Projectile Particles Research Articles

Near-Surface Nanocomposite Structure on Commercial Purity Aluminum Induced by Fine Particle Bombardment

Commercial purity aluminum (A1070) was subjected to fine particle bombardment (FPB) with 1.0 mass% carbon steel and pure nickel projectile particles. Nanocomposite structures formed at the near-surface region, which contained refined aluminum grains of less than 100 nm in diameter and dispersed projectile fragments several tens of nanometer to several micrometer in size. Beneath the nanocomposite structure was found a fine-grained matrix with approximately 1-μm-diameter grains.Observation of the microstructural transition at the near-surface region suggested that the nanocomposite structures developed via severe plastic deformation (SPD), accompanied by a folding and imposing of the convex part of the surface, and by mechanical mixing with the fragments of the projectile particles.The nanocomposite structures exhibited high hardness values of approximately HV200, which are superior to those of extra-super duralumin (A7075-T6). The relationship between the grain size and hardness value in the structures corresponds well to the Hall–Petch relationship extrapolated from previous studies. Therefore, the increase in hardness is thought to be mainly the result of grain refinement strengthening.

Simulation of desorption of gold nanoclusters deposited on the (111) surface of Al and Au under bombardment with Au1 ions and Au400 clusters using the classical molecular dynamics method

The mechanisms of desorption of gold nanoclusters deposited on a substrate under low-energy bombardment with ions and clusters (in the mode of elastic stopping predominance) are analyzed. The classical molecular dynamics method is employed for computer simulation of both “direct” and “indirect” impact of bombarding particles (that is, when a projectile particle either directly interacts with the deposited cluster or penetrates into the substrate without hitting the cluster). Au1 ions and Au400 clusters with an energy of 38 keV and 0.18 keV/atom, respectively, are used as projectile particles. The spherical Au6051 gold nanocluster deposited on a substrate of Al(111) or Au(111) is applied as a target. It is shown that indirect impact does not lead to desorption of the nanocluster from the Al substrate in all considered cases; however, it can initiate desorption from the Au substrate. This phenomenon is quite efficient when the heat spike appearing upon penetration of a projectile particle involves the region of contact between the substrate and the nanocluster deposited on it. As this takes place, an intense flow of the sputtered substrate material transfers a sufficient-for-ejection momentum to the deposited nanocluster.

Code OK3 – An upgraded version of OK2 with beam wobbling function

For computer simulations on heavy ion beam (HIB) irradiation onto a target with an arbitrary shape and structure in heavy ion fusion (HIF), the code OK2 was developed and presented in Computer Physics Communications 161 (2004). Code OK3 is an upgrade of OK2 including an important capability of wobbling beam illumination. The wobbling beam introduces a unique possibility for a smooth mechanism of inertial fusion target implosion, so that sufficient fusion energy is released to construct a fusion reactor in future. New version program summary Program title: OK3 Catalogue identifier: ADST_v3_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADST_v3_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 221 517 No. of bytes in distributed program, including test data, etc.: 2 471 015 Distribution format: tar.gz Programming language: C++ Computer: PC (Pentium 4, 1 GHz or more recommended) Operating system: Windows or UNIX RAM: 2048 MBytes Classification: 19.7 Catalogue identifier of previous version: ADST_v2_0 Journal reference of previous version: Comput. Phys. Comm. 161 (2004) 143 Does the new version supersede the previous version?: Yes Nature of problem: In heavy ion fusion (HIF), ion cancer therapy, material processing, etc., a precise beam energy deposition is essentially important [1]. Codes OK1 and OK2 have been developed to simulate the heavy ion beam energy deposition in three-dimensional arbitrary shaped targets [2, 3]. Wobbling beam illumination is important to smooth the beam energy deposition nonuniformity in HIF, so that a uniform target implosion is realized and a sufficient fusion output energy is released. Solution method: OK3 code works on the base of OK1 and OK2 [2, 3]. The code simulates a multi-beam illumination on a target with arbitrary shape and structure, including beam wobbling function. Reasons for new version: The code OK3 is based on OK2 [3] and uses the same algorithm with some improvements, the most important one is the beam wobbling function. Summary of revisions: 1. In the code OK3, beams are subdivided on many bunches. The displacement of each bunch center from the initial beam direction is calculated. 2. Code OK3 allows the beamlet number to vary from bunch to bunch. That reduces the calculation error especially in case of very complicated mesh structure with big internal holes. 3. The target temperature rises during the time of energy deposition. 4. Some procedures are improved to perform faster. 5. The energy conservation is checked up on each step of calculation process and corrected if necessary. New procedures included in OK3 1. Procedure BeamCenterRot( ) rotates the beam axis around the impinging direction of each beam. 2. Procedure BeamletRot( ) rotates the beamlet axes that belong to each beam. 3. Procedure Rotation( ) sets the coordinates of rotated beams and beamlets in chamber and pellet systems. 4. Procedure BeamletOut( ) calculates the lost energy of ions that have not impinged on the target. 5. Procedure TargetT( ) sets the temperature of the target layer of energy deposition during the irradiation process. 6. Procedure ECL( ) checks up the energy conservation law at each step of the energy deposition process. 7. Procedure ECLt( ) performs the final check up of the energy conservation law at the end of deposition process. Modified procedures in OK3 1. Procedure InitBeam( ): This procedure initializes the beam radius and coefficients A1, A2, A3, A4 and A5 for Gauss distributed beams [2]. It is enlarged in OK3 and can set beams with radii from 1 to 20 mm. 2. Procedure kBunch( ) is modified to allow beamlet number variation from bunch to bunch during the deposition. 3. Procedure ijkSp( ) and procedure Hole( ) are modified to perform faster. 4. Procedure Espl( ) and procedure ChechE( ) are modified to increase the calculation accuracy. 5. Procedure SD( ) calculates the total relative root-mean-square (RMS) deviation and the total relative peak-to-valley (PTV) deviation in energy deposition non-uniformity. This procedure is not included in code OK2 because of its limited applications (for spherical targets only). It is taken from code OK1 and modified to perform with code OK3. Running time: The execution time depends on the pellet mesh number and the number of beams in the simulated illumination as well as on the beam characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost all of the practical running tests performed, the typical running time for one beam deposition is about 30 s on a PC with a CPU of Pentium 4, 2.4 GHz.

Measurements of stopping cross sections of liquid water for fast protons and helium ions

Stopping cross sections of liquid water for MeV energy protons and helium ions have been measured by using a liquid jet target in vacuum. Energy loss spectra after passing through the target were measured at scattering angles from 5.0 to 50 mrad. The energy loss spectra have been successfully reproduced by Monte Carlo simulation calculations (GEANT4 v9.1.p03 toolkit) by taking account of multiple scattering of projectile particles inside the target. For protons, the stopping cross sections were deduced in an energy range from 0.3 to 2.0 MeV. It was found that the present data are in fairy good agreement with recent theoretical calculations.

How the sensitivity in PIXE elemental analysis is affected by the type of particle, cross-sections, background radiation and other factors?

The purpose of this paper is to review the relevant factors to be taken into account to obtain a more sensitive PIXE (Particle induced X-ray emission) elemental analysis. In quantitative PIXE analysis, matrix effects become a fundamental factor. Depending on the analyzed element, the projectile particle type and its energy, material composition can have a major effect on the X-ray yields. Background in the X-ray spectrum, detection limits, particle stopping powers and X-ray photons attenuation, should be considered. Also the ionization cross-sections could be affected by the previous state of the projectile, conditioned by the passage in the material producing multiple ionizations and changes in its state of charge. A variety of experimental results and theoretical models, are analyzed here for protons, deuterons and heavier incident ions.

Cross sections for ionization of K, L and M shells of atoms by impact of electrons and positrons with energies up to 1 GeV: Analytical formulas

Analytical formulas are presented for the easy calculation of cross sections for ionization of K, L and M shells of neutral atoms by impact of electrons and positrons with kinetic energies up to 1 GeV. Each formula contains a number of parameters that are characteristic of the element, the active electron shell and the projectile particle. The values of these parameters were determined by fitting the cross section values in an extensive database that was calculated recently by means of a composite algorithm that combines the distorted-wave and plane-wave Born approximations. Tables of parameter values are given for all elements, from hydrogen ( Z = 1 ) to einsteinium ( Z = 99 ) . The proposed analytical expressions yield ionization cross sections that agree with those in the numerical database to within about 1%, except for projectiles with near-threshold energies.

Scattering resonances in a degenerate Fermi gas

We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas and a configuration-interaction description of the excitations. We determine the scattering phase shifts for the system and predict Fano-type scattering resonances that are a direct consequence of interatomic pairing. We describe the main characteristics of the scattering resonances and make a comparison with the results of BCS mean-field theory.

Edge effects caused by enhancement of DD/DT fusion reactions in metals at low energy of projectile particles in an ITER-type fusion reactor

Experimental data on enhancement of the yield of DD/DT reactions in metal targets at low energies of projectile deuterons (E d < 5 keV) were analyzed. A semiempirical expression was obtained to describe the dependence of the screening energy for deuterons upon the effective number of mobile deuterium atoms on the target metal surface. Numerical estimates showed that the edge plasma effects in ITER-type fusion reactors can be an additional source of generation of α-particles and of the buildup of 4He atoms in first-wall and divertor materials.

Impact-parameter-dependent multifragmentation ofC60in charge-changing collisions with2‐MeVC+ions

Multifragmentation of C{sub 60} was investigated for 2 MeV C{sup +} projectile ions by means of a time-of-flight triple coincidence technique. Fragment ions and secondary electrons were measured simultaneously in coincident with charge-selected outgoing projectile particles scattered into forward angles smaller than 1.0 mrad. Fragment ion distributions were found to change remarkably with respect to the scattering angle {theta}. Relationships between {theta} and the impact parameter b measured from the center of C{sub 60} were calculated classically. We found evidently that small-size fragment ions are produced only from cage-penetration collisions, while intact parent ions and their daughter ions are created in collisions nearby but outside a C{sub 60}. Furthermore, charge state distributions of prefragmented C{sub 60}{sup r+} ions and correlated fragment ion pairs were both found to be essentially independent of {theta} when plotted for individual C{sub m}{sup +} ions of fixed size. These results indicate that the production of a size-fixed specific ion may be restricted to a certain impact parameter region in which equivalent electronic energies are deposited irrespectively of {theta}. This was confirmed also from our calculation of the energy deposition as a function of b carried out using the local density approximation.

Elastic collisions of classical point particles on a finite frictionless linear track with perfectly reflecting endpoints

Repeated elastic collisions of point particles on a finite frictionless linear track with perfectly reflecting endpoints are considered. The problem is analysed by means of an elementary linear algebra approach. It is found that, starting with a state consisting of a projectile particle in motion at constant velocity and a target particle at rest in a fixed known position, the points at which collisions occur on track, when plotted versus progressive numerals, corresponding to the collisions themselves, show periodic patterns for a rather large choice of values of the initial position x(0) and on the mass ratio r. For certain values of these parameters, however, only regular behaviour over a large number of collisions is detected.

Ionization cross-sections for ion–atom collisions in high-energy ion beams

Knowledge of ion–atom ionization cross-sections is of great importance for many accelerator applications. We have recently investigated theoretically and experimentally the stripping of more than 18 different pairs of projectile and target particles in the range of 3–38 MeV/amu to study the range of validity of both the Born approximation and the classical trajectory calculation. In most cases, both approximations give similar results. However, for fast projectile velocities and low-ionization potentials, the classical approach is not valid and can overestimate the stripping cross-sections by neutral atoms by an order-of-magnitude. Therefore, a hybrid approach that automatically chooses between the Born approximation and the classical mechanics approximation depending on the parameters of the collision has been developed. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. Based on experimental data and theoretical predictions, a new fit formula for ionization cross-sections by fully stripped ions is proposed. The resulting plots of the scaled ionization cross-sections of hydrogen by fully stripped ions are presented. The new fit formula has also been applied to the ionization cross-sections of helium. Again, the experimental and theoretical results merge close together on the scaled plot.

SIMS profiling of GaAs/δ-AlAs/GaAs/… heterostructures using polyatomic ionized oxygen clusters

We have studied the possibility of using polyatomic ions as the primary projectile particles for the depth profiling of solid heterostructures by means of secondary ion mass spectrometry (SIMS) in combination with ion etching. Bombardment of a target by ionized oxygen clusters of the On+ (n=3, 4) type allows the specific impact energy per primary atom to be reduced, which significantly improves the depth resolution. It is shown that a beam of primary On+ (n=3, 4) clusters with the specific impact energy as low as 1 keV per oxygen atom can be obtained using a standard ion source with a magnetic mass separator. High-resolution depth profiles of a test heterostructure of the GaAs/δ-AlAs/GaAs/… type were obtained using a magnetic sector mass spectrometer and a primary beam of O3+ ions with a specific energy of 1 keV per oxygen atom. The experimental data are compared with the results of computer simulation of the ion sputtering process performed using the DITRIRS code.

Code OK2—A simulation code of ion-beam illumination on an arbitrary shape and structure target

For computer simulations on heavy ion beam (HIB) irradiation on a spherical fuel pellet in heavy ion fusion (HIF) the code OK1 was developed and presented in [Comput. Phys. Commun. 157 (2004) 160–172]. The new code OK2 is a modified upgraded computer program for more common purposes in research fields of medical treatment, material processing as well as HIF. OK2 provides computational capabilities of a three-dimensional ion beam energy deposition on a target with an arbitrary shape and structure. Program summary Title of program: OK2 Catalogue identifier: ADTZ Other versions of this program [1] : Title of the program: OK1 Catalogue identifier: ADST Program summary URL: http://cpc.cs.qub.as.uk/summaries/ADTZ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: PC (Pentium 4, ∼1 GHz or more recommended) Operating system: Windows or UNIX Program language used: C++ Memory required to execute with typical data: 2048 MB No. of bits in a word: 32 No. of processors used: 1CPU Has the code been vectorized or parallelized: No No. of bytes in distributed program, including test data: 17 334 No of lines in distributed program, including test date: 1487 Distribution format: tar gzip file Nature of physical problem: In research areas of HIF (Heavy Ion Beam Inertial Fusion) energy [1–4] and medical material sciences [5], ion energy deposition profiles need to be evaluated and calculated precisely. Due to a favorable energy deposition behavior of ions in matter [1–4] it is expected that ion beams would be one of preferable candidates in various fields including HIF and material processing. Especially in HIF for a successful fuel ignition and a sufficient fusion energy release, a stringent requirement is imposed on the HIB irradiation non-uniformity, which should be less than a few percent [4,6,7]. In order to meet this requirement we need to evaluate the uniformity of a realistic HIB irradiation and energy deposition pattern. The HIB irradiation and non-uniformity evaluations are sophisticated and difficult to calculate analytically. Based on our code one can numerically obtain a three-dimensional profile of energy deposition onto an arbitrary shape and structure target. Method of solution: OK2 code works on the base of OK1 [1–9]. The code simulates a multi-beam illumination on a target with arbitrary shape and structure, and obtains the 3D energy deposition profile. Restrictions on the complexity of the problem: None Typical running time: The execution time depends on the pellet mesh number and the number of beams in the simulated illumination as well as on the beam characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost of the practical running tests performed, the typical running time for one beam deposition is about 40 s on a PC with a CPU of Pentium 4, 2.4 GHz. Unusual features of the program: None

Code OK1—Simulation of multi-beam irradiation on a spherical target in heavy ion fusion

Code OK1 is a fast and precise three-dimensional computer program designed for simulations of heavy ion beam (HIB) irradiation on a direct-driven spherical fuel pellet in heavy ion fusion (HIF). OK1 provides computational capabilities of a three-dimensional energy deposition profile on a spherical fuel pellet and the HIB irradiation non-uniformity evaluation, which are valuables for optimizations of the beam parameters and the fuel pellet structure, as well for further HIF experiment design. The code is open and complete, and can be easily modified or adapted for users' purposes in this field. Program summary Title of program: OK1 Catalogue identifier: ADST Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADST Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: PC (Pentium 4, ∼1 GHz or more recommended) Operating system: Windows or UNIX Program language used: C++ Memory required to execute with typical data: 911 MB No. of bits in a word: 32 No. of processors used: 1 CPU Has the code been vectorized or parallelized: No No. of bytes in distributed program, including test data: 16 557 Distribution format: tar gzip file Keywords: Heavy ion beam, inertial confinement fusion, energy deposition, fuel pellet Nature of physical problem: Nuclear fusion energy may have attractive features as one of our human energy resources. In this paper we focus on heavy ion inertial confinement fusion (HIF). Due to a favorable energy deposition behavior of heavy ions in matter [J.J. Barnard et al., UCRL-LR-108095, 1991; C. Deutsch et al., J. Plasma Fusion Res. 77 (2001) 33; T. Someya et al., Fusion Sci. Tech. (2003), submitted] it is expected that heavy ion beam (HIB) would be one of energy driver candidates to operate a future inertial confinement fusion power plant. For a successful fuel ignition and fusion energy release, a stringent requirement is imposed on the HIB irradiation non-uniformity, which should be less than a few percent [T. Someya et al., Fusion Sci. Tech. (2003), submitted; M.H. Emery et al., Phys. Rev. Lett. 48 (1982) 253; S. Kawata et al., J. Phys. Soc. Jpn. 53 (1984) 3416]. In order to meet this requirement we need to evaluate the non-uniformity of a realistic HIB irradiation and energy deposition pattern. The HIB irradiation and non-uniformity evaluations are sophisticated and difficult to calculate analytically. Based on our code one can numerically obtain a three-dimensional profile of energy deposition and evaluate the HIB irradiation non-uniformity onto a spherical target for a specific HIB parameter value set in HIF. Method of solution: OK1 code is based on the stopping power of ions in matter [J.J. Barnard et al., UCRL-LR-108095, 1991; C. Deutsch et al., J. Plasma Fusion Res. 77 (2001) 33; T. Someya et al., Fusion Sci. Tech. (2003), submitted; M.H. Emery et al., Phys. Rev. Lett. 48 (1982) 253; S. Kawata et al., J. Phys. Soc. Jpn. 53 (1984) 3416; T. Mehlhorn, SAND80-0038, 1980; H.H. Andersen, J.F. Ziegler, Pergamon Press, 1977, p. 3]. The code simulates a multi-beam irradiation, obtains the 3D energy deposition profile of the fuel pellet and evaluates the deposition non-uniformity. Restrictions on the complexity of the problem: No Typical running time: The execution time depends on the number of beams in the simulated irradiation and its characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost of the practical running tests performed, the typical running time for one beam deposition is less than 2 s on a PC with a CPU of Pentium 4, 2.2 GHz (e.g., in Test 2 when the number of beams is 600, the running time is about 18 minutes). Unusual features of the program: No

Long-term Damage Induced by Hadrons in Silicon Detectors for Uses at the LHC-accelerator and in Space Missions

In the present paper, the phenomenological model developed by the authors in previous papers has been used to evaluate the degradation induced by hadron irradiation at future accelerator facilities or by cosmic protons in high resistivity silicon detectors. The damage has been analysed at the microscopic (defects production and their evolution toward equilibrium) and at the macroscopic level (changes in the leakage current of the p–n junction). The rates of production of primary defects, as well as their evolution toward equilibrium have been evaluated considering explicitly the type of projectile particle and its energy. Vacancy-interstitial annihilation, interstitial migration to sink, divacancy and complex (VP, VO, V2O, CiOi, CiCs) formation are taken into account for differently doped initial silicon material. The influence of these defects on the leakage current density has been compared with experimental data from the literature, and predictions for the LHC (Large Hadron Collider) radiation fields, as well as for space missions in the near Earth orbits have been done, in the frame of the Schokley–Read–Hall model.

Some recent activities of the International Atomic Energy Agency in the field of nuclear data

Results of recent IAEA activities related to assembly, maintenance and verification of databases of relevance to radiochemistry are presented. These include: (1) integral and differential nuclear constants for prompt gamma neutron activation analysis; (2) excitation functions for cyclotron production of medical radioisotopes using proton, deuteron and alpha particle projectiles; (3) data for dose calculations in radiation medical treatment/diagnosis and (4) nuclear cross section standards.

Pixel mapping analysis to characterize long-range order interactions in crystals under ion irradiation

High-dose irradiation can cause agglomeration of projectile particles if the impurity concentration exceeds a certain level. In previous classical molecular-dynamics calculations we have investigated the importance of ionimpacts for agglomeration. This has also shown that some long-range network forces exist in a crystal, which may relate phase transition and ion bombardment. In order to investigate the long-range order interactions, we propose a method to describe the lattice interactions macroscopically. We call it pixel mapping (PM). With the help of PM, we can clearly describe details of the intermediate processes and estimate the degree of crystallinity during ion irradiation. B implantation into a B doped Si crystal at different bombarding energies was analyzed by PM. Sudden changes from a crystalline to an amorphous state after a certain number of ion impacts were observed and analyzed by PM. PM described clearly these change as cooperative lattice reactions and revealed the long-range order interactions between target atoms in a crystal. Therefore, we can conclude that impurity agglomeration is cooperatively triggered by long-range interactions of atoms in a mesoscopic regime, and PM is a powerful method to elicit the long-range interactions of atoms in a crystal.

Mechanism of 238U disintegration induced by relativistic particles

In heavy-nucleus disintegration induced by a relativistic projectile particle, the production of collinear massive fragments accompanied by numerous charged particles and neutrons is explained in terms of the mechanism of projectile-momentum compensation due to the emission of a particle whose mass is greater than the projectile mass.

Design of an ion trap apparatus for nuclear astrophysics research

A design of an ion trap apparatus for measurements of excitation functions of d(d,p)t and He3(d,p)He4 reactions with bare beam and target at energies below the Coulomb barrier is presented. It aims to deduce the exact astrophysical S factor (cross section) without any modification due to the atomic electrons of target or both projectile and/or target particles in the region 1.5&amp;lt;Ecm&amp;lt;12 keV and 6.5&amp;lt;Ecm&amp;lt;15 keV. The technology of electron beam ion sources and traps has been applied substantially to solve luminosity and background problems for the measurement of nuclear reactions with less than a nanobarn cross section for astrophysical interest.

Radiation Defects in Silicon due to Hadrons and Leptons, their Annealing and Influence on Detector Performance

A phenomenological model was developed to explain quantitatively, without free parameters, the production of primary defects in silicon after particle irradiation, the kinetics of their evolution toward equilibrium and their influence on detector parameters. The type of the projectile particle and its energy is considered in the evaluation of the concentration of primary defects. Vacancy-interstitial annihilation, interstitial migration to sinks, vacancy-impurity complexes (VP, VO, V2O), and divacancy (V2) formation are taken into account in different irradiation conditions, for different concentrations of impurities in the semiconductor material, for 20 and 0°C. The model can be extended to include other vacancy and interstitial complexes. The density of the reverse current in the detector after irradiation is estimated. Comparison with experimental measurements is performed. A special application considered in the paper is the modelled case of the behaviour of silicon detectors operating in the pion field estimated for the LHC accelerator, under continuum generation and annealing.