Short Pulse Research Articles

Investigation of traps in halide vapor-phase epitaxy-grown β-Ga2O3 epilayers/n+-Ga2O3 using deep-level transient spectroscopy

Abstract A detailed investigation of deep traps in halide vapor-phase epitaxy (HVPE)-grown β-Ga2O3 epilayers has been done by performing deep-level transient spectroscopy (DLTS) from 200 K to 500 K on Pt/β-Ga2O3 and Ni/β-Ga2O3 Schottky diodes. Similar results were obtained with a fill pulse width of 100 ms irrespective of the different Schottky metal contacts and epilayers. Two electron traps at E2 (E C–E T = 0.65 eV) and E3 (E C–E T = 0.68–0.70 eV) with effective capture cross-sections of 4.10 × 10−14 cm2 and 5.75 × 10−15 cm2 above 300 K were observed. Below 300 K, a deep trap with a negative DLTS signal peak was also observed at E1 (E C–E T = 0.34–0.35 eV) with a very low capture cross-section of 3.28 × 10−17 cm2. For a short pulse width of 100 μs, only two electron traps, E2 and E3, at energies of 0.72 eV and 0.73 eV were observed, and one order of higher corresponding effective capture cross-sections. All traps were found to be unaffected by the electric field during the field-dependent DLTS study. From the filling pulse width dependence DLTS study, a decrease in the capacitance transient amplitude with the increasing pulse width was observed opposite to the capture barrier kinetics of the traps and attributed to the emission of carriers during the capture process. Trap concentrations were found to be high at the interface using depth profiling DLTS. Based on the available literature, it is suggested that these traps are related to FeGa, Fe-related centers, and complexes with hydrogen or shallow donors, and might be affected or generated during metallization by the electron beam evaporator and chemical mechanical polishing.

Size and Surface Effects in the Ultrafast Dynamics of Strongly Cooperative Spin‐Crossover Nanoparticles

AbstractCooperative photoinduced switching of molecular materials at the nanoscale is still in its infancy. Strongly cooperative spin‐crossover nanomaterials are arguably the best prototypes of photomagnetic and volume‐changing materials that can be manipulated by short pulses of light. Open questions remain regarding their non‐equilibrium dynamics upon light excitation and the role of cooperative elastic interactions in nanoscale systems that are characterized by large surface/volume ratios. Femtosecond‐resolved broadband spectroscopy is performed on nanorods of the strongly cooperative Fe‐triazole, which undergoes a reversible low‐spin to high‐spin (HS) phase transition ≈360 K. Supported by density functional theory and mechano‐elastic Monte Carlo simulations, a marked difference is observed in the photoswitching dynamics at the surface of the nanoparticles compared with the core. Surprisingly, under low excitation (<2%) conditions, there occurs a transient increase in the HS population at the surface on the picosecond time scale, while the HS population in the core decays concomitantly. These results shed light onto the importance of surface properties and dynamical size limits of nanoscale photoresponsive nanomaterials that can be used in a broad range of applications.

Exploring Fast Domain Wall Motion and DMI Realization in Compensated Ferrimagnetic Nanowires

Abstract Recent advancements in spintronics have spurred interest in current-induced domain wall motion (CIDWM) as a promising avenue for next-generation memory technologies. While previous research has predominantly focused on thin ferromagnetic films, recent attention has shifted towards ferrimagnetic materials due to their potential for magnetization compensation and efficient domain wall (DW) motion. In this study, we investigated the dynamics of DWs in compensated ferrimagnetic Pt/GdxFe1-x nanowires through experimental characterization and analysis. Our results reveal fast DW motion around the magnetic compensation point, indicating the influence of spin-orbit torque induced by current flow. We systematically explore the Dzyaloshinskii-Moriya interaction (DMI) field across different compositions of GdFe, observing elevated DMI field values near the compensation compositions. Additionally, we examine the impact of wire width and pulse duration on DW velocity, demonstrating higher velocities in narrower wires and shorter pulse durations. In the 1 μm wire, a DW velocity of around 3200 m/s was achieved by applying a 3 ns short pulse current. Our findings elucidate the intricate interplay between film composition, magnetic properties, wire width, pulse duration, and DW dynamics, providing valuable insights for the design and optimization of ferrimagnetic materials for future magnetic memory technologies.

Review on peak detect and hold circuits and their applicability in partial discharge detection

Abstract This article reviews various designs of electrical peak detect and hold circuits and tests their applicability for the detection of partial discharge pulses. Since partial discharges are very short pulses in the nanosecond range, the peak detector circuit must be very fast and thus work precisely over a wide bandwidth up to the GHz range. The article begins with a comprehensive literature review and gives an overview of the state of the art of peak detector circuits. As a result of the literature research, four different peak detector designs are identified that appear suitable for measuring partial discharges. These four circuits are then simulatively tested for their performance in measuring the pulse height of various partial discharge pulses. It turns out that two of the identified circuits are able to measure nanosecond pulses of small amplitude. These two circuits must be further optimized for partial discharge detection in the future. In addition, the circuit should be tested prototypically with real partial discharge pulses.

One- and two-photon excitation dynamics using semiclassical electron force field model.

We have extended the semiclassical-based electron force-field simulation by introducing field-electron interaction to enable us to describe linear and nonlinear electronic excitation dynamics of a condensed matter system with low computational cost. To verify the simulation method, as a first step, numerical examples of interaction dynamics of simple systems (H atom, SiH4 molecule, and Si crystalline solid) with applied short electric field pulse as well as the obtained absorbed energies by the one- and two-photon excitations have been reported along with comparison with quantum dynamics calculations as reference.

Semiconductor WO3 thin films deposited by pulsed reactive magnetron sputtering

A pulsed reactive magnetron sputtering system with a tungsten target and a gas mixture of argon and oxygen was investigated as a source for the deposition of semiconductor WO3 thin films on soda lime glass substrates and on the glass with transparent conductive SnO2:F (FTO) electrode. The reactive sputtering process was performed in HiPIMS mode with low pulse repetition frequency fp ≈ 50–100 Hz and short pulse duration in HiPIMS discharge Ton = 100 μs. The second mode investigated was the mid-frequency (MF) magnetron discharge with pulse frequency fp = 40 kHz and pulse length Ton = 15 μs. The plasma parameters were investigated for both HiPIMS and MF modes using the planar RF probe operating at the frequency fprobe = 350 kHz and the grid QCM with biased collector electrode. Ion density ni and tail electron temperature (Te) were determined in both pulsed reactive magnetron sputtering discharge modes with time resolution. The maximum value ni ≈ 5 · 1017 m−3 was found in the reactive HiPIMS mode, and the maximum value ni ≈ 7 · 1016 m−3 was found in the reactive MF (40 kHz) mode. The degree of ionization of sputtered particles in reactive HiPIMS was determined for different values of (QO2) and was found to be in the range of ri ≈ 0.1–0.3. The deposition rate determined by QCM in reactive HiPIMS was practically independent on (QO2), but in the case of reactive MF, the measured deposition rate decreased significantly with increasing (QO2). The WO3 films deposited in both modes have a predominantly monoclinic crystal structure. The light and dark conductivity and the light/dark conductivity ratio (Ld) were measured under dark conditions and UV light illumination. At higher (QO2), the maximum value of Ld ≈ 300 was found for MF deposited WO3 and the maximum value of Ld ≈ 30 was found for HiPIMS deposited WO3. The photoelectrochemical measurement of WO3 deposited on FTO electrodes confirmed the n-type conductivity, and these films functioned as photoanodes in photoelectrochemical cells. MF deposited WO3 films systematically exhibited slightly higher photocurrents than HiPIMS deposited WO3. It was shown that these optimum photocurrents for HiPIMS and MF were found at QO2 ≈ 80 sccm and could not be improved by further increasing of (QO2).

Automated surface crack detection with inductive thermography

In recent years, inductive thermography has become established as a non-destructive inspection technique for detecting surface cracks in metallic parts. A short inductive heating pulse (0.1 – 1 s) is applied to the sample and an infrared camera records the surface temperature during and after the heating pulse. Since a surface crack obstructs both the eddy current flow and the heat flow, the defect becomes well visible in the infrared images. The technique has the advantage of being contact-free, fast and it can be fully automated. Additionally, it also provides information about the crack depth, because the deeper the crack, the greater the obstacle to the eddy current and to the heat flow. In order to detect the cracks in the infrared images of castings and forgings with complex geometry, a comparison method has been developed. The images of the inspected parts are compared with images of reference parts, and in this way artefacts caused by edges and corners of the parts are filtered out and not marked as defects. This greatly increases the robustness of the fully automated inspection, which can test parts 24 hours a day, and 7 days a week, without any human interaction, and the results of each part are well documented and stored.

A new fast and robust thermo-hydraulic code for ITER superconducting magnet simulation

A new software is being developed for plasma pulse scenario validation of the ITER magnet system behaviour and prediction of the margin to quench in superconductors. The principal idea behind this project has been to develop a software tool for the thermo-hydraulic simulation of superconducting magnets that is able to simulate different operations scenarios for the magnets at least an order of magnitude faster than real time. To achieve this level of performance, a tight coupling between the Cable-In-Conduit-Conductors and the structure of the magnet is performed. All the equations for the flow and heat conduction parts of the global model are put in a single sparse system that is integrated in time. Such tight coupling in combination with implicit time stepping allows much longer time steps whilst keeping high accuracy of the solution. The code named REIMS (Riemann Explicit Implicit Magnet Simulator) is still under development. Both central solenoid (CS) and toroidal field (TF) ITER magnets are available at this stage. The development of the different intermediate steps that led to the current version of the code required verification/validation against exact solutions, experimental data and/or comparisons with existing codes. In the same way, results obtained with REIMS for the simulation of both CS and TF loops after application of a short plasma pulse scenario have been compared to results from existing reference codes, showing a good agreement.

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.

Wigner function and intensity moments of spatio-temporal light fields

Abstract The Wigner distribution function and its spatial-angular moments (intensity-moments) are known as efficient instruments for characterization of complex quasimonochromatic light beams and their transformations. In this paper, the generalization of the WF-based approach to spatio-temporal (ST) light fields (wave packets, short pulses) is considered. It is shown that the ST intensity moments are related with the important characteristics of the wave-packet structure, especially, with the transverse orbital angular momentum (OAM) being a specific feature of the ST optical vortices (STOV). The ST moments’ transformations in a paraxial optical system obey simple and unified rules involving the ray-transfer ABCD-matrix of the system. On this base, and with simple examples of the OAM-carrying optical pulses, the schemes and mechanisms of the STOV generation and transformation are presented. Examples of non-vortex ST wave packets with the transverse OAM, their possible realizations are discussed as well as the relations between the OAM and the visible pulse rotations. The regular and unified formalism, developed in this paper, can be generalized and applied to more complex situations where the ST field propagates through inhomogeneous and random (scattering) media.

Safety and quality of life assessment at 6 months follow-up of the valvosoft pivotal study

Abstract Background Calcific Aortic stenosis (CAS) is currently the most common heart valve disease. Patients suffering from severe CAS are treated with invasive surgeries based on valve replacement. Symptoms heavily impact quality of life, including chest pain, shortness of breath, dizziness, fatigue, and major risks as heart failure or sudden death, and daily activities might also be strongly impacted. Purpose A prospective, multi-centre, single-arm, pivotal study (NCT05235568) was initiated in 2021 to treat severe CAS patients with Valvosoft, a medical device based on Non-Invasive Ultrasound Therapy (NIUT) intended to treat CAS in patients not eligible for immediate aortic valve replacement (SAVR/TAVR) or refusing such a treatment, to confirm safety and performance at 1-, 3-, 6- and 12 months. We present here the safety and quality of life results at 6M follow-up. Methods Valvosoft NIUT procedure is based on a trans-thoracic delivery of focused, high intensity short therapeutic ultrasound pulses, to precisely generate a cavitation bubble cloud on the aortic valve. Echocardiographic imaging enables to monitor the valve in real-time while cavitation causes both non-thermal tissue softening and calcification fractionation of the diseased valve. 60 planned subjects, suffering from severe calcific aortic stenosis, not recommended for aortic valve replacement or refusing such a procedure, were enrolled in 11 centres in Europe. Patients were awake or lightly sedated, NIUT was delivered during up to 70 minutes per patient per procedure. DSMB and CEC were installed to monitor safety, performance and effectiveness of Valvosoft device, and safety related to participation in the clinical investigation. Results Sixty high-risk patients advanced in age (85.2 ± 9.1) with multiple severe comorbidities were included. Primary safety endpoint (less than 25% MACE) was met at 30D (p=0.002). Furthermore patients experienced an overall quality of life improved. 6 minutes’ walk test increases from baseline towards 6 months with 10 %. At 6M follow-up, no stroke was reported, an average KCCQ score improvement of 17% was noticed, and NYHA class improved or stabilized for 78% of patients. The calcium score or volume on the aortic did not change pre- and post-procedure. Conclusion Valvosoft NIUT safety and quality of life improvement are proven at 6MFU, and the technology is presented as potentially disruptive, in the treatment of severe calcific aortic stenosis.

A cost-consequence analysis comparing three distinct cardiac ablation strategies for the treatment of paroxysmal atrial fibrillation

Abstract Background Cardiac ablation is a well-established treatment option for preventing atrial fibrillation (AF). While radiofrequency, cryo-energy, and laser energies are commonly employed in catheter ablation, they present the risk of potential damage to adjacent organs such as the oesophagus and phrenic nerve. To address these concerns, new technologies are being explored including pulsed field ablation (PFA), a non-thermal energy approach that employs high-voltage, short-duration pulses to selectively destroy target cells. Purpose The present analysis aims at: i) quantifying the short-term costs related to three ablation strategies for paroxysmal AF (PFA, radiofrequency ablation -RFA-, and cryo-balloon ablation -CRYO-), identify the cost drivers, and assess potential variations in resource consumption for each treatment alternative; ii) comparing the medium-term (1-year) economic implications of adopting the three alternatives, in terms of redo procedures (effectiveness) and complications (safety). Methods A cost-consequence model was developed to compare economic outcomes of the three ablation strategies for paroxysmal AF in the short- (during procedure) and medium-term (1-year). Resource consumption data during the procedure were collected by two European medical centres specialized in cardiac ablation (N=61 patients). For the medium-term analysis, costs were correlated to the effectiveness and safety of the procedures. The clinical data (i.e., redo and complication rates) considered in the model were retrieved from published literature. Costs and tariffs were collected from economic formularies of the respective hospitals. A scenario analysis was conducted to evaluate economic outcomes under various hypothetical difference in the prices of treatment kits. Results A significant difference was registered in terms of pre-procedural (mean±SD: 13.9±4.4 min for PFA, 20.1±7.6 min for CRYO and 20.5±7.7 min for RFA; ANOVA test p=0.003) and procedural time (skin-to-skin), favouring PFA over RFA and CRYO (53.6±26.8 min for PFA, 72.4±28.1 min for CRYO and 149.9±99.9 min for RFA; p<0.0001; Table 1). PFA was associated with lower procedural costs vs CRYO (-€400) and RFA (-€827). A similar economic advantage was observed in the medium-term (Table 2). The scenario analysis showed that PFA would be cost-saving vs CRYO (Δtotal costs ≤ 0) up to a price difference of +€881 (i.e., PFA kit is more expensive than CRYO kit), and similarly, up to a price difference of +€1,306 vs RFA. Above these thresholds, PFA would be considered cost-effective vs CRYO or RFA, due to its efficacy despite being more expensive. Conclusion In summary, PFA emerges as cost-effective or even cost-saving over CRYO and RFA, thanks to its faster execution, lower redo, and complications rate. Moreover, PFA time predictability would facilitate hospital planning. For a complete analysis, these benefits should be evaluated against the difference in acquisition costs among treatments.Procedural time by phase and techniqueCumulative savings per technique

Short-pulse of systemic steroids in acute pericarditis: an alternative in refractory cases

Abstract Introduction Acute pericarditis accounts for 5% of emergency room admissions for chest pain. First line treatment consists of non-steroidal anti-inflammatory drugs (NSAIDs) and colchicine. Systemic corticosteroids (SCS) are usually reserved as a second-line therapy due to a higher rate of recurrences and side effects. Whether a short pulse of low-dose SCS is safe and effective during the acute phase of the disease remains unknown. Purpose To investigate safety and efficacy of a 3 day pulse of 40 mg intravenous methylprednisolone in patients hospitalized for acute pericarditis with a lack of response to NSAIDs and colchicine. Methods A retrospective, observational and unicentric study was performed including patients hospitalized for acute pericarditis between 2019 and 2023. Patients with asymptomatic pericardial effusion or predominance of myocardial injury were excluded. Patients were considered to be refractory to conventional treatment when at least one of the following criteria was present despite five days of high-dose NSAIDs and colchicine: 1- Moderate/severe pericardial effusion persistence. 2- Chest pain persistence. 3- Increase of inflammatory biomarkers. These patients received methylprednisolone 40mg for three days on top of standard treatment. Baseline characteristics, treatment received during hospitalization and events during follow-up were analysed. Data were expressed as mean and standard deviation (quantitative variables) and percentages (categorical variables). Two-sided P value of less than 0.05 was considered statistically significant. Results 70 patients with acute pericarditis requiring hospitalization were included (54±19 years; 71% male) with a mean follow-up of 10±21 months. 26 of them (37%) received methylprednisolone 40mg for three days due to lack of response to standard treatment. Table 1 includes a comparison of patients who received systemic corticosteroids versus those who did not (control group). C-reactive protein (CRP) was significantly higher in the group receiving corticosteroids (188±86 mg/L vs 135±85 mg/L; p=0.014) and it significantly decreased during hospital stay compared to the control group (151±87 mg/L vs 97±74 mg/L; p=0.013). 14 patients (20%) experienced a recurrence of chest pain during follow-up with no significant difference according to the treatment received (27% vs 16%; p=0.266) Conclusion A 3-day pulse of low-dose SCS seems to be useful and safe for hospitalized patients with acute pericarditis who show lack of response to NSAIDs and colchicine, with no increase in recurrence rate. However, more evidence based on randomized control trials is needed to support this therapeutic approach.Table 1

Needle-Free Targeted Injections Using Bubble Laser Technology in Therapeutics.

This work explores bubble laser technology as an alternative to needles in injection systems for vaccination, cancer treatment, insulin delivery, and catheter hygiene. The technology leverages laser-induced microfiltration and bubble dynamics to create high-speed pneumatic jets that penetrate the skin without needles, addressing discomfort, infection risk, and needle-related concerns. The system's performance is analyzed based on laser wavelength, pulse duration, and Gaussian beam droplet size. The findings indicate a significant increase in spot size at 1064 nm compared with 400 nm, consistent with the diffraction theory. Induced bubble dynamics reveal bubble generation, jetting, and fluid interactions as the Weber number increases, as well as jet velocity and fluid inertia. For femtosecond pulses, increasing the pulse duration from 100 to 1500 fs reduces the bubble lifespan from 0.8 to 0.3 arbitrary units, and the collapse pressure decreases from 2.1 to 0.4 bar. For picosecond pulses, the bubble lifetime decreases from 0.9 to 0.5 arbitrary units, and the pressure drop decreases from 2.0 to 0.4 bar as the pulse length extends from 2000 to 8000 ps. Jet formation in laser jet injection systems is enhanced by short pulses in water that produce longer-lasting bubbles. Drug delivery based on the Rayleigh-Plesset equation is characterized by a low-pressure collapse and short bubble lifetime. Thus, this relationship suggests that bubble laser technology can provide a more controlled and safer method of needle-free procedures, increasing compliance and reducing tissue trauma.

Few-femtosecond time-resolved study of the UV-induced dissociative dynamics of iodomethane

Ultraviolet (UV) light that penetrates our atmosphere initiates various photochemical and photobiological processes. However, the absence of extremely short UV pulses has so far hindered our ability to fully capture the mechanisms at the very early stages of such processes. This is important because the concerted motion of electrons and nuclei in the first few femtoseconds often determines molecular reactivity. Here we investigate the dissociative dynamics of iodomethane following UV photoexcitation, utilizing mass spectrometry with a 5 fs time resolution. The short duration of the UV pump pulse (4.2 fs) allows the ultrafast dynamics to be investigated in the absence of any external field, from well before any significant vibrational displacement occurs until dissociation has taken place. The experimental results combined with semi-classical trajectory calculations provide the identification of the main dissociation channels and indirectly reveal the signature of a conical intersection in the time-dependent yield of the iodine ion. Furthermore, we demonstrate that the UV-induced breakage of the C-I bond can be prevented when the molecule is ionized by the probe pulse within 5 fs after the UV excitation, showcasing an ultrafast stabilization scheme against dissociation.

Circuit Modeling of the Impact of Heavy Charged Particles on Transient Processes in Bipolar Analog Microcircuits

One of the factors causing the failure of spacecraft integrated circuits is exposure to heavy charged particles. The entry of heavy charged particles into electronic devices leads to the appearance of single event transients (short current pulses), which in analog microcircuits manifest themselves in distortion of the output signal shape, and in digital microcircuits can cause a single event upset. The article discusses a technique for circuit mode-ling of the effect of heavy charged particles on bipolar analog microcircuits, including the developed equivalent electrical circuit of a bipolar transistor for LTSpice and the procedure for modeling transient processes. Despite the simplifications adopted, namely: failure to take into account the dependence of the duration of the rise and fall of the current pulse generated by a charged particle on the parameters of the transistor structure, the assumption that the entire charge is generated in the active base and the space charge regions of the emitter and collector junctions, an equivalent circuit has been developed made it possible to determine that the shape of the collector current pulse for circuit with a common emitter when exposed to a heavy charged particle is determined by the speed of the transistor and its operating mode. Using the developed methodology, the “critical” transistors of the two studied analog microcircuits were determined, and the need to bypass the current-setting resistors with a small capacitor was justified.

Ion motion in strongly magnetized cluster laser plasma

Abstract This paper investigates the interaction of high intensity, circularly polarized, short laser pulses with heavy cluster plasma through analytical modelling and numerical simulations. The optimal parameters were found for the generation of several GigaGs, quasi-stationary magnetic field by using the upgraded analytical model and detailed 3D PIC simulations. It was confirmed that a field of such strength slows down the thermal expansion of the cluster core in the direction transverse to the laser beam axis, which can be used in nuclear physics. The generated inward shocks produce ion core compression, which is relevant to nuclear fusion. The electrostatic interaction between the rotating laser field, electrons and ions leads to ion spiral density distribution in the cluster’s transversal plane, which is absent in a cluster irradiated by linearly polarized pulses with the same parameters.

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.

Effects of axial launch spacing on cavitation interference and load characteristics during underwater salvo

This paper analyzes the effect of launch interval on cavitation flow interference and load characteristics during underwater salvo. The study employs the Improved Delayed Detached Eddy Simulation and the Schnerr-Sauer cavitation model, Volume of Fluid (VOF) multiphase flow model, and overlapping grid. Additionally, decompression experiment systems are designed, and numerical simulations are found to be in good agreement with experimental results, thus verifying the effectiveness of the simulation. Detailed discussions are provided on multiphase flow field and load distribution. The results reveal a top-down collapse process of the cavity, with collapse shrinking to an isolated bubble at the end. Synchronized collapse pressure is characterized by short pulse widths at the peaks, all located at the lowermost part of the cavity. During the underwater stage, when the axial launch spacing ranges between 0.5 times and 1.0 times the length of the projectile, the head of the second projectile acts on the area below the center of mass of the first. This leads to gradual stabilization of the initial cavity and a decrease in deviation of the center of mass toward the inside. Despite experiencing large-scale fracture and detachment due to interference from the wake of the first engine, the motion stability of the inside cavity of the second projectile remains intact. In the water exit stage, when the axial launch spacing ranges between 0.75 times and 1 time the length of the projectile, it causes expansion and contraction of the inside cavity of the second projectile. However, asymmetric synchronous collapse loads may occur, leading to unstable motion posture.

Antiferromagnetic standing spin waves generated in NiO thin films by short strain pulses

Antiferromagnetic standing spin waves generated in NiO thin films by short strain pulses