Pulsed Source Research Articles

Model of spatiotemporal coherent summation of ultra-wideband chaotic radio pulses formed by independent emitters

A model of spatiotemporal summation of ultra-wideband chaotic radio pulses is proposed. The feasibility of using this model for analyzing scenarios of time-coherent radiation from independent sources of ultra-wideband chaotic radio pulses in wireless ultra-wideband systems is substantiated. Two scenarios are considered: where the distance between receiving point and emitters is much greater than the typical size of a group of emitters and where the receiving point is located between the emitters. Distributions of the total pulse energy in space for these scenarios are obtained.

Mid-infrared pulsed fiber laser source at 4.3 µm based on a CO2-filled anti-resonant hollow-core silica fiber

Fiber lasers in the mid-infrared (mid-IR) band are of great interest due to their wide range of applications such as manufacturing, defense, spectroscopy, and free-space communication. Due to the immaturity of the soft glass fiber fabrication technology and the limitation of the type of doped rare earth, laser power scaling and wavelength expansion above 4 µm are greatly limited. Lasers based on gas-filled hollow-core fibers (HCFs) have proved to be an effective way of generating mid-IR lasers. We demonstrate a pulsed 4.3 µm laser source based on a CO2-filled HCF for the first time. The pulse energy characteristics and output spectrum of the mid-IR laser have been investigated. The maximum pulse energy of the mid-IR laser is 236 nJ. The maximum average power of the mid-IR laser is 297.8 mW with a slope efficiency of 17.3%. A step-tunable mid-IR output is achieved from 4293.718 nm to 4392.085 nm including 8 emission lines. Furthermore, the time-domain and frequency-domain properties of the mid-IR laser have been studied to understand laser operation better. This work has an important reference value for the development of pulsed mid-IR fiber gas laser sources.

Features of propagation in the atmosphere of nonlinear acoustic disturbances from pulse sources

The features of the propagation of nonlinear pulsed acoustic disturbances in the atmosphere are considered. Data are presented on the experimental observation of the formation of a shock front and the transition of a shock wave into a low-intensity acoustic wave with transformation of the pulse shape and expansion of the front at distances of more than 1000 km under conditions of both spherical and cylindrical propagation. The influence of Kelvin-Helmholtz instability during rapid gas compression on the formation of the shock front structure is discussed. Under atmospheric conditions, such instability significantly affects dissipative processes in the air and forms the front of a nonlinear wave.

X-ray communication system with high-repetition-rate pulsed X-ray source and LYSO(Ce) and YAP(Ce) scintillators

X-ray communication offers significant advantages over traditional microwave methods due to its shorter wavelength and higher theoretical bandwidth, enabling efficient space communication and penetration through complex electromagnetic environments. However, current systems face limitations in X-ray emission modulation and high-precision timing detection. To meet the high-frequency transmission demands of space missions, we developed a pulsed X-ray emission source capable of high-frequency modulation. Additionally, we identified specific scintillators with distinct advantages for different transmission frequency ranges, allowing for performance optimization. Experimental results demonstrated a successful transmission rate of 10 MHz, validating the feasibility of MHz-frequency X-ray communication.

Industry-First Deployment of Simultaneous Source Acquisition Using a Dispersed Source Array with Tuned Pulse Source and Conventional Airgun for a Shallow Water Seismic Survey Offshore Malaysia

Industry-First Deployment of Simultaneous Source Acquisition Using a Dispersed Source Array with Tuned Pulse Source and Conventional Airgun for a Shallow Water Seismic Survey Offshore Malaysia

XFEL SASE pulses can enhance time-dependent observables

Abstract X-ray free electron lasers (XFELs) have emerged as powerful sources of short and intense X-ray pulses. We propose a simple and robust procedure which takes advantage of the inherent stochasticity of self-amplified stimulated emission (SASE) pulses to enhance the time-resolution and signal strength in the recorded data. Notably, the proposed method is able to enhance the average signal without knowledge of the signal strength of individual shots. Simple metrics for the probe pulses are introduced, such as an effective pulse duration applicable to SASE pulses characterised in the time domain using {\it{e.g.}}\ an X-band transverse cavity (XTCAV). The approach is evaluated using simulated and real pulse data in the context of ultrafast electron dynamics in a molecule. Utilising H$_2$ as a model system, we demonstrate the efficacy of the method theoretically, successfully enhancing the predicted nonresonant ultrafast X-ray scattering signal associated with electron dynamics. The method presented is broadly applicable and offers a general strategy for enhancing time-dependent observables at XFELs.

Detection of Veterinary Drugs in Food Using a Portable Mass Spectrometer Coupled with Solid-Phase Microextraction Arrow.

A portable mass spectrometer (PMS) was combined with a mesoporous silica material (SBA-15) coated solid-phase microextraction (SPME) Arrow to develop a rapid, easy-to-operate and sensitive method for detecting five veterinary drugs-amantadine, thiabendazole, sulfamethazine, clenbuterol, and ractopamine-in milk and chicken samples. Equipped with a pulsed direct current electrospray ionization source and a hyperboloid linear ion trap, the PMS can simultaneously detect all five analytes in approximately 30 s using a one-microliter sample. Unlike traditional large-scale instruments, this method shows great potential for on-site detection with no need for chromatographic pre-separation and minimal sample preparation. The SBA-15-SPME Arrow, fabricated via electrospinning, demonstrated superior extraction efficiency compared to commercially available SPME Arrows. Optimization of the coating preparation conditions and SPME procedures was conducted to enhance the extraction efficiency of the SBA-15-SPME Arrow. The extraction and desorption processes were optimized to require only 15 and 30 min, respectively. The SBA-15-SPME Arrow-PMS method showed high precision and sensitivity, with detection limits and quantitation limits of 2.8-9.3 µg kg-1 and 10-28 µg kg-1, respectively, in milk. The LOD and LOQ ranged from 3.5 to 11.7 µg kg-1 and 12 to 35 µg kg-1, respectively, in chicken. The method sensitivity meets the requirements of domestic and international regulations. This method was successfully applied to detect the five analytes in milk and chicken samples, with recoveries ranging from 85% to 116%. This approach represents a significant advancement in food safety by facilitating rapid, in-field monitoring of veterinary drug residues.

τSPECT: a spin-flip loaded magnetic ultracold neutron trap for a determination of the neutron lifetime

The confinement of ultracold neutrons (UCNs) in three-dimensional magnetic field gradient or magneto-gravitational traps allows for a measurement of the free neutron lifetime τ n with superior control over loss channels related to UCNs interacting with material surfaces. The most precise measurement τ n has been achieved using a magneto-gravitational trap, in which UCN are prevented from escaping at the top of their trap by gravity. More compact horizontal confinement geometries with variable energy acceptance ranges can be obtained by using steep magnetic field gradients in all spatial directions, generated by combinations of either permanent or (variable) superconducting magnets. In this paper, we present the first successful implementation of a pulsed spin-flip based loading scheme to fill a three-dimensional magnetic trap with externally produced UCN. The measurements with the τSPECT experiment were performed at the pulsed UCN source of the research reactor TRIGA Mainz. The extracted neutron storage time constant of τ = 859(16) s is compatible with the most precise determinations of τ n . We report on detailed, but statistically limited, investigations of major systematic effects influencing the neutron storage time. The statistical limitations are mitigated by the relocation of the experiment to a stronger UCN source.

Directed pulsed neutron source generation from inverse kinematic reactions driven by intense lasers

Neutron production driven by intense lasers utilizing inverse kinematic reactions is explored self-consistently by a combination of particle-in-cell simulations for laser-driven ion acceleration and Monte Carlo nuclear reaction simulations for neutron production. It is proposed that laser-driven light-sail acceleration from ultrathin lithium foils can provide an energetic lithium-ion beam as the projectile bombarding a light hydrocarbon target with sufficiently high flux for the inverse p(Li7,n) reaction to be efficiently achieved. Three-dimensional self-consistent simulations show that a forward-directed pulsed neutron source with ultrashort pulse duration 3 ns, small divergence angle 26°, and extremely high peak flux 3 × 1014n/(cm2⋅s) can be produced by petawatt lasers at intensities of 1021 W/cm2. These results indicate that a laser-driven neutron source based on inverse kinematics has promise as a novel compact pulsed neutron generator for practical applications, since the it can operate in a safe and repetitive way with almost no undesirable radiation.

Spatiotemporal-coupled partially coherent pulsed source and its propagation

Spatiotemporal-coupled partially coherent pulsed source and its propagation

Widely wavelength-tunable high-repetition-rate femtosecond pulse source with highest average power up to 28 W

We have proposed and demonstrated a high-repetition-rate ultrashort pulse fiber amplification system based on a wavelength-tunable oscillator. This fiber amplification system produces an average power exceeding 20 W in bursts of 200 pulses with a 578 MHz intra-burst pulse repetition rate and a 1 MHz burst repetition rate. The center wavelength of the amplified pulses can be tuned from 1030 to 1080 nm. By utilizing pre-chirp management nonlinear amplification technique, the achieved shortest pulse duration is 27 fs with an average power of 25 W at 1032 nm. For all the amplified pulses with different wavelengths, the pulse duration after optimal compression is below 60 fs. To the best of our knowledge, this is the first time that a widely wavelength-tunable high-power laser with a repetition rate exceeding 100 MHz and a pulse duration of several tens of femtoseconds has been realized. Additionally, using only common double-cladding Yb-doped fiber as the gain fiber, without any large-mode-area Yb-doped photonic crystal fiber or rod-type Yb-doped fiber, makes the system compact and reliable due to the simple fusion operation.

Efficient temporal compression of 10-µJ pulses in periodic layered Kerr media.

Pulse compression based on periodic layered Kerr media has been demonstrated as an effective technique for femtosecond pulses with energies around 100 µJ or more. We report such a compressor designed for pulses in the 10-µJ range, which is valuable for many applications. Pulses from a fiber chirped-pulse amplifier are compressed from 300 fs to as short as 60 fs, with good pulse and beam quality. The compressor is a simple and efficient way to extend the performance of common Yb-based sources of pulses with microjoule energies.

Comparison of methods for changing the spectrum of radiation of a pulse x-ray source to determine the most effective two-energy image processing

For detecting substances with similar chemical composition and density, one of the promising methods of non-destructive testing is dual-energy processing of X-ray images. In particular, dual-energy transformation algorithms can be used to search for minerals hidden within barren rock. This method is most effective when the conditions for registering X-ray images and energy levels are properly selected. This study compares the effectiveness of image processing using the dual-energy method for three cases of spectral composition variation: firstly, as a result of adjusting the voltage on the X-ray tube; secondly, by attenuating low-energy radiation through the use of a copper filter; and thirdly, by combining these two methods. Beryl particles embedded in ground muscovite are used as samples for detection. The study utilizes a pulsed X-ray radiation source that generates radiation pulses of nanosecond duration. An original high-voltage generator scheme has been implemented for the method of regulating radiation energy by changing the peak voltage on the X-ray tube. The use of X-ray sources of this type enables the acquisition of high-resolution X-ray images of moving objects.

A pulsed neutron source with a sealed dense plasma focus chamber

Compared with other pulsed neutron sources, dense plasma focus (DPF) devices have the advantages of simple in construction, extremely compact and cost-effective. In this paper, a DPF device was developed for used as pulsed neutron source. The Mather-type sealed chamber was adopted for long duration and multishot operations without vacuum system, which is convenient for transport, use and storage. The maximum D-D neutron yield of the device is approximately 1.1 × 109 n/pulse when the storage capacitors are charged with 22 kV and the deuterium gas filling pressure is 750 Pa. The neutron pulse width (FWHM) was measured to be 45 ns ± 10 ns.

Discrete Analysis of Electrical Circuit with Sources of Rectangular Pulses

Abstract Discrete transients and stationary process are described in series RC-circuits when the supplied voltage contains periodic rectangular pulses. The analysis is performed using z - transformation to obtain analytical dependencies for the capacitive voltage in any time of the rectangular pulses. The approach is used for discrete analysis of various circuits in which rectangular pulses have different characteristics. The calculated capacitive voltages by the obtained discrete dependencies are identical, compared to the results obtained by SPICE simulation. The method proposed in the present work allows, together with the transient process, to investigate the corresponding stationary process. Cases of stable and unstable transients are shown.

Investigation in improving the Cs-free negative hydrogen ion production with short-pulse low power in the afterglow of pulse-power-modulated plasma sources

Abstract Pulse plasma ion sources have been shown to be capable of achieving high negative hydrogen ion densities ( n H − ) or currents. The fast cooling of the electrons and reduction in the electron density (n e) provide favorable plasma conditions to improve the H− production, with a high density ratio of negative hydrogen ions to electrons during the pulse-off period. The purpose of this research is to further improve the performance of volume-produced H− ion sources based on the pulse power modulation. In this study, a time-modulated negative hydrogen plasma sustained by 10 kHz pulse power at the typical gas pressure of 0.3 Pa was numerically investigated using a global model. The model is compared with measurements obtained in a pulsed radio frequency ion source and shows a reasonable agreement. A steplike low-high power strategy in the active glow period and a short-pulse low power in part of the afterglow period are employed to mitigate overshoot of the electron temperature (T e) in the initial stage of the pulse period and to optimize H− production in the afterglow, respectively. The model predicts that a small-magnitude, short-duration low power operation in the afterglow increases n H − and decreases n e from the onset of the low power until the beginning of the next high power pulse, due to a modest temporary increase in the T e (less than 2 eV). It facilitates dissociative electron attachments and thus H− formation. The reduction in the n e indicates that positive ions lost to the walls cannot be compensated by weak ionization. H− production with a low number of co-extracted electrons can be optimized by adjusting the magnitude and duration of the low power in the afterglow.

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

Optimization of laser patterning process for eco-friendly tin-halide perovskite solar module – with a nanosecond green laser

The tin-based perovskite solar cells are promising future eco-friendly photovoltaic technology with increasing efficiency, which relies on fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) as a transparent conducting oxide (TCO) for front contact. In the monolithic module fabrication process interconnections are executed by a series of three scribes with two different lasers 1064 nm and 532 nm. This study aims to simplify the interconnection process in tin-based perovskite solar modules by using a single visible laser source to perform all three scribes. The study uses an inverted device structure of Glass/TCO/ Poly(3,4-ethylenedioxythiophene): Polystyrene sulfonate (PEDOT: PSS)/Formamidinium-tin-iodide (FASnI3)/C60/Bathocuproine (BCP)/Ag and a 532 nm nanosecond pulsed laser source to pattern the ITO and FTO (P1 scribe), the PEDOT: PSS/FASnI3/C60/BCP stack (P2 scribe), and the PEDOT: PSS/FASnI3/C60/BCP/Ag (P3 scribe). The quality of the P1 scribe is assessed by examining the edges, completeness of film removal, cracking, film delamination, and elemental mapping using a stylus profiler, optical microscope, and energy dispersive x-ray spectroscopy. The P1 scribe is completely removed with line widths of 70 µm and 110 µm of ITO and FTO, respectively, without damage to the glass substrate. The profiles are steep, and the electrical isolation is greater than 40 MΩ. The same 532 nm laser is used for P2 and P3 scribes. The ablation of PEDOT: PSS during P2 and P3 scribe is studied by Raman spectroscopy. The results show that the use of a single 532 nm laser source can simplify the patterning process of monolithic tin-based perovskite solar modules, and potentially reduce production costs.

An avalanche transistor-based Marx circuit pulse generator with sub-nanosecond, high frequency and high-voltage for pathogenic Escherichia coli ablation

Pathogenic Escherichia coli, which will easily cause environmental pollution, is a potentially hazardous microorganism that enters the environment through various routes such as biological feces. The presence of this bacterium poses a serious health risk, especially in water sources. When consuming water containing excessive amounts of pathogenic Escherichia coli, both humans and animals may experience severe health issues, such as diarrhea and gastrointestinal infections. However, current treatment methods for this bacterium are not ideal, and traditional means sometimes struggle to completely eliminate these stubborn microorganisms. In recent years, the scientific community has been exploring new sterilization techniques to address this challenge without causing secondary environmental pollution. Among them, pulsed electric field (PEF) technology has garnered significant attention. By applying high-intensity electric field pulses, PEF technology can have a fatal impact on microbial cells in a very short period of time. Studies have shown that this technology can cause cell membrane perforation, destroying the integrity of the cell and leading to cell death. This method is not only capable of decomposing organic pollutants, but also has a significant bactericidal effect. Nevertheless, despite the theoretical potential of PEF technology, there is still relatively little research on its application, especially in terms of treating pathogenic Escherichia coli. Further studies and experimental verification are needed. This article investigates the bioelectromagnetic effects of electric pulses on pathogenic Escherichia coli in sewage through a self-developed pulse source device (capable of providing a voltage range from 1.7 kV to 2.2 kV, with a rise time of 190 ps and a maximum repetition rate of 20 kHz). The feasibility of using a pulsed electric field to purify water bodies is verified in this report.