Interaction Of Energetic Ions Research Articles

Use of Particle Induced X-Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF) for Detecting Trace Elements in Soil Sample

This review paper provides a comprehensive overview of trace element analysis utilizing ion-atom interaction techniques, focusing on the principles, applications, and recent advancements in the field. Ion- atom interaction techniques, including Particle Induced X- Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF), Rutherford backscattering spectroscopy (RBS), and ion beam analysis (IBA), offer unique capabilities for trace element analysis with high sensitivity and minimal sample preparation requirements. The paper begins by discussing the fundamental principles underlying ion-atom interaction techniques, such as the interaction of energetic ions with matter and the subsequent detection of emitted X-rays or backscattered particles. It explores the various analytical parameters that influence the sensitivity, resolution, and depth profiling capabilities of these techniques. Furthermore, the review highlights the diverse applications of ion-atom interaction techniques in fields such as environmental monitoring, forensic science, biomedical research, and materials science. It showcases how these techniques have been utilized to address specific analytical challenges, such as the detection of trace contaminants in environmental samples or the characterization of thin films and semiconductor materials.

External Beam IBA Measurements for Cultural Heritage

Ion beam analysis (IBA) methods refer to a set of analytical techniques based on the interactions of energetic ions, produced by a particle accelerator, with matter. The result of such interactions is the emission of characteristic radiation, X and gamma rays, and charged particles, which, upon detection, provide valuable information on the absolute concentration and depth distribution of the elements in the bombarded material. Moreover, IBA techniques can be performed while maintaining the object to be investigated at atmospheric pressure, without placing it in vacuum, in an analysis chamber, with the impinging ion beam extracted from the in-vacuum beamline of the accelerator, avoiding the need of invasive sampling and greatly easing the object positioning, thus allowing precious and big or large artefacts to be studied. This feature has opened the way for applications of IBA techniques for compositional analysis in cultural heritage studies, providing detailed and complete information about elemental compositions and depth distributions of analysed materials that are otherwise difficult or impossible for other analytical techniques. In this paper, the basic principles of the main IBA techniques applied to cultural heritage, namely, particle induced X-ray emission (PIXE), particle induced Gamma-ray emission (PIGE), and Rutherford or elastic backscattering spectrometry (RBS/EBS), will be recalled, and specific and practical details on how these techniques can be used for analysing cultural heritage objects with external beam set-ups will be provided.

Room temperature fabrication of poly-crystalline Si thin films via Al-induced crystallization under 500 keV Xe+ ion irradiation

Poly-crystalline Si film is an important material for its applications in microelectronics and solar cells. In order to realize poly-crystalline Si for practical application with high performance, it needs to be fabricated at room temperature. In this paper, we present a novel technique to develop poly-crystalline Si thin films at room temperature using 500 keV Xe+ ion irradiation. Here, the Al-induced crystallization process is employed to reduce the crystallization temperature. For that, c-Al (50 nm)/a-Si (150 nm) bilayer thin films have been used for ion irradiation experiments. Structural studies show that crystallization of Si starts at a threshold fluence of 3 × 1015 ions cm−2, and crystallinity is found to increase with increasing ion fluence. The results are explained in terms of displacement spike and thermal spike due to the interaction of energetic ions with target atoms. The transport of ions in matter Monte Carlo computer simulation code has been used to estimate the number of displacements due to ion irradiation. Generation of a sufficient amount of free Si atoms at threshold fluence and diffusion of these free Si atoms along the Al grain boundary starts the nucleation process.

Transformations of micron-sized PbTe surface structures induced by low energy ions

Formation and transformation of micron-sized structures on PbTe crystal surfaces under impact of low energy Ar+ ions is studied. New phenomena occurring due to interaction of energetic ions and atoms forming the main crystallographic planes of solid crystalline compounds, namely the transformation of ion-induced conical structures into pyramidal ones and the formation of facets of the micropyramids with well-ordered ripples during the process of transformation are revealed. We show that conical-pyramidal transformations occur on any PbTe sputtering surface, but the shape of pyramidal structures depends on the surface crystallographic orientation. If the pyramid originates from the ion-induced conical structure on PbTe target of (100) orientation it has the tetrahedral shape and its facets are covered with pronounced well-ordered ripples arranged in parallel to the base of the pyramid and closed at its edges. We show that: (i) micro-sized conical structures ion-induced on PbTe surface are transformed into pyramidal ones due to the tendency of the PbTe compound to the easy cleavage along crystallographic planes of high reticular density; (ii) the well-ordered ripples on the facets of the tetrahedral pyramids forming from conical structures appear due to self-organization of {111} and {110} crystallographic planes shaping pyramidal facets.

Multiscale simulations of electron and ion dynamics in self-irradiated silicon

The interaction of energetic ions with the electronic and ionic system of target materials is an interesting but challenging multi-scale problem and understanding of the early stages after impact of heavy, initially charged ions is particularly poor. At the same time, energy deposition during these early stages determines later formation of damage cascades. We address the multi-scale character by combining real-time time-dependent density functional theory for electron dynamics with molecular dynamics simulations of damage cascades. Our first-principles simulations prove that core electrons affect electronic stopping and have an unexpected influence on the charge state of the projectile. We show that this effect is absent for light projectiles, but dominates the stopping physics for heavy projectiles. By parameterizing an inelastic energy loss friction term in the molecular dynamics simulations using our first-principles results, we also show a qualitative influence of electronic stopping physics on radiation-damage cascades.

Resonant interaction of energetic ions with bulk-ion plasma micro-turbulence

A significant fast ion-induced stabilization is observed in linear and nonlinear GENE gyrokinetic simulations, which can be attributed to a resonant interaction between energetic particles and the main-ion-temperature gradient driven plasma turbulence. Elaborating on the findings in Di Siena et al. [Nucl. Fusion 58, 054002 (2018)], a detailed study of this mechanism is conducted for realistic JET-like parameters. In view of further exploitation of the beneficial role of energetic ions and corresponding confinement optimization, linear scans over the main fast ion parameters and magnetic plasma geometry are performed. All these results can be reproduced with a reduced Vlasov-Poisson theoretical model and be explained in terms of modifications on the fast ion energy production/dissipation in the energy balance equation. Finally, despite the essentially linear nature of the resonant interaction, a corresponding nonlinear analysis is also performed and its main dependences are captured with a quasi-linear model.

Ab Initio Study of Electronic Excitation Effects on SrTiO3

Interaction of energetic ions or lasers with solids often induces electronic excitations that may modify material properties significantly. In this study, effects of electronic excitations on stron...

Interactions of energetic ions with fullerenes, PAHs, and their weakly bound clusters

This brief review highlights recent advances in our understanding on how fullerenes, Polycyclic Aromatic Hydrocarbons (PAHs), and their clusters respond to singly and multiply charged keV-ion impact. These studies reveal how the projectile charge, mass, and velocity may be tuned to investigate, e.g., the stabilities of multiply charged monomers and clusters, different monomer and cluster cooling processes, molecular heating by Coulomb explosions of highly charged clusters, and impulse driven molecular growth processes.

Monte Carlo simulations of nanoscale Ne+ ion beam sputtering: investigating the influence of surface effects, interstitial formation, and the nanostructural evolution

We present an updated version of our Monte-Carlo based code for the simulation of ion beam sputtering. This code simulates the interaction of energetic ions with a target, and tracks the cumulative damage, enabling it to simulate the dynamic evolution of nanostructures as material is removed. The updated code described in this paper is significantly faster, permitting the inclusion of new features, namely routines to handle interstitial atoms, and to reduce the surface energy as the structure would otherwise develop energetically unfavorable surface porosity. We validate our code against the popular Monte-Carlo code SRIM-TRIM, and study the development of nanostructures from Ne+ ion beam milling in a copper target.

The dynamics of a neoclassical tearing mode (NTM) influenced by energetic ions on EAST

In the 2014 year’s campaign of experimental advanced superconducting tokamak (EAST), a series of Magnetohydrodynamics (MHD) instabilities were observed as the launching of Neutral Beam Injection (NBI), the most interesting one of which is the neoclassical tearing mode (NTM). Evidence clearly shows that a kink mode present after a strong sawtooth-like (ST-like) crash leaves a perturbation near the location of the magnetic island, providing the initial seed. The interaction of energetic ions makes the magnetic island oscillate both in island width and in rotation frequency. Analysis indicates that the bulk plasma still dominates the dynamics of NTM, and the orbit excursion of energetic ions induces a polarization current and modifies the width and rotation frequency of the neoclassical magnetic island.

Synergy of elastic and inelastic energy loss on ion track formation in SrTiO₃.

While the interaction of energetic ions with solids is well known to result in inelastic energy loss to electrons and elastic energy loss to atomic nuclei in the solid, the coupled effects of these energy losses on defect production, nanostructure evolution and phase transformations in ionic and covalently bonded materials are complex and not well understood due to dependencies on electron-electron scattering processes, electron-phonon coupling, localized electronic excitations, diffusivity of charged defects, and solid-state radiolysis. Here we show that a colossal synergy occurs between inelastic energy loss and pre-existing atomic defects created by elastic energy loss in single crystal strontium titanate (SrTiO3), resulting in the formation of nanometer-sized amorphous tracks, but only in the narrow region with pre-existing defects. These defects locally decrease the electronic and atomic thermal conductivities and increase electron-phonon coupling, which locally increase the intensity of the thermal spike for each ion. This work identifies a major gap in understanding on the role of defects in electronic energy dissipation and electron-phonon coupling; it also provides insights for creating novel interfaces and nanostructures to functionalize thin film structures, including tunable electronic, ionic, magnetic and optical properties.

Alpha and recoil track detection in poly(methyl methacrylate) (PMMA)—Towards a method for in vitro assessment of radiopharmaceuticals internalized in cancer cells

A method for detection and characterization of single MeV α-particle and recoil tracks in PMMA photoresist by atomic force microscopy (AFM) analysis has been demonstrated. The energy deposition along the track is shown to lead to a latent pattern in the resist due to contrast reversal. It has been shown that the pattern, consisting of conical spikes, can be developed by conventional processing as a result of the dissolution rate of poly(methyl methacrylate) (PMMA) being greater than that for the modified material in the cylindrical volume of the track core. The spikes can be imaged and counted by routine AFM analysis. Investigations by angular-resolved near-grazing incidence reveal additional tracks that correspond to recoil tracks. The observations have been correlated with modelling, and shown to be in qualitative agreement with prevailing descriptions of collision cascades. The results may be relevant to technologies that are based on detection and characterization of single energetic ions. In particular, the direct visualization of the collision cascade may allow more accurate estimates of the actual interaction volume, which in turn will permit more precise assessment of dose distribution of α-emitting radionuclides used for targeted radiotherapy. The results could also be relevant to other diagnostic or process technologies based on interaction of energetic ions with matter.

Diagnosis of physical parameters of fast particles in high power fusion plasmas with high resolution neutron and gamma-ray spectroscopy

High resolution neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS) measurements of fast ions in high power fusion plasmas are reviewed. NES is a well established diagnostics of the velocity distribution of fast fuel ions and was recently used to investigate the interaction of energetic ions with MHD instabilities. High energy resolution GRS on fusion plasmas is a more recent application and was shown to provide information on the distribution function of fast minority ions accelerated by ICRH, such as 4He and 3He. Starting from measurements on today's high power D plasmas, fast ion measurements with NES and GRS in a DT burning plasma of next step tokamaks, such as ITER, are discussed. The enhanced neutron and gamma-ray fluxes expected on ITER will allow for time-resolved measurements of the fast fuel and minority ion dynamics in the ms time scale. The intensity of the alpha knock-on component in the 14 MeV neutron spectrum and of the 4.44 and 3.21 MeV gamma-ray peaks from the 9Be(α,nγ)12C reaction is studied as a diagnostics for the α particle slowing down distribution in a DT plasma. The results show that the two techniques are sensitive to different regions of the α particle phase space and thus provide complementary information.

Damage evolution and amorphization in semiconductors under ion irradiation

The interaction of energetic ions with crystalline semiconductors may cause defect formation and amorphization both by nuclear and electronic energy deposition which occur simultaneously with different strength.In the energy range of dominating nuclear energy loss the transition to the amorphous state depends on the energy received by the target atoms through nuclear interactions, i.e. on ion mass and energy, and on the irradiation temperature which can favour dynamic defect annealing. Regarding the damage evolution, different groups of semiconductors are observed. In many materials (e.g. elemental and binary III–V semiconductors, SiC) a continuous increase of the damage concentration up to amorphization is found below characteristic critical irradiation temperatures. In some other materials (AlAs, GaN) the damage concentration increases stepwise until amorphorphization occurs, and in few other cases (ZnO, CdTe) amorphization is prevented even at 15K.In case of swift heavy ion (SHI) irradiation with dominating electronic energy loss, heavily damaged tracks are formed above critical values of the energy deposition in some materials (e.g. InP, InAs, InSb, GaSb), which may agglomerate to continuous amorphous layers. In other semiconductors (e.g. Si, Ge, GaP, GaAs, AlAs) so far no track formation but only the formation of point defects and point defect complexes was observed.In the present contribution the state of the art of damage evolution and amorphization occurring at temperatures equal to and below room temperature in covalent and ionic-covalent semiconductors is summarized and possible mechanisms are discussed to understand the experimental results.

Convective beam ion losses due to Alfvén eigenmodes in DIII-D reversed-shear plasmas

Coherent losses of neutral beam ions are observed at frequencies corresponding to toroidal and reversed-shear Alfvén eigenmodes (RSAEs) in DIII-D. Reversed-shear profiles are created by injecting beam power during the plasma current ramp. Beam ion losses stemming from Alfvén eigenmode activity contribute to flattening of the energetic ion density profile in such discharges. This is the first observation of convective beam ion losses due to RSAEs. The energies and pitch angles of lost ions are measured and found to exist within a well-defined region of phase space. Loss flux signals decrease in time as current penetrates and Alfvén eigenmode activity becomes more core localized. Preliminary Monte Carlo simulations of energetic ion interactions with measured mode structures show the dominant loss mechanism is a transition from a counter-passing orbit to a trapped orbit that is lost to the wall.

Fast ion ignition with ultra-intense laser pulses

Fast ignition by laser-driven ion beams benefits from the strong collisional interaction of energetic ions with the imploded fuel. However, conditions for an efficient transformation of the laser pulse energy into ion kinetic energy and for the transport of these ions from the acceleration region to the fusion pellet core without significant temporal and angular spread have to be clarified. The laser ponderomotive force may provide efficient ion acceleration in bulk dense targets such as a precompressed DT capsule and evacuate a channel for further laser beam propagation. The main characteristics of ponderomotive ion acceleration and channel formation inferred from analytical theory and confirmed by particle-in-cell simulations are applied for the design of a new scheme of ion fast ignition. Contrary to schemes based on the mechanism of target normal sheath ion acceleration, at least two laser pulses are used in our proposal. The first pulse (or a sequence of several pulses) creates a channel with a diameter of ∼20 µm through the plasma corona up to a fuel density of ∼1 g cm−3. The second pulse with a higher intensity of ∼1022 W cm−2 accelerates the deuterium and tritium ions at the head of this channel to energies 5–25 MeV on a time scale less than 1–3 ps. The overall ignition energy in this proposal is relatively high, ≳100 kJ, but no additional target arrangements will be required. This feature makes the scheme attractive for a high repetition rate operation.

A simplified Monte-Carlo calculation to model ion–solid interactions in the classroom

We have developed an Ion–Solid Interaction course, for graduate and undergraduate students, which combines lecture, experimental work, and computational modeling. The lectures cover the basic physical principles necessary to understand the interactions of energetic ions with solids, as well as practical technological applications such as sputtering (deposition, patterning, depth profiling), ion beam analysis, and ion implantation. The experiments involve the fabrication of thin films by sputtering deposition and their characterization by ion beam analysis, as well as other techniques. In the computational modeling the students develop a ‘TRIM-like’ or Monte-Carlo calculation to determine the various parameters associated with the slowing down and penetration of ions in solids. In doing so they have the opportunity to put into practice most of the basic concepts learned in class. We describe here this computational modeling, and present examples of calculations performed by the students.

A molecular dynamics model for the interaction of energetic ions with SiOCH low-κ dielectric

A molecular dynamics model is used to investigate the interaction of energetic ions with fluorocarbon passivated Si, O, C, and H (SiOCH) based low-κ dielectrics. The model includes a set of interatomic potentials required for the SiOCH–CFx interaction system, where the two- and three-body pseudopotentials have either been obtained from published literature or computed using ab initio techniques. The test structure used for the ion interaction simulations is put together through deposition of low energy SiOx+, CHy+, and H+ ions on a crystalline Si substrate. A thin fluorocarbon passivation layer is grown on the low-κ test structures by bombarding them with moderate energy CFx+ ions. Simulations of CF2+ ion interaction with the fluorocarbon passivated SiOCH samples show that the sputter yield of sample constituents (Si, O, and H) increases with ion energy and peaks at about 60°. H sputters more easily compared to other species, and the surface layer is expected to become H deficient over time. Sputtered H atoms are also generated over a broader region near the surface compared to other species. Most sputtered clusters with origin in the bulk film are ejected with energies less than 10eV and their angular and energy distributions are not sensitive to the energy or angle of the incident ion. Incident CF2+ ion breaks apart on contact with the test structure and, at high energies and near normal incidence, virtually no CF2 reflects back from the sample. Fragments of the incident ion have reflectionlike properties: peak in angular dependence function shifts towards larger angles as ion angle of incidence increases and reflected fragments are more energetic as ion angle of incidence increases. Comparison of CF2+ ion etching properties of SiOCH low-κ dielectric with SiO2 shows that more atoms are sputtered from SiOCH under identical conditions. However, as many of the sputtered atoms from the SiOCH material are light H atoms, mass etch yield from SiOCH and SiO2 is comparable. Si and O are both found to sputter more easily from SiOCH relative to SiO2. SiOCH low-κ ion etching properties are compared for several ions (CFx+, CHFy+, SiFz+, and Ar+). Results show that the etch yield from F containing ions is larger than that of Ar+, and the etch yield increases as the F content of the ion increases. Comparison of the ion etching properties of porous and nonporous low-κ dielectrics shows that, under similar conditions, the fluorocarbon passivation layer is thicker on the porous material. Due to this thicker passivation layer, mass yield from the porous dielectric material is smaller for the same ion energy.

Laser-ablation treatment of short-pulse laser targets: Toward an experimental program on energetic-ion interactions with dense plasmas

This new project relies on the capabilities collocated at LosAlamos in theTrident laser facility of long-pulse laser drive, for laser-plasma formation, and high-intensity short-pulse laser drive, for relativistic laser-matter interaction experiments. Specifically, we are working to understand quantitatively the physics that underlie the generation of laserdriven MeV0nucleon ion beams, in order to extend these capabilities over a range of ion species, to optimize beam generation, and to control those beams. Furthermore, we intend to study the interaction of these novel laser-driven ion beams with dense plasmas, which are relevant to important topics such as the fast-ignition method of inertial confinement fusion ~ICF!, weapons physics, and planetary physics. We are interested in irradiating metallic foils with the Trident short-pulse laser to generate medium to heavy ion beams ~Z 20–45! with high efficiency. At present, target-surface impurities seem to be the main obstacle to reliable and efficient acceleration of metallic ions in the foil substrate.Inordertoquantifytheproblem,measurementsofsurfaceimpuritiesontypicalmetallic-foillasertargetswere made. To eliminate these impurities, we resorted to novel target-treatment techniques such as Joule-heating and laser-ablation, using a long-pulse laser intensity of ;10 10 W0cm 2 . Our progress on this promising effort is presented in this paper, along with a summary of the overall project.

Learning ion–solid interactions hands-on: An activity based, inquiry oriented, graduate course

Experimental work, using state of the art instrumentation, is integrated with lectures in a “real life”, learning by discovery approach, in the Ion–Solid Interactions graduate/undergraduate course offered by the Department of Physics of the University of Central Florida. The lecture component of the course covers the underlying physical principles, and related scientific and technological applications, associated with the interaction of energetic ions with matter. In the experimental section the students form small groups and perform a variety of projects, experimental and computational, as part of a participative, inquiry oriented, learning process.In the most recent offering of the class, the students deposited a compound semiconductor thin film by dual-gun sputtering deposition, where each group aimed at a different stoichiometry of the same compound (Zn1−xSxOy). Then they analyzed the composition using Rutherford backscattering spectrometry, measured electrical transport properties using Hall effect and conductivity measurements, and determined the band gap using spectrophotometry. Finally the groups shared their results and each wrote a ‘journal-like’ technical article describing the entire work. In a different assignment, each group also developed a Monte Carlo computer program (‘TRIM-like’) to simulate the penetration of ions into a solid, in ion implantation, calculating the stopping cross-sections with approximate models, taught in class, which can be analytically solved.The combination of classroom/laboratory activities is very well received by the students. They gain real life experience operating state of the art equipment, and working in teams, while performing research-like projects, and simultaneously they learn the theoretical foundations of the discipline.