Ns Duration Research Articles

Molecular study on the growth mechanism of CO2-H2 binary hydrate promoted by electric field

The storage and transportation of hydrogen (H2) are widely recognized as the main challenge of hydrogen utilization technology. The hydrate-based method is one of the safe and environmentally friendly hydrogen storage methods. However, the harsh generation conditions and slow growth rate of H2 hydrate hinder its industrial application. Therefore, exploring methods to reduce the reaction conditions of H2 hydrate and improve growth efficiency is worth further research. This study investigated the effect of different intensities of electrostatic fields (0–0.9 V/nm) on the growth of CO2-H2 binary hydrates through molecular dynamics (MD) simulation. Representative parameters such as growth configuration, number of cages, dipole moment, four body angular order parameters, mean square displacement, occupancy rate, etc. were analyzed. The T, P conditions used for the simulation were 255 K, 80 MPa, and 400 ns in duration. The results suggest that a certain range of electric field strength can increase the growth rate of CO2-H2 binary hydrates and reduce the conditions required for hydrogen hydrate formation. The growth-promoting effect of the electric field is primarily manifested in the increased growth rate of binary hydrates. Detailed analysis reveals that electric field of a certain strength can to some extent promote the multiple occupancy of H2 within cage structures, thereby enhancing the hydrate's ability to capture H2. These molecular insights are beneficial for the application of electrostatic field in hydrate-based technologies to improving the storage efficiency of H2 hydrate and the reuse of CO2.

Analysing the temporal amplitude and average output power distribution in the mode-locked regions of an erbium-doped figure-eight fibre laser (theoretical and experimental results)

The noise like pulses (NLPs) are ultrashort light pulses that present very complex dynamics, they are a particular case of the multiple light pulses generated by the partial mode-locked regime. These ultrashort light pulses exhibit very complex behaviour in amplitude and width, in the temporal domain and subsequently in the frequency domain. In this paper we present a theoretical and experimental analysis of temporal amplitude distribution of NLPs within the mode-locked regions of an erbium-doped figure-eight Fibber laser. The mode-locked regions were studied at different settings of the four polarization controllers (HWR1, QWR1) in the ring section and in the nonlinear optical loop mirror (HWR2, QWR2, NOLM) of the fibre laser cavity. We found a wide variety of values of the temporal amplitude of NLPs. The experimental results of the temporal amplitude are compared with simulations generated with the theoretical model based on the theory of polarization of light and the theoretical model of the NOLM. Also, we discovered experimentally that the theoretical model performs well in predicting the complex dynamics of the temporal distribution of amplitude. Finally, we experimentally discovered that the average power output distribution of the cavity has a behaviour which is close to proportional to the temporal amplitude distribution. We analyse NLPs with a carrier wavelength of 1562 nm with typical duration of ns and a repetition rate of 0.9 MHz.

Domain wall motion at low current density in a synthetic antiferromagnet nanowire

The current-driven motion of magnetic domain walls (DWs) is the working principle of magnetic racetrack memories. In this type of spintronic technology, high current densities are used to propel DW motion in magnetic nanowires, causing significant wire heating that corresponds to wasted energy. Synthetic antiferromagnets are known to show very fast DW motion at high current densities, but lower current densities around onset of motion have received less attention. Here we use scanning transmission x-ray microscopy to study the response of DWs in a SAF multilayer to short current pulses. We observe that the DWs depin at A m−2 and move more quickly in response to 5 ns duration current pulses than in comparable multilayers that lack antiferromagnetic coupling. The results suggest that DWs in SAF structures are superior to conventional Néel DWs for low energy consumption racetrack technologies.

Generation of super high frequencies by graphene on piezoelectric buffer layer upon applied nanosecond electrical pulse

An unforeseen phenomenon occurred when measuring the current–voltage (I–U) characteristics of graphene samples in the pulsed regime. The graphene monolayer of the samples was grown by chemical vapor deposition and transferred onto 50 nm buffer HfO2 and AlO3 layers. Bilayer graphene was obtained from epitaxial graphene grown on SiC and was transferred onto 100 nm SiO2. The distance between contacts varied from 5 to 25 µm. The measurements were performed employing cables of 50 Ω impedance to transmit the pulses and a 0–12 GHz bandwidth sampling scope was used to register them. The transmitted registered pulses through graphene/HfO2 and graphene/SiO2 samples were superposed with super high frequency (SHF) oscillations. The wave packet oscillations of about 2 ns in duration appeared on the pulses passed through graphene/HfO2. On the passed-through graphene/SiO2 pulses, the appearing wave packet turns into continuous generation along the pulse length. Spectral decomposition reveals that the base frequency of the oscillations is about 10 GHz; however, bisected frequencies are also present in the spectra. Preliminary analysis of the SHF oscillations occurrence shows that the wave packets appear as an inverse piezoelectric response to a rapidly rising voltage of the pulses. It is proposed that due to acoustic–electronic interaction, the oscillating wave packet in graphene/SiO2 turns into the continued generation, which consumes three-quarters of the pulse energy. These results show that the coupling between graphene and the piezoelectric buffer layer combined with acoustic–electronic interaction brings forth novel effects that are in demand for practical applications.

Generation of Joule-level green bursts of nanosecond pulses from a DPSSL amplifier.

A new approach to generation of a burst of high-energy green pulses by placing a high-energy multi-slab Yb:YAG DPSSL amplifier and SHG crystal inside a regenerative cavity is presented. In a proof-of-concept test, stable generation of a burst of six green (515 nm) pulses, each 10 ns in duration and separated by 29.4 ns (34 MHz), with 2.0 J total energy has been demonstrated at 1 Hz from a non-optimized ring cavity design. A maximum individual green pulse energy of 580 mJ was produced from a 1.78 J circulating infrared (1030 nm) pulse (average fluence 0.9 J/cm2), corresponding to a SHG conversion efficiency of 32%. Experimental results have been compared with predicted performance from a simple model. Efficient generation of a burst of high energy green pulses offers an attractive pump source for Ti:Sa amplifiers, providing the potential to reduce the impact of amplified stimulated emission by reducing instantaneous transverse gain.

Determination of hot-electron drift velocity in (Be)ZnMgO/ZnO 2DEG channels

Recent experimental study of electron transport in ZnO/ZnMgO and BeZnMgO/ZnO heterostructures containing two-dimensional electron gas (2DEG) channels of two polarities is reported where electrons are accelerated and become hot by a pulsed electric field. The measurements with electrical pulses ranging from 2 ns to 10 ns in duration ensure the control of self-heating effect. Electron transport in the ZnO 2DEG channels located in ZnO layers at the ZnMgO or BeZnMgO barrier or in ZnO 3DEG channels is treated mainly in terms of drift velocity. The highest values of 1.3 × 107 cm/s at 360 kV/cm, 2.0 × 107 cm/s at 270 kV/cm, and 2.5 × 107 cm/s and 320 kV/cm, respectively, are attained and explained by emphasizing the effect of hot phonons.

Gold Nanoparticles Ablated in Ethanol: Topographical and Morphological Properties for Refractive Index Sensors

The impact of wavelength of the laser on several Topographical and Morphological characteristics of gold nanoparticles (Au NPs) was ablated utilizing pulsed laser ablation in liquid in this work. We employed a gold target with an extra purity to ablate the Nano-particles and a removal of tattoo Nd:YAG Q switching pulsed laser with a 10 Ns duration of pulses, the energy are 1000 mJ, the number of pulses are 600 pulses, and a frequency of 3 Hz to explore the gold NPs' characteristics using TEM and AFM. According to the greatest intensity of shorter wavelengths.

All-optical dynamic modulation of spontaneous emission rate in hybrid optomechanical emitter-cavity systems

Optomechanics is the study of the interaction between nano-objects and light fields through radiation pressure. Recent sophisticated optomechanical systems consist of strongly coupled mechanical and optical resonators and are made using semiconductor nanofabrication techniques. Although the optomechanical systems have exhibited their powerful capability of controlling photons, they are scarcely used to control the solid-state artificial atoms that emit photons. The main reason is that an efficient coupling mechanism remains unexplored. Here, we hybridize a silicon-integrated optomechanical resonator with two-level atom-like emitters to demonstrate an optomechanical cavity quantum electrodynamic (cQED) effect. With this system and the effect, we realize the dynamic modulation of the spontaneous emission rate. We choose copper dopants in silicon as the emitters for its narrow linewidth (0.3 nm) and long lifetime ( ∼ 30 n s ). Our judiciously designed coupled-nanobeam optomechanical resonator achieves a strong Purcell effect and high cavity-modulation performances. The optical cavity of the optomechanical resonator is dynamically coupled to the emission line and, as a result, on-demand sharp pulses (up to 9.5-fold intensity enhancement and 3.5 ns in duration, which is one ninth of the emission lifetime) appear along the photoluminescence decay. These experimental results are exactly explained with an analytical model that combines optomechanical and cQED theories. Considering that dopants in silicon are highly competitive qubits, we believe that our optomechanical cQED technology will find important applications in the quantum era.

Multiframe point-projection radiography imaging based on hybrid X-pinch.

This paper demonstrates the possibility of using a new configuration of the hybrid X-pinch to produce a set of spatially and temporarily separate x-ray bursts that could be used for the radiography of dynamic events. To achieve this, a longer than normal wire is placed between the conical electrodes of the hybrid X-pinch, and a set of small spacers (fishing weights) is placed along the wire. Each subsection of the wire then acts as a unique X-pinch, producing its own radiation burst from a small (∼3 µm) spot. The timing between bursts is 20-50ns, and each is <2ns in duration. For comparison, if a longer wire is simply employed without spacers, hotspots of radiation occur in random positions and the time between any two bursts does not exceed 20ns. Examples of two and three frame point-projection radiography of solid-state and plasma test objects are given.

Agility of Spin Hall Nano-Oscillators

Spin Hall nano-oscillators can generate radio-frequency output from direct-current input, and being planar structures with well defined geometry leaves them suitable for integration into microwave technologies. Control over output amplitude and frequency can be achieved by tuning magnetic field and direct current, but little is known about how these oscillators respond to input that changes rapidly, on the nanosecond time scale. This study shows that input current pulses just a few ns in duration are sufficient to generate rf output. Also, pulsing current and external rf inputs further improves the frequency and amplitude stability of the magnetization oscillations.

Picosecond semiconductor generator for capacitive sensors calibration

The paper describes a semiconductor picosecond pulse generator that can be used to calibrate capacitive high voltage sensors of MV range. The generator is designed as a base unit, to which external pulse converters are connected. In the base unit, semiconductor devices – first a semiconductor opening switch (SOS) and then a semiconductor sharpener (SS) – generate an output pulse with a rise time of 220 ps and a subsequent flat-top of 2 ns in duration. The pulse amplitude is around 1 kV across 50 Ω load. An external diode sharpener generates a pulse with 120 ps rise time and 500-ps flat-top at the amplitude of 850 V. To switch the semiconductor sharpeners to the conducting state, the shock-ionization wave mode is used. Additional pulse converters make it possible to generate output pulses across 50 Ω load with the rise time of 70-150 ps, the pulse duration of 135-310 ps, and the amplitude of 130–480 V. The electrical diagram of the generator and waveforms of the output pulses are presented. An example of the calibration of capacitive sensors of a multi-gigawatt picosecond generator is also shown.

Single shot radiography by a bright source of laser-driven thermal neutrons and x-rays

Thermal neutron (∼25 meV) beam is a powerful tool for investigating the structure and properties of materials used in science and technology. A laser-driven neutron source generating 1010 neutrons within 1 ns duration is utilized to a single shot radiography with a dual beam of thermal neutrons and X-rays. As a proof of principle, we show the non-destructive inspection of hazardous substances (Cadmium) contained in a typical battery, when the cadmium anode thickness is evaluated from the transmittance of thermal neutrons. The fact that the neutron inspection above is performed with a single laser shot, i.e. with a single bunch of neutrons leads to a safer neutron source that is optically controlled on/off, and provides a novel tool for science and engineering.

Ultranarrow bandwidth pulses from a regeneratively mode-locked fiber laser.

We report on the generation of transform-limited nanosecond pulse with an ultranarrow bandwidth from a regeneratively mode-locked erbium-doped fiber laser. A narrow bandwidth fiber Bragg grating is combined with a bulk amplitude electro-optic modulator to shape pulse evolution inside a ring cavity, and regenerative mode locking is applied to produce a stationary shape of pulses in the nanosecond regime (2.05 ns in duration). Spectral characterization via high bandwidth optoelectronic devices shows that optical pulses have an ultranarrow bandwidth of 220 MHz. Numerical simulation reveals that the shape of the narrow spectral filter has a strong effect on the duration and bandwidth of output pulses.

Effect of the magnetic field on the synthesis of colloidal silver and gold nanoparticles by laser ablation in bidestilated water

The effect of magnetic field of 0.3 T on the concentration, distribution of sizes in suspension and zeta potential of colloidal gold and colloidal silver nanoparticles, obtained by considering the pulsed laser ablation in double distilled water was studied. The magnetic field was transverse to the direction of incidence of the laser radiation and parallel to the surface of a submerged target. An Nd: YAG laser was used (1064 nm in wavelength, 10 ns in duration, repetition rate of 10 Hz and 37 mJ of energy) to ablate targets. The colloids were characterized by inductively coupled plasma optical emission spectroscopy, ultraviolet-visible spectroscopy, dynamic light scattering and zeta potential. Concentration analysis suggested that applying magnetic field of 0.3 T during nanoparticle synthesis leads to higher concentration. Applying magnetic field led to an eleven percent increase in the concentration of the colloid with gold nanoparticles and a five percent increase in the concentration of the colloidal silver nanoparticles. The absorption spectra suggested the presence of spherical nanoparticles. When analyzing the effect of the magnetic field on the hydrodynamic size distribution of the nanoparticles and the zeta potential of the colloids, no significant changes were evidenced. The magnetic confinement of the plasma induced by laser ablation caused changes in the characteristics of the colloids.

Linear four-element cylindrical helix antenna array in boreside and scanning radiation modes

A cylindrical equidistant helix antenna has been created. The helix geometry of the antenna determined its central frequency of the operating band, equal to 1 GHz. This frequency corresponds to the maximum spectra of a bipolar voltage pulse with duration of 1 ns. Helixes identical to those of a single antenna were used in horizontal four-element linear arrays. Antenna arrays with different periods of d were studied in the axial mode with simultaneous excitation of elements by a bipolar voltage pulse of 1 ns duration and in the mode of scanning at a fixed angle in the horizontal plane. Experimental measurements were carried out in the frequency and time domains.

Superconducting protector against electromagnetic pulses based on YBCO film prepared on an Al2O3 substrate with a CeO2 sublayer

The electric and magnetic properties of microbridges made from 440 nm thick Y–Ba–Cu–O films prepared on Al2O3 substrates with CeO2 sublayers by the pulsed injection metal organic chemical vapor deposition (MOCVD) method were studied in temperatures ranging from 20 K to 300 K in order to investigate the possibilities of using these microbridges as fast fault current limiters. The application of an external magnetic field () causes the flux flow induced magneto-resistive effect, which is proportional to and to at low and high temperatures, respectively. The experimentally obtained S-shaped I–V characteristic and the change of the microbridge resistance over time when affected by a step-like magnetic field can be well explained using a thermo-electrical model based on Joule heating and the flux flow nature of the resistive state (RS). The transition from the superconducting to the RS, studied using ns duration rectangular waveform electrical pulses able to create up to ≈2106 A cm−2 current densities without rises of microbridge temperatures, demonstrated that the I–V characteristics of the RSs consisting of an assembly of straight lines corresponding to the different pinning centers. At temperatures close to the critical temperature of superconductivity, the number of these lines increases, and the I–V characteristics can be described with high accuracy by a power law. It was concluded that microbridges made from these films can be used as protectors against complicated waveform electromagnetic pulses having short rise times, high voltage peak amplitudes and long low-value over-current ‘tails’.

An induction voltage adder with MHz repetition rates and nanosecond duration based on printed circuit board stacked Blumlein lines.

By utilizing the radio-frequency metal-oxide-semiconductor field-effect transistor switch, the multi-stage stacked printed circuit board Blumlein lines, and the induction voltage adder, a voltage generator with MHz repetition rates and nanosecond duration was designed and fabricated. The shunting current of the multi-stage stacked Blumlein lines, which consists of the coupling current at the load ends and the leakage current at the switch ends, is clarified. The circuit simulation and experiment of the three-stage stacked Blumlein lines are carried out; the result shows that the experiment and simulation agree well. The five-stage IVA prototype is designed for generating voltage pulses of ∼10 kV in amplitude and 8-11 ns in duration with MHz burst repetition rates. The voltage generator with MHz repetition rates and nanosecond duration demonstrated an important application prospect to reduce the electron beam initial emittance of the high energy accelerator.

Nanosecond pulsed electric fields induce the integrated stress response via reactive oxygen species-mediated heme-regulated inhibitor (HRI) activation.

The integrated stress response (ISR) is one of the most important cytoprotective mechanisms and is integrated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). Four eIF2α kinases, heme-regulated inhibitor (HRI), double-stranded RNA-dependent protein kinase (PKR), PKR-like endoplasmic reticulum kinase (PERK), and general control nonderepressible 2 (GCN2), are activated in response to several stress conditions. We previously reported that nanosecond pulsed electric fields (nsPEFs) are a potential therapeutic tool for ISR activation. In this study, we examined which eIF2α kinase is activated by nsPEF treatment. To assess the responsible eIF2α kinase, we used previously established eIF2α kinase quadruple knockout (4KO) and single eIF2α kinase-rescued 4KO mouse embryonic fibroblast (MEF) cells. nsPEFs 70 ns in duration with 30 kV/cm electric fields caused eIF2α phosphorylation in wild-type (WT) MEF cells. On the other hand, nsPEF-induced eIF2α phosphorylation was completely abolished in 4KO MEF cells and was recovered by HRI overexpression. CM-H2DCFDA staining showed that nsPEFs generated reactive oxygen species (ROS), which activated HRI. nsPEF-induced eIF2α phosphorylation was blocked by treatment with the ROS scavenger N-acetyl-L-cysteine (NAC). Our results indicate that the eIF2α kinase HRI is responsible for nsPEF-induced ISR activation and is activated by nsPEF-generated ROS.

Electric Pulse Pretreatment for Enhanced Lipid Recovery from Chlorella protothecoides

Developing effective, energy-efficient methods to extract lipids from microalgae remains a challenge in bioenergy. This study assesses electric pulse (EP) pretreatments to enhance lipid extraction from Chlorella protothecoides. In tandem with solvent extraction, we applied 10, 50, 100, 200, and 300 60 kV/cm, 60 ns duration EPs or 3, 17, 33, 67, and 100 60 kV/cm, 300 ns duration EPs to match the energy density u applied to the sample for each EP duration. Lipid recovery increased with increasing u for each EP duration until reaching a maximum for 17 300 ns EPs (the second lowest u) and 100 60 ns EPs (the third lowest u) to achieve a 13.3% and 16.1% increase in lipid extraction, respectively. Lipid extraction declined at higher u due to increased cell lysis. The largest net energy released calculated from the difference between the energy available from the extracted lipids and the applied energy of the EPs occurred at the lowest u for each EP duration. Applying trains of 100 μs EPs induced qualitatively similar behavior. These results suggest that a more detailed parametric study may optimize EP parameters for net energy release for specific microalgae and solvents.

The true spectrum of tribo-generated X-rays from peeling tape

X-rays generated through tribological processes differ from those obtained with conventional X-ray tubes in that a substantial portion of the total energy is emitted in pulses of order 10 ns in duration. The short duration of these pulses usually causes solid-state detectors to register pileup events that can make the corresponding spectrum unreliable as a characterization tool. In this work, we find that a solid angle subtended by the detector of 5×10−6 is necessary to obtain the true spectra of X-rays generated from peeling adhesive tape in a moderate vacuum. The maximum individual photon energy is found to be 30 keV, which is about half of that reported in previous studies that overlook the effects of pileup. Being able to obtain a reliable spectrum may help us understand the physical processes behind this phenomenon so that it can be optimized for present and future applications.