Projectile Particles Research Articles

Development of a velocity measurement method for a microparticle projectile and high-speed impact testing of metallic materials for grain refinement

Since grain refinement, such as the nano-twinning and nano-crystallization of metallic materials, can improve mechanical properties, surface modification to generate nano-structures is an in-demand technology. This study aims to conduct ultrahigh velocity impact testing using microparticle projectiles to generate indentation craters via impact. Due to the resulting extreme plastic deformation with high strain rate, grain refinement is expected to occur. This study conducts the laser-induced particle impact test (LIPIT), in which laser ablation induces supersonic ejection of a microparticle, resulting in the generation of an impact crater. We first propose a method for measuring particle projectile velocity using a mechanoluminescent (ML) material. A particle collision against the ML material emits light as a result of the mechanical stimulus. The light is detected to determine the timing of particle arrival, thus, the particle projectile velocity is obtained. This measurement method is verified using a high-speed video camera. Next, LIPIT is applied to pure copper (Cu) and pure iron (Fe), thus producing nano-structures including twinning around the impact indentation craters. To clarify this mechanism, a molecular dynamics (MD) simulation is conducted to reveal the formation of nano-twinning around the impact craters. In addition, nano-indentation testing is conducted, indicating plastic hardening around the impact craters unlike the craters obtained using quasi-static indentation. This indicates that plastic deformation due to LIPIT improves mechanical properties, owing to the extreme plastic strain and strain rates involved. Therefore, our LIPIT has potential as a new surface modification technique to induce extreme plastic deformation with ultrahigh strain rates, resulting in grain refinement.

Detection of fragments of an obstacle and a projectile in a gunshot injury

BACKGROUND: Law enforcement agencies look for the presence of an obstacle between the human body and the muzzle of a firearm at the time of the shot when assigning forensic medical examination of a firearm injury. Imported particles removed from the corpse, a skin flap, or damaged clothing could be sent for a laboratory examination.
 CASE PRESENTATION: Here, we present a case from expert practice which demonstrates the possibility of establishing the presence of barrier particles on surrounding objects in the case of a gunshot injury caused to a person. In the given case, detecting the fragments of an obstacle (triplex ― the windshield of a car) played a leading role in proving the suspects involvement in the incident under investigation. Described are the violations of an expert method of particle removal (in one case only, the material obtained from the clothing was placed on a special carbonic adhesive tape during a targeted search of micro overlays) and evaluation of the obtained data which contributed to incorrect findings in the experts conclusion.
 Experts of the Federal State-Owned Institution 111 Main State Center for Medical and Forensic Examinations conducted a re-examination of the above-stated objects, as well as experimental target shooting with similar weapons through a similar barrier. Presented are the possibilities of modern scanning electron microscopy and energy dispersion analysis, which allow not only to establish the presence of barrier particles on surrounding objects but also to identify the signs of gunshot damage inflicted upon a human body and clothing, identify the destroyed projectile particles, and establish the elemental composition of all the detected microparticles.
 CONCLUSION: This study demonstrated the methodological gaps in establishing the existence of a passage of a firearm projectile through an obstacle in the case of a gunshot injury. The methods for identifying the fragments of a firearm projectile and particles of an obstacle, which we are currently developing, are aimed at solving this problem by improving the corresponding research methods in forensic medicine and science.

First-principles simulation of the electronic stopping power of He ions in Al at finite temperature

The electronic stopping power of low-energy He projectile particles moving through an Al film under channeling and off-channeling trajectories and its temperature dependence are studied by combining the time-dependent density-functional-theory method with molecular dynamics simulations. The results show that the effect of target temperature on target stopping power can be divided into two aspects which are derived from the target electron and target ion. Below 500 K, the effect of the target-electron temperature on target stopping power is almost negligible. The influence of the target-ion temperature on target stopping power can be divided into two aspects which are derived from the displacement and energy dissipation of target ions. The displacement of the target ion can result in two trends that change the target stopping power: (1) The target ion is closer to the center of lattice channel after displacement, which leads to the increase of target stopping power. (2) The target ion is farther away from the center of the lattice channel after displacement, which leads to the decrease in target stopping power. As the temperature increases, the target ions are more likely to appear farther away from the lattice channel than closer to the center of the lattice channel, so the average displacement of the target ions will lead to a decreasing trend of the target stopping power with the increase of temperature. Under the condition of a given ionic density in the target, the energy dissipation capacity of target ions increases with the increase of temperature, resulting in the tendency of the target stopping power to increase with the increase of temperature. Our calculated stopping powers are in good agreement with the experimental data and reproduced the deviation from velocity proportionality found in the experimental results for a ${\mathrm{He}}^{+}$ ion in Al, validating our approach and numerical implementation.

Influence of Inter-Particle Friction and Damping on the Dynamics of Spherical Projectile Impacting Onto a Soil Bed

This study investigates the dynamics of a spherical projectile impact onto a granular bed via numerical simulations by discrete element method (DEM). The granular bed is modeled as an assembly of polydisperse spherical particles and the projectile is represented by a rigid sphere. The DEM model is used to investigate the cratering process, including the dynamics of the projectile and energy transformation and dissipation. The cratering process is illustrated by tracking the motion of the projectile and granular particles in the bed. The numerical results show that the dynamics of the projectile follows the generalized Poncelet law that the final penetration depth is a power-law function of the falling height. The numerical results can match well the experimental data reported in the literature, demonstrating the reliability of the DEM model in analyzing the impact of a spherical projectile on a granular bed. Further analyses illustrate that the impact process consists of three main stages, namely the impact, penetration and collapse, as characterized by the evolution of projective velocity, strong force chains and crater shape. The initial kinetic and potential energy of the projectile is dissipated mainly by inter-particle friction which governs the projectile dynamics. The stopping time of projectile decreases as the initial impact velocity increases. The final penetration depth scales as one-third the power of total falling height and is inversely proportional to the macroscopic granular friction coefficient.

Features of the ejection and topography of the distribution of metal particles of a destroyed projectile after overcoming an obstacle made of triplex glass of a car

BACKGROUND: The article describes experimental studies aimed at studying the features of post-retrograde gunshot trauma using the latest modern methods of forensic medical research.
 AIMS: The aim of the work was to study the nature of the distribution of metal particles of a destroyed firearm projectile after passing through an obstacle ― triplex glass.
 MATERIAL AND METHODS: As a barrier, car windshield triplex windows are used, located at an angle of 60 to the aiming line. The shots were fired from the Saiga-MK carbine with 5.4539 BPZ FMJ cartridges. During the experiments, shots were fired from a distance of 10 m (a total of 30 shots were fired). White cotton fabric (calico) with dimensions of 100150 cm, fixed on a chipboard, was used as targets. The distance between the target and the barrier was 100 cm. The targets were studied using a scanning electron microscope Hitachi FlexSem 1000 II and an energy-dispersive X-ray spectrometer Bruker Quantax 80. In the course of the experiment, high-speed video shooting was carried out with a Sony RX0 video camera with a frequency of 1000 fps.
 RESULTS: A frame-by-frame study of the obtained video recordings showed that the deviation of the flight of the projectile fragments from the original trajectory was up to 10 side of the normal to the back surface of the glass. The fragments of the projectile, having overcome the barrier, moved in stages, in 3 phases: overcoming the barrier, ejecting fragments in the form of a cone, breaking through the target and retrograde movement of the fragments of the barrier. The scanning electron microscope and energy dispersive spectroscopy studies showed that the topography and morphology of the distribution of metals on the target surface correspond to the data of the analysis of the movement of parts of a firearm during high-speed video shooting. The metal alloy found on the target contained the following elements: plumbum (Pb), cuprum (Cu), antimony (Sb), and kalium (K).
 CONCLUSION: When conducting an experimental study, it was found that various types of particles that were destroyed during the passage of the barrier, a firearm projectile, are registered on the surface of the target. The nature of the particle distribution and their morphology are very specific, and most likely a qualitative assessment of the projectile particles on the target will allow us to determine the distance of the shot beyond the barrier.

Channeling and radiation of electrons and positrons in the diamond heterocrystals

We analyze numerically the radiation and channeling properties of ultrarelativistic electrons and positrons propagating through a periodically bent diamond crystal grown on a straight single-crystal diamond substrate. Such systems can be called hetero-crystals and they are one of the experimentally realized samples for the implementation of crystalline undulators. We state that in such systems the channeling and radiation properties of projectiles are sensitive to the projectile particles energy as well as on the beam propagation direction, i.e. on whether the beam of particles enters the crystal from the side of substrate or from the side of periodically bent crystal. The predictions made are important for design and practical realization of new crystalline undulators.

Fragmentation of carbon on elemental targets at 290AMeV

The total charge-changing cross-sections and the partial cross-sections for projectile fragments (PFs) production for the fragmentation of 12C on C, Al, Cu, Pb and CH2 targets at the highest energy of 290[Formula: see text]A[Formula: see text]MeV were studied. It was found that the total charge-changing reaction cross-sections and the partial reaction cross-sections of PFs production were independent of the beam energy, and increased with increase of mass of target for the same beam energy. The total charge-changing reaction cross-section was the same as the prediction of Bradt–Peters semi-empirical formula, PHITS and NUCFRG2 simulation models. The partial cross-section of PFs production increased with the increase of the mass of target, and it was the same as the prediction of NUCFRG2 models. The mean scattering angle of projectile particle was smaller than the average emission angle of PF, and the width of scattering angle distribution of projectile particle was smaller than that of emission angle distribution of PFs. The mean emission angle of PFs does not obviously depend on the target mass and beam energy in our studied beam energy regions.

Investigation of α-induced Reaction on Copper Isotopes for Energy Range of 15-50 Mev

The present work was done on alpha induced reaction mechanics on two natural coppers isotopes for the energy range of 15 to 30 Mev were investigated. The reaction channels for the total cross section 63Cu (α, n) 66Ga, 65Cu (α, 2n)67Ga, 63Cu(α, pn) 65Cu and 65Cu(α, n)68Ga were studied. The experimental data of reaction cross section COMPLETE code have been used. The aim study was compared experimental and theoretical reaction cross section both compound and pre-compound reaction and know the property, the reaction mechanism of the projectile particle reacts with target nuclei. The theoretical result was obtained from international atomic energy agency, exchange format data source. We understood the reaction mechanisms and the property of fragment particles during the reaction. Level density parameter and exaction number were varied to become good agreement between the calculated and measured data. In this study different dependency reaction cross section, the projectile energy was observed between the production of 67Ga and 65Zn. In alpha induced reaction with copper isotopes 66Ga, 67Ga, 68Ga and 65Zn are produced. Normally the calculation using a COMPLET code provides good outcome for the reaction cross-section of alpha induced reaction on low projectile energy. During the study of the reaction compound and pre-equilibrium reaction are occurred but direct reaction was almost not expected. Direct reaction is required to very large amount of energy.

DFMSPH22: A C-code for the double folding interaction potential of two spherical nuclei

This is a new version of the DFMSPH (DFMSPH14, DFMSPH19) code published earlier. The new version is designed to obtain the nucleus–nucleus potential between two spherical nuclei using the double folding model (DFM). In particular, the code enables one to find the Coulomb barrier. Using the new version, one can employ three types of effective nucleon–nucleon interaction: the M3Y, Migdal, and relativistic mean-field interactions. The main functionalities of the original code (the nucleus–nucleus potential as a function of the distance between the centers of mass of colliding nuclei and the characteristics of the Coulomb barrier) are retained. The new version enables using proton or neutron as the projectile particle for all nucleon–nucleon interactions but the Migdal one. New version program summaryProgram title: DFMSPH22CPC Library link to program files:https://doi.org/10.17632/n6bsf4zxcz.3Code Ocean capsule:https://codeocean.com/capsule/1595275Licensing provisions: GLPv2Programming language: CJournal reference of previous version: Comput. Phys. Commun. 242 (2019) 153–155Does the new version supersede the previous version? YesReason for new version: Different versions of the relativistic mean-field effective NN-forces are used in the literature by different groups of researchers but seldom within the same numerical scheme; proton or neutron could not be used as the projectile nucleus in the previous version.Summary of revisions: Two extra options have been added in comparison with the previous version: •In the DFMSPH19 [1], the effective nucleon–nucleon (NN) M3Y and Migdal forces were used as the basis for the nucleus–nucleus interaction potential obtained by means of the double-folding model. In the new version, DFMSPH22, the user still has the same options, but there is an extra possibility to use one of the Relativistic Mean-Field (RMF) effective NN-forces. The nucleus–nucleus potential based on these forces is applied in the literature every now and again to evaluate the nucleus–nucleus potential energy (see, e.g. [2–5]). The corresponding equations and different parameter sets of the RMF forces implemented in DFMSPH22 are presented in the Supplementary material file. In this file, one finds also the comparison of the total potential as well as the nuclear part of it obtained using the RMF NN forces with those obtained using M3Y NN forces [1,6].•In the present version, we include a possibility for using proton or neutron as the projectile particle which was absent before. This option works for all the NN-forces but the Migdal one due to the structure of the latter. A restriction when using this option is that the density dependence does not work with proton or neutron as the projectile. See details in the Supplementary material file. The code consists now of 6 C-files and one header file. It reads the data from 5 input files and prints the results into 4 output files. The details of the changes in each source file as well as the description of the input and output files are presented in file <Program_changes.txt>. The input and output files corresponding to two test runs are included in the program files archive.Some misprints in Refs. [1, 6] are corrected (see the Supplementary material file).Nature of problem: The code calculates the bare (i.e. ignoring the channels coupling) interaction potential between two spherical colliding nuclei as a function of the center of mass distance in a semi-microscopic way. The height and radius, as well as the curvature and skewness of the Coulomb barrier, are evaluated. Dependence of these barrier parameters upon the type and/or characteristics of the effective NN forces (like e.g. M3Y, Migdal, or relativistic mean-field type; the range of the exchange part of the nuclear term) as well as upon the parameters of the density distributions can be studied.Solution method: The nucleus–nucleus potential is calculated using the double folding model with the Coulomb and effective NN interactions. For the direct parts of the Coulomb and nuclear terms, the Fourier transform method is used. For the exchange part most often the zero-range approximation is used. To calculate the exchange part of the nucleus–nucleus potential based on the M3Y interaction with the finite range, the density matrix expansion method is applied.Acknowledgment The authors are indebted to Dr. Wasiu Yahya for finding misprints in Refs. [6, 7].ReferencesI.I. Gontchar, M.V. Chushnyakova, N.A. Khmyrova, Comput. Phys. Commun. 242 (2019) 153–155.B. Singh, M. Bhuyan, S.K. Patra, R.K. Gupta, J. Phys. G Nucl. Part. Phys. 39 (2012) 025101.C. Lahiri, S.K. Biswal, S.K. Patra, Int. J. Mod. Phys. E 25 (2016) 1650015.M. Bhuyan, R. Kumar, Phys. Rev. C 98 (2018) 054610.M. V Chushnyakova, I.I. Gontchar, N.A. Khmyrova, J. Phys. G Nucl. Part. Phys. (2020) doi: 10.1088/1361-6471/ab907a.I.I. Gontchar, M.V. Chushnyakova, Comput. Phys. Commun. 181 (2010) 168–182.I.I. Gontchar, M.V. Chushnyakova, Comput. Phys. Commun. 206 (2016) 97–102.

Floquet theory for the electronic stopping of projectiles in solids

A theoretical framework for the study of electronic stopping of particle projectiles in crystalline solids is proposed. It neither relies on perturbative or linear-response approximations nor on an ideal metal host. Instead, it exploits the discrete translational invariance in a space-time diagonal for a constant velocity projectile following a trajectory with crystalline periodicity. By means of Floquet theory, (stroboscopically) stationary solutions are characterized, and previous perturbative and jellium models are recovered. The threshold-velocity effect in insulators is analyzed based on quasienergy conservation.Received 16 September 2019Revised 30 June 2020Accepted 2 July 2020DOI:https://doi.org/10.1103/PhysRevResearch.2.033151Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBand gapIrradiation effectsScattering theoryPhysical SystemsFloquet systemsCondensed Matter, Materials & Applied Physics

Reduction of the isotropic S-formula for the energy spectrum of nuclear fusion products to a triple integral

Energetic and angular distributions of the products of nuclear fusion reactions involving two colliding nuclei and two resulting particles are important in neutron spectrometry, as well as in studies of the behaviour of fast electrically charged particles in plasma, such as protons, tritons, helions and α-particles in the megaelectronvolt range. This also applies to primordial nucleosynthesis and astrophysics since the reaction rates in cosmic plasma can also be affected by suprathermal particles. The possibility of a reduction of the S-algorithm to a triple integral is demonstrated for the case of isotropic velocity distributions of projectile and target particles.

Studies of equation of state properties of high-energy-density matter generated by intense ion beams at the facility for antiprotons and ion research.

The work presented in this paper shows with the help of two-dimensional hydrodynamic simulations that intense heavy-ion beams are a very efficient tool to induce high energy density (HED) states in solid matter. These simulations have been carried out using a computer code BIG2 that is based on a Godunov-type numerical algorithm. This code includes ion beam energy deposition using the cold stopping model, which is a valid approximation for the temperature range accessed in these simulations. Different phases of matter achieved due to the beam heating are treated using a semiempirical equation-of-state (EOS) model. To take care of the solid material properties, the Prandl-Reuss model is used. The high specific power deposited by the projectile particles in the target leads to phase transitions on a timescale of the order of tens of nanosecond, which means that the sample material achieves thermodynamic equilibrium during the heating process. In these calculations we use Pb as the sample material that is irradiated by an intense uranium beam. The beam parameters including particle energy, focal spot size, bunch length, and bunch intensity are considered to be the same as the design parameters of the ion beam to be generated by the SIS100 heavy-ion synchrotron at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. The purpose of this work is to propose experiments to measure the EOS properties of HED matter including studies of the processes of phase transitions at the FAIR facility. Our simulations have shown that depending on the specific energy deposition, solid lead will undergo phase transitions leading to an expanded hot liquid state, two-phase liquid-gas state, or the critical parameter regime. In a similar manner, other materials can be studied in such experiments, which will be a very useful addition to the knowledge in this important field of research.

Model Optimization and Calculation Method of Multi-Target Curved Motion Parameters Measurement Using Multi-Screen Intersection Test Mechanism

The parameters calculation model of a six-screen intersection with linear motion is used to test the projectile explosion location parameter under the condition of long-range artillery firing, which brings a significant test error, the main reason for the error is that the projectile has its own gravity during the flight, it makes the flight path of the projectile is a curved trajectory. To improve the test accuracy, this paper uses the projectile particle motion equation and six-screen intersection geometry relationship and considers the impact of the projectile's gravity acceleration and air resistance; it studies a calculation model and method of relative location for projectile proximity explosion under the spatial projectile curved motion. Then, it analyzes the error reason for calculating relative coordinate of projectile passing through the detection screen interval by using six-screen intersection test method based on linear motion. By introducing the gravitational acceleration and air resistance during the projectile flight process, establishes the variable trajectory parameters calculation model for a projectile with the curved motion passing through a six-screen intersection test system. Through the high-altitude projectile proximity explosion location test, this paper uses the method of the ballistic lateral camera to obtain the experimental data of projectile explosion location parameter. It compares the experimental data by using the six-screen intersection test method with linear motion and curved motion. The results show that the calculation model based on the curved motion model is closer to actual coordinate data of the projectile proximity explosion location.

Microstructure characterization of 7055-T6, 6061-T6511 and 7A52-T6 Al alloys subjected to ballistic impact against heavy tungsten alloy projectile

A spray formed 7055 Al alloy, and traditional formed 6061 Al and 7A52 Al alloy were subjected to extrusion. Later 7055Al and 7A52 treated with T6 and 6061 Al treated with T6511 heat treatment. To investigate the microstructure evolution by optical microscopy (OM), scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) and X-rays diffraction pattern (XRD) analysis were employed to observe the variation in mechanical properties and damages patterns of single layered aluminum alloys impacted by heavy tungsten alloy (WHA) projectile. During impact a substantial increase in temperature inside the target material caused melting on crater wall. The hard metastable intermetallic compound and pores were produced on penetration path owing to diffusion of projectile particles and rapid melt re-solidification. These compounds enhance the hardness (600-650 HV0.1/10) in the middle deformed channels of 7055 Al alloy target. In addition, small size pores, whirl-pool and white adiabatic shear bands were observed in 7A52 and 6061 Al alloys, respectively. The variation in hardness and microstructure of Al alloys target was limited within the 2mm area from the perforation path. 7055-T6 Al alloy has demonstrated better ballistic protection in terms of strength, mass efficiency (N), depth of penetration (DOP) and penetration path diameter in comparison of other Al alloys.

Kinematics Simulation Analysis of Shot Blasting Projectile Based on EDEM

In order to study the acceleration process of projectiles in the shot blaster, Discrete Element Method was used to establish the discrete element model of the shot blaster. With the help of the 3D discrete element software EDEM, this thesis points out the main factors that affecting the movement of projectiles by observing the movement of projectiles in the shot blaster. The results show that the movement of projectiles in the shot blaster can be divided into three phases: the gravity acceleration period, the rapidly acceleration period and the stable blasting period; the throwing velocity of projectiles are positively correlated with the pellet wheel rotating speed, the blade length and the projectile particle size, and are independent of the initial velocity; the initial velocity and the projectile particle size can effectively shorten the acceleration phase of projectiles, while the pellet wheel rotating speed and the blade length have no significant effect on every phase of projectiles acceleration.

Investigation of fusion hindrance in a soft asymmetric system deep below the barrier

A steeper fall of fusion excitation function, compared to the predictions of coupled-channel (CC) models, at energies below the lowest barrier between the reaction partners, is termed as deep sub-barrier fusion hindrance. This phenomenon has been observed in many symmetric and nearly symmetric systems. Different physical origins of the hindrance have been proposed though a complete understanding is yet to be achieved. This work reports the measurement of the fusion (evaporation residue) cross sections for the system 19F+181Ta, from above the barrier down to the energies where fusion hindrance is expected to come into play. CC calculation with standard Woods–Saxon potential gives a fair description of the fusion excitation function down to energies ≃14% below the barrier. This is in contrast with the observation of increasing fusion hindrance in asymmetric reactions induced by increasingly heavier projectiles, viz. 6,7Li, 11B, 12C and 16O. The most likely reason for non-observation of fusion hindrance in the present system is the ‘softness’ of the collision partners. The ‘threshold’ for the onset of fusion hindrance in reactions involving well-deformed nuclei is expected to be at an energy lower than that estimated from the systematics. It is also noted that the asymmetric reactions, which have not shown any signature of fusion hindrance within the measured energy range, are induced by projectiles with low α-particle break-up threshold and have positive Q-values for most light particle pick-up channels. Since CC calculation reproduces the fusion excitation functions for these systems, probable roles of projectile break-up and particle transfer in fusion deep below the barrier are not conclusively proven. Further measurements and inclusion of break-up and transfer channels within the framework of CC formalism would be of interest.

Responses of jointed rock masses subjected to impact loading

Impact-induced damage to jointed rock masses has important consequences in various mining and civil engineering applications. This paper reports a numerical investigation to address the responses of jointed rock masses subjected to impact loading. It also focuses on the static and dynamic properties of an intact rock derived from a series of laboratory tests on meta-sandstone samples from a quarry in Nova Scotia, Canada. A distinct element code (PFC2D) was used to generate a bonded particle model (BPM) to simulate both the static and dynamic properties of the intact rock. The calibrated BPM was then used to construct large-scale jointed rock mass samples by incorporating discrete joint networks of multiple joint intensities into the intact rock matrix represented by the BPM. Finally, the impact-induced damage inflicted by a rigid projectile particle on the jointed rock mass samples was determined through the use of the numerical model. The simulation results show that joints play an important role in the impact-induced rock mass damage where higher joint intensity results in more damage to the rock mass. This is mainly attributed to variations of stress wave propagation in jointed rock masses as compared to intact rock devoid of joints.

Abstract ID: 240 A probabilistic-based nuclear reaction model for Monte Carlo ion transport in particle therapy

In order to expand the Monte Carlo transport program AMOS to particle therapy applications, the ion module is being developed in the radiation physics group (ASP) at the TU Dresden. This module simulates the three main interactions of ions in matter for the therapy energy range: elastic scattering, inelastic collisions and nuclear reactions. The simulation of the elastic scattering is based on the Binary Collision Approximation and the inelastic collisions on the Bethe-Bloch theory. The nuclear reactions, which are the focus of the module, are implemented according to a probabilistic-based model developed in the group. The developed model uses probability density functions to sample the occurrence of a nuclear reaction given the initial energy of the projectile particle as well as the energy at which this reaction will take place. The particle is transported until the reaction energy is reached and then the nuclear reaction is simulated. This approach allows a fast evaluation of the nuclear reactions. The theory and application of the proposed model will be addressed in this presentation. The results of the simulation of a proton beam colliding with tissue will also be presented.

The influence of the electron correlations on dynamic of two-electron charge exchange between ions and polar molecules

Introduction. In the theory of electron capture the exchange interactions at large internuclear distances R between projectile and target particles are the most important ones, since they are associated with the largest cross sections. However, their accurate calculation in the asymptotic region of large R by standard ab initio techniques still requires significant computational effort. In the case of two-electron exchange interaction the situation is much complicated due to necessity of the usage of analytic approximation for the two-electron wave function which must have correct asymptotic (at large R ) behavior in whole configuration space of the electronic coordinates. This requirements can be satisfied by using the method of surface integrals and the Green’s function formalism. The present studies devoted to construction of asymptotically correct two-electronic wave function and two-electronic exchange interaction of the system which consist of the atomic ion and polar molecule. Purpose. To construct a closed analytical expression for two-electron exchange interaction potential, which defines the charge-exchange processes between the polar molecule and multicharged ion. Results . Within the framework of a semiclassical approach and approximation of a coulomb-dipole potential the closed analytical expression of the two-electron exchange interaction responsible for two-step mechanism of charge-exchange between the polar molecule and multicharged ion has been obtained. Conclusion . We have constructed the semiclassical representation for two-electron wave function of the quasimolecular system which consist of polar molecule and atomic ion for large separation R between heavy particles. Using obtained results a closed analytical form (in terms of full elliptic integrals) of the leading asymptotic term of exponentially small two-electron exchange interaction between the polar molecule and atomic ion has been obtained. The derived expression for exchange interaction can be used for study of the two-electron transfer processes in collision of polar molecules with atomic ions.

A New Mechanism of Sediment Attachment to Oil in Turbulent Flows: Projectile Particles.

The interaction of oil and sediment in the environment determines, to a large extent, the trajectory and fate of oil. Using confocal microscope imaging techniques to obtain detailed 3D structures of oil-particle aggregates (OPAs) formed in turbulent flows, we elucidated a new mechanism of particle attachment, whereby the particles behave as projectiles penetrating the oil droplets to depths varying from ∼2 to 10 μm due to the hydrodynamic forces in the water. This mechanism results in a higher attachment of particles on oil in comparison with adsorption, as commonly assumed. The projectile hypothesis also explains the fragmentation of oil droplets with time, which occurred after long hours of mixing, leading to the formation of massive OPA clusters. Various lines of inquiry strongly suggested that protruding particles get torn from oil droplets and carry oil with them, causing the torn particles to be amphiphillic so that they contribute to the formation of massive OPAs of smaller oil droplets (<∼5-10 μm). Low particle concentration resulted in large, irregularly shaped oil blobs over time, the deformation of which without fragmentation could be due to partial coverage of the oil droplet surface by particles. The findings herein revealed a new pathway for the fate of oil in environments containing non-negligible sediment concentrations.