Nuclear Stopping Research Articles

Accessing the in-medium effects on nucleon-nucleon elastic cross section with collective flows and nuclear stopping

A systematic study of the in-medium correction factor (F) on nucleon-nucleon elastic cross section is performed within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. The effects of the beam energy dependence of F on the directed, elliptic flow and nuclear stopping in 197Au+197Au collisions with energy ranging from 0.09 to 0.8A GeV are explored. It is found that the directed, elliptic flow and nuclear stopping at relatively low energies are very sensitive to F, and the sensitivity gradually weakens with increasing beam energy. The beam energy dependent in-medium correction factor F is deduced from the comparison of the excitation functions of the directed, elliptic flow and nuclear stopping between the calculated results and the FOPI experimental data.

DEUTERON INDUCED FUSION REACTION TARGET FOR INERTIAL CONFINEMENT FUSION (ICF)

Objective: Energy efficiency enhancement is one of the most effective ways to achieve Fast ignition (FI) in inertial confinement fusion ICF. High energy output gain is essential for ICF reactors and greater energy efficiency can reduce energy costs. The injection of Ion beam is one method used to achieve FI fusion reaction in ICF. A fusion of deuteron with lithium-6 isotope, DLi6 is reviewed in this work alongside the fusion of Deuterium – Tritium (DT), Deuterium – Deuterium (DD), Deuterium – Helium-3 (DHe3) and Proton – Boron-11 (PB11).
 Materials and Methods: In this work, it is proposed the projection of laser-driven deuteron beam in the FI scheme for ICF in the DLi6 plasma. Fusion occurs as the projected deuteron ion beam hits the lithium-6 target in the thermonuclear fusion reaction.
 Results: The results show that the fusion reactions of DD, DHe3 and PB11 all require high input kinetic energy (Mega-electronvolts) for the fusion process to occur because of higher Coulomb barrier and the probability of fusion increases by increasing the input energy drive with low output energy gain. DT fusion which require low input kinetic energy of about 400 KeV with high cross section and generated considerable high output energy gain of about 17.59 MeV, However this fusion reaction require large tritium inventory and tritium does not occur naturally, therefore the need for tritium breeding. When the energy of deuteron beam is projected at 200 keV to lithium-6 isotope target, although D + Li6 has a low total cross section of about 19.409 mbarn, the stopping power of the electrons would be more than ions, nuclear stopping power is considerable at very low deuterons energies, the Coulomb interaction of deuteron and lithium-6 occurs with output energy gain of about 22.373 MeV.
 Conclusion: The investigations indicate that fusion target energy gain efficiency is independent of lithium-6 numerical density. The highest value of energy efficiency gain occurs with lower input kinetic energy of deuteron beam of about 200 KeV to lithium-target.
 Recommendation: This findings contribute to the core mission of NIF in achieving fast ignition with low ignition energy input to achieve Lawson break-even or "ignition" point of the fusion fuel pellet, where it gives off 100% or more energy than it absorbs. However the simulation results were based on programmed model of Geant4 Hadr03. This results can be validated with the appropriate experimental design of the Hadr03 process.

Investigation of radiation damage using thermal spike model for SHI irradiation on Al2O3

The material exposed to energetic radiation may change its properties and performance. Ion beam irradiation is an established method to investigate radiation damage in materials. In the present study, SRIM code is employed as a tool to determine the electronic and nuclear energy losses and displacement per atom (DPA) associated with the damage induced in Al2O3 using 100 MeV Au ion. We have further studied the creation of 100 MeV Au ion induced molten zone along the ion track in Al2O3 in the framework of the thermal spike (TS) model. Using the in-elastic thermal spike model, elastic thermal spike model, and unified thermal spike model, the evolution of lattice temperature and latent track radius as a function of depth of Al2O3 for 100 MeV Au ion irradiation are investigated. The current results demonstrate that the latent track radius shows a U-shaped variation based on the combined effect of electronic stopping power and nuclear stopping power. In order to corroborate these results, an additional irradiation experiment was performed using swift heavy ion (SHI), 100 MeV Au ions with fluence 1×1014 ions/cm2 for Al2O3. To investigate the structural properties, surface morphology and to identify the defects in the samples, pristine and irradiated Al2O3 samples were characterized by Grazing Incident X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM) and Photoluminescence Spectroscopy (PL). AFM study shows the increase in roughness after SHI irradiation. A decrease in intensity of PL spectra upon SHI irradiation indicates the formation of new defects and disordered structures in the material, which is quite in agreement with the theoretical results.

Sputtering Yields of Si Bombarded with 10–540-keV C60 Ions

Sputtering yields of Si have been measured for C60 ions in the energy range from 10 to 540 keV, where the nuclear stopping is dominant, by measuring thickness change of a pre-amorphized layer with conventional Rutherford-backscattering spectroscopy. The measured sputtering yield shows the maximum, which is approximately 600 Si/C60, around 100 keV. Comparing with the sputtering yields for a monatomic ion calculated both based on the linear-collision-cascade theory of Sigmund and using the SRIM2008 code, nonlinear effect on the sputtering yield has been observed. The nonlinear effect depends on the energy of C60 ions: it is very large around the energies where the sputtering yield has the maximum and hardly observed at 10 keV.

Properties of the natural MoS2 crystal irradiated by medium- and high-energy Ni ions

Natural MoS2 single crystals are irradiated with Ni ions with different fluences at 1 MeV and 357 MeV. The Stopping and Range of Ions in Matter software packages are used to simulate the process of Ni-ion beam peneration through the natural MoS2 single crystal. The electronic and nuclear stopping powers, displacement per atom and atoms vacancy profiles are simulated. The results show that S atoms are susceptible to the Ni-ion irradiation of natural MoS2 single crystals. Redshifts of the out-of-plane vibrations of S atoms and in-plane Mo–S phonon mode and the magnetic hysteresis loops are both recorded in the bulk and Ni-ion-irradiated natural MoS2 single crystals.

Modulation of lattice strain in ZnO thin films by ion implantation

Present work reports the modulation of lattice stress in ZnO thin films implanted using Ar, Mn and Ag ions. The ZnO thin films were fabricated using RF magnetron sputtering and the thickness of films was almost 150 nm. Scanning electron micrographs show that the granular nature of these films were remained for implanted ions, and morphological changes were observed. Crystalline phase of each films remained unchanged at various doses of these ions. However, disorder is observed with the dose. The lattice stress increased as the increases of ion implantation amount. It was difficult to explain the lattice strain with the ion radius of the injected ions, but it was found that it had a certain relationship with the total energy loss governed by both electronic and nuclear stopping process.

Bragg's additivity rule and core and bond model studied by real-time TDDFT electronic stopping simulations: The case of water vapor

The electronic stopping power (Se) of water vapor (H2O), hydrogen (H2) and oxygen (O2) gases for protons in a broad range of energies, centered in the Bragg peak, was calculated using real-time time-dependent density functional theory (rt-TDDFT) simulations with Gaussian basis sets. This was done for a kinetic energy of incident protons (Ek) ranging from 1.56 keV/amu to 1.6 MeV/amu. Se was calculated as the average over geometrically pre-sampled short ion trajectories. The average Se(Ek) values were found to rapidly converge with 25–30 pre-sampled, 2 nm-long ion trajectories. The rt-TDDFT Se(Ek) curves were compared to experimental and SRIM data, and used to validate the Bragg's Additivity Rule (BAR). Discrepancies were analyzed in terms of basis set effects and omitted nuclear stopping at low energies. At variance with SRIM, we found that BAR is applicable to our rt-TDDFT simulations of 2H2 + O2 → 2H2O without scaling for Ek > 40 keV/amu. The hydrogen and oxygen Core and Bond (CAB) contributions to electronic stopping were calculated and found to be slightly smaller than SRIM values as a result of a red-shift in our rt-TDDFT Se(Ek) curves and a re-distribution of weights due to some bond contributions being neglected in SRIM.

The Gluon Exchange Model in Proton–Nucleus Collisions

We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton-nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of N rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the N-dependence of the baryon stopping process, are included in the letter.

Calculation of Nuclear Stopping in the Semiclassical Approximation

Calculation of Nuclear Stopping in the Semiclassical Approximation

MD simulation of two-temperature model in ion irradiation of 3C-SiC: Effects of electronic and nuclear stopping coupling, ion energy and crystal orientation

We present a numerical study on swift ion induced effects in crystalline 3C silicon carbide (SiC) by the two-temperature model, which considering the electronic stopping and electronic-phonon coupling effects simultaneously. Given the results of overlapping radiation, there is only a minority of defects formed in the system during the ionization dominance stage. When the incident energy is braked from 20 MeV to 500 keV by ionization after the first 0.91 ps, the system enters the nuclear stopping stage, the incident energy decreases to 50 keV in 0.44 ps, accomplished with a dramatic increase of damage. In addition, for the low-energy ion implantation process, the sparse atomic arrangement perpendicular to the implantation direction will reduce the response of the atomic subsystem. Insights into the complex correlations between electronic and atomic response may pave the way to elucidate the mechanism behind the experimentally observed defect formation and evolution under extreme energy deposition.

Nuclear stopping powers for DFT potentials

Interaction potentials were obtained by the density functional theory (DFT) and nuclear stopping powers (NSP) were calculated for 48 systems in the energy range above 10 eV. It was shown that NSP calculated using the DFT potentials in the collision energy range of 10–1000 eV give more accurate values comparing with the SRIM data, obtained data differs from SRIM data by 15–70%. The presence of a potential well leads to the emergence of an additional NSP peak at low energies. Comparison of classical calculations of the transport cross section with semiclassical ones showed their identity at energies of up to 1 eV. The criterion for the applicability of classical calculations for the transport cross section and NSP cross sections is the condition ℓ>1 (ℓ is the angular momentum). The importance of including multichannel scattering in NSP calculations was demonstrated, for the case of energies below 20 eV.

Structural phase modifications induced by energetic ion beams in graphene oxide

Different ion beams, with energy from 2 MeV up to 16 MeV at different atomic number, have been employed to irradiate graphene oxide (GO) foils in vacuum. Due to effects of electron and nuclear ion stopping powers, the ion energy deposition reduces the irradiated GO foils and structurally modifies them. The ion bombarded GO foils X-ray diffraction (XRD) investigations have permitted to shed light on the different structural phases induced by the ion energy deposition. The changes in the GO foils pristine structure shift the diffraction main peak towards larger angles and produce new diffraction peaks indicating the presence of new phases, such as reduced GO (rGO), carbon nanotubes (CNT), amorphous carbon (a-C), onion like carbon (OLC) and probably new carbon allotropes. The obtained results indicate that the inner structure of the GO foils becomes more and more compact and dense with the absorbed dose, suggesting that the removal of the functional oxygen groups leads to a near graphite structure with a significant increase of the material mass density. The different structural phase modifications induced by the different ion beams as a function of the stopping power, fluence and dose will be presented and discussed in detail.

On the use of SRIM for calculating vacancy production: Quick calculation and full-cascade options

The vacancy production behavior for a broad range of incident ion-target combinations were examined by using both the full cascade (F-C) and quick calculation of damage (Q-C) options of Stopping and Range of Ions in Matter (SRIM-2013) code. Vacancy production for each option was evaluated using both the convenient vacancy text file in SRIM, and by manual manipulation of the energy transfer, ionization, and phonon text file data to calculate the depth-dependent damage energy for the Norgett-Robinson-Torrens (NRT) defect production model. The F-C vacancy text file method was observed to overpredict vacancy production by a factor of ~1.1 to 4 times when compared to values calculated using the F-C damage energy method or either of the SRIM Q-C methods. Based on our extensive data set obtained for 142 unique bombarding ion-target combinations, we show that the SRIM F-C vacancy text file method should not be used for vacancy production calculations. This error appears to be due to mischaracterization within the SRIM F-C option of some near-threshold replacement events as vacancies instead of replacements. Use of the latest SRIM stopping powers in the SRIM F-C approach provides a better calculation of electronic and nuclear stopping compared to the Lindhard stopping power analytical approximation used to calculate the damage energy of recoil atoms in the SRIM Q-C option, and therefore SRIM F-C approach is deemed to provide the best accuracy for vacancy production (within the binary collision approximation) as long as the damage energy method is used. Alternately, the SRIM Q-C option using either the vacancy.txt or damage energy method provides relatively fast calculation speeds with moderate quantitative differences from the F-C damage energy results (~0 to ~ 30% for the investigated ion-target cases).

Theoretical uncertainties on the extraction of in-medium NN cross sections by different Pauli blocking algorithms * *This work was partly inspired by the transport code comparison project, and it was supported by the National Natural Science Foundation of China (11875323, 11705163, 11790320, 11790323, 11961141003), the National Key R&D Program of China (2018YFA0404404), the Continuous Basic Scientific Research Project (WDJC-2019-13, BJ20002501)

Three typical Pauli blocking algorithms in quantum molecular dynamics type models are investigated in the nuclear matter, the nucleus, and heavy ion collisions. In nuclear matter, the blocking ratios obtained with the three algorithms are underestimated by 13%-25% compared to the corresponding analytical values. For a finite nucleus, spurious collisions occur around the surface of the nucleus owing to the defects of the Pauli blocking algorithms. In the simulations of heavy ion collisions, the uncertainty of stopping power arising from the different Pauli blocking algorithms is less than 5%. Furthermore, the in-medium effects of nucleon-nucleon (NN) cross sections on the nuclear stopping power are discussed. Our results show that the transport model calculations with free NN cross sections result in the stopping power decreasing with beam energy when the beam energy is less than 300 MeV/u. To increase or decrease the values of the stopping power, the transport model calculations need enhanced or suppressed model dependent in-medium NN cross sections that are expected to be smaller than the true in-medium NN cross sections.

Velocity effect on the nanostructure creation at a solid surface by the impact of slow highly charged ions

The energy necessary for the nanostructure creation by the impact of highly charged ions (charge Z ≫ 1) on solid surface consists of the neutralization energy and the deposited kinetic energy. We analyze the relative importance of these two contributions for very low to moderate ionic velocities and introduce the critical velocity as a measure of interplay of these two energies. In the study of the velocity effect on the neutralization energy, we employ the recently developed micro-staircase model based on the quantum two-state vector model of the ionic Rydberg states population. The final ionic charges after the neutralization cascade in front of the surface are used for the calculation of the (nuclear) stopping power and the deposited kinetic energy below the surface. We discuss the nanohillocks and nanocraters formation by the impact of XeZ + ions on titanium and gold nanolayers, and formation of the nanorings on gold surface, from the standpoint of the required energy.

Assessing electronic energy loss of heavy ions detected in reflection geometry

We study energy loss spectra of bromine ions scattered from silver thin films in the energy range of 4 to 36 MeV in forward reflection geometry. The different contributions to the energy loss are analyzed by complementary Monte Carlo simulations. We assess the dependence of the scattering yield and nuclear and electronic losses on the penetration depth of detected ions. For scattering from larger depth, we observe decreased elastic losses and increased trajectory length in comparison with predictions from single scattering, with increasing effects for lower energies. To investigate the entanglement of energy loss and depth information, electronic stopping cross sections are deduced from the experimental spectra by two different approaches: (a) assuming a single scattering model and (b) making use of Monte Carlo simulations. The data obtained from the two approaches are compared, and we assess the relative contributions from nuclear stopping and from the effect of multiple scattering on trajectory length. Results of both methods are discussed in the context of composition depth profiling and compared with data from literature and with Stopping and Range of Ions in Matter (SRIM) predictions resulting in good agreement.

Structural and spectroscopic investigations on graphene oxide foils irradiated by ion beams for dosimetry application

Different ion beams, from protons up to gold ions, with energy from 2 MeV up to 16 MeV, have been employed to irradiate graphene oxide (GO) foils in vacuum. The ion energy deposition reduces GO releasing functional oxygen groups. The effect of radiating ions – GO foils interaction has been investigated by Raman spectroscopy, X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). All the performed analyses show that both reduction and damaging depend on the fluence, the energy and the type of radiating ions. In the regime of electron stopping power the reduction is linearly dependent on the absorbed dose, while in the regime of nuclear stopping power an intense damage is produced in GO, altering the Raman spectrum and producing defects and amorphization of the material. The achieved goal was to quantify the GO's response to ionizing radiation with the aim of using the GO foil as a dosimeter for high energy ion beams.

MeV TOF SIMS Analysis of Hybrid Organic/Inorganic Compounds in the Low Energy Region.

The low energy range (a few 100 keV to a few megaelectronvolts) primary ion mode in MeV secondary ion mass spectrometry (MeV SIMS) and its potential in exploiting the capabilities of conventional (keV) SIMS and MeV SIMS simultaneously were investigated. The aim is to see if in this energy range of both types of materials, inorganic and organic, can be simultaneously analyzed. A feasibility study was conducted, first by analyzing the dependence of secondary ion yields in indium tin oxide (ITO, In2O5Sn) and leucine (C6H13NO2) on various primary ion energies and charge states of a Cu beam, within the scope of equal influence of electronic and nuclear stopping. Expected behavior was observed for both targets (mainly nuclear sputtering for ITO and electronic sputtering for leucine). MeV SIMS images of samples containing separate regions of Cr and leucine were obtained using both keV and MeV primary ions. On the basis of the image contrast and measured data, the benefit of a low energy beam is demonstrated by Cr+ intensity leveling with leucine [M + H]+ intensity, as opposed to a significant contrast at a higher energy. It is estimated that, by lowering the energy, the leucine [M + H]+ yield efficiency lowers roughly 20 times as a price for gaining about 10 times larger efficiency of Cr+ yield, while the leucine [M + H]+ yield still remains sufficiently pronounced.

The effect of deuteron beam injection on the efficiency of energy production in the D6Li plasma

One of the major problems for attaining fusion is to heat the plasma particles to very high temperatures.High gain is essential for a fusion reactor and greater energy efficiency can reduce energy costs. Ion beam injection is one method used to heat plasma inside a fusion reactor. A fusion of deuteron with the isotope lithium-6, D6Li is more difficult than a fusion of deuterium and tritium,DT. In this paper, it is proposed to inject laser-driven deuteron beam in the fast ignition (FI) scheme for inertial confinement fusion (ICF) in the D6Li plasma. Fusion occurs as injected high-energy deuteron ions slow down in the plasma. The results show that the reaction probability increases by increasing electron temperature. The stopping power of electrons and ions decrease with the increase of temperature. When the energy of deuteron beam is achieved at a few hundred keV, stopping power of the electrons would be more than ions. Nuclear stopping power is considerable at very low deuterons energies. The deuteron beam range reduces as incident energy decreases. At low hot spot temperatures, deuterons can be deposited immediately within a very little range. The contribution of the released energy due to the deuteron beam interaction with ions into D6Li plasma provides the additional heating, which generally increases the energy efficiency. The investigations indicate that fusion energy efficiency is independent of lithium-6 numerical density, initial deuteron beam range and increases with electron temperature. The highest value of energy efficiency occurs with lower energy deuteron beam around the 2.5-MeV range from deuteron beam-target fusion.

Regularities of PLA mechanical property modification under ion implantation conditions

The investigations of the surface physicochemical properties of polylactic acid (PLA) modified by argon, carbon and silver ion implantation to fluences of 1∙1014, 1∙1015 and 1∙1016 cm−2 and energies of 20 keV, 20 keV and 42 keV respectively are described. The projected ion ranges in the polymer matrix are estimated by the computer simulation with the TRIDYN code, as well as energies of electron and nuclear stopping are assessed according to the SRIM modelling. The microhardness and elastic modulus are established to be dependent on the degree of crystallinity of the material. It was found that the microdistortions and strains of the PLA crystal lattice increase after ion implantation due to the structural alteration and defect formation. Long-range effect expressed as bigger depth of modified surface layer than the ion range in the material is suggested as a result of the radiation-stimulated diffusion and thermal restructuring of the material.