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In this work, the effects of stringing termination capacitors on the external circuit parameters, plasma parameters, and mode transition in radio frequency (RF) inductively coupled Ar discharges are investigated. It has been demonstrated that at low pressure (1 Pa), in the absence of termination capacitors, the plasma parameters and external circuit parameters exhibit a continuous variation with increasing RF power. The plasma density is observed to decrease with decreasing capacitance value in the E mode when the termination capacitor is inserted, while the plasma density is increased with decreasing capacitance value in the H mode. During the E–H mode transition process, both the plasma parameters and the external circuit parameters undergo a discontinuous change characterized by a distinct "jump" in each parameter. By increasing and then decreasing RF power, the evolution of each parameter creates a significant hysteresis. As the termination capacitance decreases, the power threshold of the H–E mode transition decreases, resulting in a larger hysteresis loop. The termination capacitor, which is connected in series at the end of the coil, can alter the voltage distribution on the RF antenna. This alteration results in a reduction in the potential difference between the coil and the "common ground," which effectively diminishes the electrostatic field. Furthermore, the electron energy probability function indicates that the addition of the termination capacitor results in a reduction in the proportion of energetic electrons in the E mode, accompanied by a reduction in the plasma potential. [ABSTRACT FROM AUTHOR]

Despite the widespread applications of high-pressure plasma in semiconductor and display industry, such as deposition and ashing process, the use of cutoff probes for diagnosing high-pressure plasma was rarely studied. In this study, we investigated a method of measuring electron density in a cutoff probe using the resonance peak in a high-pressure plasma environment. This method is validated through both electromagnetic wave simulations and experimental methodologies. Our findings reveal that the proposed method demonstrates discrepancies of less than 1.47% compared to the input plasma frequency in the results of electromagnetic wave simulations at a gas pressure of 10 mTorr, while at 2.5 Torr, it exhibited a maximum discrepancy of 13.3% when selecting resonance frequencies lower than the electron–neutral collision frequency. This discrepancy at high pressure is reduced to within 1.92% by selecting a resonance frequency higher than the electron–neutral collision frequency. Also, the feasibility of these electron density measurements has been confirmed under conditions of high gas pressure where the cutoff frequency is not measurable, as evidenced by both simulation and experimental results. Our research on the diagnostic methods in high-pressure plasmas could significantly enhance the measurement and interpretation of plasma parameters in various industrial processes. [ABSTRACT FROM AUTHOR]

Closing or opening the first two photonic bandgaps (PBGs) of plasma photonic crystals (PPCs) by adjusting the plasma parameters are studied. We first calculated the impedance of the band structure of one-dimensional PPCs and found that in the presence of plasma, the impedance under two certain frequencies can match that of the air. We have verified through simulation that when the two PBG frequencies and two impedance-matched frequencies are equal to each other, the two PBGs can be closed simultaneously under the same plasma density. On the other hand, a more common situation is that we need two plasma densities to, respectively, close the two PBGs located near different impedance-matched frequencies. At this point, by adjusting the plasma density, the PBGs can be closed in segments, that is, we can choose to close or open the corresponding PBGs at different plasma densities. [ABSTRACT FROM AUTHOR]

The effects of discharge parameters on the discharge process and plasma transport characteristics of a coaxial gun in the gas-prefilled mode are studied. The plasma optical intensity and ejection velocity are measured by photodiodes, the optical emission spectrum is taken by a spectroscopic system, and the plasma evolution in the transport process is captured by a high-speed camera. The plasma acceleration characteristics under different discharge parameters show that the velocity and electron density of the ejection plasma are mainly determined by the pre-filled pressure and discharge current, which is consistent with the snowplow model. The kinetic energy of ejection plasma can be significantly increased by reducing the outer loop inductance, which is conducive to increasing the energy utilization efficiency. The time-varying images of plasma radiation and the plasma density at different transport locations illuminate the transmission characteristics of coaxial gun discharge plasma. The results show that the snowplow effect continues to play a role in the plasma transport process, and the plasma accumulation is induced by the combination of shock wave compression. The current-driven magneto hydrodynamics instability occurs during the transport process, and the luminous signal of the plasma current sheet oscillates periodically. In addition, the plasma impact effect is obvious and the gas retarding effect is enhanced with the increase in the gas pressure. These results give us a more comprehensive view of the coaxial gun discharge process and plasma transport and provide a certain reference for optimizing the parameters selection and physical design of coaxial gun discharge plasma characteristics. [ABSTRACT FROM AUTHOR]

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]

In this study, we present a novel pulsed microwave-induced plasma (MIP) source coupled with a glow discharge for optical emission spectrometry (MIP-OES), operating at 1000 W power and a frequency of 2.45 GHz. The MIP cavity consists of a stainless steel cylindrical waveguide connected to a circular resonator made of the same material, joined through a dielectric quartz disc. The output of the MIP cavity is linked to a closed glow discharge quartz tube and a mechanical pump. Numerical simulations were employed to optimize the structure and dimensions of the MIP cavity. The nozzle position of the cylindrical resonator's output was precisely adjusted to align with the maximum magnetic field, achieving the TM011 mode, which results in a point plasma with high density. This configuration enables the cavity to produce a dense, warm plasma emission zone with a consistent emission rate around the circumference of the emitting source. The results demonstrate that the designed MIP source exhibits a significantly higher density and temperature compared to other sources with similar microwave parameters. [ABSTRACT FROM AUTHOR]

The term "Medium-Scale Traveling Ionospheric Disturbances" is used to describe a number of different propagating phenomena in ionospheric plasma density with a scale size of hundreds of km. This includes multiple generation mechanisms, including ion-neutral collisions, plasma instabilities, and electromagnetic forcing. Observational limitations can impede characterization and identification of MSTID generation mechanisms. We discuss inconsistencies in the current terminology used to describe these and provide a set of recommendations for description and discussion. [ABSTRACT FROM AUTHOR]

The Stellarator de Costa Rica 1 (SCR-1) is a small modular stellarator that serves as a valuable research and training tool for plasma magnetic confinement. This study aimed to analyze the characteristics of SCR-1, including its peripheral systems, technical plasma discharge processes, and advancements in plasma characterization. In addition, this study explored a new heating mechanism and the factors that influence it. The current state of the device and plasma discharge are initially presented. Subsequently, the measurement process was utilized to determine the electronic density and plasma temperature using a single Langmuir probe and the results were compared with theoretical predictions based on the particle and energy balance. Additionally, the VMEC code was employed to calculate magnetic flux surfaces with characteristics such as a low aspect ratio, low beta parameter, negative magnetic shear, and decreasing rotational transform along magnetic flux surfaces. The Mercier criterion was employed to conduct a linear stability analysis, which identified a magnetic well that played a crucial role in the linear stability of the majority of magnetic flux surfaces. Feasibility studies of electron Bernstein waves (EBW) were conducted using the IPF-FMDC full-wave code. The results obtained from the IPF-FMDC full-wave code revealed that the O-X conversion percentage reached a maximum of 63% when considering radiation reflection in the vacuum vessel. Significant effects of plasma curvature on the O-X wave conversion and normalized electron density scale length were observed, while the change in the SCR-1 heating position did not produce a significant impact. Three damping mechanisms affecting O-X conversion were studied, and one of the principal effects was the SX-FX conversion due to steep electron density gradient. Additionally, stochastic electron heating showed a low electron field amplitude, which is important for limiting the EBW propagation. [ABSTRACT FROM AUTHOR]

Measurement errors of meteors can substantially affect the accuracy of meteoroid trajectory and orbit determinations, potentially leading to spurious meteoroid orbits. Here, we evaluate the measurement errors associated with the meteor and ionospheric irregularity observation system (MIOS) developed at low-latitude Ledong and Sanya, China, aimed at observing various meteors and their associated plasma density irregularity phenomena, and investigate how these errors affect the determination of meteor trajectories and orbits. The measurement error of meteor position is estimated to be |$\sim$| 2 pixels, corresponding to 0.04 |$^\circ$|⁠ , which is sufficient to detect true radiant dispersion and structural characteristics in younger meteor showers. By simulating meteoroids from the Draconid, Geminid, and Perseid meteor showers with the |$\sim$| 2 pixels measurement error and the Monte Carlo trajectory method, the precision of corresponding meteoroid trajectories is derived. The radiant accuracy is 1.09 |$^\circ$|⁠ , with right ascension and declination accuracies of 0.78 |$^\circ$| and 0.77 |$^\circ$|⁠ , respectively. The velocity accuracy is 0.64 km/s. The comparison of estimated and true radiant uncertainties shows that the estimated errors of the MIOS are generally consistent with the true meteor trajectory errors. Finally, we estimate the orbital measurement errors, which include an eccentricity of 0.05, a perihelion distance of 0.0086 au, an inclination of 1.4 |$^\circ$|⁠ , and an argument of the perihelion of 1.86 |$^\circ$|⁠. Based on observations of eight representative meteor showers during 2019–2023, the accuracy of the MIOS in detecting meteor trajectories and orbits is further validated. [ABSTRACT FROM AUTHOR]

Microstructure-enhanced discharges are critical for achieving higher plasma electron density and energy, offering significant potential in advanced plasma applications. A two-dimensional fluid model of pulsed dielectric barrier discharge was developed in atmospheric helium with a dielectric microhole. Two distinct high-electron-density regions, the T-region and L-region, were identified, driven, respectively, by transverse and longitudinal electric fields as the ionization wave traversed the microhole. The axisymmetric T-region is approached and squeezed as the radius decreases, in which the discharge intensity and electron density are enhanced. Based on the electron reaction source item, a virtual electrode is proposed in the dielectric microhole, which segregates the T- and L-regions. The width of the virtual electrode decreases with the microhole radius, and the virtual electrode extinguishes with the discharge ignition in the lower chamber and the formation of ionization wave in the dielectric microhole. These findings offer insights into plasma behavior in microstructures for advanced applications. [ABSTRACT FROM AUTHOR]

A three-dimensional, regional simulation is used to investigate ionospheric plasma density irregularities associated with Equatorial Spread F. This simulation is first driven with background electric fields derived from ISR observations. Next, the simulation is driven with electric fields taken from the WAM-IPE global model. The discrepancies between the two electric fields, particularly in the evening prereversal enhancement, produce disagreeing simulation results. The WAM-IPE electric fields are then studied through a simple sensitivity analysis of a field-line integrated electrodynamics model similar to the one used in WAM-IPE. This analysis suggests there is no simple tuning of ion composition or neutral winds that accurately reproduce ISR-observed electric fields on a day-to-day basis. Additionally, the persistency of the prereversal enhancement structure over time is studied and compared to measurements from the ICON satellite. These results suggest that WAM-IPE electric fields generally have a shorter and more variable correlation time than those measured by ICON. [ABSTRACT FROM AUTHOR]

The absorption characteristics of cylindrical surface plasmon resonance (CSPR) have been studied. We demonstrated that a single plasma column with CSPRs can achieve high absorptivity at the plasmon frequency. We also studied the effects of plasma density and collision frequency on the absorptivity. As both of them increase, the corresponding absorptivity tends to increase first and then decrease, but with different reasons. Such manifestation is explained by analyzing transmission and reflection spectra in both cases, as well as magnetic field distribution patterns at the frequency of plasmon. On the one hand, the increase in plasma density leads to the enhancement of plasmons, improving transmittance; On the other hand, the increase in collision frequency leads to a weakening of plasmons and an increase in reflectivity. Finally, we investigated the absorption characteristics of plasmons in the plasma photonic crystals (PPCs) structure and overcame the absorption attenuation caused by the increase in plasma density by increasing the number of plasma columns. Meanwhile, the absorption generated by surface plasmon resonance is not affected by the lattice constant of PPCs. The research has shown that efficient absorption can be achieved using CSPR, resulting in extremely high absorptivity when using fewer plasma columns. Finally, we verified the absorption ability of CSPRs through experiments. [ABSTRACT FROM AUTHOR]

To gain a deeper understanding of how the size of the nanoparticles synthesized by Electric Field-Assisted Laser Ablation in Liquids (EFLAL) changes with the applied electric field, we use Laser-Induced Breakdown Spectroscopy (LIBS) and a Beam Deflection Set-up (BDS). These tools help us examine how the electric field strength affects the plasma parameters and the bubble dynamics. The findings show that the electron density and plasma temperature are perturbed as the electric field strength can alter the interaction region. The strength of the electric field can cause the bubble size to increase, which also elevates its pressure and temperature. These alterations at the breakdown region lead to changes in the size, properties, and production of the Mn2O3 nanoparticles. Thus, the interplay of laser plasma and fluid-assisted bubble phenomena in the presence of an electric field is probed for Mn2O3 nanoparticles thereby optimizing as UV emitters. [ABSTRACT FROM AUTHOR]

The semiconductor industry increasingly relies on remote plasma sources (RPS) for advanced processing techniques. In this study, we numerically explored the performance optimization of inductively coupled plasma at pressures above 1 Torr, suitable for RPS applications. Using a two-dimensional fluid model, we examined how process parameters affect plasma density and analyzed the contributions of various chemical reactions to plasma density changes in an argon discharge. Our findings show that increasing radio frequency (RF) power, gas pressure, and flow rate elevates electron and ion densities in the downstream region of the RPS. The increase in RF power generates strong inductive heating, which leads to convective transport of thermal energy in the downstream region of the RPS. This transferred thermal energy is expected to efficiently transfer radicals downstream through dissociation reactions with low threshold energy. Increased flow rates boost ion flux and improve axial electron transport, while elevated pressures lower electron temperatures and reduce the ambipolar field. We also observed that ion distribution is influenced by multi-component diffusion downstream. Thus, optimizing power, flow rate, and pressure enhances radical transport efficiency to the lower stage of the RPS. These results were validated experimentally using a Langmuir probe in argon discharge, confirming our numerical predictions. [ABSTRACT FROM AUTHOR]

In this theoretical investigation, two-photon decay of an amplitude-modulated Gaussian laser (ω 0 , k 0) into a pair of electromagnetic waves with frequencies ω 1 , ω 1 and wave numbers k 1 , k 2 , respectively, is shown to be susceptible in the presence of a Langmuir wave ω r , k r in a density rippled unmagnetized plasma. The decay waves propagate in sideward direction so that the momentum remains conserved. The density ripple plasma compensates for the wave number mismatch between pump and decay waves; otherwise, such decay of electromagnetic wave is not allowed. The necessary phase matching conditions for the interaction are considered as k → r = k → 0 - k → 1 - k → 2 , ω r = ω 0 - ω 1 - ω 2 . The discrepancy can be attributed to the static density ripple. The momentum transfers between the pump and decay wave by the density ripple. The decay of pair of electromagnetic waves occurs at plasma densities below one-fourth of the critical density. The decay waves propagate at finite angles to the amplitude-modulated Gaussian laser beam. The obtained growth rate is strongly dependent on the rippled density and laser beam modulation index. At the centre of laser beam propagation transverse distance, the growth rate of decay wave is attained the peak value. The various graphical diagrams show that growth rate decreases with the increase in the normalized frequency of pump laser beam and angle θ r . [ABSTRACT FROM AUTHOR]

The characterization and manipulation of ultrashort high-intensity laser pulses were investigated both numerically and experimentally using an ultrathin foil as plasma shutter. Our work revealed a laser intensity enhancement with a clean and steepened leading edge when the pulse passed through an expanded moderate-density plasma. The fast dynamics of laser–plasma interaction in underdense, transparent, and overdense regimes were elucidated by measuring the temporal-spatial intensity and phase profiles of the transmitted pulses. Key nonlinear effects such as relativistic self-focusing, self-phase modulation, self-induced transparency, and hole-boring were identified as factors influencing laser pulse shaping, with their impact determined by the plasma density. Our approach allows for the robust utilization of the plasma shutter in existing laser facilities without additional requirements. By controlling the spatiotemporal properties of high-power laser pulses, it opens up the possibility for developing compact laser-driven particle accelerators, ultrabright radiation sources, and plasma photonics. [ABSTRACT FROM AUTHOR]

Two-dimensional particle-in-cell simulations in the (radial-azimuthal) plane perpendicular to the axial direction of a cylindrical E × B Penning discharge are presented. The low-pressure discharge is self-consistently supported by plasma ionization from the electron beam injected axially, along the direction of the external magnetic field. It is shown that with the increasing strength of the external magnetic field, the discharge undergoes a sequence of transitions between several azimuthal modes. Azimuthal m > 1 spiral arm structures are excited at low magnetic field values as plasma confinement improves and the radial density profile becomes peaked. With a larger field, spiral arms with m > 1 are replaced by the m = 1 spoke mode, most clearly seen in plasma density. A transition from spiral arms to the spoke regime occurs when the plasma potential in the center changes from weakly positive (or zero) to negative. Further increase in the magnetic field results in a well-developed m = 1 spoke mode with additional small-scale higher-frequency m > 1 structures inside and around the spoke. It is shown that while ionization and collisions affect some characteristics of the observed fluctuations, the basic features of the spoke and m > 1 spiral structure remained similar without ionization. The role of energy conservation in small-scale high-frequency modes and spoke dynamics is discussed. It is demonstrated that in regimes with the m = 1 spoke mode, additional m = 4 harmonics of the ion and electron fluxes to the wall appear due to the square boundary. The frequency of the m = 1 mode is weakly affected by the geometry of the boundary. [ABSTRACT FROM AUTHOR]

Coupled antennas are critical for the discharge characteristics of high-density helicon plasma. This paper compared the coupling effects of Nagoya III antenna and double-saddle antenna on the blue core discharge characteristics in a nonhomogeneous helicon plasma. Langmuir probe, Nikon D90 camera, intensified charge-coupled device camera, and optical emission spectrometer were used to characterize the plasma mode transition, discharge image, spatial distribution of plasma density, and electron temperature. The results showed that the Nagoya III antenna was more likely to excite the helicon plasma discharge. It can enter W mode discharge at 200 W and appear blue core phenomenon at about 500 W with a higher plasma density. The axis distribution of spectral line intensity indicated that Nagoya III antenna has a stronger coupling ionization effect. The radial distributions of the plasma density and electron temperature demonstrated the stronger electron-neutral collision frequency under the excitation of Nagoya III antenna. It can be contributed to the higher antenna coupling efficiency, which was calculated to around 93% for Nagoya III antenna after 300 W. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of helical wiggler magnetic field on the terahertz (THz) radiation amplification generated by beating of two super-Gaussian laser beams in a collisional and rippled density plasma. We derive the equations governing the THz radiation and show that the wiggler magnetic field has significant effects on enhancing the THz radiation field, power, and efficiency. For instance, the wiggler magnetic field can enhance the THz radiation electric field more than one order of magnitude, which can be very important in the generation of THz radiation. Also, under the same conditions, we compare the effects of wiggler magnetic field and conventional (uniform) magnetic field, used vastly in literature, and show that the THz radiation field generated in the presence of wiggler magnetic field is several times greater than the THz radiation field generated in the presence of conventional magnetic field. [ABSTRACT FROM AUTHOR]

Mitigation of large edge-localized modes (ELMs) has been achieved by actively reducing the pedestal density gradient with the EAST new right-angled lower divertor through changing the strike point position from the vertical target to the horizontal target. A series of dedicated experiments in the 2021–2024 EAST campaigns demonstrate that this ELM control solution is highly reproducible in a broad parameter space of edge safety factor q95 = 4.7–7.1, heating power Ptotal = 2.3–5 MW, and pedestal collisionality ν e , ped * = 1–6, under both favorable and unfavorable magnetic configurations. Higher plasma density could facilitate the achievement of this ELM control solution. Statistical results indicate that the ELM mitigation effect can be observed at relatively larger Greenwald density fraction of fGW > 0.47. In addition, this ELM mitigation effect can be achieved with both lithium-coated and boronized metal walls. The pedestal density gradient is systematically lower in the horizontal target case than that of the vertical target case when the ELM mitigation effect can be observed. SOLPS-ITER simulation results indicate that the pedestal fueling from divertor recycling is significantly lower in the horizontal target case. This could contribute to the formation of a flattened pedestal density profile with small ELMs. [ABSTRACT FROM AUTHOR]

In tokamaks, it is commonly observed that the application of resonant magnetic perturbations (RMPs) leads to a reduction in plasma density. In this study, we show that this decrease in density is accompanied by kink-like modes in the plasma edge region in KSTAR. The dynamics of these modes is observed in the toroidal and poloidal directions using multiple diagnostics. It is captured that the phase of the edge kink-like modes aligns with the phase of the applied RMPs. In particular, a nonuniform plasma surface displacement due to these modes is measured along the poloidal direction using a novel image processing technique on in-vessel TV data. The symmetry-breaking effect of the displacement is known to be much larger than that of the applied RMPs. Thus, the modification in the magnetic field strength B on the distorted surface due to the displacement can lead to significant enhancement of the neoclassical particle transport. In this study, we calculate the enhanced neoclassical electron particle flux using the experimentally estimated variation of B in the presence of the edge kink-like modes. Transport analysis shows that the enhanced particle transport caused by the broken symmetry in the presence of the edge kink-like modes can account for a significant portion of the observed density pump-out by RMPs. [ABSTRACT FROM AUTHOR]

T. H. Rider investigated the challenges of sustaining p-11B fusion away from ThermoNuclear Steady-State accounting for Bremsstrahlung losses (TNSSB) in his 1997 paper [Phys. Plasmas 4, 1039 (1997)]. We revisit part of his work using first-principles particle simulations, which more accurately capture the underlying physical processes. This study supports the aspects of Rider's analysis by considering non-Maxwellian electron velocity distributions and significantly lowering electron temperatures compared to ion temperatures. Under these conditions, the minimum recirculating power needed to sustain a non-TNSSB state remains much higher than the fusion power output. However, by using updated fusion cross section data and expanding Rider's parameter space to include higher electron temperatures, we find a net energy gain window. This is consistent with findings by Putvinski et al. [Nucl. Fusion 59, 076018 (2019)]. Higher electron temperatures increase Bremsstrahlung radiation losses but reduce electron-ion energy transfer. For non-TNSSB p-11B fusion plasmas, as the system approaches a TNSSB state, achieving net energy gain requires lower energy conversion efficiencies. Near ignition conditions ( Q fuel ≥ 10) are found when ion temperatures (Ti) range from 200 to 600 keV in a TNSSB. At these conditions, an optimal electron-to-ion temperature ratio ( T e / T i ) between 0.4 and 0.6 minimizes the required product of plasma density and confinement time, provided Bremsstrahlung losses are offset by electron-ion interaction power. Reducing T e / T i below this range for a given Ti increases the required recirculating power and reduces the achievable Q. Finally, deviations from Maxwellian velocity distributions for electrons and ions may offer additional pathways toward achieving ignition. [ABSTRACT FROM AUTHOR]

We demonstrate and analyze the use of an ion chamber for measuring laser-induced ionization in cesium gas for the first time, which is of recent interest due to research in diode pumped alkali lasers (DPALs). In this report, the viability of an ion chamber diagnostic with high plasma density and ionization localized to a laser beam is investigated. A simulation of the laser-induced plasma in the ion chamber, based on the Thomson model with diffusion, is developed and will be shown to display similar qualitative behavior to measurements, and bound test results within model uncertainty. The analysis will show that complex processes occur: (1) space-charge limited ion drift, (2) Debye shielding preventing the electric field from penetrating a bulk plasma region, and (3) ambipolar diffusion across the bulk with possibly elevated electron temperature. However, these processes are well understood and do not limit the accuracy of an ion chamber diagnostic for laser-induced ionization rate measurement. [ABSTRACT FROM AUTHOR]

Plasma plumes are the end products ejected from electric propulsion after complex ionization and acceleration processes. The physics behind the plasma plumes has attracted significant interest due to their interactions with the critical components of satellites and an increased understanding of the relevant processes. Recently, in the front view from a pulsed plasma thruster (PPT), we observed an unclosed vortex structure in the plasma plume, which led us to reconsider the propagation process and the current flux directions inside a plasma plume. To study this plume structure in depth, a highly sensitive Rogowski coil is used here to obtain the current density of the plume over the operating period of a PPT in 3 perpendicular directions. Vector-time-resolved current flux maps were obtained through experimental measurements and the peak current densities were found to reach 50000 mA/cm2 to 250000 mA/cm2. From successive 3-D current flux maps, the complete process of current flow inside a transient plasma plume is observed. The vortex plume structure was found to form during the initial discharge period. The plasma in-plume current is shown to be involved by discharge circuit. After the main discharge is completed, the plasma plume tends to circuit-independent and in self-equilibrium. • A highly sensitive Rogowski coil is used here to obtain the current density in 3 perpendicular directions. • 3-D measurements of the current density flux in a pulsed plasma thruster are proposed. • The vortex plume structure is found to form during the initial discharge period. [ABSTRACT FROM AUTHOR]

Using the data from the first satellite of the Republic of China (ROCSAT-1) obtained during high-solar-activity periods (2000–2003), the distributions of plasma density enhancement (plasma blobs) with local time, season and longitude were investigated. Some new features of plasma blobs can be concluded: (a) The distribution of plasma blobs shows remarkable seasonal and interhemispheric asymmetries, with the higher occurrence in June solstice months and in the winter hemisphere. (b) The occurrence of plasma blobs displays longitude dependence, more in the −180~−90°E, −60~0°E and 90~180°E longitude regions. (c) The seasonal and interhemispheric asymmetries of plasma blobs also depend on the longitude. Meridional wind plays an important role in the formation and evolution of low-latitude plasma blobs. Inclination and declination may control the longitudinal distribution of plasma blobs. [ABSTRACT FROM AUTHOR]

Efficiently and accurately calculating the plasma transport process is one of the difficulties in aerospace plasma application simulation, especially in the magnetic sail spacecraft applications that have a huge size. This paper develops a three-dimensional trilinear anisotropic immersed-finite-element direct-implicit particle-in-cell (IFE-DIPIC) model to solve the problem of large-scale, long-term evolution plasma with complex interfaces. The model uses the DIPIC method to track the motion of particles in the plasma while simulating the anisotropic electric field containing an interface by using a modified trilinear anisotropic IFE method. Compared to the previous models, the developed model in this paper allows for the use of larger spatial and time steps in the Cartesian meshes without inducing numerical divergence. Using an interface-independent mesh avoids redundant interpolation in the PIC method, further improving efficiency. These advantages significantly improve the efficiency in solving actual complex three-dimensional plasma physics problems. The accuracy, efficiency, stability, and applicability of the proposed model are proved through numerical examples and the application in magnetic sail. The simulation results indicate that the developed model can efficiently simulate the actual working conditions of magnetic sails. The performance is significantly influenced by both the direction and magnitude of the magnetic moment. [ABSTRACT FROM AUTHOR]

The solar corona is the prototypical example of a low-density environment heated to high temperatures by external sources. The plasma cools radiatively, and because it is optically thin to this radiation, it becomes possible to model the density, velocity, and temperature structure of the system by modifying the MHD equations to include an energy source term that approximates the local heating and cooling rates. The solutions can be highly inhomogeneous and even multiphase because the well-known linear instability associated with this source term, thermal instability, leads to a catastrophic heating and cooling of the plasma in the nonlinear regime. Here we show that there is a separate, much simpler linear instability accompanying this source term that can rival thermal instability in dynamical importance. The stability criterion is the isochoric one identified by Parker (1953), and we demonstrate that cooling functions derived from collisional ionization equilibrium are highly prone to violating this criterion. If catastrophic cooling instability can act locally in global simulations, then it is an alternative mechanism for forming condensations, and due to its nonequilibrium character, it may be relevant to explaining a host of phenomena associated with the production of cooler gas in hot, low density plasmas. [ABSTRACT FROM AUTHOR]

The influence of quartz tube size on the surface distributions of reactive oxygen species (ROS) in model tissue treated with a He + O2 plasma jet was investigated. Gelatin gel was used to construct the model tissue, and a KI-starch color agent was mixed with the model tissue to visualize the distribution of ROS. With increasing quartz tube diameter, the uniformity of the ROS distribution on the model tissue decreased, and the change in the surface distribution area of the ROS on the model tissue over the irradiation distance was quite different for different quartz tube diameters. The surface distribution of ROS on the model tissue was affected mainly by the working gas flow; thus, the diffusion range of the working gas flow on the model tissue surface determined the surface distribution area of ROS on the model tissue. The working gas flow was accelerated, and the diffusion range of the working gas flow on the model tissue surface expanded when the plasma was ignited, resulting from the modification of the working gas flow by the electrohydrodynamic (EHD) effect. The EHD effect on the expansion of the diffusion range of working gas flow on the model tissue was different for different quartz tube diameters, and the effect was determined mainly by the discharge current density of the plasma jet and the plasma propagation length. [ABSTRACT FROM AUTHOR]

The magnetic field can effectively affect the properties of capacitively coupled plasma (CCP) modulated by electron beam injection, leading to improved discharge performance. In this study, a one-dimensional particle-in-cell/Monte Carlo collision model is used to simulate electron beam injected CCP under various magnetic fields. At a pressure of 20 mTorr, increasing the magnetic field from 0 to 50 G initially caused the plasma density to increase and then fall, with a peak density observed at 20 G. This is because the gyroradius of the injected electrons in the magnetic field is comparable to the electrode gap. When the pressure is increased, this effect is significantly weakened due to the disruption of the electrons' gyration. Additionally, the electron energy distribution is significantly impacted by increasing the magnetic field. An increase in the magnetic field reduces the maximum ion energy and significantly enhances ion flux at the powered electrode. At the grounded electrode, when the maximum cyclotron radius of the injected electrons is comparable to the electrode spacing, the ion flux reaches its maximum. Further increasing the magnetic field results in a decrease in ion flux. This is crucial for semiconductor etching processes aiming to reduce electrode damage and improve etching efficiency. It also provides new insights for plasma research. [ABSTRACT FROM AUTHOR]

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We investigated, for the first time, the impact of the disappearing solar wind (DSW) event [26–28 December 2022] on the deep nightside ionospheric species using MAVEN data sets. An enhanced plasma density has been observed in the Martian nightside ionosphere during extreme low solar wind density and pressure periods. At a given altitude, the electron density surged by ∼2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it enhanced by > 10 times, respectively, compared to their typical average quiet‐time periods. This investigation suggests that an upward ionospheric expansion likely took place in a direct consequence to the contrasting low dynamic/magnetic pressure and relatively higher nightside ionospheric pressure (by 1–2 orders) causing an increased ionospheric density. Moreover, the day‐to‐night plasma transport may also be a contributing factor to the increased plasma density. Thus, this study offers a new insight about planetary atmosphere/ionosphere during extreme quiescent solar wind periods. Plain Language Summary: The evolution of the Mars climate over time depends upon the solar wind‐Mars interactions. The varying activity over the Sun intermittently produce extreme low density solar wind or also called as disappearing Solar Wind (DSW), which can affect the planetary environment in many ways. Beyond Earth, the effect of DSW on other planetary atmospheres is not well studied. In order to understand this aspect, we have explored the behavior of Martian nightside plasma environment (species: e−, NO+, O2+, CO2+, C+, N+, O+, and OH+) during the DSW event. A dense ionosphere is observed during DSW compared to non‐DSW periods. During DSW, the magnitude of peak nightside electron and ions density are increased by ∼2.5 and more than 10 times, respectively compared to their typical average quiet‐time scenario. The higher plasma density could be due to an expansion from the lower to the topside ionosphere, in consequence to the higher ionospheric pressure as compared to the low solar wind pressure. Furthermore, it could also be enhanced by the transport of plasma from dayside to nightside. Hence, this study, for the first instance, guides us to a new understanding of the impact of a rarest solar wind phenomenon on the Martian ionosphere. Key Points: An increased plasma density is observed in the nightside ionosphere during the disappearing solar wind periods around MarsThe electron and ions abundance surged by a factor of ∼2.5 and >10 respectively, compared to the average quiet‐time periodsThe contrast between the higher nightside ionospheric pressure and the dynamic/magnetosheath pressure led to increased plasma densities [ABSTRACT FROM AUTHOR]

This paper considers a method for estimating bounce-averaged quasi-linear diffusion coefficients due to whistler-mode waves for a specified ratio of plasma frequency to gyrofrequency, ω p / Ω e , using values precomputed for a different value of that ratio. This approach was recently introduced to facilitate calculations associated with the "POES technique," generalized to infer both wave intensity and cold plasma density from measurements of particle fluxes near the loss cone. The original derivation was justified on the basis of parallel-propagating waves but applied to calculations with much more general models of the waves. Here, we justify the estimates, which are based on equating resonant frequencies for differing values of ω p / Ω e and energy, for wide ranges of wave normal angle, resonance number, energy, and equatorial pitch angle. Refinements of the original estimates are obtained and tested numerically against full calculations of the diffusion coefficients for representative wave models. The estimated diffusion coefficients can be calculated rapidly and generally give useful estimates for energies in the 30-keV–300-keV range, especially when both relevant values of the ratio ω p / Ω e are large. [ABSTRACT FROM AUTHOR]

The effective polytropic index of plasmas is typically determined from the analysis of the plasma temperature (or pressure) and density, which are plasma bulk parameters determined from analyses of in situ plasma observations. Here, we show that the use of the typical chi-squared minimization method in plasma observation analyses results in artificial correlations between the plasma density and temperature, which will introduce errors in the determination of the plasma polytropic relationship. We quantify this potential error by analyzing simulated plasma observations. We specifically show that even in cases of nonvarying plasma, a significant statistical uncertainty in the observations leads to the determination of plasma parameters, which seemingly follow a nearly adiabatic model. Moreover, we consider isobaric plasma variations and discuss the error in the determined polytropic relationship as a function of the actual plasma variations and the statistical uncertainties of the determined parameters. We finally show that the use of an alternative analysis method improves the accuracy of the results. [ABSTRACT FROM AUTHOR]

In this study, we investigated terrestrial-origin O+ ions below 1 keV around the Moon using data from the Kaguya satellite between December 2007 and June 2009. These terrestrial-origin low-energy O+ ions were identified based on three parameters: the periodicity of O+ ion count enhancement corresponding to Kaguya's 2-h orbital period, the count ratio of O+ ions to Na+ and Al+ ions, and the direction of ion bulk velocity in the Sun–Earth direction. We identified three intervals that included such O+ ions: 14:30–20:30 UT on June 19, 2008, 19:00 UT on July 16, 2008 to 03:00 UT on July 17, 2008, and 14:00–24:00 UT on June 7, 2009. These intervals were found in the dawn sector, the dusk sector, and the midnight to dawn sector within the magnetotail, respectively. We examined the relation between geomagnetic storm conditions and increases in terrestrial-origin O+ ion counts and found that all three intervals occurred during the late recovery phase of moderate/weak magnetic storms. Since moderately/weakly disturbed conditions (Dst = –40 nT to –20 nT) account for approximately 21% of the total time between 1957 and 2016, we suggest that low-energy O+ ions from the Earth have a non-negligible impact on the ion composition and the ion mass density in the lunar plasma environment. [ABSTRACT FROM AUTHOR]

Understanding the effects of east‐west component of interplanetary magnetic field (IMF‐By) on the equatorial ionospheric electrodynamics is challenging due to the complex response caused by the simultaneous occurrence of multiple mechanisms during disturbed times. The extreme geomagnetic storm on 10 May 2024 caused by multiple‐ICME interactions accompanied with unprecedented IMF‐By magnitudes and its polarity, changed from west to east by 130 nT during northward IMF‐Bz turning. The ground ionosonde observations of h'F from near‐equatorial locations, along with the latitudinal profiles of plasma densities from Swarm satellites reveal the first observational evidence of the impact of strong IMF‐By near the dusk‐terminator (17–19.5 LT), causing strong dawn‐to‐dusk ionospheric electric fields during northward IMF‐Bz. This electric field produces large uplift of the ionospheric plasma near equator and subsequent super‐fountain effect near the dusk. The combined effect of increased IMF‐By amplitudes and viscous terms might have resulted into the enhanced coupling of solar wind with the magnetosphere. Plain Language Summary: The southward component of interplanetary magnetic field (IMF‐Bz) is a primary driver for the solar wind‐magnetosphere coupling, which produces geomagnetic disturbances on the Earth. Whereas east‐west component of IMF (IMF‐By) can modify the effects of these disturbances. Understanding the effects of IMF‐By on the equatorial ionosphere is challenging due to the complex response caused by the simultaneous occurrence of multiple mechanisms during disturbed times, such as ring current, prompt penetration and disturbance dynamo electric fields etc. During the extreme geomagnetic storm which occurred on 10 May 2024, the IMF‐By component was very intense. Both, Bz and By components of IMF made sudden and giant transitions, changing their orientation rapidly. We have investigated the effects of this rarest event on the equatorial ionospheric electric fields. We find penetration of strong eastward electric field near dusk during northward and eastward IMF conditions. Key Points: Unprecedented IMF‐By amplitudes during northward IMF show strong eastward ionospheric electric fields at dusk near equatorThe effects are strongest near dusk and overshielding effects are evident near noonFirst observational evidence of the impact of strong IMF‐By on the equatorial ionosphere near dusk [ABSTRACT FROM AUTHOR]

Spherical Gd 2 Zr 2 O 7 (GZO) powders with a uniform particle size distribution are successfully prepared using a novel industrial approach, which combines spray-drying process and thermal plasma sintering technology together. In this, GZO powders with pyrochlore structure as the main phase are first synthesized via a solid-state reactive route using a mixture of the milled Gd 2 O 3 powders and ZrO 2 powders as starting materials. The influence of sintering temperature on the microstructure of prepared powders is researched. Then, GZO granules are prepared after wet-grinding and spray-drying process, which exhibit a spherical shape with the average particle size of 46.5 μm. RF induction thermal plasma is finally used to sinter the granulated particles, and the influence of feeding rate on the properties of spherical powders is investigated. The apparent density of plasma sintered GZO spherical powders is increased from 1.53 g/cm3 to 2.29 g/cm3 when the feeding rate of granulated powders is 80 g/min, and further increased up to 3.90 g/cm3 when the feeding rate is 15 g/min. Such powders are in potential demand for plasma sprayed coatings and additive manufacturing techniques, and the successful synthesis of spherical GZO powders may guide the way toward the preparation of many other spherical rare earth zirconates powders. [ABSTRACT FROM AUTHOR]

• An algorithm for efficient digitalization of chorus has been developed. • Data indicate the presence of complex conjugate roots of the characteristic equation. • The BPA mechanism for chorus excitation mainly in upper frequency band is confirmed. In this paper, we focus on studying the quantitative characteristics of the excitation mechanism of chorus emissions closely related to the problem of relativistic electron flux formation in the radiation belts. The study is based on the processing of information accumulated by the Van Allen Probe spacecraft through the analysis of high-resolution data. We have chosen two typical examples of chorus emissions with spectral forms predominantly in the upper-frequency band (above half the electron cyclotron frequency) in the region of the local minimum of the magnetic field outside the plasmapause in the middle magnetosphere. We have developed and implemented a calculation algorithm that enables us to represent the results of wave field measurements in a high-resolution data channel in the form of a rectangular event matrix, each row of which corresponds to a cycle of the wave process. In the event matrix, we select the rows corresponding to fragments of chorus emissions that best characterize the natural source of short electromagnetic pulses. This method made it possible to determine the complex eigenvalues of the characteristic equation of the chorus emissions source. The proposed method for processing experimental information makes it possible to determine the main characteristics of the linear mechanism of chorus excitation. The results obtained in this way from observational data are in good agreement with relevant theory of chorus emissions excitation by amplifying noise electromagnetic pulses in a duct with a depleted density of a cold plasma. [ABSTRACT FROM AUTHOR]

The existence of continuous cooling and heating processes is an important condition governing the behavior of the solar corona, which is characterized by temperatures of several million Kelvin. These processes can be significantly influenced by small-scale coronal formations, which largely determine the thermal balance of the corona and solar-wind disturbances. High-sensitivity observations of polarized radiation allow us to evaluate the complex structure of magnetic fields that accumulate the energy necessary to excite coronal eruptions, bursts and flares. However, at high altitudes the corona becomes optically thin, and observations of it pose a major challenge, requiring the use of instruments with a large effective area. Many researchers note that the emerging field of coronal magnetometry is hard to develop due to the fact that experimental observations in optical range are limited by the low plasma density in the corona, high temperature, and insufficient sensitivity of the instruments. In contrast, higher sensitivity is achievable in the radio frequency range. In particular, the 1–3 GHz range is optimal for detecting very weak coronal structures of emerging activity, despite limitations in spatial resolution. To carry out radio requency observations of the corona on the RATAN-600 large reflector-type radio telescope, a wide-range spectrometer in the range of 1–3 GHz was created. It has continuous coverage of the entire frequency range with maximum frequency and time resolutions, as well as high sensitivity to radiation flux. The results of the first series of observations of weak coronal structures are presented, and their interpretation in terms of their effect on thermal processes in the corona is discussed. [ABSTRACT FROM AUTHOR]

Measurements of heavy (M/q > 3) ions on the Phobos-2 satellite revealed that the density of these ions in the central plasma sheet of the areomagnetic tail is proportional to the proton density of the solar wind flowing around the planet. ISEE-2 ion measurements in the near-Earth plasma sheet close to the neutral line were also compared to solar wind data obtained on the ISEE-3 satellite. It was found that the density of protons in the near-Earth plasma sheet is proportional to the density of solar wind protons as well. Analysis of the magnetic and plasma pressure balance in the solar wind and inside the magnetotails of the Earth and Mars showed that the previously found correlations are the result of the necessary equality of pressures at the magnetosphere boundary and inside the magnetic tails of the planets. [ABSTRACT FROM AUTHOR]

High-power lasers are at the forefront of science in many domains. While their fields are still far from reaching the Schwinger limit, they have been used in extreme regimes, to successfully accelerate particles at high energies, or to reproduce phenomena observed in astrophysical settings. However, our understanding of laser–plasma interactions is limited by numerical simulations, which are very expensive to run as short temporal and spatial scales need to be resolved explicitly. Under such circumstances, a non-collisional approach to model laser–plasma interactions becomes numerically expensive. Even a collisional approach, modeling the electrons and ions as independent fluids, is slow in practice. In both cases, the limitation comes from a direct computation of electron motion. In this work, we show how the generalized Ohm's law captures collisional absorption phenomena through the macroscopic interactions of laser fields, electron flows, and ion dynamics. This approach replicates several features usually associated with explicit electron motion, such as cutoff density, reflection, and absorption. As the electron dynamics are now solved implicitly, the spatial and temporal scales of this model fit well between multi-fluid and standard magnetohydrodynamics scales, enabling the study of a new class of problems that would be too expensive to solve numerically with other methods. [ABSTRACT FROM AUTHOR]

Liquid-phase plasma is widely used in industry, so it is important to study its characteristics. In this paper, an experimental system utilizing a cylindrical pressure tank with adjustable hydrostatic pressure for studying liquid-phase pulsed discharge plasma is designed, and the components and experimental principles of the system are introduced in detail. Based on this experimental system, the influence of hydrostatic pressure on the characteristics of liquid-phase plasma was investigated under varying voltage levels and electrode spacings. The results demonstrate that the experimental system can effectively generate and observe liquid-phase plasma. As hydrostatic pressure increases, the pre-breakdown delay at 15 kV and a 2 mm electrode gap increases from 25.6 μs at 0.1 MPa to 447.2μs at 0.5 MPa, while the duration of the main discharge stage decreases from 224.4 to 210.4μs. At 13 kV with a 2 mm electrode gap, the emission spectrum intensity and the electron density of the discharge plasma decrease with increasing hydrostatic pressure. The electron temperature in the plasma channel ranges from 11,000 K to 16,500 K. In addition, the discharge process phenomena were analyzed using typical high-speed camera images, highlighting the characteristics of the discharge plasma at each stage. Finally, the shortcomings and improvement of the experimental system are analyzed. [ABSTRACT FROM AUTHOR]