Nuclear Stopping Research Articles

Theoretical Calculation of Different Ion Surface Interaction Parameters of Si Target

Longitudinal projected range, energy losses, and sputtering yield are calculated of silicon
 target that bombarded with inert ion gases such as He, Ne, Ar, Kr, and Xe using SRIM package.
 Obtained results show increasing of longitudinal projected range with ion energy and decreasing
 with incident ion mass. The energy losses originated by the nuclear and electronic depending on ion
 ranges, generally at low ion energy the nuclear stopping power is dominated in comparison with the
 electronic stopping power, and the range of domination varies with changing ion species. Further,
 the sputtering yield founded, increasing with ion energy up to maximum value then tending to
 decrease, as well as it increases with increasing ion incident angle and decreases with decreasing ion
 mass.

Nuclear Stopping in Central Au+Au Collisions at RHIC Energies

Nuclear stopping in central Au+Au collisions at relativistic heavy-ion collider (RHIC) energies is studied in the framework of a cascade mode and the modified ultrarelativistic quantum molecular dynamics (UrQMD) transport model. In the modified mode, the mean field potentials of both formed and “preformed” hadrons (from string fragmentation) are considered. It is found that the nuclear stopping is increasingly influenced by the mean-field potentials in the projectile and target regions with the increase of the reaction energy. In the central region, the calculations of the cascade model considering the modifying factor can describe the experimental data of the PHOBOS collaboration.

Nuclear stopping for heavy-ion induced reactions in the Fermi energy range : from 1-Body to 2-Body dissipation

We study the stopping in heavy-ion induced reactions around the Fermi energy in central collisions. The stopping is minimal around the Fermi energy and corresponds to the crossover between the Mean-Field and the nucleonic regimes. This is attributed to the change in the energy dissipation going from 1-body (Mean-Field) to 2-body (nucleonnucleon collisions) dissipation. For this latter, a connection to in-medium transport properties of nuclear matter is proposed and comprehensive values of the nucleon mean free path and nucleon-nucleon cross section are extracted.

Analyzing the Role of Fragment Charge on Nuclear Stopping for Symmetric Colliding Nuclei

Analyzing the Role of Fragment Charge on Nuclear Stopping for Symmetric Colliding Nuclei

Selective Detection of Low-Velocity Ions Using Nuclear Emulsion Films

We focused on the difference between the photographic sensitivities of nuclear emulsion films by the electronic stopping power (ESP) and nuclear stopping power (NSP) of charged particles. The effects of high-velocity particles, in which ESP was dominant, and of low-velocity particles, where both ESP and NSP were effective, were compared. Low-velocity Kr ions formed internal latent images by the interaction with NSP. This may be due to the formation of crystal defects by atomic collisions along the route of these ions in silver halide crystals, and such defects are detected only by internal development. On the other hand, high-velocity ions like α-rays did not form internal latent images in the emulsion with Au+S sensitization, because sensitization centers on the surface of crystals accumulated excited electrons by ESP and only surface latent images were formed. It is demonstrated that internal latent images are characteristic signals by NSP. Low-velocity ions are selectively detectable by the internal development, even in high background fields like γ-rays, β-rays, or other high-velocity ions.

Angular and lateral distributions from small angle multiple scattering including elastic and inelastic energy loss effects based on the Valdes and Arista model

The aims of this work are to compare and to include two energy loss effects in multiple scattering caused by elastic and inelastic collisions in angular and lateral distributions based on Valdes and Arista (VA) theory. VA developed small angle multiple scattering theory including energy loss effects based on the Sigmund and Winterbon model for the first time. However, the energy loss effects on lateral distributions have not yet been estimated. In the VA model, target thickness and energy loss are independently treated. In this study, those effects are successfully introduced on the basis of the VA model. We considered the lateral spread and angular distribution separately and included the nuclear and electronic energy loss effects as a function of target thickness. Our results indicate that discrepancies occur between the two distributions, including nuclear and electronic stopping for several target thickness. Moreover, we constructed a multiple scattering model that includes both elastic and inelastic energy losses.

Ion activation in boron-doped polycrystalline Si thin films prepared on glass substrates

Boron-implanted polycrystalline Si thin films were subjected to thermal annealing. Their evolving electrical and structural features were characterized using Hall measurements, Raman Spectroscopy, transmission electron microcopy, and UV-Visible transmittance spectrophotometry. The Raman analysis indicated that boron implantation did not induce structurally significant damage, i.e., lattice distortion. Even low-temperature annealing at 350 °C provided a high degree of activation, keeping the atomic structure restored on the short-range order, as confirmed by transmission electron microscopy and optical transmittance data. At temperatures above 350 °C, the charge carriers exhibited temperature-independent behaviors, with a charge carrier concentration of 6 or 7 × 1019/cm3. The boron-implanted Si thin films were found to be subject to electronic stopping rather than nuclear stopping, thus allowing for low-temperature activation.

A generic algorithm for Monte Carlo simulation of proton transport

A mixed (class II) algorithm for Monte Carlo simulation of the transport of protons, and other heavy charged particles, in matter is presented. The emphasis is on the electromagnetic interactions (elastic and inelastic collisions) which are simulated using strategies similar to those employed in the electron–photon code penelope. Elastic collisions are described in terms of numerical differential cross sections (DCSs) in the center-of-mass frame, calculated from the eikonal approximation with the Dirac–Hartree–Fock–Slater atomic potential. The polar scattering angle is sampled by employing an adaptive numerical algorithm which allows control of interpolation errors. The energy transferred to the recoiling target atoms (nuclear stopping) is consistently described by transformation to the laboratory frame. Inelastic collisions are simulated from DCSs based on the plane–wave Born approximation (PWBA), making use of the Sternheimer–Liljequist model of the generalized oscillator strength, with parameters adjusted to reproduce (1) the electronic stopping power read from the input file, and (2) the total cross sections for impact ionization of inner subshells. The latter were calculated from the PWBA including screening and Coulomb corrections. This approach provides quite a realistic description of the energy-loss distribution in single collisions, and of the emission of X-rays induced by proton impact. The simulation algorithm can be readily modified to include nuclear reactions, when the corresponding cross sections and emission probabilities are available, and bremsstrahlung emission.

Radiation damage study of MeV ions-implanted Nd:YVO4 crystal

• Damage formation mechanism in MeV ion-implanted Nd:YVO 4 is studied. • 3 MeV Si + implantation results in substantial surface damage in Nd:YVO 4 . • Electronic energy loss plays a key role in surface damage formation. • The contributions of nuclear and electronic energy loss to damage are analyzed. • Threshold of electronic stopping power for damage formation is about 1.7 keV/nm. Damage formation mechanism of Nd:YVO 4 implanted with MeV ions is investigated. MeV Si + ions were implanted into Nd:YVO 4 crystal, and the lattice damage was measured using Rutherford backscattering spectroscopy/channeling (RBS/C) method. The damage creation kinetic indicates a significant contribution from electronic energy loss to the surface damage. A detailed analysis allows us to deduce the different contributions from electronic and nuclear stopping powers to the lattice damage production. An obvious difference in extent of damage from 1 MeV and 3 MeV Si + implantations also implies that there exists a threshold value of the electronic energy deposition for damage formation. The exact value of threshold is obtained by comparison with the experimental data obtained from 3 MeV O + , F + and Si + implantation results, which turns out to be (1.7 ± 0.1) keV/nm.

Energy loss of low-energy ions in transmission and backscattering experiments

The determination of the electronic stopping power for low-energy ions is an experimentally demanding task. In this paper we elaborate on the different effects of nuclear stopping and multiple scattering on the energy spectra for different experimental geometries, i.e., transmission through thin foils and backscattering from thin films. By calculating distributions of path lengths and scattering angles we demonstrate how electronic stopping, nuclear stopping, and multiple scattering add up to the total energy loss. We show that at low energies it is important to properly disentangle these effects to extract electronic stopping from the measured energy loss spectra.

Stopping power for alpha particles in hot dense Au plasmas

Self-consistent calculations of the stopping power for alpha particles in hot dense Au plasmas are performed in a wide projectile energy range with a fixed density ρAu = 19.3 g cm−3 and the electron temperature range from 0.4 to 5 keV on the basis of the relativistic ion-sphere model. All the mechanisms, which have strong influences on stopping power, are discussed in detail. The distribution of the free electron velocity component is found to be much flatter than the Maxwellian distribution due to the strong electrostatic field within the ion sphere in the hot dense plasmas, which results in the suppression of the stopping mechanism by plasma polarization and close collision for a projectile energy below 1 MeV u−1. The influence of inelastic scattering is considerably weakened due to the strong neutralization from the impact excitation, ionization and their reverse processes almost in the entire energy range below 10 MeV u−1 although the contribution of each process is quite large. Nuclear stopping is found to increase with the temperature. Our calculations are compared with other models and some explanations are presented for the difference between our results and other models. The Bethe equation is found to overestimate the contribution of inelastic processes by at least 10%. Different mechanisms are found to play their role in different energy ranges and all the mechanisms should be considered in order to get reliable data of stopping power.

Ion-induced luminescence and damage process of LiTaO3

In order to examine the basic characteristics of light emission and damage accumulation in lithium tantalate (LiTaO3), ion-induced luminescence was measured. A broad peak centered at about 540nm was observed under ion bombardment. The ion-induced luminescence was essentially the same as the luminescence under UV photon irradiation. The initial intensity of the luminescence was proportional to the projected range of the incident ions and independent of the electronic energy loss. The shape of the spectra was independent of the species, energy, and fluence of incident ions. The luminescence monotonically decreased with an increase in ion fluence. Assuming first-order kinetics in the annihilation and recovery process of the luminescent centers, the annihilation rate was proportional to the nuclear energy stopping power. It was considered that the luminescent center was mainly damaged by nuclear collisions, and the recovery of the damaged luminescent center was caused by local heating by the ion beam.

Visible and near-infrared optical properties of chalcogenide glass waveguides formed by swift Kr ion irradiation

Planar waveguide structures in chalcogenide glass were fabricated with 17MeV or 150MeV swift Kr ion irradiation. Images of the polished end faces of the Kr-irradiated chalcogenide glass were measured with a metallographic microscope using reflected polarized light. SRIM 2010 was used to simulate the electronic and nuclear stopping powers for swift Kr ion irradiation. The micro-Raman spectra were measured in air. The near-field intensity distributions were investigated at visible (633nm) and near-infrared (1300nm, 1500nm, 1539nm and 1620nm) bands. These intensity distributions make the waveguide candidates for infrared laser devices. The estimated propagation loss of the waveguide fabricated by 150MeV swift Kr ion irradiation was approximately 4dB/cm at a wavelength of 633nm.

Studies of the nuclear stopping power in PbPb collisions at 2.76 TeV with CMS

Abstract The energy density, d E / d η , in PbPb collisions at 2.76 A TeV nucleus-nucleus center-of-mass energy is measured as a function of pseudorapidity, η , and collision centrality using the CMS detector at the LHC. The very large pseudorapidity coverage of this measurement is used as a powerful constraint for various hadronic interaction models. The CASTOR calorimeter extends the η coverage of CMS up to | η | = 6.6 , which is only 1.4 units away from the beam rapidity for s NN = 2.76 TeV . This is comparable to the most forward measurements at RHIC. A comparison of the centrality dependence of the very forward energy density to that at smaller pseudorapidities is presented and compared to event generator predictions of models for nuclear collisions. The very wide pseudorapidity range of the presented measurement is unique at this center-of-mass energy and the average energy weighted pseudorapidity can be estimated which is compared with results at lower center-of-mass energy. The comparison shows the same energy dependence of the average energy weighted pseudorapidity as seen by RHIC.

Synthesis of nanowires via helium and neon focused ion beam induced deposition with the gas field ion microscope

The ion beam induced nanoscale synthesis of platinum nanowires using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPtIVMe3) precursor is investigated using helium and neon ion beams in the gas field ion microscope. The He+ beam induced deposition resembles material deposited by electron beam induced deposition with very small platinum nanocrystallites suspended in a carbonaceous matrix. The He+ deposited material composition was estimated to be 16% Pt in a matrix of amorphous carbon with a large room-temperature resistivity (∼3.5 × 104–2.2 × 105 μΩ cm) and temperature-dependent transport behavior consistent with a granular material in the weak intergrain tunnel coupling regime. The Ne+ deposited material has comparable composition (17%), however a much lower room-temperature resistivity (∼600–3.0 × 103 μΩ cm) and temperature-dependent electrical behavior representative of strong intergrain coupling. The Ne+ deposited nanostructure has larger platinum nanoparticles and is rationalized via Monte Carlo ion-solid simulations which show that the neon energy density deposited during growth is much larger due to the smaller ion range and is dominated by nuclear stopping relative to helium which has a larger range and is dominated by electronic stopping.

Synergy between electronic and nuclear energy losses for color center creation in AlN

Optical absorption induced by swift heavy-ion irradiations in AlN was studied in situ at 15 K. Detailed analysis of the influence of both electronic and nuclear stopping power indicates that the electronic energy loss does not create the point defects inducing the observed absorption band at 4.7 eV. Elastic displacements are required. Nevertheless, an unexpected non-linear enhancement is induced by the electronic energy loss. The intensity of the synergy between electronic excitations and elastic collisions increases markedly with the electronic stopping power. For the heaviest projectiles, the enhancement of the color center creation yield amounts to two orders of magnitude.

Materials modification using ions with energies below 1 MeV/u

Materials modifications using swift heavy ion beams provided by large scale accelerators have been used for many years in a wide variety of ways, e.g. to produce ion tracks or to modify the shape of nanoparticles. In all those applications the most relevant parameter for the materials modification is the electronic stopping power and not the ion kinetic energy. For many materials, ions with energies below 1MeV/u delivered from medium and small size accelerators have already sufficiently high electronic stopping power to modify materials in different ways. Also, in this energy range the nuclear stopping power can be large enough to provide additional opportunities for materials modifications. In the present paper, we review recent experimental activities of the Zagreb group where ion beams with energies below 1MeV/u, obtained from a 6MV EN Tandem Van de Graaff accelerator have been used. Additionally, we present several novel examples of materials modifications and their analysis with such ion beams.

Absolute detection efficiencies for keV energy atoms incident on a microchannel plate detector

The absolute detection efficiencies of a microchannel plate detector (MCP) were determined experimentally for neutral hydrogen, carbon, and tungsten atoms with impact energies of 0.5–4.5keV. We measured detection efficiencies using our recently developed method, which uses coincidence counting between neutralized incident ions and ionized target atoms in single-electron capture collisions. The obtained detection efficiencies showed similar impact-energy and mass dependence to those of rare gas atoms (Ne, Ar, Kr, and Xe), measured previously using our method. The detection efficiencies increased with increasing impact energy and converged to the open area ratio (∼50%) of the MCP used. The efficiencies at fixed energies decreased as the mass of the incident atom increased. The absolute detection efficiencies obtained for H, C, W, Ne, Ar, Kr, and Xe atoms could be scaled according to the average electron emission yield estimated using the formulas for electronic and nuclear stopping powers.

Optimizing the rapidity limit for nuclear stopping in intermediate energy heavy-ion collisions

A systematic study regarding the role of participant matter and spectator matter in nuclear stopping using isospin-dependent quantum molecular dynamics model is presented. The simulations have been carried out with soft equation of state along with the reduced isospin-dependent cross section to study the effect of different types and sizes of rapidity distributions on nuclear stopping for the whole colliding geometry with density-dependent symmetry energy. In addition to that, we attempt to investigate the role of isospin in heavy-ion collisions by calculating the individual contribution of neutrons and protons in nuclear stopping for different systems having different isotopic content.

Nd–Mo-borosilicate glass–ceramic: Synthesis, characterization and response to ionizing radiation

A new borosilicate glass–ceramic with high content of Mo and Nd was synthesized and thoroughly characterized. The structure of the material after it was subjected to 5MeV He+ was investigated. 5MeV He+ was chosen since it deposits most of the energy as ionizing radiation rather than as nuclear stopping and therefore can be used to simulate self-radiation in advanced nuclear waste-forms. As a result of irradiation, slight Mo reduction occurred together with increased numbers of crystalline precipitates. Those results are interesting for understanding the behavior of systems with high Mo and Nd content such as nuclear waste-forms demonstrating an influence that ionizing radiation can have on the chemistry, environmental stability and microstructure of the waste-forms.