Ion Energy Research Articles

Ion velocity effect governs damage annealing process in defective KTaO3

Effects of electronic to nuclear energy losses (S e/S n) ratio on damage evolution in defective KTaO3 have been investigated by irradiating pre-damaged single crystal KTaO3 with intermediate energy O ions (6 MeV, 8 MeV and 12 MeV) at 300 K. By exploring these processes in pre-damaged KTaO3 containing a fractional disorder level of 0.35, the results demonstrate the occurrence of a precursory stage of damage production before the onset of damage annealing process in defective KTaO3 that decreases with O ion energy. The observed ionization-induced annealing process by ion channeling analysis has been further mirrored by high resolution transmission electron microscopy analysis. In addition, the reduction of disorder level is accompanied by the broadening of the disorder profiles to greater depth with increasing ion fluence, and enhanced migration is observed with decreasing O ion energy. Since S e (∼3.0 keV nm−1) is nearly constant for all 3 ion energies across the pre-damaged depth, the difference in behavior is due to the so-called ‘velocity effect’: the lower ion velocity below the Bragg peak yields a confined spread of the electron cascade and hence an increased energy deposition density. The inelastic thermal spike calculation has further confirmed the existence of a velocity effect, not previously reported in KTaO3 or very scarcely reported in other materials for which the existence of ionization-induced annealing has been reported. In other words, understanding of ionization-induced annealing has been advanced by pointing out that ion velocity effect governs the healing of pre-existing defects, which may have significant implication for the creation of new functionalities in KTaO3 through atomic-level control of microstructural modifications, but may not be limited to KTaO3.

Core performance predictions in projected SPARC first-campaign plasmas with nonlinear CGYRO

This work characterizes the core transport physics of SPARC early-campaign plasmas using the PORTALS-CGYRO framework. Empirical modeling of SPARC plasmas with L-mode confinement indicates an ample window of breakeven (Q > 1) without the need of H-mode operation. Extensive modeling of multi-channel (electron energy, ion energy, and electron particle) flux-matched conditions with the nonlinear CGYRO code for turbulent transport coupled to the macroscopic plasma evolution using PORTALS reveals that the maximum fusion performance to be attained will be highly dependent on the near-edge pressure. Stiff core transport conditions are found, particularly when fusion gain approaches unity, and predicted density peaking is found to be in line with empirical databases of particle source-free H-modes. Impurity optimization is identified as a potential avenue to increase fusion performance while enabling core-edge integration. Extensive validation of the quasilinear TGLF model builds confidence in reduced-model predictions. The implications of projecting L-mode performance to high-performance and burning-plasma devices is discussed, together with the importance of predicting edge conditions.

A physics-informed deep learning description of Knudsen layer reactivity reduction

A physics-informed neural network (PINN) is used to evaluate the fast ion distribution in the hot spot of an inertial confinement fusion target. The use of tailored input and output layers to the neural network is shown to enable a PINN to learn the parametric solution to the Vlasov–Fokker–Planck equation in the absence of any synthetic or experimental data. As an explicit demonstration of the approach, the specific problem of Knudsen layer fusion yield reduction is treated. Here, the predictions from the Vlasov–Fokker–Planck PINN are used to provide a non-perturbative solution of the fast ion tail in the vicinity of the hot spot, thus allowing the spatial profile of the fusion reactivity to be evaluated for a range of collisionalities and hot spot conditions. Excellent agreement is found between the predictions of the Vlasov–Fokker–Planck PINN and the results from traditional numerical solvers with respect to both the energy and spatial distribution of fast ions and the fusion reactivity profile, demonstrating that the Vlasov–Fokker–Planck PINN provides an accurate and efficient means of determining the impact of Knudsen layer yield reduction across a broad range of plasma conditions.

Effects of power on ion behaviors in radio-frequency magnetron sputtering of indium tin oxide (ITO)

This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide (ITO) target. The positive ion energies exhibit an upward trajectory with increasing RF power, attributed to heightened plasma potential and initial emergent energy. Simultaneously, the positive ion flux escalates owing to amplified sputtering rates and electron density. Conversely, negative ions exhibit broad ion energy distribution functions (IEDFs) characterized by multiple peaks. These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential, alongside ion transport time. This elucidation finds validation in a one-dimensional model encompassing the initial ion energy. At higher RF power, negative ions surpassing 100 eV escalate in both flux and energy, posing a potential risk of sputtering damages to ITO layers.

Plasma potential and ion energy characteristics in BP-HiPIMS discharge with double layer

Plasma potential and ion energy characteristics in BP-HiPIMS discharge with double layer

Magnetohydrodynamics simulation of magnetic reconnection process based on the laser-driven Helmholtz capacitor-coil targets

Magnetic reconnection is an important rapid energy release mechanism in astrophysics. Magnetic energy can be effectively converted into plasma kinetic energy, thermal energy, and radiation energy. This study is based on the magnetohydrodynamics simulation method and utilizes the FLASH code to investigate the laser-driven magnetic reconnection physical process of the Helmholtz capacitor-coil target. The simulation model incorporates the laser driving effect, and the external magnetic field consistent with the Helmholtz capacitor-coil target is written in. This approach achieves a magnetic reconnection process that is more consistent with the experiment. By changing the resistivity, subtle differences in energy conversion during the evolution of magnetic reconnection are observed. Under conditions of low resistivity, there is a more pronounced increase in the thermal energy of ions compared to other energy components. In simulations with high resistivity, the increase in electrons thermal energy is more prominent. The simulation gives the evolution trajectory of magnetic reconnection, which is in good agreement with the experimental results. This has important reference value for experimental research on the low-β magnetic reconnection.

Experimental study of the plasma flow created by a low-power helicon source and approaches to increase the average energy of its ion component

The article presents the results of an experimental study of the characteristics of a low-power helicon ion source. Particular attention is paid to the parameters of the particle flow emerging from the source and the possibilities for increasing ion energy. It was found that the voltage drop at the output of the source is small (10–15 V), and the main voltage drop is localized at the grounded elements. The ion flux density non-monotonically depends on the magnetic field, while the ion energy remains constant. Applying a constant voltage to the additional electrode inside the discharge chamber does not increase the potential drop at the output of the source. Switching to a lower operating frequency or narrower output orifices allows increasing ion energy, but leads to a decrease in ion flux. At the exit from the source, in the presence of a magnetic field, a directed flow of electrons was detected, the energy of which increases significantly with increasing magnetic field induction. The presence of wave processes in the discharge chamber, which may be responsible for the appearance of an accelerated electron flow, has been demonstrated.

Heavy ions and alpha particles irradiation impact on III-V broken-gap gate-all-around TFET

This report deals with the impact of radiation on III-V and Si gate-all-around tunnel field effect transistors (GAA TFET). The highly energetic particles (HEPs) such as heavy ions and alpha particles are allowed to strike the device at several locations along the channel to determine the sensitive location of the device. Once the sensitive location is determined, then the device is irradiated to different energies of heavy ions and alpha particles. Further, to get a proximate match as a practically exposed device, the device has been irradiated to several incident angles. Before analyzing the device's behaviour, the models used for the analysis are calibrated with the transfer characteristics of an experimentally published report on III-V GAA TFET. Thereafter, analysis of charge collection, transient current, hole generation in the channel, and different incident angles are analyzed. Finally, it is concluded that III-V GAA TFET shows better immunity towards different incident angles under a radiation environment when compared to Si GAA TFET.

Comparative analysis of heavy ions and alpha particles impact on gate-all-around TFETs and gate-all-around MOSFETs

The single-event-transient (SET) effect due to heavy ions and alpha particles irradiation on n-type gate-all-around tunnel field effect transistor (GAA TFET) and n-type gate-all-around MOSFET (GAA MOSFET) has been carried out. Due to differences in carrier injection mechanisms, the generated electron-hole pairs (EHPs) due to high-energy particles (HEPs) act differently on the device. In addition, the impact of HEPs (i.e., heavy ions and alpha particles) on several locations along the channel are analyzed followed by the analysis of different energies of heavy ions and alpha particles irradiation on the device. Further, the impact of varying striking angles of HEPs on the device is also analyzed to get a close match as practically exposed device characteristic. Finally, the bipolar gain of the device has been analyzed which shows GAA TFET device has more immunity toward heavy ions strike and weak immunity toward alpha particle strikes when compared to the GAA MOSFET counterpart.

Toward Safe and Reliable Aqueous Ammonium Ion Energy Storage Systems

AbstractAqueous batteries using non‐metallic charge carriers like proton (H+) and ammonium (NH4+) ions are becoming more popular compared to traditional metal‐ion batteries, owing to their enhanced safety, high performance, and sustainability (they are ecofriendly and derived from abundant resources). Ammonium ion energy storage systems (AIBs), which use NH4+ ions with tetrahedral geometry, a small hydrated ionic radius, and relatively low ionic weight, are emerging as strong candidates in non‐metal ion battery chemistry. Various electrode materials (both inorganic and organic) are investigated as hosts for NH4+ ions, however, a comprehensive understanding of these mechanisms is still lacking. This gap limits the ability to optimize performance and identify further research opportunities in AIBs. In this review, the charge storage mechanisms in AIBs are discussed, offering insights into the interactions between NH4+ ions and different electrode materials. Additionally, existing literature on electrode materials, highlighting key structural, and electrochemical achievements are summarized. The review also outlines various electrolytes and examines how their properties influence AIB performance. Finally, the shortcomings of current research are discussed and potential solutions are suggested to advance AIB technology, with the goal of inspiring researchers to explore real‐world applications for ammonium ion batteries.

Enhanced Acceleration and Escape of Hydrogen Pickup Ions Upstream from Mars by Interplanetary Shocks

The pickup process of newly ionized hydrogen (H) from the Martian extended exosphere represents an important H+ escape channel on Mars. It is generally believed that interplanetary (IP) shocks can accelerate the pickup ions and, in turn, affect the pickup process. However, the underlying processes inherent to the acceleration are not yet fully understood. Here, we concentrate on the dynamic processes involved in acceleration arising from IP shock compression. We examine two typical IP shock events characterized by a sudden increase in the average energy of upstream H+ pickup ions across the shock. The H+ pickup ions continuously enter the field of view of Supra-Thermal And Thermal Ion Composition or Solar Wind Ion Analyzer on board the Mars Atmosphere and Volatile EvolutioN spacecraft in a narrow angular range. Moreover, they correspond to a similar part of their respective ring distributions in velocity space. By comparing measured and theoretical H+ pickup ion energies, we attribute the more energetic H+ pickup ions to the enhanced convection electric field acceleration caused by the shock compression. An increase in the guiding center drift speed across the shock implies a higher escape rate of the H+ pickup ions. Furthermore, the pitch-angle scattering could facilitate the escape of the higher energy H+ pickup ions from Mars. The results may shed light on the understanding of the energization and escape of planetary pickup ions in the solar system.

Void swelling in pure iron after sequential self-ion-irradiation at different energies: Effect of injected interstitials and additional damage in regions containing pre-existing voids

The use of ion irradiation to add displacement dose onto previously neutron-irradiated material is becoming popular, especially since ion irradiation precedes on neutron-typical microstructures and microchemical distributions that would not be produced with ion irradiation alone. One issue to be addressed in these “neutron-preconditioned” specimens concerns the consequences of ion-injected interstitials on preexisting neutron-produced voids, especially since voids have been observed to disappear over a significant portion of the ion range in some recent preconditioning experiments. This situation can be explored using innovative ion simulation, thereby avoiding working with radioactive material.Two self-ion irradiation series of pure single-crystal iron were performed at 475 °C. The first series used 5 MeV Fe2+, reaching 50, 100 and 150 peak dpa, producing voids to ∼2 µm depth. The second series used 2.5 MeV Fe2+ to introduce additional 50 peak dpa onto each of the three first-step specimens with the ion range reaching ∼1.2 µm. Importantly, 1.2 × 10−3 peak dpa/s was used for both ions to minimize the influence of dpa rate. The major objective was to measure the influence of injected interstitials from the 2.5 MeV Fe2+ irradiation on previously existing voids. Another objective was to observe the behavior of voids exposed to additional dose and time, focusing not only on injected interstitials, but also on the effects of coalescence, ripening, and aging.There were significant changes in depth distribution of swelling following the second irradiation, especially void density. Whereas injected interstitials are well-known to suppress void nucleation at the end of ion range, it was shown in this study that injected interstitials are important in another manner, reducing growth of previously existing voids, producing a ‘notch” in both the swelling vs. depth profile and void size profile. At depths where the injected atoms for both ion energies are not significant, swelling proceeds at ∼0.2 %/dpa.

Focus on lithiation kinetics of selenium-doped NiO@C electrodes with multistage pore structure

Nickel oxide (NiO) has received considerable attention as an anode for lithium-ion batteries (LIBs) due to its superior theoretical specific capacity and cycling stability. However, its low conductivity as a wide bandgap semiconductor and sluggish lithiation kinetics are still obstacles to its widespread commercial use. In this study, we have developed a Se-doped NiO@C microsphere with a multistage pore structure. The Se-doped NiO@C shows satisfactory specific capacity and cycling stability when used as an anode for LIBs. Specifically, it exhibits a specific capacity of 1622.2 mAh g−1 after 190 cycles at 0.1 A g−1, and a capacity retention of 79.3 % after 1500 cycles at 2 A g−1. The Se-doped NiO@C exhibited improved lithiation reaction kinetics due to its hierarchical pore structure, as indicated by rate performance, pseudocapacitance contribution, and galvanostatic intermittent titration technique. Furthermore, DFT calculations revealed that the addition of selenium altered the band structure of NiO, resulting in a narrower forbidden band width and faster charge transfer. Meanwhile, the electrons provided by selenium enhance the density of states of elemental oxygen and improve the adsorption energy of lithium ions. This study provides insights into the structure and composition necessary for improving the hysteresis kinetics of oxide electrodes.

Argon admixture-driven enhanced ionization and performance of a 5 kW Hall thruster on krypton

Utilizing alternative propellants has been recognized as a strategy to reduce the total cost of propellants in electric propulsion-based missions. The aim of this study is to quantify the Hall effect thruster (HET) performance and operating characteristics using a Kr–Ar mixture to enable mission designers to evaluate the impact on mission and spacecraft design. We present the performance and plume plasma properties of the P5 5 kW-class HET operated with a Kr–Ar mixture with Ar volumetric flow rate fractions from 0 to 100%. The thruster is characterized at discharge power levels of 2.6 kW and 4.1 kW at constant discharge current and voltage over the range of Ar fractions. Despite higher ionization energy and lower mass of Ar, the thruster exhibited a similar level of thrust within 2% when comparing the pure Kr and 26%-Ar mixture cases. The derived ion energy distribution functions and analytical modeling suggest that the characteristic length for the ionization region is extended as the Ar fraction increases. The increased residence time of Kr at the extended ionization region and background energetic electrons from the ionized Ar neutrals are considered to cause this enhanced ionization of the injected Kr neutrals. This leads to a 6% higher Kr ion density at the 26%-Ar case even at the 16% less injected Kr neutral density than in the pure Kr case. The enhanced Kr ionization and generated Ar ions in the 26%-Ar case consequently led to a comparable thrust with that of the pure Kr case. The study indicates that mixing Ar with approximately 26% volumetrically with Kr can provide a similar or even higher thrust performance at the same discharge power. This will be particularly advantageous for various space missions that require high impulses by reducing the total cost of the propellant.

Achieving a High Thermally Conductive One Micron AlN Deposition by High Power Impulse Magnetron Sputtering plus Kick.

High-power impulse magnetron sputtering (HiPIMS) plus kick is a physical vapor deposition method that employs bipolar microsecond-scale voltage pulsing to precisely control the ion energy during sputter deposition. HiPIMS plus kick for AlN deposition is difficult since nitride deposition is challenged by low surface diffusion and high susceptibility to ion damage. In this current study, a systematic examination of the process parameters of HiPIMS plus kick was conducted. Under optimized main negative pulsing conditions, this study documented that a 25 V positive kick biasing for AlN deposition is ideal for optimizing a high quality film, as shown by X-ray diffraction and transmission electron microscopy as well as optimal thermal conductivity while increasing high speed deposition (25 nm/min) and obtaining ultrasmooth surfaces (rms roughness = 0.5 nm). HiPIMS plus kick was employed to deposit a single-texture 1 μm AlN film with a 7.4° rocking curve, indicating well oriented grains, which correlated with high thermal conductivity (121 W/m·K). The data are consistent with the optimal kick voltage enabling enhanced surface diffusion due to ion-substrate collisions without damaging the AlN grains.

Breakdown of Quasilinear Theory in the Tokamak Edge.

In the edge of an L-mode tokamak plasma, particle transport and ion energy transport are shown to follow a strong microturbulence (SMT) scaling, whereas in the plasma core the transport is shown to follow quasilinear turbulence scaling. The dependence of diffusivity on potential fluctuation amplitude is linear in the SMT regime, and quadratic in the quasilinear regime. The transition to strong microturbulence results from larger E×B drift velocities in the edge compared to the plasma core. At these larger velocities, ions traverse the spatially correlated range faster than the stochastic evolution of the electric potential. Hence, these particles do not experience a time-stochastic field as required by the quasilinear approximation. Instead, scattering of particles in the SMT regime is caused by spatial stochasticity. In contrast, electron energy transport remains quasilinear due to decorrelations caused by collisions and fast parallel motion. Improved understanding of transport beyond quasilinear theory opens the path to more accurate modeling of transport in the tokamak plasma edge.

Neutralized, intense-ion beams for fusion

A charge- and current-neutralized, intense-ion beam (IIB) will propagate undeflected in a magnetized plasma by the E×B , or diamagnetic, drift for a distance large compared to the beam-ion gyro-radius. This propagation occurs because of collective plasma effects when the beam-energy density is sufficient to sustain the polarization-electric field, or diamagnetic-screening currents. Our principal interest is the E×B drift, with β=Ebeam/Efield<1 . IIBs are characterized by parameters in the range: 0.1–2 MeV ion energy, 1–100 MA m−2 ion-current density, and 17–350 kW average power produced on repetitively-pulsed systems. Multi-MW average-beam power is possible with appropriate modifications to the power supply and ion-source/accelerator. IIBs can be focused geometrically, and/or magnetically, to spot sizes of the order of a few cm’s and their angular divergence is typically, ∼15 mRadians, suitable for long-range propagation in a vacuum beam-line. IIBs lose energy and momentum in the same manner as particles injected by a neutral-beam injector (NBIs), hence could be useful for fusion applications, including: heating, current drive, fueling, profile modifications, etc and such applications have yet to be thoroughly studied. Summarized here are the physical principles accounting for IIB propagation; ion-source designs used to produce the IIB; and pulsed-power methods for energizing the IIB accelerator. This technology base informs scalable metrics for the ion-source/accelerator (excluding the HV power supply and interconnects) used in a conceptual injector that provides the same ion energy and injected power (1 MeV, 17 MW) as NBIs used on ITER. A comparison indicates that the IIB injector would be much smaller in size, lower cost, and have much greater efficiency, while also providing for real-time modulation of the beam energy and intensity and the use of small-diameter injection ports that could minimize fuel contamination and magnetic-field leakage between the IIB injector and tokamak.

Effective combinations of features in predicting the range of incident ions using machine learning

Machine learning techniques were used to predict the range of ions in material, even when stopping power data is unknown. Simple features such as atomic and mass numbers were used in learning process. Two different machine learning models, Decision Tree (DT) and Kernel Ridge Regression (KRR), were used to assess each feature’s importance and the effect of combining them. The results showed that the chosen features were sufficient for accurate prediction. Furthermore, it was found that the combination and features are essential for accurate results. Analysis by KRR established a relationship between the range of the implanted ions and the energy of the incident ions, showing that the range is approximately proportional to the energy in the dataset used in this work.

Toward Selective Transport of Monovalent Metal Ions with High Permeability Based on Crown Ether-Encapsulated Metal-Organic Framework Sub-Nanochannels.

Achieving selective transport of monovalent metal ions with high precision and permeability analogues to biological protein ion channels has long been explored for fundamental research and various applications, such as ion sieving, mineral extraction, and energy harvesting and conversion. However, it still remains a significant challenge to construct artificial nanofluidic devices to realize the trade-off effects between selective ion transportation and high ion permeability. In this work, we report a bioinspired functional micropipet with in situ growth of crown ether-encapsulated metal-organic frameworks (MOFs) inside the tip and realize selective transport of monovalent metal ions. The functional ion-selective micropipet with sub-nanochannels was constructed by the interfacial growth method with the formation of composite MOFs consisting of ZIF-8 and 15-crown-5. The resulting micropipet device exhibited obvious monovalent ion selectivity and high flux of Li+ due to the synergistic effects of size sieving in subnanoconfined space and specific coordination of 15-crown-5 toward Na+. The selectivity of Li+/Na+, Li+/K+, Li+/Ca2+, and Li+/Mg2+ with 15-crown-5@ZIF-8-functionalized micropipet reached 3.9, 5.2, 105.8, and 122.4, respectively, which had an obvious enhancement compared to that with ZIF-8. Notably, the ion flux of Li+ can reach up to 93.8 ± 3.6 mol h-1·m-2 that is much higher than previously reported values. Furthermore, the functional micropipet with 15-crown-5@ZIF-8 sub-nanochannels exhibited stable Li+ selectivity under various conditions, such as different ion concentrations, pH values, and mixed ion solutions. This work not only provides new opportunities for the development of MOF-based nanofluidic devices for selective ion transport but also facilitates the promising practical applications in lithium extraction from salt-like brines, sewage treatment, and other related aspects.

Dual-network fiber-hydrogel membrane for osmotic energy harvesting.

Osmotic energy harvesting was a promising way to alleviate energy crisis with reverse electrodialysis (RED) membrane-based technology. Charged hydrogel combined with other materials was an effective strategy to overcome problems, including restricted functional groups and complicated fabrication, but the effect of the respective charges of the two materials combined on the membrane properties has rarely been studied in depth. Herein, a new method was proposed that charged hydrogel was equipped with charged filter paper to form dual network fiber-hydrogel membrane for osmotic energy harvesting, which had excellent ion selectivity (beyond 0.9 under high concentration gradient), high ion transference number and energy conversion efficiency (beyond 32.5% under wide range concentration gradient), good property of osmotic energy conversion (∼4.84W/m2 under 50-fold KCl and ∼6.75W/m2 under simulated sea water and river water). Moreover, the power density was attributed to the surface-space charge synergistic effect from large amounts overlapping of electric double layer (EDL), so that the transmembrane ion transport was enhanced. It might be a valid mode to extensively develop the osmotic energy harvesting.