High-power Pulses Research Articles

Improving energy storage performance of barium titanate-based ceramics by doping MnO2

MnO2 was used as a sintering additive to reduce sintering temperature of the 0.92(Ba0.94Li0.02La0.04)(Mg0.04Ti0.96)O3-0.08Bi(Zn1/2Ti1/2)O3 (0.92BLLMT-0.08BZT) ceramic thick film and promote sintering process. At the same time, MnO2 doping is beneficial for reducing dielectric loss and leakage current, and improving insulation performance, thus, breakdown field strength (BDS) of ceramics is increased. In addition, MnO2 doping introduces defect energy levels, and increases lattice distortion and polarization intensity, thereby changing the crystal structure and microstructure morphology, and improving energy storage density and thermal stability. The BDS reaches 650 kV/cm electric field with 0.5 mol% MnO2 doping, where the ceramic thick film achieves a discharge density (Wdis) of 5.51 J/cm3, ultra-high power density (PD = 443.87 MW/cm3) and current density (CD = 1365.74 A/cm2). The ceramic thick film exhibits good thermal stability with Wdis change rate of only 16.47 % within room temperature to 170 °C under 200 kV/cm. Such excellent comprehensive performance can be attributed to the decrease of grain size, defect concentration, and leakage current, and the formation of polar nano regions in the BT-based ceramics caused by MnO2 doping and cations substitution at A-site and B-site of the perovskite structure. This study provides valuable insights for the research of lead-free dielectric ceramic capacitors, and the 0.92BLLMT-0.08BZT-0.5 mol% Mn ceramic thick film presents good development prospect in high-power pulse energy storage system.

Distributed feedback broad area lasers with multiple epitaxially stacked active regions and tunnel junctions

Distributed feedback (DFB) broad area (BA) lasers with multiple epitaxially stacked active regions and tunnel junctions designed for emission around 900 nm are investigated. DFB BA lasers with a cavity length of 1 mm and different stripe widths are compared in terms of their electro-optical performance and beam quality. The laser with a 200 µm stripe width achieved a high optical pulse power of 100 W in 10 ns long pulses at an injection current of 63 A, resulting in a brightness of 81 MW/cm2sr. The optical spectrum of both lasers is centered at around 886 nm, exhibiting a narrow spectral bandwidth of 0.2 nm (64 pm/K).

Self-similar pulse compression in a tapered Pb-silicate photonic crystal fiber at 2 µm

We report a 2-µm all-fiber nonlinear pulse compressor based on a tapered Pb-silicate photonic crystal fiber (PCF), which is capable of achieving large compression with low pedestal energy. A tapered Pb-silicate photonic crystal fiber with increased nonlinear coefficients is proposed for achieving self-similar pulse compression (SSPC) at 2 µm. The dynamic evolution of the fundamental order soliton is numerically analyzed based on the designed tapered fiber. After pulse compression in a tapered fiber with a length of 2.2 m, an initial 1.76 ps pulse can be compressed to 88 fs, increasing the peak power from 4.4 to 86 W with a compression factor of 20 and a quality factor of 98%. The results reveal that exponential variation yields superior compression performance and provides a promising solution for generating high-power femtosecond pulses at 2 µm.

Threshold Characteristics of 1.56-to-2.84 μm SRS Conversion in Methane under Broadband Pumping by High-Power Frequency-Modulated Pulses of an Erbium Fiber Source

Threshold Characteristics of 1.56-to-2.84 μm SRS Conversion in Methane under Broadband Pumping by High-Power Frequency-Modulated Pulses of an Erbium Fiber Source

A Generator of Nanosecond High-Voltage Pulses Based on Shock-Ionized Dynistors

—A generator of high-power nanosecond pulses consisting of four stages that are switched on in a relay-race mode is described. Each stage contains a storage capacitor with an operating voltage of 8 kV and an assembly of series-connected shock-ionized dynistors. The possibility of switching current pulses with an amplitude of 800 А to a load of 30 Ω a rise time of 4 ns, and a repetition rate of 100 Hz is demonstrated. The prospects for increasing the output voltage and the output energy of the generator are determined.

Tightly coupled arrays with time-domain beam scan for the radiation of high-power ultrawideband electromagnetic pulses.

In this paper, a kind of tightly coupled array (TCA) with time-domain beam scan is developed for the radiation of high-power ultrawideband (UWB) electromagnetic pulses, and the peak-power pattern is proposed to characterize the directivity. First, the active voltage standing wave ratio (AVSWR) bandwidth of the TCA is optimized, which is the precondition for the beam scan. It indicates that the lower-cutoff frequency (LCF) is inversely proportional to the total length of the whole array; an increase in the distance between the array and the ground plane could remarkably reduce the LCF; and an increase in the element number can also decrease the LCF because of the increase in length, but more elements would make the center elements difficult to match in the low-frequency range, so there is a limitation on the number of elements for a certain LCF. Based on these results, a six-element linear array is designed. Then, the definition of the peak-power pattern is proposed to characterize the directivity of the UWB pulsed antenna. Finally, the optimized six-element array is developed, and the measured working band is 276 MHz-6.4GHz (AVSWR < 3). The effective potential gain is 1.76, and it improves by 51.7% with a reduction in the aperture area by 68.4% compared with the previous TCA, which means that the aperture efficiency is remarkably improved. The half-power beam width of the developed TCA with the scan angle of 0° is 45°. The time-domain beam scan could be performed with time-delay feeding lines, and the maximum scan angle is over ±30° in the E-plane. The developed TCA can be applied for the generation of high-power electromagnetic environments for the study of intentional electromagnetic interference.

Damage Properties of a Limiter-Protected LNA Caused by High-Power Microwave Pulses

Damage Properties of a Limiter-Protected LNA Caused by High-Power Microwave Pulses

Pulsed swept-source FDML-MOPA laser with kilowatt picosecond pulses around 1550 nm.

Swept-source lasers are versatile light sources for spectroscopy, imaging, and microscopy. Swept-source-powered multiphoton microscopy can achieve high-speed, inertia-free point scanning with MHz line-scan rates. The recently introduced spectro-temporal laser imaging by diffractive excitation (SLIDE) technique employs swept-source lasers to achieve kilohertz imaging rates by using a swept-source laser in combination with a diffraction grating for point scanning. Multiphoton microscopy at a longer wavelength, especially in the shortwave infrared (SWIR) region, can have advantages in deep tissue penetration or applications in light detection and ranging (LiDAR). Here we present a swept-source laser around 1550 nm providing high-speed wavelength agility and high peak power pulses for nonlinear excitation. The swept-source laser is a Fourier-domain mode-locked (FDML) laser operating at 326 kHz sweep rate. For high peak powers, the continuous wave (cw) output is pulse modulated to short picosecond pulses and amplified using erbium-doped fiber amplifiers (EDFAs) to peak powers of several kilowatts. This FDML-master oscillator power amplifier (FDML-MOPA) setup uses reliable, low-cost fiber components. As proof-of-principle measurement, we show third-harmonic generation (THG) using harmonic nanoparticles at the 10 MHz pulse excitation rate. This new, to the best of our knowledge, laser source provides unique performance parameters for applications in nonlinear microscopy, spectroscopy, and ranging.

High power pulse delivery over a short distance through an all-solid anti-resonant microstructured optical fiber at [formula omitted] wavelength

We propose an all-solid silica-based, large mode area (LMA) anti-resonant microstructured optical fiber through which optical pulses of high-power can be delivered at the near mid-infrared wavelength range. Anti-resonant guidance of light has been achieved in the silica-based microstructured geometry by embedding 15 high-index solid cylinders in a low-index background matrix that essentially creates a node-less negative curvature cladding region surrounding the low-index core. The fiber geometry has been optimized in such a way that a large mode area of ∼2000μm2 is achieved for the fundamental mode with a loss in the order of 0.04 dB/m at 2μm wavelength. Moreover, the higher-order modes are at least one order of magnitude lossy than the fundamental mode at the operating wavelength. The optimized fiber structure has exhibited that a pulse of peak power as high as 1 kW and width of 2.2 ps can be sustained without any alteration in shape and degradation of power when the pulse is delivered through the fundamental mode over the proposed fiber length of 25 m. Hence, this proposed unique silica-based all-solid anti-resonant fiber structure is suitable for short-distance delivery of high-power pulses at 2μm wavelength with effective single mode separation.

Comprehensive energy-storage performance enhancement in relaxor anti-ferroelectrics via strengthening local polarization

Lead-free dielectric capacitors with excellent energy-storage performance have gained much attention for their remarkable potential applications in pulsed power electronic systems and devices. However, the large recoverable energy-storage density Wrec is usually accompanied with low efficiency η, hindering their practical applications. Such performance deterioration occurs because the large polarization is generally linked with strong reversal hysteresis, making the synergetic optimization of energy-storage density and efficiency a great challenge. Here we develop a strategy of constructing strengthened local polarization in the lead-free relaxor anti-ferroelectric ceramics 0.9NaNbO3-0.1Bi(Ni2/3Nb1/3)O3 by carefully manipulating the microstructures, the ultrahigh Wrec ∼ 11.2 J/cm3 and large η ∼ 90.5 % have been simultaneously achieved. Moreover, superior charge/discharge performances (power density PD ∼ 548 WM/cm3, discharge speed t0.9 ∼ 27 ns) and outstanding temperature (up to 160 °C) and cycling (up to 106) stabilities are also ensured. The excellent overall properties are mainly attributed to the stabilized antiferroelectric phase, the strong relaxation characteristic, as well as the enhanced local polarization in the polar nano-regions (PNRs) caused by the introduction of Bi(Ni2/3Nb1/3)O3. This work not only provides a lead-free system with remarkable energy-storage performance that demonstrates great potential in the application field of high-power pulse electronic devices, but also proposes a convenient and efficient strategy to design new dielectric materials with excellent energy-storage performance.

Natural Disasters are Not All Natural

For a half century, the military has been developing technologies to turn climate and extreme environmental phenomena into weapons.&#x0D; This study is a literature review, which was conducted with the following objectives: 1/ to expose the known powerful military technologies of climate and environmental modification; 2/ to emphasize that many extreme environmental events observed in recent years coincide with the effects that these military technologies are able to generate; 3/ to analyze the conclusions of the Intergovernmental Panel on Climate Change (IPCC) on the origins of the increase in natural disasters.&#x0D; The literature used comes from official sources: peer-reviewed scientific articles (except one); patents; intergovernmental organizations; military documents; policy documents; university documents; national newspapers; news agencies; writings by respected scientists in their fields.&#x0D; Results of the literature review reveal that HAARP (High-frequency Active Auroral Research Program), the most powerful ionospheric heater in operation, is able to influence climate. High-power electromagnetic pulses in the earth's crust, produced by a mobile magneto-hydrodynamic generator, is a technique developed since the 1970s to trigger earthquakes. Directed energy weapons, a real technology, can ignite destructive fires at range. For several years, official documents report effects on health and the environment similar in all aspects to those that would be detected if solar geoengineering by stratospheric aerosol injection, a climate-altering technique, was used. Due to numerous biases and a lack of objectivity, the IPCC's arguments on the causes of the growth in extreme environmental phenomena (heat and cold waves, storms, hurricanes, tornadoes, droughts, floods, wildfires, air pollution, etc.) are flawed. The solar hypothesis isn't appropriate either, given its low activity for several years.&#x0D; In conclusion, the use of military climatic and environmental modification technologies appears to be the most relevant explanation to understand the increase in natural disasters over the last 20 years.

Formation and properties of spatially inhomogeneous plasma density gratings.

Volume plasma density gratings receive increasing interest since, compared to solid-state optical media, they posses significantly higher damage thresholds. The gratings are produced by counterpropagating laser pulses in underdense plasma. When analyzing their optical properties, usually they are assumed to be homogeneous in space. The latter assumption, however, breaks down, especially when the gratings are produced by short high-power laser pump pulses. Then, generically the plasma grating posses an inhomogeneous envelope which results from the superposition of the pump pulses envelopes. The present paper discusses the effect of grating inhomogeneity on reflection and transmission of probe pulses. A Gaussian plasma density grating becomes an apodized grating which offers significant improvement over homogeneous gratings due to side-lobe suppression while maintaining reflectivity and a narrow bandwidth. On the other hand, the reflected probe pulses receive a chirp which depends on the spatial scale. For a Gaussian grating a cubic spectral phase appears. Numerical particle-in-cell simulations are supported by theoretical analysis based on coupled mode equationsas well as an effective medium approach.

Improving energy storage performance of BLLMT ceramic by doping BZT combining with defect engineering and film scraping process

The (1-x)(Ba0.94Li0.02La0.04)(Mg0.04Ti0.96)O3-xBi(Zn1/2Ti1/2)O3 ((1-x)BLLMT-xBZT, x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) ceramic thick films were prepared by traditional solid-state sintering method combined with film scraping process. Li+ and La3+ ions doping at A-site, and Mg2+ and Zn2+ ions doping at B-site of the perovskite structure, and adding BZT component enhance charge compensation, enlarge polarization difference, increase breakdown strength, and enhance relaxation degree, leading to the improved pulse charging and discharging energy storage performance of the BaTiO3-based ceramic films. The 0.92BLLMT-0.08BZT ceramic film has high discharge energy density of 4.61 J/cm3, high pulse power density PD = 224.14 MW/cm3, high current density CD = 896.58 A/cm2, high discharge speed of 234 ns, and high pulse discharge density Wd = 4.61 J/cm3 under 500 kV/cm combined with high breakdown strength of 500 kV/cm, relating to charge compensation, multiple ferroelectric phases coexistence, and formation of polar nanoregions. The strategy by equivalent and heterovalent ions doping at A-site and B-site of the perovskite structure and introducing Bi-based component combined with film scraping process strengthens charge compensation, enhances relaxation characteristic, and reduces grain size, providing an efficient route to develop prospect BT-based dielectric ceramic capacitors for potential application in high-power pulse energy storage such as 0.92BLLMT-0.08BZT.

A Compact High Gain Pulse Power Generator Employed With Magnetic Pulse Compression and Push-Pull Charger for Applications in Dielectric Barrier Discharge

A Compact High Gain Pulse Power Generator Employed With Magnetic Pulse Compression and Push-Pull Charger for Applications in Dielectric Barrier Discharge

Dense plasma diagnostics with a Nomarski interferometer using a frequency-tripled Ti:sapphire laser

An overdense plasma is considered as a new tool for high-power laser pulse compression. For this purpose, a high density plasma was generated by illuminating an intense fs Ti:sapphire laser pulse onto a surface of an aluminum disk and its spatio-time-resolved dynamics was investigated by a Nomarski interferometer. To probe the laser-produced high density plasma, the original Ti:sapphire laser pulse with a wavelength of 800 nm was frequency-tripled and the UV laser pulse of 266 nm in wavelength was used in the interferometer. It turned out that the fs UV laser interferometer can provide a fairly high density information up to 8.5 × 1020 cm-3. Our experimental result shows that the initial high density plasma near the solid target surface expands rapidly and its density profile in space is gradually reduced to exponential in the ns time scale. This result will provide an important information towards the next step for experimental demonstration of the laser pulse compression using a plasma.

Boosting capacitive performance of lead-free relaxor ferroelectrics by introducing a linear dielectric

As an important core component used in high-power pulse electronic systems, dielectric ceramic capacitors have gained great interest because of their ultrahigh powder density (PD) and fast discharge speed (t0.9). However, inferior energy storage performance (ESP) greatly limits the development of energy storage devices with the requirement of miniaturization and integration. Herein, we propose a feasible approach to introduce linear dielectric CaTiO3 (CT) into (Bi0.5Na0.5)TiO3 (BNT) for the design of engineered relaxor ferroelectrics to tune ESP at the grain, domain, and macroscopic scales. The results demonstrate that introducing CT generates enhanced relaxor behavior with highly dynamic polar nanoregions, refines grain size, and suppresses dielectric loss, synergistically yielding increased breakdown strength, negligible remnant polarization, and a nearly linear polarization hysteresis loop. Consequently, superior ESP is achieved in BNT-0.3CT relaxor ferroelectric ceramics with a large energy density (∼5.65 J/cm3) and a high efficiency (∼88.1 %). Based on CT-induced merits, the excellent temperature/frequency/cycling stabilities and remarkable charge-discharge properties featuring a high PD of 200.4 MW/cm3, high discharge energy density of 2.27 J/cm3 and ultrashort t0.9 of 58 ns of the designed ceramics broaden the actual application prospects. This work demonstrates that introducing linear dielectric CT holds great promise for developing high-performance energy storage dielectrics.

Hybrid energy storage power allocation strategy based on parameter-optimized VMD algorithm for marine micro gas turbine power system

The power system onboard ships is typically a low-inertia, small-capacity isolated grid that is highly susceptible to system disturbances and instability, especially when connected to high power pulse loads. To mitigate power fluctuations and ensure stable operation, a hybrid energy storage system (HESS), which comprises the battery system and flywheel energy storage devices, has emerged as a promising solution. This paper explores the control strategy and coordinated operation of marine gas turbine power generation systems operating under pulse load conditions and presents a novel hybrid energy storage power allocation strategy based on variational mode decomposition (VMD). Specifically, we propose to implement parameter optimization of VMD using an artificial hummingbird algorithm (AHA), which enables effective primary allocation of hybrid energy storage power. To achieve secondary power allocation, we design two fuzzy controllers to optimize the state of charge (SOC) of battery system and speed of flywheel device. To evaluate the feasibility and effectiveness of the proposed control strategy, we establish a theoretical model of a shipboard micro gas turbine (MGT) direct current (DC) power system, which includes an MGT, generator, HESS, and pulse power load. Our simulation results demonstrate that the artificial hummingbird algorithm outperforms the particle swarm algorithm concerning search speed and calculation accuracy for parameter optimization of variational mode decomposition. Moreover, the proposed parameter-optimized VMD method can adaptively decompose pulse load power fluctuations and achieve optimal allocation of the flywheel and battery power in the HESS. Finally, the parallel fuzzy controller design effectively optimizes the operation ranges of the flywheel device and battery system, prevents over-charging and over-discharging of energy storage equipment, ensures that the SOC of energy storage equipment remains within a fixed interval, and reduces frequent and high-power charging and discharging of batteries.

High Power Electromagnetic Pulse Damage Effect of a Low Noise Amplifier

Low noise amplifier (LNA) is the most sensitive component in the front end of a wireless communication system, which is very vulnerable to coupling attack of high-power electromagnetic pulse (HPEMP). This paper first analyzes the damage mechanism of a high-power electromagnetic pulse to a low noise amplifier, then designs the damage experiment of high-power electromagnetic pulse injection to the low noise amplifier, and verifies the damage mechanism and damage threshold of a certain radar low noise amplifier. The experimental results show that the LNA is not affected by the linear effect of high-power electromagnetic pulse. When the high-power electromagnetic pulse exceeds the damage threshold, thermal melting occurs between the FET grid sources in the device, causing permanent damage to the LNA and performance failure. This conclusion can provide data support for the high-power electromagnetic pulse protection design of this type of LNA.

Magneto-optical measurement of magnetic field and electrical current on a short pulse high energy pulsed power accelerator

We describe a direct magneto-optical approach to measuring the magnetic field driven by a narrow pulse width (&amp;lt;10 ns), 20 kA electrical current flow in the transmission line of a high energy pulsed power accelerator. The magnetic field and electrical current are among the most important operating parameters in a pulsed power accelerator and are critical to understanding the properties of the radiation output. However, accurately measuring these fields and electrical currents using conventional pulsed power diagnostics is difficult due to the strength of ionizing radiation and electromagnetic interference. Our approach uses a fiber coupled laser beam with a rare earth element sensing crystal sensor that is highly resistant to electromagnetic interference and does not require external calibration. Here, we focus on device theory, operating parameters, results from an experiment on a high energy pulsed power accelerator, and comparison to a conventional electrical current shunt sensor.

Laser Diodes (850 nm) Based on an Asymmetric AlGaAs/GaAs Heterostructure with a Bulk Active Region for Generating High-Power Subnanosecond Optical Pulses

Laser Diodes (850 nm) Based on an Asymmetric AlGaAs/GaAs Heterostructure with a Bulk Active Region for Generating High-Power Subnanosecond Optical Pulses