on the underlying physical mechanisms of pressure waves and vortices for plasma-based flow control. The generation of pressure waves is attributed to the rapid gas heating by pulsed discharge, whereas the formation and development of the vortex are related to the ionic wind (EHD effect) provided by the plasma. To thoroughly understand and optimize flow control performance, an investigation into the effects of various discharge parameters, such as voltage amplitude and polarity, is conducted. Additionally, several SDBD modules are arranged in series, each featuring a dual three-electrode configuration. Subsequently, the dynamic behaviors of multiple streamers, pressure waves, and vortices, along with their interactions, are explored.

Deicing and status characteristics of dual-side pulsed surface dielectric barrier discharge

The deicing process and its status characteristics of dual-side pulsed surface dielectric barrier discharge (SDBD) are studied via electro-optical diagnostics, thermal properties, and numerical simulation. Experimental results show that the dual-side pulsed SDBD can remove the glaze ice compared to the traditional pulsed SDBD under the applied pulse voltage of 8 kV and a pulse frequency of 1 kHz. The maximal temperature of dual-side pulsed SDBD reaches 39.5 °C under the discharge time of 800 s, while the maximal temperature of traditional pulsed SDBD is still below ice point about −7.8 °C. Surface temperatures of dual-side pulsed SDBD demonstrate that the SDBD with a gap of 1 mm possesses prospects in deicing. The maximal surface temperature reaches 37.1 °C under the pulse of 8 kV after the discharge time of 90 s. Focusing on the thermal effect, a two-dimensional plasma fluid model is implemented, and the results also indicate that the dual-side pulsed SDBD with a gap of 1 mm produces a highest heat density among the three different configurations. Comparing the spatial-temporal evolutions of plasma on both dielectric sides, primary positive streamer has a longer propagation length of 8.6 mm than the secondary negative streamer, the primary negative streamer, and the secondary positive streamer, which induces a long heat covered area. Four stages of deicing process are analyzed through a series of electrical parameters under different covered ice conditions.

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%.

Design and Simulation of Reliability Test System of a Charging Generator

The DC voltage pulsation factor of twelve-phase rectification is much smaller than that of three- and six-phase rectification. Twelve-phase rectifier charging generators are often used where a high quality DC power supply is required. The probability of failure of charging generator is gradually increasing due to its complex structure and function. The reliability test of charging generator can provide a scientific basis for the operation condition, maintenance and determination of the repair cycle of this type of motor. The article combines the basic theory of reliability test, analyses the charging generator constant stress accelerated reliability test scheme, designs the energy feedback test drag system with the generator output as the power source of DC motor, and carries out the dynamic performance simulation and analysis of the reliability test system based on PSCAD/EMTDC. The simulation results show that the energy feedback reliability test system has fast response and good stability.

Strategy to improve synaptic behavior of ion-actuated synaptic transistors—the use of ion blocking layer to improve state retention

Synaptic transistors (STs) with a gate/electrolyte/channel stack, where mobile ions are electrically driven across the solid electrolyte, have been considered as analog weight elements for neuromorphic computing. The current (ID) between the source and drain in the ST is analogously updated by gate voltage (VG) pulses, enabling high pattern recognition accuracy in neuromorphic systems; however, the governing physical mechanisms of the ST are not fully understood yet. Our previous physics-based simulation study showed that ion movement in the electrolyte, rather than the electrochemical reactions that occur in the channel, plays an important role in switching. In this study, we experimentally explore the properties of the HfOx electrolyte and show that by tuning the density of oxygen vacancies, it can assume the dual role of electrolyte and channel. We demonstrate analog synaptic behavior using a novel ST with a two-layer stack of CuOx/HfOx, where the CuOx is the gate and Cu ion reservoir, and the HfOx is the electrolyte and channel. To improve state retention and linearity, we introduce a Cu ion transport barrier in the form of a dense and stoichiometric Al2O3 layer. The CuOx/Al2O3/HfOx exhibits excellent state retention and improved potentiation and depression response. Energy dispersive spectroscopy mapping following potentiation confirms the role of the Al2O3 layer in confining the Cu ions in the HfOx layer. We also show that a two-step programming scheme can further enhance synaptic response and demonstrate high recognition accuracy on the Fashion-MNIST dataset in simulation.