Energy Loss Of Ions Research Articles

ON IONIZATION LOSS DISTRIBUTION OF RELATIVISTIC PARTICLES IN THIN DETECTORS

Ionization energy loss distribution of high-energy charged particles in thin detectors is considered. Its modification due to the fact that a part of δ-electrons, kicked out from the atoms by the incident particles, escape from the detector and do not dispose of all their kinetic energy inside it, is estimated and shown to be negligibly small. The physical reasons for this are discussed. The parameters responsible for the magnitude of this modification are obtained.

Reduction of neoclassical bulk-ion transport to avoid helium-ash retention in stellarator reactors

Abstract The reduction of neoclassical energy transport in stellarators has traditionally focussed on optimizing magnetic fields for small values of ‘effective helical ripple’ — ϵ eff , the geometric factor associated with electron 1 / ν transport—and relying on the radial electric field, E r , needed to maintain ambipolarity in the plasma, to simultaneously diminish ion energy losses to a tolerable level. As one must generally expect E r < 0 , such a strategy has a drawback for reactor operation, however, as negative values of E r tend to hinder the exhaust of helium ash, and this will become intolerable if it results in excessive fuel dilution. Theoretically, one can show that the neoclassical transport of low-Z impurities depends critically on the ratio L 11 e / L 11 i , where the L 11 σ are the neoclassical particle diffusion coefficients of the bulk-plasma electrons ( σ = e ) and ions ( σ = i ). Increasing the value of this ratio is shown here to counteract impurity retention, but maintaining good confinement of the bulk species requires this to be achieved by decreasing L 11 i rather than increasing L 11 e , implying the need for more than just minimization of ϵ eff in reactor design. To assess the prospects of such an endeavor, a predictive 1-D transport code is used here to determine the range of L 11 e / L 11 i values which arises in simulations of conventionally optimized reactor candidates. This range is found to be considerable, and includes examples with L 11 e / L 11 i values large enough to provide neoclassical temperature screening of the helium ash and even to flip the sign of the neoclassical convective velocity from inward- to outward-directed. More intriguingly, the strong reduction of L 11 i in such cases can also lead to the appearance of E r > 0 (a so-called ‘electron root’) within the core of plasmas having central densities as large as 2 × 10 20 m−3. Having E r > 0 in the plasma core produces the ideal situation in which all thermodynamic forces aid in the exhaust of helium ash, although this benefit is tempered by the small values of L 11 z which accompany an electron root (where σ = z denotes helium ash). Means are discussed for improving the results presented here, so that avoiding helium-ash retention can be explicitly targeted in future reactor optimizations.

A unified global model accompanied with a voltage and current sensor for low-pressure capacitively coupled RF discharge

A global model (GM) assumes ion energy ( ε ) on the electrode equals the time-averaged sheath voltage ( Vshtt ). However, using particle-in-cell simulation, we found that ε differs from Vshtt. We propose a unified global model (UGM) that calculates ε and collisional energy losses of ions by employing plasma circuit and sheath models, accompanied by a voltage and current sensor. We compared the results of the UGM with the experimental measurements and the results revealed that UGM is closer to the experiment than GM. UGM shows a linear relationship with the experiment, indicating that the UGM is applicable for plasma monitoring.

Deeper-band electron contributions to stopping power of silicon for low-energy ions.

This study provides accurate results for the electronic stopping cross sections of H, He, N, and Ne in silicon in low to intermediate energy ranges using various non-perturbative theoretical methods, including real-time time-dependent density functional theory, transport cross section, and induced-density approach. Recent experimental findings [Ntemou et al., Phys. Rev. B 107, 155145 (2023)] revealed discrepancies between the estimates of density functional theory and the observed values. We show that these discrepancies vanish by considering the nonuniform electron density of the deeper silicon bands for ion velocities approaching zero (v → 0). This indicates that mechanisms such as "elevator" and "promotion," which can dynamically excite deeper-band electrons, are active, enabling a localized free-electron gas to emulate ion energy loss, as pointed out by Lim et al. [Phys. Rev. Lett. 116, 043201 (2016)]. The observation and the description of a velocity-proportionality breakdown in electronic stopping cross sections at very low velocities are considered to be a signature of the contributions of deeper-band electrons.

Synchrotron-based x-ray diffraction analysis of energetic ion-induced strain in GaAs and 4H-SiC

Strain engineering using ion beams is a current topic of research interest in semiconductor materials. Synchrotron-based high-resolution x-ray diffraction has been utilized for strain-depth analysis in GaAs irradiated with 300 keV Ar and 4H-SiC and GaAs irradiated with 100 MeV Ag ions. The direct displacement-related defect formation, anticipated from the elastic energy loss of Ar ions, can well explain the irradiation-induced strain depth profiles. The maximum strain in GaAs is evaluated to be 0.88% after Ar irradiation. The unique energy loss depth profile of 100 MeV Ag (swift heavy ions; SHIs) and resistance of pristine 4H-SiC and GaAs to form amorphous/highly disordered ion tracks by ionization energy loss of monatomic ions allow us to examine strain buildup due to the concentrated displacement damage by the elastic energy loss near the end of ion range (∼12 μm). Interestingly, for the case of SHIs, the strain-depth evolution requires consideration of recovery by ionization energy loss component in addition to the elastic displacement damage. For GaAs, strain builds up throughout the ion range, and the maximum strain increases and then saturates at 0.37% above an ion fluence of 3×1013 Ag/cm2. For 4H-SiC, the maximum strain reaches 4.6% and then starts to recover for fluences above 1×1013 Ag/cm2. Finally, the contribution of irradiation defects and the purely mechanical contribution to the total strain have been considered to understand the response of different compounds to ion irradiation.

Hysteresis between gas breakdown and plasma discharge

In direct-current (DC) discharge, it is well known that hysteresis is observed between the Townsend (gas breakdown) and glow regimes. Forward and backward voltage sweep is performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model considering a ballast resistor. When increasing the applied voltage after reaching the breakdown voltage (Vb), transition from Townsend to glow discharges is observed. When decreasing the applied voltage from the glow regime, the discharge voltage (Vd) between the anode–cathode gap can be smaller than the breakdown voltage, resulting in a hysteresis, which is consistent with experimental observations. Next, the PIC-MCC model is used to investigate the self-sustaining voltage (Vs) in the presence of finite initial plasma densities between the anode and cathode gap. It is observed that the self-sustaining voltage coincides with the discharge voltage obtained from the backward voltage sweep. In addition, the self-sustaining voltage decreases with increased initial plasma density and saturates above a certain initial plasma density, which indicates a change in plasma resistivity. The decrease in self-sustaining voltage is associated with the electron heat loss at the anode for the low pd (rarefied) regime. In the high pd (collisional) regime, the ion energy loss toward the cathode due to the cathode fall and the inelastic collision loss of electrons in the bulk discharge balance out. Finally, it is demonstrated that the self-sustaining voltage collapses to a singular value, despite the presence of a initial plasma, for microgaps when field emission is dominant, which is also consistent with experimental observations.

Discovering quirks through timing at FASER and future forward experiments at the LHC

Quirks are generic predictions of strongly-coupled dark sectors. For weak-scale masses and a broad range of confining scales in the dark sector, quirks can be discovered only at the energy frontier, but quirk-anti-quirk pairs are produced with unusual signatures at low pT, making them difficult to detect at the large LHC detectors. We determine the prospects for discovering quirks using timing information at FASER, FASER2, and an “ultimate detector” in the far-forward region at the LHC. NLO QCD corrections are incorporated in the simulation of quirk production, which can significantly increase the production rate. To accurately propagate quirk pairs from the ATLAS interaction point to the forward detectors, the ionization energy loss of charged quirks traveling through matter, the radiation of infracolor glueballs and QCD hadrons during quirk pair oscillations, and the annihilation of quirkonium are properly considered. The quirk signal is separated from the large muon background using timing information from scintillator detectors by requiring either two coincident delayed tracks, based on arrival times at the detector, or two coincident slow tracks, based on time differences between hits in the front and back scintillators. We find that simple cuts preserve much of the signal, but reduce the muon background to negligible levels. With the data already collected, FASER can discover quirks in currently unconstrained parameter space. FASER2, running at the Forward Physics Facility during the HL-LHC era, will greatly extend this reach, probing the TeV-scale quirk masses motivated by the gauge hierarchy problem for the broad range of dark-sector confining scales between 100 eV and 100 keV.

Closer scrutiny of cosmic ray proton energy losses

The percent-level precision attained by modern cosmic ray (CR) observations motivates reaching a comparable or better control of theoretical uncertainties. Here we focus on energy-loss processes affecting low-energy CR protons (∼0.1–5 GeV), where the experimental errors are small and collisional effects play a comparatively larger role with respect to collisionless transport ones. We study three aspects of the problem: (i) We quantitatively assess the role of the nuclear elastic cross section, for the first time, providing analytical formulas for the stopping power and inelasticity; (ii) We discuss the error arising from treating both elastic and pion production inelastic interactions as continuous energy loss processes, as opposed to catastrophic ones. The former is the approximation used in virtually all modern numerical calculations; (iii) We consider subleading effects such as relativistic corrections, radiative and medium processes in ionization energy losses. Our analysis reveals that neglecting (i) leads to errors close to 1%, notably around and below 1 GeV, neglecting (ii) leads to errors reaching about 3% within the considered energy range, (iii) contributes to a minor effect, gauged at the level of 0.1%. Consequently, while (iii) can currently be neglected, (ii) warrants consideration, and we also recommend incorporating (i) into computations. We conclude with some perspectives on further steps to be taken towards a high-precision goal of theoretical CR predictions regarding the treatment of energy losses. Published by the American Physical Society 2024

Experimental Investigations of Quasi-Coherent Micro-Instabilities in J-TEXT Ohmic Plasmas

Quasi-coherent micro-instabilities is one of the key topics of magnetic confinement fusion. This work focuses on the quasi-coherent spectra of ion temperature gradient (ITG) and trapped-electron-mode instabilities using newly developed far-forward collective scattering measurements within ohmic plasmas in the J-TEXT tokamak. The ITG mode is characterized by frequencies ranging from 30 to 100 kHz and wavenumbers (kθρ s) less than 0.3. Beyond a critical plasma density threshold, the ITG mode undergoes a bifurcation, which is marked by a reduction in frequency and an enhancement in amplitude. Concurrently, enhancements in ion energy loss and degradation in confinement are observed. This ground-breaking discovery represents the first instance of direct experimental evidence that establishes a clear link between ITG instability and ion thermal transport.

Long-lived doubly charged scalars in the left-right symmetric model: Catalyzed nuclear fusion and collider implications

We show that the doubly charged scalar from the SU(2)R-triplet Higgs field in the Left-Right Symmetric Model has its mass governed by a hidden symmetry so that its value can be much lower than the SU(2)R breaking scale. This makes it a long-lived particle while being consistent with all existing theoretical and experimental constraints. Such long-lived doubly charged scalars have the potential to trigger catalyzed fusion processes in light nuclei, which may have important applications for energy production. We show that it could also bear consequences on the excess of large ionization energy loss (dE/dx) recently observed in collider experiments.

First experimental time-of-flight-based proton radiography using low gain avalanche diodes

Objective. Ion computed tomography (iCT) is an imaging modality for the direct determination of the relative stopping power (RSP) distribution within a patient’s body. Usually, this is done by estimating the path and energy loss of ions traversing the scanned volume utilising a tracking system and a separate residual energy detector. This study, on the other hand, introduces the first experimental study of a novel iCT approach based on time-of-flight (TOF) measurements, the so-called Sandwich TOF-iCT concept, which in contrast to any other iCT systems, does not require a residual energy detector for the RSP determination. Approach. A small Sandwich TOF-iCT demonstrator was built based on low gain avalanche diodes (LGADs), which are 4D-tracking detectors that allow to simultaneously measure the particle position and time-of-arrival with a precision better than 100 μm and 100 ps, respectively. Using this demonstrator, the material and energy-dependent TOF was measured for several homogeneous PMMA slabs in order to calibrate the acquired TOF against the corresponding water equivalent thickness (WET). With this calibration, two proton radiographs (pRads) of a small aluminium stair phantom were recorded at MedAustron using 83 MeV and 100.4 MeV protons. Main results. Due to the simplified WET calibration models used in this very first experimental study of this novel approach, the difference between the measured and theoretical WET ranged between 37.09% and 51.12%. Nevertheless, the first TOF-based pRad was successfully recorded showing that LGADs are suitable detector candidates for Sandwich TOF-iCT. Significance. While the system parameters and WET estimation algorithms require further optimization, this work was an important first step to realize Sandwich TOF-iCT. Due to its compact and cost-efficient design, Sandwich TOF-iCT has the potential to make iCT more feasible and attractive for clinical application, which, eventually, could enhance the treatment planning quality.

Energy losses of highly charged Arq+ ions during grazing incidence on tungsten surfaces

In this study, we investigate the energy loss of highly charged ions interacting with various tungsten surfaces. The analysis primarily focuses on elucidating the impact of electron density distributions on energy loss of ions. Furthermore, we explore the correlation between surface azimuthal angles and energy loss under both uniform and inhomogeneous electron density distributions. Utilizing the classical over-the-barrier model (COBM), simulations involving trajectory calculations, energy loss, charge-exchange processes, and surface electron distributions, etc., were performed. Remarkably, the significant influence of axial channeling of surfaces on ion energy loss is observed. For the comparison of ion energy loss under uniform and inhomogeneous electron density distributions, the results reveal a more pronounced effect of electron density inhomogeneity on ion energy loss at higher energy-loss values. Additionally, the calculated energy-loss spectra of Ar16+ ions grazing on graphite surfaces show reasonable agreement with experimental data. These findings are crucial for understanding the surface structure of crystals.

Unraveling radiation damage and healing mechanisms in halide perovskites using energy-tuned dual irradiation dosing

Perovskite photovoltaics have been shown to recover, or heal, after radiation damage. Here, we deconvolve the effects of radiation based on different energy loss mechanisms from incident protons which induce defects or can promote efficiency recovery. We design a dual dose experiment first exposing devices to low-energy protons efficient in creating atomic displacements. Devices are then irradiated with high-energy protons that interact differently. Correlated with modeling, high-energy protons (with increased ionizing energy loss component) effectively anneal the initial radiation damage, and recover the device efficiency, thus directly detailing the different interactions of irradiation. We relate these differences to the energy loss (ionization or non-ionization) using simulation. Dual dose experiments provide insight into understanding the radiation response of perovskite solar cells and highlight that radiation-matter interactions in soft lattice materials are distinct from conventional semiconductors. These results present electronic ionization as a unique handle to remedying defects and trap states in perovskites.

Ionization energy losses of cosmic rays in graphene nanostructures calculation

Currently, in the Republic of Kazakhstan, within the framework of the strategic directions of the space industry, fundamental and applied scientific space research is being developed, and practical problems are being solved using space technology. In these studies, special attention is paid to the reliability of on-board equipment under the complex influence of outer space factors. In the development and design of such work as docking and assembly of elements of orbital stations, remote control of automatic interplanetary stations and many others, mathematical and computer modeling is used, which is a highly effective and relatively low-cost method. The purpose of this work is to study the dependence of the energy losses of relativistic ions of cosmic radiation when particles pass through graphene nanostructures in order to predict their radiation resistance when exposed to cosmic radiation particles. The simulation of the trajectories and energy losses of relativistic ions during passing through graphite crystals were performed. Numerical values ​​of the critical channeling angles in a graphite crystal are obtained. It is shown that ion energy losses do not depend on the point of entry of the ion into the crystal and increase sharply with decreasing energy in the energy range less than 1000 MeV/nucleon.

Damage Energy Threshold Anisotropy in Non Ionizing Energy Loss Calculation

Damage Energy Threshold Anisotropy in Non Ionizing Energy Loss Calculation

Electron transport characteristics in water under electrostrictive effect

The transport characteristics of electrons are crucial for the initiation and development of pulse discharge in water. In this work, we develop a physical model of electron transport that consides elastic and inelastic collision cross sections. The purpose of this study is to investigate frequency variations of elastic collisions, ionization and excitation collisions with different initial electron energy values, and to explore the characteristic of electron energy loss in water. The Monte Carlo method is employed to track structure characteristics of electron transmission and scattering under varying energy values. The results show that the electrons of lower energy (~20 eV) are significantly impacted by the water molecule scattering, hence their transmission capacities are weakened. When the incident energy of electron reaches 100 eV, the scattering deviation distance is roughly equivalent to the transmission depth, about 6–8 nm, and the maximum deviation angle <i>θ</i><sub>shift</sub> ~ 60°. When the electron incident energy is in a range of 10–1000 eV, the number of elastic collisions is much greater than the number of excitation and ionization collisions, and the number of ionization collisions and excitation collisions increases significantly with the increase of electron energy. The higher the electron incident energy, the greater the energy loss is. However, the energy loss decreases sharply with the extension of penetration distance. For the ionization collision, the average ionization energy loss, <i>W</i>, decreases rapidly with the increase of electron energy, and ultimately maintains at a level of 20–30 eV, which is consistent with the experimental results reported.

Determination of Ionization Energy Loss of Electron-Positron Pair in Multi-GeV Region

The suppression of ionization energy loss owing to the Chudakov effect is discussed using the opening angles of the electron-positron pairs from the GEANT4 simulation package. The expected Borsellino and Olsen angles for photon energies between 1-178 GeV were presented and compared with the simulated opening angles. The simulated opening angles of the electron-positron pair are mostly compatible with the Borsellino angle for energies below 30 GeV. The ionization-suppression effect was reproduced using known theoretical approaches and compared with the corresponding simulated results. The results showed that the GEANT4 simulation package is suitable for adopting the Chudakov effect in a simulation environment, with a dataset that provides theory-experiment consistency.

Exploring the mechanism of axial ion energy acquisition and loss in an magnetoplasmadynamic thruster plume

In order to investigate the mechanism of axial ion energy acquisition and loss in an applied-field magnetoplasmadynamic thruster (AF-MPDT) plume plasma, a 10 kW level MPDT was tested using a Gauss meter, a Langmuir probe, a Faraday probe, a retarding potential analyzer (RPA) and a thrust target stand. Axial ion energy (Eiz) and axial Lorentz force density (Fz) distributions are obtained and interconnected. In the R direction, a local peak in Eiz exists as a result of the presence of maximum Fz in proximity. This localized Fz surge is instigated by the diamagnetic current, a consequence of the abrupt density reduction near the beam edge. In the Z direction, Eiz first increases to a maximum and subsequently decreases. The increase is due to the dominant Fz in ion acceleration in the vicinity of the thruster exit. Further downstream, the Fz decreased and the effect of charge-exchange collisions became apparent, leading to the decrease of Eiz.

Study of High-Energy Proton Irradiation Effects in Top-Gate Graphene Field-Effect Transistors

In this article, the effects of high-energy proton irradiation on top-gate graphene field-effect transistors (GFETs) were investigated by using 20 MeV protons. The basic electrical parameters of the top-gate GFETs were measured before and after proton irradiation with a fluence of 1 × 1011 p/cm2 and 5 × 1011 p/cm2, respectively. Decreased saturation current, increased Dirac sheet resistance, and negative drift in the Dirac voltage in response to proton irradiation were observed. According to the transfer characteristic curves, it was found that the carrier mobility was reduced after proton irradiation. The analysis suggests that proton irradiation generates a large net positive charge in the gate oxide layer, which induces a negative drift in the Dirac voltage. Introducing defects and increased impurities at the gate oxide/graphene interface after proton irradiation resulted in enhanced Coulomb scattering and reduced mobility of the carriers, which in turn affects the Dirac sheet resistance and saturation current. After annealing at room temperature, the electrical characteristics of the devices were partially restored. The results of the technical computer-aided design (TCAD) simulation indicate that the reduction in carrier mobility is the main reason for the degradation of the electrical performance of the device. Monte Carlo simulations were conducted to determine the ionization and nonionization energy losses induced by proton incidence in top-gate GFET devices. The simulation data show that the ionization energy loss is the primary cause of the degradation of the electrical performance.

Identification of deuterons at BESIII* *Supported by the National Natural Science Foundation of China (11975118, 12205141, 12375071)

The identification of deuterons with momenta in the range of 0.52−0.72 GeV/c is studied with specific ionization energy loss information using a data sample collected by the BESIII detector at center-of-mass energies between 4.009 and 4.946 GeV. Clean deuteron samples are selected using time of flight information. For all data samples, the deuteron identification efficiencies are higher than 95%, with a maximum difference of % between data and Monte Carlo simulation. This verifies the effectiveness of the deuteron identification method based on specific ionization energy loss and provides valuable information for future studies on processes involving deuterons in the final state at BESIII.