Pulsed Irradiation Research Articles

A Study of the Influence of Additives of Nanostructured Functional Ceramics in the Coating of Welding Electrodes on their Welding and Technological Properties

The present work aims to study the influence of Nanostructured Functional Ceramics Photocatalysts (PNFC) under the brand name ZB-2, obtained using a synthesis method deploying pulsed radiation activation technology on welding and technological properties. This method of obtaining ceramic material allows the latter to be produced on an industrial scale. Therefore, it can replace the technology for producing PNFC under the influence of concentrated solar radiation at the Big Solar Furnace (BSF) of the Institute of Materials Science, Academy of Sciences of the Republic of Uzbekistan. The ZB-2 ceramic material has shown its effectiveness when used as an additive in the coating charge of the MR-3 welding electrode. Thus, the breaking arc length of the MR-3 welding electrode is increased up to 2% with the addition of ZB-2 to the coating charge. With additions of more than 2%, the breaking arc length decreases. The additive ZB-2 has the same effect on the diameter of the deposited point of the MP-3 welding electrode. When its content in the coating is up to 2%, the diameter of the deposited point increases, and a further increase in the additive content reduces this indicator. Adding up to 1% ZB-2 into the coating composition has a beneficial effect on the size of the peak at the end of the electrode. When its content exceeds 1%, the latter decreases. Also, an increase in the content of the PNFC additive in the coating of the MR-3 electrode reduces the value of the melting coefficient and increases the value of the deposition coefficient, which contributes to a sharp reduction in losses due to waste and spattering up to 53% when the additive content in the coating mass is up to 8%.

A Bidirectional Bent Vivaldi-Connected Array With Short-Circuited Branches for UWB Pulse Radiation

A Bidirectional Bent Vivaldi-Connected Array With Short-Circuited Branches for UWB Pulse Radiation

Propagation of strong electromagnetic waves in tenuous plasmas

We study the propagation of electromagnetic waves in tenuous plasmas, where the wave frequency ω0 is much larger than the plasma frequency ωP. We show that in pair plasmas, nonlinear effects are weak for a0≪ω0/ωP, where a0 is the wave strength parameter. In electron-proton plasmas, a more restrictive condition must be satisfied, namely, either a0≪1/ωPτ0, where τ0 is the duration of the radiation pulse, or a0≪1. We derive the equations that govern the evolution of the pulse in the weakly nonlinear regime. Our results have important implications for the modeling of fast radio bursts. We argue that (i) millisecond duration bursts with a smooth profile must be produced in a proton-free environment, where nonlinear effects are weaker, and (ii) propagation through an electron-proton plasma near the source can imprint a submicrosecond variability on the burst profile. Published by the American Physical Society 2024

Non-existence of causal, standard classical electrodynamics with point charged particle

Abstract The existence of consistent, standard and causal theory of point charged particle (for example electron) interacting with electromagnetic field was the subject of many investigations. This problem is often stated as the description of the system of electromagnetic pulse of radiation interacting with single point charged particle (for example electron). The correct theory should give the causal particle trajectory for any electromagnetic pulse of radiation. Up to now no such theory was formulated. We show that for certain electromagnetic pulse of radiation and point particle being initially at rest, there does not exist a causal and physical particle trajectory that satisfies energy and momentum conservation. This shows that the causal, standard electrodynamics of scalar point particles, valid for all possible external pulses, does not exist.

Crystallization behavior of amorphous GST films under an ultrafast laser irradiation

The crystallization behaviors of amorphous Ge2Sb2Te5 films induced by an ultrafast laser with a time-shaping Gaussian intensity distribution have been studied. The crystalline regions were characterized using optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. It is found that the region ablated by a single pulse undergoes recrystallization, with a reflectivity higher than that of the non-ablated crystalline region. While preserving the integrity of the film, the diameter of the region with high and uniform reflectivity induced by burst mode is twice that of a single pulse, and the reflectivity is 3 % higher than the 31 % achieved with a single pulse. Additionally, the energy window for laser-induced crystallization expands with an increasing number of burst pulses; specifically, it increases by approximately 2.4 times when the number of sub-pulses is 4 or 5. The Raman results at low pulse energy show a high peak intensity at the 105 cm−1 in related to the vibrations of Te-rich tetrahedra, indicating that the degree of crystallinity in the burst mode region is superior to that achieved with single pulse irradiation. Furthermore, the blue shift of this Raman peak with increased pulse energy further supports that burst mode provides sufficient time for nucleation growth. This work offers insights into achieving more controllable crystallization, which can enhance its applications in phase change memory and other reconfigurable devices.

Rapid activation of a solution-processed aluminum oxide gate dielectric through intense pulsed light irradiation.

In this study, we report rapid activation of a solution-processed aluminum oxide gate dielectric film to reduce its processing time under ambient atmosphere. Aluminum precursor films were exposed to a high energy light-pulse and completely converted into dielectric films within 30 seconds (450 pulses). The aluminum oxide gate dielectric film irradiated using intense pulsed light with 450 pulses exhibits a smooth surface and a leakage current density of less than 10-8 A cm-2 at 2 MV cm-1. Moreover, dielectric constants of the aluminum oxide layer were calculated to be approximately 7. Finally, we fabricated a solution-processed indium gallium zinc oxide thin-film transistor with AlO x using intense pulsed light irradiation, exhibiting a field-effect mobility of 2.99 cm2 V-1 s-1, threshold voltage of 0.73 V, subthreshold swing of 180 mV per decade and I on/I off ratio of 3.9 × 106.

Molecular Characteristics and Processing Technologies of Dairy Products from Non-Traditional Species.

Non-bovine dairy animals, commonly referred to as non-traditional dairy species, include goats, sheep, yaks, buffalo, donkeys, alpacas, llamas, and other less commonly farmed species. These animals have been integral to livestock systems since ancient times, providing milk and other essential products. Despite their historical significance, dairy production from many of these species remains predominantly confined to rural areas in developing countries, where scientific advancements and technical improvements are often limited. As a consequence of this, the scientific literature and technological developments in the processing and characterization of dairy products from these species have lagged behind those for cow's milk. This review aims to compile and analyze existing research on dairy products derived from non-traditional animals, focusing on their molecular characteristics, including proteins (alpha, beta, kappa, and total casein), fats (cholesterol and total fat), lactose, albumin, ash, total solids, and somatic cell count, among others, for each of these species. Additionally, we discuss emerging technologies employed in their processing, encompassing both non-thermal methods (such as high-pressure processing, pulsed electric fields, ultrasound processing, UV-C irradiation, gamma radiation, microfiltration, and cold plasma processing) and thermal methods (such as ohmic heating). This review also explores the specific potential applications and challenges of implementing these technologies. By synthesizing recent findings, we aim to stimulate further research into innovative technologies and strategies that can enhance the quality and yield of non-bovine dairy products. Understanding the unique properties of milk from these species may lead to new opportunities for product development, improved processing methods, and increased commercialization in both developing and developed markets.

Efficacy of indirect intense pulsed light irradiation on meibomian gland dysfunction: a randomized controlled study.

To investigate the efficacy and mechanisms of indirect intense pulsed light (IPL) irradiation on meibomian gland dysfunction (MGD). A total of 60 MGD patients was included in this prospective randomized controlled trial. Patients were randomly assigned 1:1 into two groups (3-mm group and 10-mm group) in which IPL was applied at distances from the lower eyelid margin of 3 and 10 mm, respectively. Both groups received three times treatment with 3-week interval. Meibomian gland yield secretion score (MGYSS), standard patient evaluation of eye dryness (SPEED) questionnaire, tear break-up time (TBUT), corneal fluorescein staining (CFS), and in vivo confocal microscopy were performed at baseline and after every treatment. After three IPL treatments, both groups had significant improvement in MGYSS (both P<0.05). The non-inferiority test showed that improvement in 10-mm group was not inferior to that in 3-mm group (P<0.001). In both groups, temporal regions of both upper and lower eyelids showed significant improvement in MGYSS. Scores of SPEED questionnaire in both groups declined significantly (both P<0.001) and changes of SPEED had no difference between two groups (P=0.57). Density of central corneal subepithelial nerves and TBUTs showed no statistically significant changes. The 3-mm group had improvement on corneal fluorescein staining (P=0.048) and meibomian gland morphology (acini wall thickness P=0.003, hyperreflective points P=0.024) while the 10-mm group had not. The efficacy of IPL indirect irradiation in improving meibomian gland secretion and alleviating dry eye symptoms remains unchanged with increase in treatment distance. IPL may primarily act on the functional improvement of the meibomian glands and corneal nerves.

Toxicity assessment following conventional radiation therapy and pulsed low dose rate radiation therapy: an in vivo animal study

BackgroundPulsed low dose rate radiotherapy (PLDR) is a new radiation delivery method, in which the fractional dose is divided into sub-fractional doses with periodical time breaks in between. The goal of our study is to assess the toxicity on healthy tissues resulting from PLDR as compared to conventional radiotherapy (CRT) using the same physical X-ray dose.MethodsWe analyzed the weight and survival time for CRT and PLDR groups and studied the inflammatory cytokine transforming Growth Factor-β (TGF-β), usually released following irradiation. Histopathological and immunohistochemical analyses were conducted for intestinal and bone marrow tissues from rats subjected to 8 Gy whole- body irradiation using CRT and PLDR techniques. We investigated genotoxicity by performing a comet assay (CA) in splenic tissues.ResultsOur findings showed an improvement in survival time with PLDR versus CRT by 82%.The mean survival time for CRT rats’ group was 6.3 days, while it was 35.9 days for PLDR group.The weight of CRT group decreased gradually by 3.7%, while weight of PLDR group increased gradually by 2.4%.CRT resulted in more cellular atrophy in bone marrow and intestinal tissues than in PLDR treatments as shown by hematoxylin and eosin staining analysis. In addition, the transforming growth factor-β (TGF-β) expression in bone marrow and intestinal tissues of CRT was higher than those expressed in tissues from PLDR as demonstrated by the Immuno reactive score (IRS). It was10(0.53) and 9.8(0.55) for BM and intestinal tissues, respectively from CRT group and 5.8(0.63) for PLDR for both tissues. The measured CA parameters were larger with CRT compared to PLDR, where the Tail Length (TL), Tail DNA % (TD%) and Tail Moment (TM) measurements were 25.4(3.4), 56.5(7.6) % and 20.5(3.5) for CRT, 7.3(1.9), 30.0(7.2) % and 5.7(1.8) for PLDR, with P value 0.000064, 0.0004 and 0.00017, respectively.ConclusionThis study indicates that PLDR can reduce the toxicity on normal tissues compared to CRT.

Formation of optical resonances at the initial stage of radiation destruction of disperse medium made of a transparent dielectric by means of a powerful laser

By means of numerical simulation, we study optical resonances that arise when radiation from an ytterbium fiber laser (λ = 1065 ± 3.25 nm), a blue diode laser (λ = 450±8 nm) or a CO2 laser (10.6 μm) is scattered on a single particle of a transparent dielectric (an oxide, a fluoride, ZnSe), as well as in an ensemble of randomly packed particles of various sizes. If the particle diameter is comparable to the radiation wavelength (but is no less than 3λ/4) then, at a certain ratio between the particle diameter, the refractive index of its material and the radiation wavelength, the particle becomes a microresonator. The maximum intensity of scattered radiation inside or outside such particle depends on the combination of the above-said parameters and can exceed the intensity of the incident radiation dozens of times. In case of a powder, the interference pattern is formed by all particles at once and, occurrence of an optical resonance is more likely. Even with a slight change in the radiation wavelength of an ytterbium laser or a blue diode laser (within the lasing line width), some particles in the powder become microresonators, while others cease to be microcavities. Therefore, concentration of scattered radiation of the ytterbium laser in individual particles plays a key role at the initial stage of optical destruction of the powder. As the experiment shows, this allows to overcome the threshold of optical destruction of porous targets made of various transparent substances (CaF2, SiO2, BaF2, YbF3, Fe:MgAl2O4, Al2O3, 1mol.%Nd:Y2O3, YSZ, TiO2, ZnSe) by means of a radiation pulse from an ytterbium laser having low intensity (0.46 MW/cm2). With the refractive index of the material increasing from 1.429 (CaF2) to 2.479 (TiO2), the average delay in the formation of a laser plume decreases from 46 ms to 25 μs, i.e. by three orders of magnitude. This correlates with the fact that in the calculations, the maximum intensity of this laser's radiation scattered in the powder increases with n increasing. In compliance with this are the results of obtaining nanopowders from transparent oxides and ZnSe by means of pulse-periodic radiation of an ytterbium laser. Output of the nanopowder Yb0.05:Y1.95O3:(ZrO2)0.05 with n = 1.901 (for Y2O3) is 15 g/h, and the maximum output (100 g/h) is realized in case of ZnSe (n = 2.482). At the same time, it is not possible to obtain nanopowder from CaF2 (n = 1.429), because the moving target does not evaporate.

Analyzing the Temperature Dependence of Titania Photocatalysis: Kinetic Competition between Water Oxidation Catalysis and Back Electron-Hole Recombination.

This study examines the kinetic origins of the temperature dependence of photoelectrochemical water oxidation on nanostructured titania photoanodes. We observe that the photocurrent is enhanced at 50 °C relative to 20 °C, with this enhancement being most pronounced (by up to 70%) at low anodic potentials (<+0.6 V vs RHE). Over this low potential range, the photocurrent magnitude is largely determined by kinetic competition between water oxidation catalysis (WOC) and recombination between surface holes and bulk electrons (back electron-hole recombination, BER). We quantify the BER process by transient photocurrent analyses under pulsed irradiation. Remarkably, we find that the kinetics of BER (∼90 ms half-time) are independent of temperature. In contrast, the kinetics of WOC, determined from the analysis of the photoinduced absorption of accumulated surface holes, are found to accelerate up to 2-fold at 50 °C relative to 20 °C. We conclude that the enhanced photocurrent densities observed in the low-applied potential region result primarily from the accelerated WOC, reducing losses due to the competing BER pathway. At higher applied potentials (>+0.6 V vs RHE), a smaller (∼10%) enhancement in photocurrent density is observed at 50 °C relative to 20 °C. Photoinduced absorption studies, correlated with studies using triethanolamine as a hole scavenger, indicate that this more modest enhancement at anodic potentials primarily results from an enhanced charge separation efficiency. We conclude by discussing the implications of these results for the practical application of photoanodic WOC under solar irradiation, influenced by these temperature-independent and -dependent underlying kinetic processes.

Depth-dependent energy absorption control of large pulsed electron beam (LPEB) irradiations for defect-free surface modification of metallic alloys

Electron beam surface finishing offers the ability to treat various materials and shapes while enhancing surface properties such as wear and corrosion resistance. However, its industrial application is limited by the formation of crater-like defects' pulse count, irradiation angle, and energy density, were optimized to achieve defect-free surfaces. By systematically investigating the synergistic effects of previously studied parameters (irradiation angle and energy density), the optimal conditions were established through strategic combination of these parameters, demonstrating enhanced surface quality and reduced defect formation. These were compared to previously optimized conditions that focused solely on increasing pulse counts. The new conditions significantly reduced the density of crater-like defects and produced smoother surfaces. This improvement is attributed to concentrated energy absorption near the surface and the creation of a high-temperature gradient, which prevents the introduction of non-metallic inclusions. Unlike conventional methods, where accumulated heat leads to phase transformations and reduces hardness and corrosion resistance, the new approach maintains a rapid cooling rate. This allows the surface to retain a fully martensitic phase even at 45 pulses, resulting in higher surface hardness. These findings highlight that the newly developed conditions not only produce defect-free surfaces but also impart enhanced mechanical properties. This approach suggests that future improvements in surface quality for electron beam-based processes can be achieved by considering adjustments to the irradiation angle and energy density.

Supercontinuum saturation of a femtosecond laser filament in pressurized gases.

Filamentation of high-power femtosecond optical pulses in high-pressure gases has gained increasing academic and practical interest from the viewpoint of studying large-scale spectral and temporal transformations occurring with pulsed laser radiation and obtaining super-broadened spectra and extremely short (attosecond) wave packets. Experimentally and theoretically, for the first time to the best of our knowledge, we show that as a result of a 45 fs Ti:sapphire laser pulse filamentation in an optical cell filled with pressurized up to 50 bar nitrogen or argon, the pulse spectrum can reach maximally about eightfold broadening. This limiting pulse spectral width is reached at a gas pressure of about 20 bar and with further pressure increase exhibits saturation and even a slight decrease relative to the limiting value. As a possible reason for this finding, we suppose the increase of pulse energy depletion in the self-created plasma at high gas pressure.

New experimental methodology for determining the second crossover energy in insulators under stationary e-irradiation in a SEM

A new experimental methodology is proposed which uses the electrostatic influence method (EIM) in scanning electron microscope (SEM) in order to estimate the second crossover energy EC2 for uncharged insulators. This experimental methodology based on simultaneous time measurement of the displacement and leakage currents, is approached to the short pulse irradiation technique but under stationary e-irradiation and allows determining the intrinsic secondary electron emission yield, σ0 (σ0 is the value of the total secondary electron yield just at the beginning of the irradiation before significant charge accumulation or before the formation of a surface potential). The obtained value of EC2 for soda-lime glass is confirmed by two additional experiments based on secondary electron imaging. This value is in good agreement with those previously obtained by other studies based on the surface potential measurement or the pulsed irradiation technique.

Follow-up Timing of 12 Pulsars Discovered in Commensal Radio Astronomy FAST Survey

We present phase-connected timing ephemerides, polarization pulse profiles, and Faraday rotation measurements of 12 pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey. The observational data for each pulsar span at least 1 yr. Among them, PSR J1840+2843 shows subpulse drifting, and five pulsars are detected to exhibit pulse nulling phenomena. PSR J0640−0139 and PSR J2031−1254 are isolated millisecond pulsars (MSPs) with stable spin-down rates ( Ṗ ) of 4.8981(6) × 10−20 s s−1 and 6.01(2) × 10−21 s s−1, respectively. Additionally, one pulsar (PSR J1602−0611) is in a neutron star−white dwarf (WD) binary system with an 18.23-day orbit and a companion of ≤0.65 M ⊙. PSR J1602−0611 has a spin period, companion mass, and orbital eccentricity that are consistent with the theoretical expectations for MSP−helium WD (He WD) systems. Therefore, we believe that it might be an MSP−He WD binary system. The locations of PSR J1751−0542 and PSR J1840+2843 on the P−Ṗ diagram are beyond the traditional death line. This indicates that FAST has discovered some low- Ė pulsars, contributing new samples for testing pulsar radiation theories. We estimated the distances of these 12 pulsars based on NE2001 and YMW16 electron density models, and our work enhances the data set for investigating the electron density model of the Galaxy.

Influence of irradiation wavelength during laser-assisted doping of 4H-silicon carbide in liquid phase

Laser-assisted doping of silicon carbide (SiC) substrates is challenging due to the low diffusion coefficient of dopant atoms and the chemically inert nature of SiC. Single crystal intrinsic 4H-SiC substrate is irradiated with neodymium-doped yttrium aluminium garnet (Nd3+):YAG laser with wavelengths of 1064, 355 and 266 nm, and krypton fluoride (KrF) excimer laser with the wavelength of 248 nm under liquid phase dopant sources. Different liquid solutions were used as dopant sources for aluminium (Al) and phosphorus (P). SiC was transparent to 1064 and 355 nm due to low absorption coefficients, while 266 and 248 nm showed better coupling due to higher absorption coefficients and led to the diffusion of atoms. The electrical resistance of the substrates was measured to be lower than 1000 kΩ after diffusion. Dispersive X-ray spectroscopy (EDS) studies showed that both laser wavelengths of 248 nm and 266 nm resulted in doping of Al and P, with the surface concentrations ranging from 0.5 to 1.5 at.% and from 0.24 to 0.6 at.%, respectively. Two-dimensional thermo-temporal simulation of the laser pulse interaction in the liquid phase revealed that unlike in air, during irradiation with 266 nm laser under liquid, the surface temperature of the substrate was slightly lower. However, the subsurface temperature increased along the depth by a few microns. Similarly, simulation studies with longer pulse irradiation also show that high temperature was maintained for a longer time, indicating improved dopant diffusion into the 4H-SiC substrate.

Analysis of composite wavelength multilayer dielectric film damage based on the field-thermal effect

Taking SiO2/HfO2 multilayer dielectric films as the research object, when the total laser energy is the same, the effects of different laser parameters on film damage under 1064 nm and 355 nm composite wavelength pulse irradiation are analyzed. The results show that different energy ratios lead to exponential differences in the electron number density inside the film, but they are far from reaching the field damage threshold. Comprehensive analysis shows that film damage is mainly affected by thermal melt and stress. The greater the difference between an energy ratio of 1ω and 3ω, the greater the thermal stress in the film, the higher the stress peak, and the more obvious the damage effect of thermal stress on the film. Under the condition of 50%1ω, the thermal effect in the film is minimal, which can ensure that the film is not damaged as much as possible. The model method used in this paper only takes the current film system as an example for specific research and can be extended to all film systems for analysis.

Coil Embolization for Cerebral Aneurysm Using Low Pulse Rate Fluoroscopy.

Although coil embolization is commonly perceived as a minimally invasive procedure, the associated radiation exposure cannot be disregarded. To date, no specific study has investigated radiation exposure during coil embolization. This study aimed to investigate the potential of lowering the pulse rate to decrease radiation exposure during coil embolization while maintaining patient safety. Radiation data and clinical features of 70 patients who underwent coil embolization between 2015 and 2020 were retrospectively analyzed. Since July 2017, the pulse rate was regulated from 7.5 to 4 frames per second (f/s). Statistical analyses were performed to examine the correlation between pulse rate and radiation exposure. Out of the 70 procedures, 30 were performed at the standard pulse rate (7.5 f/s), and 40 were performed at the lower pulse rate (4 f/s). In the lower-pulse-rate group, the absorbed dose to the patient (AK) was 2580.7 (±217) mGy, whereas in the standard-pulse-rate group, it was 4760 (±411.1). Both the dose-area product (DAP) and AK were substantially reduced in the low pulse rate group (p = 0.000002). There was a significant correlation between DAP and AK and pulse rate (p = 0.004, p = 0.0017, respectively). Moreover, there was no significant correlation between pulse rate and perioperative complications. Our findings suggest that using a lower pulse rate (4 f/s) can effectively reduce radiation exposure during coil embolization for cerebral aneurysms while ensuring patient safety.

Tapering-enhanced high-efficiency THz waveguide oscillator

Using a waveguide in a THz FEL has been shown to maximize the coupling and enable efficient extraction of relativistic electron beam energy from a single passage through a tapered helical undulator. An oscillator configuration can further boost energy extraction above the single-pass limits and open the door toward very high average power THz sources. Embedding the undulator in an oscillator cavity is particularly useful in combination with high repetition rate electron sources, even if at reduced peak brightness, since recycling a fraction of the radiation as an intense seed can compensate for lower single-pass gain. In this paper, we investigate the efficiency scaling of a tapering-enhanced waveguide oscillator, showcasing its capability for frequency-tuning operation and high-efficiency operation at different wavelengths. Using a thermionic-driven beamline equipped with compression elements, numerical start-to-end simulation results indicate a 16% efficiency at 200 GHz and a 2.1% efficiency at 1.5 THz, resulting in kW-level average power out-coupled in radiation pulses with few hundred μJ energy and tens of MW peak power. Published by the American Physical Society 2024

Laser and thermal control over structure and magnetic properties of PrDy-FeCo-B microwires

Magnetic microcombs are necessary in microrobotics, MEMS technologies, actuator and magnetic flow analyzer industries. Usually, magnetic microcombs are artificial linear magnets of periodic shape. We propose another type of microcombs based of microwires, where periodicity of magnetization is caused by equidistant alternation of natural domains. We have demonstrated the presence of quasi-periodic radial magnetization and the effect of temperature and magnetic field on magnetic relief in PrDyFeCoB microwires. Accurate analysis of chemical, phase and structural composition of the microwires allowed us to reveal necessary conditions for the creation of periodical magnetic relief. Annealing affects magnetic relief and changes structure of initially amorphous microwires. Crystal structure of inclusions enriched with Fe and Co instead of Dy and Pr is body-centered cubic (BCC), while the bulk of the microwire has tetragonal structure. We have found laser stimulated amorphization of surface of PrDy-FeCo-B microwires. Partial restoration of the amorphous structure in polycrystalline microwires under single laser pulse of irradiation of 1mJ power and 120 ns duration has been found in 1–2 μm depth.