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In this study, we examined the potential errors in plasma-density measurements using the cutoff probe method under various structural conditions, such as tip distance and length. Our studies indicate that under conditions of thin sheath thickness, the length or distance of the metal tips on the cutoff probe has a slight effect on the plasma transmission spectrum or cutoff frequency. However, under conditions with a notably thick sheath, the structure of the probe tip can cause an error of up to 2% between the measured cutoff frequency and actual plasma frequency. Consequently, for precise measurements of plasma density using the cutoff probe method, it is imperative to maintain a probe tip distance exceeding five times the sheath width and utilize a sufficiently long probe tip length. This finding is anticipated to provide essential guidelines for the design and fabrication of effective cutoff probes and enhance the accuracy of plasma-density measurements using a cutoff probe. [ABSTRACT FROM AUTHOR]

A fully cylindrical Hall thruster prototype was tested in the power range of 30–300 W with the objective of understanding the behavior of the discharge as a function of input parameters. Various operating conditions were compared, including two magnetic field configurations, a set of propellant mass flow rates, and a range of discharge voltages. Plasma properties were measured in the plume, with a Langmuir probe, a retarding potential analyzer, and a Faraday cup. The experimental results showed that the mass flow rate strongly affects the ionization and, consequently, other related properties such as the plasma density, currents, and propellant utilization. The discharge voltage also appeared to influence the ion energy and propellant utilization. The performance accessible from the measured magnitudes is assessed, resulting in a maximum thrust efficiency of about 18% at 0.35 mg s − 1 and 168 W. [ABSTRACT FROM AUTHOR]

A nanosecond Nd:YAG laser was used to study the laser ablation of aluminum foil in the phase explosion regime at a laser intensity range of 0.63–3.61 × 10 12 W / cm 2. Laser ablation and plasma characteristics were studied using microscopic ablation crater images, plasma emission spectra, and plasma plume images. Measured plasma density using a Stark width of Al I (396.2 nm) showed a strong linear correlation with crater size, with a Pearson correlation coefficient (r) of 0.97. To understand the origin of this linear correlation, plasma temperature was estimated using Bremsstrahlung emission from 512 to 700 nm. The estimated plasma temperature and aspect ratio of the plasma plume were negatively correlated, having r = − 0.76. This negative correlation resulted from a laser-plasma interaction, which heated the plasma and increased its hydrodynamic length. The percentages of laser energy used for plasma heating ( E p / E L ) and Al foil ablation ( E Al / E L ) were estimated from plasma temperature. Increased E Al / E L , such as crater size, with increasing laser intensity, confirms that greater mass ablation is the fundamental reason for the strong linear correlation between crater size and plasma density. [ABSTRACT FROM AUTHOR]

The microwave electrothermal thruster (MET) utilizes wave-exited microdischarges to heat gas flows, enhancing the specific impulse of the thruster. Our computational study investigates a 17.5 GHz helium-propellant MET, employing a two-dimensional, axisymmetric fluid model of plasma coupled with electromagnetic wave and gas flows. The discharges operate in the glow regime, remaining weakly ionized, and in thermal non-equilibrium. The plasma densities reach approximately 10 20 m − 3 , and the gas temperature is around 2000 K. Even a slight off-resonant frequency operation results in a significantly lower plasma density and gas temperature. Gas heating, primarily driven by electromagnetic Joule heating, plays a critical role in influencing the overall discharge behavior. The measured peak thrust and specific impulse are 8.24 mN and 292 s, respectively, at a mass flow rate of 3.2 mg/s with 30 W of power. Compared to a cold gas thruster, there is a significant increase in the specific impulse by a factor of approximately 1.7. The enhanced performance trades off with propulsive efficiency, which decreases by a factor of 1.5 from the peak 65% at 10 W. This is due to higher energy losses to cavity walls from heat conduction with increased power. These findings underscore the critical balance between the input power and mass flow rate to improve the MET performance, highlighting the importance of power management to maximize thrust and efficiency. Furthermore, the predicted thrust and specific impulse agree well with experimental values for nominally similar MET thruster studies in the literature. [ABSTRACT FROM AUTHOR]

We use a 2.5D hybrid simulation to study the breathing mode (BM) dynamics in Hall thrusters (HTs). This involves a 1D Euler fluid simulation for neutral dynamics in the axial direction, coupled with a 2D axial–azimuthal Particle-in-Cell (PIC) simulation for charged species. The simulation also includes an out-of-plane virtual dimension for wall losses. This setup allows us to replicate the BM's macroscopic features observed in experiments. A comprehensive analysis of plasma parameters in BM's phases divides it into two growth and two decay sub-phases. Examining 1D axial profiles of electron temperature, gas and plasma densities, and particle creation rate shows that an increase in electron temperature alone cannot sustain ionization. Ionization seems to be influenced by the spatial correlation between electron and gas densities and the ionization rate coefficient. Investigating ion back-flow reveals its impact on modulating neutral flux entering the ionization region. The hybrid simulation's outcomes let us assess the usual 0D predator–prey model's validity and identify its limitations. The ionization and ion convection term approximations hold, but the gas convective term approximation does not. Introducing an alternative gas convective term approximation involving constant density ejection from the ionization region constructs an unstable BM model consistent with simulation results. In addition, this paper explores how varying the imposed voltage and mass flow rate impacts the BM. The BM frequency increases with imposed voltage, aligning with theoretical predictions. The mass flow rate variation has a limited effect on BM frequency, following the theoretical model's trend. [ABSTRACT FROM AUTHOR]

Laser diode absorption spectroscopy is used to experimentally measure Ar(1s5) metastable density and translational gas temperature within a 94 GHz microplasma. A square two-dimensional photonic crystal (PhC) at this resonance frequency serves to ignite and sustain the plasma from 20 to 200 Torr (2.7 × 103–2.7 × 104 Pa) by using millimeter wave power from 300 to 1000 mW. Metastable density within the plasma is estimated from the absorption line shape of the laser traversing the PhC. The metastable density reaches an order of 1019 m−3 at lower pressure and decreases as pressure increases. From the Lorentzian line shape of the absorption profile at 811.53 nm, the gas temperature is extracted and found to increase from 500 K at 20 Torr to 1300 K at 200 Torr. These data are analyzed and compared with a zero-dimensional plasma model and with previous experimental plasma results at 43 GHz. [ABSTRACT FROM AUTHOR]

An analysis of plasma density distributions at arbitrary ion–atom collisionality for one-dimensional axially symmetrical cylindrical and annular plasmas is presented. Perturbations of plasma densities caused by a cylindrical probe are studied for arbitrary ion–atom collisionality. Analytical expressions for the plasma characteristics near the probe for low collisionality have been obtained. The plasma was modeled by the hydrodynamic neutral plasma equations, taking into account ionization, ion inertia, and a non-linear ion frictional force, which dominates the plasma transport at low gas pressures. Significant plasma density depletion around the probe has been observed for a wide range of ion–atom collisionality. The presented results predict underestimation of plasma density obtained from the classical Langmuir probe procedure and should provide a better understanding of electrostatic, magnetic, and microwave probes inserted into plasmas at low gas pressure. [ABSTRACT FROM AUTHOR]

This study examines the extended version of the Zakharov system characterizing the dispersive and ion acoustic wave propagation in plasma. The genuine, non-dispersive field depicts a shift in plasma ion density from its equilibrium state, whereas the complex, dispersive field depicts the fluctuating envelope of a highly oscillatory field of electricity. The main focus of the analysis is on employing the expanded Fan sub-equation approach to achieve some novel travelling wave structures including the explicit, periodic, linked wave, and other new exact solutions are developed for different values of this parameter. Three dimensional graphs are utilised to examine the properties of the obtained solutions. Furthermore, ideas from planar dynamical theory are applied in this work to analyse the intricate behaviour of the analysed model. Sensitivity analysis, multistability, quasi-periodic and chaotic patterns, Poincaré map, and the Lyapunov characteristic exponent are used to analyse the dynamical features. [ABSTRACT FROM AUTHOR]

Air plasma induced by ultrafast laser pulses is an extraordinary source of electromagnetic waves, emitting microwave, terahertz (THz) radiation, and cavityless lasing in the near‐infrared and visible ranges. The temporal dynamics of the electron density have been revealed by optical pump‐probe techniques, while the evolution of the electron temperature remains elusive due to a lack of suitable methods. Here, it is demonstrated that the intense THz‐field‐enhanced fluorescence emission from the excited molecules of nitrogen is a novel tool that allows to explore the complex dynamics of the plasma density and electron temperature simultaneously. Two relaxation times of electrons in air plasma are observed and interpreted as a competition between the excitation of a triplet state by laser or THz‐field‐heated electrons and the dissociative recombination of nitrogen molecular ions. Based on the theoretical simulations, the tens of picoseconds relaxation process is attributed to the ultrafast temperature decrease, while the longer relaxation in the range of hundreds of picoseconds is ascribed to the decay of electron density. The temporal relaxation of both the electron density and temperature revealed by applying an intense THz field provides further insights into the laser‐air plasma interaction and will benefit the engineering of this exceptional source. [ABSTRACT FROM AUTHOR]

Supersonic ion jets produced in vacuum arc discharges have a wide range of applications, where precise control of ion kinetic energy is crucial. However, a comprehensive understanding of the ion acceleration mechanism remains elusive, particularly regarding whether there is ion velocity separation in the vacuum spark stage. In this paper, a 1D spherical implicit particle-in-cell (PIC) with Monte Carlo collision (MCC) model is employed to investigate the ion velocity separation in multi-charged vacuum arc plasma with varying electrode bias voltages and plasma ion densities. The results show that ion kinetic energy can reach hundreds of electron volts due to continuous acceleration by the formed potential valley, which leads to ion velocity separation at low electrode bias voltage or low plasma density. An increasing electrode bias voltage flattens the potential valley, reducing the electric field acceleration. While increasing the plasma density deepens the valley and intensifies Coulomb collisions, resulting in nearly-equal velocities across ions in different charge states. These findings can theoretically explain the discrepancies observed in previous experiments regarding the dependence of the ion velocity on its charge state during the vacuum spark stage. [ABSTRACT FROM AUTHOR]

Introduction: We aim to examine how magnetic resistivity impacts the movement of magnetoacoustic waves near a magnetic null-point in the solar corona. Method: The resistive, nonlinear MHD simulations are solved by the PLUTO code in 2.5D for different amount of the resistivity. Results and Discussion: Propagation of magnetoacoustic waves in the vicinity of a magnetic null point has the potential to create current sheets with high current density excitation and plasmoid generation. During the entire duration of the simulation, it is discovered that plasma density became significant due to the plasmoid and also current density is high for high resistivity. It is depicted that high resistivity also leads to bigger plasmoids or magnetic islands in comparison to small resistivity. [ABSTRACT FROM AUTHOR]

The high‐density transient plasma, streaming from a pulsed plasma accelerator (PPA), was diagnosed with a Triple Langmuir probe (TLP) for spatial mapping of the stream in terms of plasma density and temperature. A contour plot for density and temperature shows a distinct form of a highly dense island of plasma with varied plasma temperatures. The formation of such highly dense islands can be correlated with the formation of distinct plasma structures, as observed in astrophysical plasmas and fusion plasma. The results of TLP were supported by the intensity variation derived from signals of a photodetector system. The plasma stream imaged with high‐speed video camera also showed the density fluctuation inside the plasma stream. The estimated maximum density and temperature were ∼7.2 × 1020 m−3 and ∼28 eV, respectively. [ABSTRACT FROM AUTHOR]

The impact of spatial and temporal evolution of nonlinear mixing of two Gaussian laser pulses propagating in plasma on generation of terahertz (THz) radiation have been investigated taking into account the ponderomotive nonlinearity. By calculating the modified electron density of plasma caused by the finite ponderomotive force of the pump lasers and using wave equation and paraxial ray approximation, two coupled governing equations for temporal and spatial pulse‐width parameters have been derived. The electric field of the THz wave as a result of nonlinear current density induced by the beat ponderomotive force of the pulses was extracted. Combined effects of initial laser and plasma parameters on the behavior of self‐compression and self‐focusing as well as THz radiation generation were investigated. The numerical results indicated a considerable spatiotemporal compression takes place within a specific range of laser intensity, exhibiting a saturation intensity point where the compression process reaches its maximum extent. It is observed that the generated THz radiation also strongly depends on the spatiotemporal dynamics of the pump pulses. The maximum THz amplitude corresponds to the strongest pump pulse compression extent. [ABSTRACT FROM AUTHOR]

The injection of energy into the Earth's magnetosphere during geomagnetic storms and substorms has a direct impact on the ionosphere in the auroral and sub-auroral regions. This influence can be observed through phenomena such as the expansion of the auroral oval, and fluctuations in plasma density and the intensity of the field-aligned current (FAC) system. Changes in the geomagnetic environment significantly affect the main ionospheric trough (MIT) and field-aligned currents (FACs). In this study, we analysed two geomagnetic storms of different origins—October 2015 and September 2017 that occurred during solar cycle 24. Both storms were characterised by two minima of the Dst index and classified as two-step storms. In this work, we investigate the evolution of FACs density, the displacement of MIT and FACs during the development of geomagnetic storms, and we quest for the relationship between field-aligned currents and the main ionospheric trough. We noticed a connection between the positions of the main ionospheric trough minima and the Dst index, found cases especially during the main and recovery phase of the storms when FACs increase after leaving the ionospheric trough, and observed the predominance of downward currents in the area of the MIT which suggest their influence on the formation of this region of depleted plasma density. [ABSTRACT FROM AUTHOR]

In this study the electron density of an atmospheric plasma generated between a pin electrode and a water surface is measured by determining the Stark broadening of H α and H β emission lines. Comparable values for the electron density are achieved using the H α and H β broadening obtained in separate measurements. During the temporally evolving system, increasing electron densities are measured of 0.5 − 3 ⋅ 10 15 cm−3 during the plasma treatment of 5–10 min. The effect of the water temperature on plasma-water interaction is investigated by heating the water to ≈ 70 ∘ C prior to the measurements. This resulted in higher gas temperatures during the discharge up to 2500 K and 4000 K for positively and negatively pulsed discharge, respectively. Furthermore, an earlier increase of electron density and conductivity of the water is measured for the preheated experiments. The humidity of the gas is likely to be an important parameter causing the observed results. [ABSTRACT FROM AUTHOR]

Image plates (IPs), or phosphor storage screens, are a technology employed frequently in inertial confinement fusion (ICF) and high energy density plasma (HEDP) diagnostics because of their sensitivity to many types of radiation, including, x rays, protons, alphas, beta particles, and neutrons. Prior studies characterizing IPs are predicated on the signal level remaining below the scanner saturation threshold. Since the scanning process removes some signal from the IP via photostimulated luminescence, repeatedly scanning an IP can bring the signal level below the scanner saturation threshold. This process, in turn, raises concerns about the signal response of IPs after an arbitrary number of scans and whether such a process yields, for example, a constant ratio of signal between the nth and n + 1st scan. Here, the sensitivity of IPs is investigated when scanned multiple times. It is demonstrated that the ratio of signal decay is not a constant with the number of scans and that the signal decay depends on the x-ray energy. As such, repeatedly scanning an IP with a mixture of signal types (e.g., x ray, neutron, and protons) enables ICF and HEDP diagnostics employing IPs to better isolate a particular signal type. [ABSTRACT FROM AUTHOR]

A plasma device has been created to study dynamic plasma coupling in an E × B-drifting magnetized plasma. The E × B magnetized plasma device is a 1.2 m diameter by 2 m long cylindrical chamber with two sets of Helmholtz coils in a mirror configuration. A steady-state axial hollow cathode source injects a plasma discharge in electrical contact with a floating conductor at a range that forms a unique axisymmetric equipotential surface or Virtual Cathode Lightsaber (VCL). The VCL generates two plasma populations streaming relative to one another providing a suitable environment for the investigation of dynamic plasma coupling. The plasma density, radial electric field, and plasma rotational velocity outside the VCL are shown to be influenced by the current–voltage relationship of the cathode and applied magnetic field strength. A basic characterization of the device and plasma environment is presented with an emphasis on diagnostics systems and the analytical techniques utilized. [ABSTRACT FROM AUTHOR]

Real-time monitoring of plasma parameters at the wafer plane is important because it significantly affects the processing results, yield enhancement, and device integrity of plasma processing. Various plasma diagnostic sensors, including those embedded in a chamber wall and on-wafer sensors, such as flat-cutoff sensors, have been developed for plasma measurements. However, to measure the plasma density on the wafer surface in real-time when processing plasma with bias power, such as in the semiconductor etching process, one must analyze the transmission spectrum of the flat-cutoff sensor in an environment with bias power applied. In this study, the transmission-spectrum and measured plasma-density characteristics of an electrode-embedded flat-cutoff sensor are analyzed via electromagnetic simulations and experiments under applied bias power. Our findings indicate that the flat-cutoff sensor accurately measures the plasma density, which is equivalent to the input plasma density under low bias power. Conversely, under high bias power, the plasma density measured by the sensor is lower than the input plasma density. Also, a thick-sheath layer is formed owing to the high bias power, which may complicate the measurement of plasma parameters using the flat-cutoff sensor. Plasma diagnostics using a flat-cutoff sensor in thick-sheath environments can be achieved by optimizing the flat-cutoff sensor structure. Our findings can enhance the analysis of plasma parameters on-wafer surfaces in processing environments with bias power applied. [ABSTRACT FROM AUTHOR]

It is shown theoretically that the two-plasmon-decay instability (TPD) in laser–plasma interaction can be excited in the non-eigenmode regime, where the plasma density is larger than the quarter critical density. This appears when the laser amplitude is larger than a certain threshold value, which is found to increase with the plasma density. In this regime, the excited electrostatic modes have a constant frequency around half of the incident light frequency. The theoretical model is validated by particle-in-cell simulations. The simulation results show that the non-eigenmode TPD has a higher threshold amplitude for the pump laser than the non-eigenmode stimulated Raman scattering (SRS) excited in the plasma above the quarter critical density. In inhomogeneous plasma, competition between non-eigenmode TPD and non-eigenmode SRS occurs since the excitation of the former is normally accompanied by the latter. [ABSTRACT FROM AUTHOR]

Electrostatic particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) methods are used to compare the plasma dynamics of collisionless with collisional emissive sheaths in partially ionized environments. Space-charge limited emissive sheaths submersed in a plasma with a density of ∼1017 m−3 are examined using a PIC-DSMC solver, CHAOS. Collisionless emissive sheaths with plasma domains sufficiently long (30 and 60 Debye lengths, λD) are subject to strong oscillations due to two-stream electron instability, whereas emissive sheaths in weakly collisional conditions with a short domain (15 λD) exhibit self-spike (sawtooth) oscillations in the plasma field due to the trapped charge-exchange (CEX) ion population within the virtual cathode (VC) region. The two-stream electron instability leads to strong temporal fluctuations in the total emission current, with maximum deviations of 60% and 100% from the time-averaged current for the long plasma domains, whereas CEX collisions cause strong spikes in the emission current if the domain size is short. Our PIC-DSMC simulations show for the first time that the interaction of the two types of instabilities causes the strength of the self-spike to be weakened due to the strong fluctuations caused by the two-stream instability when a sufficiently long computational domain with ion-neutral collisions is employed. By conducting a two-dimensional Fast Fourier Transform (FFT) on the collisional and collisionless sheaths with long domains, we show that the transient evolution of CEX entrapment in the VC increases frequency of sheath oscillations up to two times the ion-acoustic frequencies observed in the collisionless sheath. CEX collisions weaken the VC region and result in a total emission current more than that obtained from the collisionless case for the same domain length. With a more rarefied neutral environment of 1019 m−3 in the plasma sheath, the total emission current increases only 4% in comparison with 14% for one order of magnitude denser environment, within 20 μs. In addition, the spike period is tested with different neutral temperatures and densities. While we do not observe any self-spike in the more rarefied environment, the spike period increased from 5 to 7.5 μs when the neutral temperature is increased from 300 to 2000 K in the denser environment with the simulation time of 20 μs. [ABSTRACT FROM AUTHOR]

Quantitative spectroscopy of molecular hydrogen has generated substantial demand, leading to the accumulation of diverse elementary process data encompassing radiative transitions, electron-impact transitions, predissociations, and quenching. However, their rates currently available are still sparse, and there are inconsistencies among those proposed by different authors. In this study, we demonstrate an experimental validation of such a molecular dataset by composing a collisional-radiative model (CRM) for molecular hydrogen and comparing experimentally obtained vibronic populations across multiple levels. From the population kinetics of molecular hydrogen, the importance of each elementary process in various parameter space is studied. In low-density plasmas (electron density n e ≲ 10 17 m − 3 ) the excitation rates from the ground states and radiative decay rates, both of which have been reported previously, determine the excited state population. The inconsistency in the excitation rates affects the population distribution the most significantly in this parameter space. However, in higher density plasmas ( n e ≳ 10 18 m − 3 ), the excitation rates from excited states become important, which have never been reported in the literature, and may need to be approximated in some way. In order to validate these molecular datasets and approximated rates, we carried out experimental observations for two different hydrogen plasmas; a low-density radio frequency heated plasma ( n e ≈ 10 16 m − 3 ) and the Large Helical Device (LHD) divertor plasma ( n e ≳ 10 18 m − 3 ). The visible emission lines from EF 1 Σ g + , H H ¯ 1 Σ g + , D 1 Π u ± , GK 1 Σ g + , I 1 Π g ± , J 1 Δ g ± , h 3 Σ g + , e 3 Σ u + , d 3 Π u ± , g 3 Σ g + , i 3 Π g ± , and j 3 Δ g ± states were observed simultaneously and their population distributions were obtained from their intensities. We compared the observed population distributions with the CRM prediction, in particular the CRM with the rates compiled by Janev et al., Miles et al., and those calculated with the molecular convergent close-coupling (MCCC) method. The MCCC prediction gives the best agreement with the experiment, particularly for the emission from the low-density plasma. However, the population distribution in the LHD divertor shows a worse agreement with the CRM than those from low-density plasma, indicating the necessity of the precise excitation rates from excited states. We also found that the rates for the electron attachment is inconsistent with experimental results. This requires further investigation. [ABSTRACT FROM AUTHOR]

The long proton beams present at CERN have the potential to evolve into a train of microbunches through the self-modulation instability process. The resonant wakefield generated by a periodic train of proton microbunches can establish a high acceleration field within the plasma, facilitating electron acceleration. This paper investigates the impact of plasma density on resonant wakefield excitation, thus influencing the acceleration of a witness electron bunch and its corresponding betatron radiation within the wakefield. Various scenarios involving different plasma densities are explored through particle-in-cell simulations. The peak wakefield in each scenario is calculated by considering a long pre-modulated proton driver with a fixed peak current. Subsequently, the study delves into the witness beam acceleration in the peak wakefield and its radiation emission. Elevated plasma density increases both the number of microbunches and the accelerating gradient of each microbunch, consequently resulting in heightened resonant wakefield. Nevertheless, the scaling is disrupted by the saturation of the resonant wakefield due to the nonlinearities. The simulation results reveal that at high plasma densities, an intense and broadband radiation spectrum extending into the domain of the hard x-rays and gamma rays is generated. Furthermore, in such instances, the energy gain of the witness beam is significantly enhanced. The impact of wakefield on the witness energy gain and the corresponding radiation spectrum is clearly evident at elevated densities. [ABSTRACT FROM AUTHOR]

In this paper, we report the excitation of coherent density and potential fluctuations induced by magnetohydrodynamic (MHD) activity in the edge plasma region of ADITYA-U tokamak. When the amplitude of the MHD mode, mainly the m/n = 2/1, increases beyond a threshold value, | B ̃ θ | / B θ ∼ 0.3 % – 0.4 % , coherent oscillations in the density and potential fluctuations are observed having the same frequency as that of the MHD mode. The mode numbers of these MHD induced density and potential fluctuations are obtained by Langmuir probes placed at different radial, poloidal, and toroidal locations in the edge plasma region. Detailed analyses of these Langmuir probe measurements reveal that the coherent mode in edge potential fluctuation has a mode structure of m/n = 2/1, whereas the edge density fluctuation has an m/n = 1/1 structure. It is further observed that beyond the threshold, the coupled power fraction scales almost linearly with the magnitude of B ̃ θ / B θ fluctuations. Furthermore, the rise rates of the coupled power fraction for coherent modes in density and potential fluctuations are also found to be dependent on the growth rate of magnetic fluctuations. The disparate mode structures of the excited modes in density and plasma potential fluctuations suggest that the underlying mechanism for their existence is the coupling of even harmonics of potential to the odd harmonics of pressure due to 1/R dependence of the toroidal magnetic field. [ABSTRACT FROM AUTHOR]

We present a numerical study on the electron and ion density perturbation in low-temperature plasmas driven by the frequency detuning of two intense laser beams. Our study is performed in the hydrodynamic regime, which becomes applicable when the plasma grating period induced by the beating of the laser beams is greater than the Debye length and collective processes such as plasma oscillations can be excited. Our findings show a resonance in electron density perturbation as the frequency detuning approaches a value consistent with the Bohm–Gross dispersion relation in low- and high-pressure plasmas. We discuss the potential of this resonance as a diagnostic tool for precisely measuring electron temperature and density in low-temperature plasmas through coherent scattering. [ABSTRACT FROM AUTHOR]

On 22 January 2024, at 18 UT, a strong earthquake (EQ), Mw = 7, occurred with the epicenter at 41°N, 79°E. This seismic event generated a complex response, the elements of which correspond to the concept of lithosphere–atmosphere–ionosphere coupling through electromagnetic processes. While flying over the EQ area on the night-ide of the Earth, the tandem of low-orbiting Swarm satellites observed small-scale irregularities in the plasma density with an amplitude of ~1.5 × 104 el/cm3, which are likely associated with the penetration of the coseismic electric field into the ionosphere. The local anomaly was detected against the background of a global increase in total electron content, TEC (although geomagnetic indices remained quiet), since the moment of EQ coincided with the ionospheric response to a solar flare. In the troposphere, specific humidity decreased while latent heat flux and aerosol optical depth increased, all exhibiting the co-located disturbances that can be attributed to the effect of increased air ionization rates, resulting in greater electrical conductivity in the near-Earth boundary layer. Anomalies started developing over the epicenter the day before and maximized on the day of the main shock and aftershocks. [ABSTRACT FROM AUTHOR]

Direct laser acceleration has proven to be an efficient source of high-charge electron bunches and high brilliance x-rays. However, an analytical description of the acceleration in the interaction with varying plasma density targets is still missing. Here, we provide an analytical estimate of the maximum energies that electrons can achieve in such a case. We demonstrate that the maximum energy depends on the local electron properties at the moment when the electron fulfills the resonant condition at the beginning of the acceleration. This knowledge enables density shaping for various purposes. One application is to decrease the required acceleration distance needed to achieve the maximum electron energy. Another use for density tailoring is to achieve acceleration beyond the radiation reaction limit. We derive the energy scaling law that is valid for arbitrary density profile that varies slowly compared with the betatron period. Our results can be applied to electron heating in exponential preplasma of thin foils, ablating plasma plumes, or gas jets with long-scale ramp-up. [ABSTRACT FROM AUTHOR]

The effect of external gas injection near the plume on the performance of a microwave discharge cathode is investigated. Experiments were conducted under two gas injection conditions: gas addition and gas distribution. Gas distribution tended to lead to better performance than gas addition. In the gas distribution experiments, the total gas consumption was kept constant, the internal gas flow rate was reduced, and external gas was supplied. The electron current increased from 0.26 to 0.49 A at 35 V when the microwave power was 15 W. When the sum of the internal and external gas flow rates was held constant, external gas injection lowered the neutralization costs and increased the gas utilization efficiency. The neutralization current was successfully increased by 48 % at 12 W of microwave power compared with 8 W of microwave power with the same level of naturalization cost and gas utilization efficiency. The electron temperature and plasma density in the plume, as measured using a Langmuir probe, suggested that an increase of ionization in the plume by the external gas injection enhanced the cathode's performance. • Supplying gas into the plume of a microwave discharge cathode improves its performance. • Neutralization current increased by 58 % with external gas injection. • External gas injection decrease naturalization cost and increase gas utilization efficiency. • An increase of ionization in the plume by the external gas injection enhanced the cathode's performance. [ABSTRACT FROM AUTHOR]

The model given by Patil et al., for the self-focusing of lowest-order Bessel–Gaussian laser beam, is revisited by introducing the exponential plasma density ramp in this paper. Plasma density changes due to combined effect of the relativistic and ponderomotive nonlinearities, which arise due to the nonuniform spatial profile of the laser beam leading to stronger self-focusing. Under paraxial ray approximation, the expression for the evolution of laser-beam width parameter is obtained and solved numerically in order to achieve self-focusing. We have observed that as Bessel beam propagates through the plasma, it does not diffract and spread out, which is in contrast to the usual behavior of light that spreads out after being focused down to the small spot. Laser spot size decreases considerably under the presence of exponential density ramp. This study will be useful for better understanding the self-focusing mechanism of lasers as it becomes effective for the optimized parameters under the proposed situation. Bessel laser beams play an important role in enhancing the energy gain in laser-driven accelerators. In addition, for all laser-driven plasma-based accelerators, it appears possible to guide a laser beam over large distances using a plasma density channel, thus enhancing the acceleration length and the energy gain. [ABSTRACT FROM AUTHOR]

The impact of electrode spacing, power supply voltage, radio frequency, and gas pressure on capacitively coupled plasma discharge under both weak and strong magnetic fields is investigated by using a one-dimensional implicit particle-in-cell/Monte Carlo collision simulation. Simulation results indicate that under both weak and strong magnetic field conditions, plasma density increases with the increase in these discharge parameters. However, the principle of density increase under weak and strong magnetic field conditions is slightly different. The strong magnetic field plays a crucial role in strongly constraining electrons. Under weak magnetic field conditions, the mutual transition between stochastic heating and ohmic heating can be observed, while under strong magnetic field conditions, ohmic heating predominantly prevails. Furthermore, the simulation results also indicate that a strong magnetic field can effectively reduce the voltage threshold for the transition from the α mode to the γ mode. The strong magnetic field strongly confines secondary electrons near the sheath, allowing them to interact multiple times with the sheath and acquire higher energy, thereby making the γ mode more likely to occur. [ABSTRACT FROM AUTHOR]

To optimize the performance of vacuum circuit breakers, it is critical to gain a comprehensive understanding of the intricate physical processes that occur during vacuum interruptions. One of these processes, postarc sheath expansion is of particular importance for dielectric recovery. Previous simulation studies have examined sheath expansion by assuming uniform residual plasma at current zero. However, this approach deviates from physical realism because the discreteness in the cathode spot typically causes a nonuniform plasma distribution. This distribution cannot be analyzed by previous 1D or 2D models. To address this deficiency, this paper presents a 3D hybrid simulation model that comprehensively considers the simulation of postarc sheath expansion with nonuniform residual plasma at current zero. The model differentiates between the treatment of ions and electrons to achieve an optimal balance between computational accuracy and efficiency. The model captures the inherent nonuniformity of the plasma distribution through 3D modeling. A comparative analysis was conducted on several factors that influence the sheath expansion rate, including plasma density, transient recovery voltage rate, and ion drift velocity. The study focused on the impact of nonuniformity in the residual plasma distribution. It was demonstrated that this nonuniformity can impede the overall sheath expansion and result in the local enhancement of the electric field. The simulation aims to study the postarc sheath expansion and provide insight into the underlying physical mechanisms that govern this complex process. [ABSTRACT FROM AUTHOR]

Plasma discharge pulse length (tPLength) was investigated for its impact on the crystallinity of GaN films deposited on a sapphire substrate using a high-density convergent plasma sputtering device (CPSD). The study covered tPLength values from 1 to 200 ms, maintaining the substrate temperature at 200 °C. GaN films showed preferential orientation along the (0002) plane for all tPLength settings. X-ray diffraction analysis revealed a heteroepitaxial-like growth pattern with a sixfold symmetric diffraction pattern corresponding to GaN{10−10} planes. At a tPLength of 200 ms, the full width at half maximum of the rocking curve at GaN (0002) diffraction angle decreased to 1.6°. Optimizing the deposition rate per plasma discharge pulse with CPSD indicated the importance of selecting an optimal tPLength for achieving desirable crystalline properties in GaN film sputtering deposition. [ABSTRACT FROM AUTHOR]

The possibilities of optimization of the two-step atomic layer etching process for HfO2 in conventional plasma etching tools were studied. The surface modification step was realized in Ar/CF4/H2 plasma, and the reaction between the modified layer and the surface was activated by Ar ion bombardment from the plasma in the second step. Investigation of the effects of activation step duration, DC bias during activation, and Ar plasma density was carried out. The mechanism of the etching process has been shown to involve fluorination of oxide during the modification step and subsequent removal of fluorine-containing particles at the activation step. An increase in parasitic sputtering rate and lower process saturation with the growth of DC bias during activation was demonstrated. The advantage of the ALE process in lower surface roughness over the conventional etching process was shown. Similar etching characteristics of HfO2 and ZrO2 suggest a similarity in the etching process for the mixed hafnium-zirconium oxide material. [ABSTRACT FROM AUTHOR]

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In this work, we investigated the magnetic annihilation and reconnection and the resulted hot electron acceleration driven by double-beam intense laser pulses in two-layer near critical density (NCD) plasma target. The results are obtained by performing two-dimensional (2D) particle-in-cell (PIC) simulations. It is found that a quasi-mono-energetic peak can be formed in the energy spectrum of electrons accelerated by the process of magnetic field annihilation (MA) at cutoff energy. Electron spectra feature depends on the length of the second low-density layer. This suggests that the process of relativistic magnetic annihilation may be controlled in experiments by target design. [ABSTRACT FROM AUTHOR]

The properties of the magnetosheath are of pivotal importance in determining the coupling between the magnetosphere and interplanetary medium. In particular, the magnetic flux pileup and plasma depletion layer (PDL) modify the boundary conditions of magnetopause reconnection. However, the spatial distribution of the magnetic field strength and plasma density in the magnetosheath and their functional dependence on the interplanetary magnetic field (IMF) orientation remain poorly understood. This study characterizes these aspects in detail through the statistical processing of decades of data from Cluster, Double Star, THEMIS, and Magnetospheric Multiscale (MMS) missions. The first part of this study focuses on the poorly known variations across the magnetosheath, from the shock to the magnetopause. The magnetic pileup and PDL are significantly correlated, with a strong dependence on the IMF cone angle. Their dependence on the IMF clock angle is found only near the magnetopause, consistent with the expected effect of magnetic reconnection. The second part of this study examines the asymmetry in the magnetic field amplitude and density between the quasi-parallel and quasi-perpendicular sides of the equatorial magnetosheath. These asymmetries are characterized for different relative distances to the magnetopause and bow shock boundaries and for different IMF orientation. The magnetic field amplitude, observed to be higher on the quasi-perpendicular side of the magnetosheath, becomes more symmetric as it approaches the magnetopause. The quasi-parallel magnetosheath exhibits a higher plasma density near the magnetopause. However, this asymmetry reverses at approximately the mid-magnetosheath with a decreasing IMF cone angle. [ABSTRACT FROM AUTHOR]

We have revisited recent results on the ideal ignition of H11B fuel, in the light of the latest available reactivity, an alternative self-consistent calculation of the electron temperature, an increased extent of the suprathermal effects and the impact of plasma density. At high density, we find that the ideal ignition temperature is appreciably relaxed (e.g., T,· 150 keV for n,· ~ 1026 cm-3 and an optimal UB/H concentration ε = 0.15) and burn becomes substantial. We have then investigated central hot-spot ignition in both isobaric and isochoric inertial confinement configurations. Although implosion-driven ignition appears to be unfeasible, the isochoric self-heating conditions foster favourable preliminary conclusions on the utilization of proton fast ignition. In the isochoric case, we find a broad minimum in the ignition energy at pR 8.5g/cm2 and 220 < T,· < 340 keV (80 < Te < 95 keV), for ε = 0.15. [ABSTRACT FROM AUTHOR]

We present a new approach for stably evolving general relativistic magnetohydrodynamic (GRMHD) simulations in regions where the magnetization |$\sigma =b^2/\rho c^2$| becomes large. GRMHD codes typically struggle to evolve plasma above |$\sigma \approx 100$| in simulations of black hole accretion. To ensure stability, GRMHD codes will inject mass density artificially to the simulation as necessary to keep the magnetization below a ceiling value |$\sigma _{\rm max}$|⁠. We propose an alternative approach where the simulation transitions to solving the equations of general relativistic force-free electrodynamics (GRFFE) above a magnetization |$\sigma _{\rm trans}$|⁠. We augment the GRFFE equations in the highly magnetized region with approximate equations to evolve the decoupled field-parallel velocity and plasma energy density. Our hybrid scheme is explicit and easily added to the framework of standard-volume GRMHD codes. We present a variety of tests of our method, implemented in the GRMHD code koral , and we show results from a 3D hybrid GRMHD + GRFFE simulation of a magnetically arrested disc (MAD) around a spinning black hole. Our hybrid MAD simulation closely matches the average properties of a standard GRMHD MAD simulation with the same initial conditions in low magnetization regions, but it achieves a magnetization |$\sigma \approx 10^6$| in the evacuated jet funnel. We present simulated horizon-scale images of both simulations at 230 GHz with the black hole mass and accretion rate matched to M87*. Images from the hybrid simulation are less affected by the choice of magnetization cut-off |$\sigma _{\rm cut}$| imposed in radiative transfer than images from the standard GRMHD simulation. [ABSTRACT FROM AUTHOR]

A proton (H+) channel, Otopetrin 1 (OTOP1) is an acid sensor in the sour taste receptor cells. Although OTOP1 is known to be activated by extracellular acid, no posttranslational modification of OTOP1 has been reported. As one of the posttranslational modifications, glycosylation is known to modulate many ion channels. In this study, we investigated whether OTOP1 is glycosylated and how the glycosylation affects OTOP1 function. Pharmacological and enzymatic examinations (using an N‐glycosylation inhibitor, tunicamycin and peptide: N‐glycanase F [PNGase F]) revealed that overexpressed mouse OTOP1 was N‐glycosylated. As the N‐glycans were Endoglycosidase H (Endo H)‐sensitive, they were most likely high‐mannose type. A site‐directed mutagenesis approach revealed that both two asparagine residues (N238 and N251) in the third extracellular loop between the fifth transmembrane region and the sixth transmembrane region (L5‐6) were the glycosylation sites. Prevention of the glycosylations by the mutations of the asparagine residues or by tunicamycin treatment diminished the whole‐cell OTOP1 current densities. The results of cell surface biotinylation assay showed that the prevention of the glycosylations reduced the surface expression of OTOP1 at the plasma membrane. These results indicate that mouse OTOP1 is N‐glycosylated at N238 and N251, and that the glycosylations are necessary for OTOP1 to show the maximum degree of H+ current densities at the plasma membrane through promoting its targeting to the plasma membrane. These findings on glycosylations of OTOP1 will be a part of a comprehensive understanding on the regulations of OTOP1 function. [ABSTRACT FROM AUTHOR]

The coupling of transport code SOLPS with the turbulence code BOUT++ was reported in Reference [D. R. Zhang et al., Phys. Plasmas 26, 012508 (2019)], while the grids of SOLPS and BOUT++ are not completely consistent with each other, especially in the divertor region. In the present work, a method of replacing the grids of BOUT++ with the grids of SOLPS is proposed to make the simulation region fully consistent with each other for the SOLPS/BOUT++ coupling. A SOLPS grid file is generated with an MHD equilibrium and used in BOUT++ code to simulate the profiles of plasma density, ion temperature, and electron temperature with the six‐field two‐fluid model. The profiles of the main plasma parameters simulated with the SOLPS grids are similar with the profiles simulated with the BOUT++ grids at the midplane, while the profiles are deformed compared with the profiles simulated with the BOUT++ grids at the outer divertor target because of the differences of the distributions of SOLPS grids and BOUT++ grids in the divertor region. The radial particle transport coefficient and heat transport coefficients are also calculated by using the BOUT++ code with the two grids, and the comparisons of the radial particle transport coefficient and heat transport coefficients simulated with the two grids at the midplane and outer divertor target plate are discussed. [ABSTRACT FROM AUTHOR]

The processes in far scrape‐off layer (SOL) and the plasma interaction with the first‐wall (FW) elements may notably affect the tokamak discharge, since they define fuel and impurity recycling, material erosion and redeposition, wall surface heating, etc. For a long time, the far SOL description in most plasma edge transport codes was insufficient or absent at all, and so particle and heat fluxes onto the FW (except divertor plates) were out of consideration. Recently some codes, for example, SOLEDGE and SOLPS‐ITER are upgraded allowing for the extension of the computational grid up to real walls and for corresponding account of the vacuum vessel shape and all in‐vessel elements. The new release of SOLPS‐ITER (the version 3.2.0) required a development of a new code data structure and new approach to numerical approximation of fluid equations compatible with unstructured non‐orthogonal computational grid. Intensive testing of the new code in different conditions is still required. In the present contribution, such a testing is performed for the EAST disconnected double null (DDN) L‐mode discharge. For the first time, the SOLPS‐ITER 3.2.0 modeling results with drifts and currents turned on are presented, and a comparison to former SOLPS‐ITER version (3.0.8) is performed. The far SOL transport and its effects on the discharge performance are studied by comparing the computational results obtained on several meshes which differ by their width in equatorial midplane. A single null (SN) one (with mesh width limited by distance to the secondary separatrix) was examined versus two DDN meshes (one with actual and one with artificially extended targets to make mesh wider) and a true unstructured (the widest) mesh. The notable difference in results obtained on different meshes appears in those places where plasma density does not vanishes at the computational domain boundaries. For the cases on true unstructured (the widest) mesh, the particle and heat fluxes onto central column, limiters, far SOL part of targets, dome umbrella and other EAST far SOL in‐vessel structures are calculated for the first time by SOLPS‐ITER, allowing assessment of the plasma interaction with those surfaces. [ABSTRACT FROM AUTHOR]

The higher harmonics generated by nonlinear sheath motion would enhance the standing wave effect, and thus lead to center-peaked plasma density profile in very-high-frequency (VHF) capacitive discharges. In this work, a nonlinear transmission line (NTL) model introduced in Zhou et al (2021 Plasma Sources Sci. Technol. 30 125017) has been extended, with radial transport of various particles and nonlinear sheath motion into account, to investigate the effects of CF4 fraction α on the nonlinear standing wave excitation and plasma radial uniformity in VHF (60 MHz) capacitively coupled Ar/CF4 plasmas at 3 Pa. The results indicate that for pure Ar discharges (i.e. α = 0%), the nonlinearly excited harmonics with short wavelength significantly enhance the electron power absorption at the radial center, resulting in a pronounced central-high plasma density profile. As α increases, the high-order harmonics are gradually damped due to the increase of resistance, as well as the longer wavelength caused by thicker sheath thickness. Thus, the radial profile of the electron absorbed power density shifts from center-peak to edge-high. Besides, at the radial center, the electron density and Ar+ ion density decrease with α , CF3+ ion density shows an increasing trend, while F− ion density initially rises and then decreases. Moreover, the density profiles of all the species become more uniform at higher CF4 fraction, due to the suppressed nonlinear standing wave excitation and the longer wavelength of the nonlinear harmonics. [ABSTRACT FROM AUTHOR]

A heavy ion beam probe (HIBP) diagnostic is being developed for studies of plasma equilibrium and turbulence in the optimized Wendelstein 7-X (W7-X) stellarator. Operation of W7-X has experimentally demonstrated that its optimized magnetic field results in improved neoclassical particle confinement and, as a result, turbulence is the predominant cause of energy transport. The HIBP will have the unique ability to provide experimental data needed to complement models of both neoclassical and turbulent transport. It will acquire direct measurements in the W7-X plasma interior of the electric potential (needed for understanding ambipolar particle flux) and fluctuations of electron density and potential (needed for understanding turbulence). The HIBP for W7-X will inject singly charged ion beams with energies of up to 2 MeV and is designed to access the upper cross section of the W7-X plasma. We use trajectory simulations to illustrate the plasma coverage that the diagnostic can achieve in the reference magnetic configurations of W7-X. We calculate beam signal levels, discuss anticipated measurement sensitivity of broadband fluctuations of electron density and plasma potential, and show how they depend on plasma density. We also discuss the diagnostic sensitivity to equilibrium plasma potential. [ABSTRACT FROM AUTHOR]

Measurement of the internal magnetic field is crucial for determining the equilibrium, stability, and current density of a plasma in a tokamak. A motional Stark Effect (MSE) diagnostic was developed to provide a measurement of the internal magnetic field in tokamaks by analyzing the emission from the interaction of the plasma particle with an injected neutral beam. The Stark effect causes the shifting and splitting of deuterium spectral lines due to the Lorentz electric field. However, it is difficult to accurately measure the internal magnetic field components since the radial electric field inherently formed inside the plasma is mixed with the Lorentz field. Under the circumstances in the Korea Superconducting Tokamak Advanced Research (KSTAR) device, one possible approach is to derive a radial electric field by measuring and comparing the polarization angles from the full and half-energy components of the neutral beam. To utilize the polychromatic MSE diagnostics in KSTAR, the half-energy component wavelength bands according to various magnetic field and beam energy combinations have been calculated, and the filter combinations required for those measurements have been selected. The Stokes-filter model used to evaluate the effect of multiple-ion-source neutral beam injection on the MSE measurements has been extended to infer the sensitivity of this approach to take the non-ideal bandpass filter effects into account. [ABSTRACT FROM AUTHOR]

The Thermal Helium Beam (THB) is a diagnostic for simultaneously measuring the electron temperature and density profiles of the plasma edge and scrape off layer (SOL). It exploits the line ratio technique of selected He line intensities, emitted by He gas puffed inside the plasma, to locally estimate the plasma properties through a dedicated collisional radiative model (CRM). Standard THB diagnostics used in nuclear fusion devices measure three HeI emission lines: 667.8, 706.5, and 728.1 nm. For the RFP experiment RFX-mod2, a new THB is designed and tested for the first time at the TCV tokamak. It acquires an additional emission line at 501.6 nm, which is exploited to estimate the radiation re-absorption, which is not negligible in regions of large neutral He densities (leading to high re-absorption) and simultaneously low electron density and temperature (lack of other excitation channels). It affects the measurements most strongly at the far SOL, while the significance of re-absorption decreases as it approaches the separatrix. In this paper, plasma density and temperature profiles of the plasma edge at the outboard midplane of TCV, measured with this newly designed THB, are presented. For the first time, the effect of radiation re-absorption on the estimation of electron temperature and density profiles is experimentally measured in a tokamak using the 501 nm line emission intensity. Different CRMs are compared with and without radiation re-absorption, showing good agreement when re-absorption is included and demonstrating how it plays an important role in the far SOL, as expected. [ABSTRACT FROM AUTHOR]

The neutron time-of-flight (nToF) diagnostic technique has a lengthy history in Inertial Confinement Fusion (ICF) and High Energy Density (HED) Science experiments. Its initial utility resulted from the simple relationship between the full width half maximum of the fusion peak signal in a distant detector and the burn averaged conditions of an ideal plasma producing the flux [Lehner and Pohl, Z. Phys. 207, 83–104 (1967)]. More recent precision measurements [Gatu-Johnson et al., Phys. Rev. E 94(8), 021202 (2016)] and theoretical studies [Munro, Nucl. Fusion 56, 035001 (2016)] have shown the spectrum to be more subtle and complicated, driving the desire for an absolute calibration of the spectrum to disambiguate plasma dynamics from the conditions producing thermonuclear reactions. In experiments where the neutron production history is not well measured, but the neutron signal is preceded by a concomitant flux of photons, the spectrum can be in situ calibrated using a set of collinear detectors to obtain a true "time-of-flight" measurement. This article presents the motivation and overview of this technique along with estimates of the experimental precision needed to make useful measurements in existing and future nToF systems such as the pulsed power Z-machine located in Albuquerque, NM, at Sandia National Laboratories. [ABSTRACT FROM AUTHOR]

Langmuir probes cannot be used to diagnose cold atmospheric plasma jet, because their presence in the high electric field after-glow region modifies the plasma parameters that they are intended to measure. Here, we propose a system to sample the plasma plume from ambient conditions into a low-pressure region, where probe analysis can be accomplished. The effect of such a sampling process on the number density and velocity of the gas has been studied through simulations and using analytical equations. Simulation results regarding the effect of chamber and orifice dimensions on these parameters, have been presented. Based on this study an experimental chamber was fabricated and Langmuir probe analysis of the sampled plasma was done. Continuum flowing plasma theory was applied and the plasma density and electron temperature were estimated to be 1.8 × 1020m−3 and 4.7 eV respectively for the operating condition of 3 W plasma power at 12 kHz. [ABSTRACT FROM AUTHOR]

Using two separate databases of in situ ionospheric observations, we present case studies and perform a statistical investigation of the link between energetic precipitating particles during the polar night and high-latitude F-region steepening density spectra. Our study covers approximately 3 years of data obtained near the peak of the 24th solar cycle from four Defense Meteorological Satellite Program satellites and from the European Space Agency's Swarm satellites. Focusing on the midnight sector of the auroral oval, we found that there is a near-perfect co-location between high-energy precipitating particles and occurrence of dissipating F-region plasma density spectra. This is because the precipitating energy flux strongly enhances the E-region Pedersen conductivity, allowing fast and efficient dissipation of kilometer-scale F-region irregularities. Spectra that are possibly non-dissipating are in turn co-located with the distribution of soft electron precipitation. Together, dissipating and non-dissipating density spectra constitute two distinct irregularity regimes. Surprisingly, we also found that efficient dissipation notwithstanding, high-energy precipitating particles cause a net increase in the F-region irregularity power, suggesting that growth and dissipation are interlinked and that some of the observed F-region irregularities may conceivably be generated in the E region. This work is expected to be beneficial for the classification of F-region in situ density spectra and suggests that such density spectra can be used to infer the presence of high-energy or low-energy precipitations based on spectral properties. [ABSTRACT FROM AUTHOR]

In isotope concentration technology, ion extraction current and ion extraction efficiency are the key factors to measure the efficiency of the isotope concentration. In order to increase the ion extraction current, researchers usually hope to produce a plasma source with large initial peak density and width; however, in reality, it is limited by the laser power, and the total number of ions in a plasma produced by laser ionization is almost certain. In this case, how to improve the ion extraction efficiency by choosing the appropriate initial density distribution of plasma has become a difficult problem. In this paper, the effects of the initial density distribution of plasma on the ion extraction characteristics are studied by using the electron equilibrium fluid model. The numerical results suggest that the ion extraction efficiency is independent of the initial density distribution of plasma while the total number of ions in the plasma, the distance between the electrodes, and the electric field intensity are kept constant. When the total number of ions and the electric field intensity are kept constant, the distance between the electrodes is shortened by one time, and the time of ion extraction is also shortened by nearly one time; thus, the plasma source with high initial peak density and small width can be chosen, and the aim of ion extraction can be achieved by shortening the distance between the electrodes. This research results provide an important reference for guiding the experimental parameters such as laser power distribution and the design of ion extraction device. [ABSTRACT FROM AUTHOR]

To explore the confinement of high-energy ions above the space charge limit, we have developed a hybrid magnetic and electrostatic confinement device called an Orbitron. The Orbitron is a crossed-field device combining aspects of magnetic mirrors, magnetrons, and orbital ion traps. Ions are confined in orbits around a high-voltage cathode with co-rotating electrons confined by a relatively weak magnetic field. Experimental and computational investigations focus on reaching ion densities above the space charge limit through the co-confinement of electrons. The experimental apparatus and suite of diagnostics are being developed to measure the critical parameters, such as plasma density, particle energy, and fusion rate for high-energy, non-thermal plasma conditions in the Orbitron. Initial results from experimental and computational efforts have revealed the need for cathode voltages on the order of 100–300 kV, leading to the development of a custom high voltage, ultra-high vacuum bushing rated for 300 kV. [ABSTRACT FROM AUTHOR]

Background: Hair loss profoundly affects women's physical appearance and psychological health. Platelet‐rich plasma (PRP) therapy has gained attention as a potential treatment for female hair loss. This systematic review and meta‐analysis aim to evaluate the efficacy and safety of PRP in treating different forms of female hair loss. Methods: A comprehensive search was conducted across PubMed, EMBASE, Scopus, Cochrane Library, Web of Science, and ClinicalTrials.gov from January 2000 to May 2024. The focus was on randomized controlled trials investigating PRP treatment for various types of hair loss in women. The research protocol is registered with International Prospective Register of Systematic Reviews (CRD42024556190). The quality of the studies was evaluated using the Cochrane risk of bias tool (RoB 2). Results: A total of 21 studies comprising 628 participants were included in the analysis. PRP treatment was found to significantly enhance hair density and thickness. Additionally, there was a significant reduction in the number of hairs pulled in the PRP group. Adverse effects were generally mild and transient, with no notable difference in pain or discomfort between the PRP and control groups (risk ratio: 1.01; 95% CI: 0.87–1.18). Conclusion: PRP therapy effectively enhances hair density and thickness in women with hair loss, with a favorable safety profile. However, the effects of PRP on hair density and thickness vary with dosage, injection duration, and ethnicity, indicating the need for tailored treatment protocols. [ABSTRACT FROM AUTHOR]