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The magnetotail current sheet plays a crucial role in substorm dynamics, affecting the entire magnetosphere. Formation and reconnection of thin (ion‐gyroscale) current sheets initiate magnetospheric substorms. Theoretical models suggest that a transient, demagnetized ion population is key element of the thin current sheet configuration. At lunar distances, the magnetotail provides a unique opportunity for in situ investigation of this population due to the high fraction of hot demagnetized ions. Using observations of thin current sheets by the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission, we show that the relative drift between demagnetized hot ions and magnetized cold ions, likely driven by a strong polarization electric field, reduces the ion current density to nearly zero in the spacecraft rest frame. Hot ions exhibit a crescent‐like velocity distribution, contributing to ion agyrotropy. We discuss this population in the context of advanced thin current sheet models, including transient ions performing Speiser‐like motion. These observations provide valuable insights for numerical and theoretical studies. Plain Language Summary The night‐side Earth's magnetosphere, the magnetotail, is characterized by stretched magnetic field lines and strong electric currents forming a narrow plasma layer, the thin current sheet. The dynamic evolution of this current sheet determines the efficiency of charged particle acceleration before their transport into Earth's radiation belts and their precipitation into the atmosphere. Its properties are largely governed by the mechanism responsible for the current density generation. Modern theoretical models suggest that demagnetized ions, which violate the conservation of the magnetic moment, play a critical role in supplying the total current density. In this study, we present unambiguous observational confirmation of the existence of such a demagnetized ion population in quiet (stationary) current sheets. Using magnetotail observations at the lunar orbit, where conditions for revealing this ion population are most favorable, we demonstrate that the main aspects of the observed ions align well with the main predictions of theories of the thin current sheet formation. Key Points We investigate ion velocity distributions in thin current sheet in the magnetotail at lunar distances We observe hot (demagnetized, agyrotropic) and cold (beam‐like) ion populations drifting duskward and dawnward, respectively The dawnward drift of cold ions, likely due to E ×${\\times} $B‐drift, suppresses the ion current in the spacecraft rest frame

This work represents the first attempt to model the full-size ITER negative ion source prototype including expansion, extraction and part of the acceleration regions keeping the resolution fine enough to resolve every single aperture of the extraction grid. The model consists of a 2.5-dimensional Particle-in-Cell/Monte Carlo Collision representation of the plane perpendicular to the filter field lines. Both the magnetic filter and electron deflection fields have been included. A negative ion current density of j H − = 500 A m − 2 produced by neutral conversion from the plasma grid is used as fixed parameter, while negative ions produced by electron dissociative attachment of vibrationally excited molecules and by ionic conversion on plasma grid are self-consistently simulated. Results show the non-ambipolar character of the transport in the expansion region driven by electron magnetic drifts in the plane perpendicular to the filter field. It induces a top-bottom asymmetry detected up to the extraction grid which in turn leads to a tilted positive ion flow hitting the plasma grid and a tilted negative ion flow emitted from the plasma grid. As a consequence, the plasma structure is not uniform around the single aperture: the meniscus assumes a form of asymmetric lobe and a deeper potential well is detected from one side of the aperture relative to the other side. Therefore, the surface-produced contribution to the negative ion extraction is not equally distributed between both the sides around the aperture but it come mainly from the lower side of the grid giving an asymmetrical current distribution in the single beamlet.

A solenoid magnetic field along the expanding laser-produced plasma is an essential technique of the laser ion source. The solenoid field can increase ion beam current at beam extraction point by a factor of 2 to over 100 by confining moving laser produced plasma in transverse direction. This technique is used everywhere from development lab to operational machine for user operation. However, the motion of ions in laser produced plasma is not fully understood. In this study, we experimentally investigated the motion of ions in a solenoid magnet (inner diameter 102 mm, coil length 1980 mm) for Al, Fe, and Ta targets. Using the following three conditions: full solenoid bore, a φ51 mm collimator on the solenoid axis, and a thin-wall φ51 mm tube at the bottom of the solenoid, we found that extracting ions at off-axis position (20∼30 mm from the solenoid axis in this study) can enhance ion intensity by a factor of three or more. We continue to investigate ion motion in a solenoid field to develop better laser ion source design.

Ion cyclotron resonance is one of the fundamental energy-conversion processes through field–particle interaction in collisionless plasmas. However, the key evidence for ion cyclotron resonance (i.e., the coherence between electromagnetic fields and the ion phase-space density) and the resulting damping of ion cyclotron waves (ICWs) has not yet been directly observed. Investigating the high-quality measurements of space plasmas by the Magnetospheric Multiscale (MMS) satellites, we find that both the wave electromagnetic field vectors and the bulk velocity of the disturbed ion velocity distribution rotate around the background magnetic field. Moreover, we find that the absolute gyrophase angle difference between the center of the fluctuations in the ion velocity distribution functions and the wave electric field vectors falls in the range of (0, 90)°, consistent with an ongoing energy conversion from wave fields to particles. By invoking plasma kinetic theory, we demonstrate that the field–particle correlation for the damped ICWs in our theoretical model matches well with our observations. Furthermore, the wave electric field vectors ( δEwave,⊥′ ), ion current density (δ J i,⊥), and energy transfer rate ( δJi,⊥·δEwave,⊥′ ) exhibit quasiperiodic oscillations, and the integrated work done by the electromagnetic field on the ions is positive, indicating that ions are mainly energized by the perpendicular component of the electric field via cyclotron resonance. Therefore, our combined analysis of MMS observations and kinetic theory provides direct, thorough, and comprehensive evidence for ICW damping in space plasmas.

Plasma parameter measurements for negative hydrogen (H−) ion sources have been playing an important role in clarifying fundamental physics related to negative ion production and destruction processes. Measured data of beam properties, such as H− ion current density with the co-extracted electron current and the emittance, were correlated to local concentration of charged particles and temperature often characterized by Langmuir probes and optical emission spectrometry. Langmuir probes coupled to pulse lasers quantified local H− ion densities from early days of H− ion source development, while the cavity ring down photodetachment method removed Langmuir probes from contemporary large-size high power density ion sources. Technological progress has made source plasma diagnostics possible during beam extraction, which has thrown light on the transport of H− ions during the application of the extraction electric field. The advancement of plasma diagnostics for high intensity H− ion sources are summarized in this report together with recent results from the research and development negative ion source being operated for collaborative research programs at National Institute for Fusion Science.

The scrape-off layer (SOL) power width (λq ) is an important parameter for predicting the heat load on divertor targets for future magnetically confined devices. Currently, the underlying physics for λq scaling is not fully understood. This paper extends the previous SOL particle flux width (λjs, λq ≈ λjs is assumed, js is the measured ion current density used as a proxy for particle flux) scaling measured by the inboard divertor Langmuir probes (Div-LPs) in deuterium plasmas (Liu et al 2019 Plasma Phys. Control. Fusion 61 045001) to the λjs scalings measured by the outboard Div-LPs in both deuterium and helium plasmas on EAST. A systematic method has been used to correct the upper-outer Div-LP measurements to reduce the measurement uncertainty of λjs . About 520 discharges are selected for the construction of six databases (H-mode, L-mode, and Ohmic for deuterium and helium plasmas) to scale λjs . Since the published λq scalings do not fit EAST λjs well in the databases, four separate λjs scalings are proposed using statistical method to minimize the scaling parameters. It is found that λjs has a robust scaling dependence on the plasma line-averaged density ( nˉe ) for both deuterium and helium plasmas and a strong positive scaling dependence on the divertor leg length (L div,leg). The scaling exponent of the stored energy agrees well with the previous λq /λjs scalings for deuterium plasmas. The near unity scaling exponents of edge safety factor and L div,leg reveal the importance of parallel connection length in determining λjs . The positive scaling dependence of λjs on nˉe and the 2 ∼ 4 times larger scaling amplitude compared with the published λq scalings probably indicate the turbulence broadening of λjs on EAST. The comparison of λjs for deuterium and helium plasmas using the constructed databases shows no significant difference. Statistical comparison of the normalized λjs with different ELM types suggests that the grassy-ELM λjs is slightly larger than the inter large-ELM (type-I ELM) λjs for both deuterium and helium plasmas.

This article is devoted to the study of the effect of ion sputtering on the alloy surface, using the example of martensitic stainless steel AISI 420 with ultrahigh-dose, high-intensity nitrogen ion implantation on the efficiency of accumulation and transformation of the depth distribution of dopants. Some patterns of change in the depth of ion doping depending on the target temperature in the range from 400 to 650 °C, current density from 55 to 250 mA/cm2, and ion fluence up to 4.5 × 1021 ion/cm2 are studied. It has been experimentally established that a decrease in the ion sputtering coefficient of the surface due to a decrease in the energy of nitrogen ions from 1600 to 350 eV, while maintaining the ion current density, ion irradiation fluence and temperature mode of target irradiation increases the ion-doped layer depth by more than three times from 25 μm to 65 µm. The efficient diffusion coefficient at an ion doping depth of 65 μm is many times greater than the data obtained when stainless steel is nitrided with an ion flux with a current density of about 2 mA/cm2.

The formation and temporal evolution of the plasma boundary layer in plasma immersion ion implantation is investigated in the presence of a magnetic field. It is assumed that the ions are thermalized. When a high-voltage pulse with a ramp function is applied to a target immersed in plasma, a positive space charge is formed and expanded around it. The rise time of the ramp function of the pulse voltage influences the formation and expansion of the plasma boundary layer near the target. The time evolution of the ion current density, ion kinetic energy and ion incident angle as well as the time evolution of the positive space charge and the boundary layer thickness are studied as a functions of the magnetic field, neutral gas pressure and rise time of the ramp function. Our findings show that the time dependency of the variables of the plasma boundary layer is more pronounced for a longer rise time. Graphical Abstract The governing equations, the simulation zone and temporal behavior of the incident angle of the ion for different magnetization parameters, neutral gas pressure and rise time

An alternative material has been proposed as an absorber for a mask blank for lithography in the vicinity of a wavelength of 11.2 nm—Ni. It has been established in this work that the optimal angle for efficient sputtering of Ru, Be, and Ni targets by accelerated argon ion sources for fabrication of a Ru/Be multilayer structure with an upper Ni layer is an angle of 60°. At this angle, the etching rate for all three materials is 35 ± 5 nm/min at an argon ion energy of 800 eV and an ion current density of 0.5 mA/cm 2 .

Current density, the membrane current value divided by membrane capacitance (C m ), is widely used in cellular electrophysiology. Comparing current densities obtained in different cell populations assume that C m and ion current magnitudes are linearly related, however data is scarce about this in cardiomyocytes. Therefore, we statistically analyzed the distributions, and the relationship between parameters of canine cardiac ion currents and C m , and tested if dividing original parameters with C m had any effect. Under conventional voltage clamp conditions, correlations were high for I K1 , moderate for I Kr and I Ca,L , while negligible for I Ks . Correlation between I to1 peak amplitude and C m was negligible when analyzing all cells together, however, the analysis showed high correlations when cells of subepicardial, subendocardial or midmyocardial origin were analyzed separately. In action potential voltage clamp experiments I K1, I Kr and I Ca,L parameters showed high correlations with C m . For I NCX , I Na,late and I Ks there were low-to-moderate correlations between C m and these current parameters. Dividing the original current parameters with C m reduced both the coefficient of variation, and the deviation from normal distribution. The level of correlation between ion currents and C m varies depending on the ion current studied. This must be considered when evaluating ion current densities in cardiac cells.