Search

The total and the partial charge-changing cross-sections of 28Si fragmentation on C, CH2 and H targets at the intermediate and high energies of 500–800AMeV are investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-sections for H target are calculated based on the results of C and CH2 targets. It is found that the total charge-changing cross-sections for fragmentation of 28Si on C, CH2 and H targets are independent on the beam energy but increase with the mass of the targets in our studied energies, and are consistent with the predictions of Bradt–Peters semi-empirical formula and NUCFRG2 simulation codes. The partial cross-sections for projectile fragment production are independent on the beam energy in our present studied energies and show a significant odd–even staggering effect. The partial cross-sections for projectile fragment production are also compared with different predicted models, such as Cummings, Nilsen, EPAX2, EPAX3 and FRACS. Only the FRACS model reproduces a significant odd–even staggering effect, while its strength is weaker than the experimental data. Generally, these models can reproduce the experimental data of 28Si on the CH2 target well compared with the C target. [ABSTRACT FROM AUTHOR]

An in-depth understanding of the fracture behavior and mechanism of metallic shells under internal explosive loading can help develop material designs for warheads and regulate the quantity and mass distribution of the fragments formed. This study investigated the fragmentation performance of a new high-carbon silicon-manganese (HCSiMn) steel cylindrical shell through fragment recovery experiments. Compared with the conventional 45Cr steel shell, the number of small mass fragments produced by the HCSiMn steel shell was significantly increased with a scale parameter of 0.57 g fitted by the Weibull distribution model. The fragmentation process of the HCSiMn shell exhibited more brittle tensile fracture characteristics, with the microcrack damage zone on the outer surface being the direct cause of its high fragmentation. On the one hand, the doping of alloy elements resulted in grain refinement by forming metallographic structure of tempered sorbite, so that microscopic intergranular fracture reduces the characteristic mass of the fragments; on the other hand, the distribution of alloy carbides can exert a ''pinning'' effect on the substrate grains, causing more initial cracks to form and propagate along the brittle carbides, further improving the shell fragmentation. Although the killing power radius for light armored vehicles was slightly reduced by about 6%, the dense killing radius of HCSiMn steel projectile against personnel can be significantly increased by about 26% based on theoretical assessment. These results provided an experimental basis for high fragmentation warhead design, and to some extent, revealed the correlation mechanism between metallographic structure and shell fragmentation.

The emission angular distributions, the transverse momentum distributions and the temperature parameters of projectile fragments produced in fragmentation of 2 8 Si on C target at 736 A MeV are measured. It is found that the scattering angle of primary silicon ions is smaller than the emission angle of their fragments. The average value and the width of the angular distribution and the transverse momentum distribution are increased with the decrease of the charge of projectile fragments. The cumulative squared transverse momentum distribution of projectile fragments can be well fitted by a single Rayleigh distribution, which indicates that the projectile fragments are emitted from a single temperature emission source. Most of the temperature parameters of projectile fragments emission source are in the range of 2–5 MeV, which does not obviously depend on the charge of the projectile fragments. [ABSTRACT FROM AUTHOR]

In this study, data on charged-pion production in relativistic oxygen-ion collisions are examined with varying degrees of centrality. Using the multiplicity of producing charged pions, it is proved that there is a relationship between centrality degrees and collision parameters (such as the impact parameter b , target size fragments, N h and the total charge of projectile spectators, Q). The various order moments of the multiplicity distributions are used in the standard way to investigate the underlying correlations. The evidence suggests that all the pions produced at the various target sizes ( N h -values) correlate. The higher moments are also investigated at various centrality classes decided by the parameter Q. The multiplicity fluctuations, as measured by the variance-to-mean ratio, showed that the multiplicity distributions of produced pions are not Poissonian, regardless of how they were examined using the two parameters N h and Q -values. [ABSTRACT FROM AUTHOR]

In this paper, the emission features of singly-charged and doubly-charged projectile fragments emitted in interactions of 8 4 Kr 3 6 with emulsion at 1 A GeV are studied. We have also observed the dependence of the singly-charged and doubly-charged projectile fragments on the interaction with different target groups of the emulsion detectors. The multi-source model can characterize the projectile fragments, and each source provides an exponential distribution, according to our calculations. The present observation shows that the emission features of the singly-charged and doubly-charged projectile fragments are independent on the interaction with different target groups of the emulsion. [ABSTRACT FROM AUTHOR]

The higher-order fluctuations of the largest fragment charge were found to exhibit the signatures of a second-order phase transition in experimental data and simulations of the statistical multifragmentation model recently (Pietrzak et al 2020 Phys. Lett. B 809 135763). This work is devoted to study the dissipation of energy and higher-order fluctuations of the largest fragment charge in projectile fragmentation. The isospin-dependent quantum molecular dynamics (IQMD) model is used to study the non-equilibrium thermalization and fragmentation. The statistical code GEMINI is applied to simulate the second decay of the pre-fragments. To reveal how the incident energy dissipates into the excitation energy of the projectile-like system, the time evolution of the density, collective velocity, and random kinetic energy are displayed. It is found that the competition between the heat conduction and heat flux affects the excitation energy of the projectile-like system, which is the key variable in the fragmenting process. Displaying the mean multiplicity of the intermediate mass fragments and the higher-order fluctuations of the largest fragment charge, it is found that the decay mechanism of the projectile-like system transfers from the multi-fragmentation at mid-peripheral collision into the nucleon-evaporation at peripheral collision. The pseudo-critical point of this transition can be indicated by the zero of third order fluctuation together with the minimum of fourth order fluctuation. The calculations of the pseudo-critical point by the IQMD + GEMINI model agree with that extracted from the experimental data. Finally, the influences of the pseudo-critical point by the second decay, the mass number of the colliding system, and the incident energy are studied. [ABSTRACT FROM AUTHOR]

The 57Fe Mössbauer spectrum obtained after 57Mn (T1/2 = 1.45 min) implantation of solid hydrogen was measured at 7 K. The spectrum was analyzed as three components, and the chemical species of each component was assigned from the obtained Mössbauer parameters and the results of density functional theory (DFT) calculations. The formation process of chemical species and the oxidation states of Fe atoms produced by β– decay of 57Mn are discussed considering the charge transfer process, in relation to previous emission Mössbauer spectroscopy experiments with 57Co implantation of solid hydrogen at low temperature. [ABSTRACT FROM AUTHOR]

In the present analysis, we have focused on the emission characteristics of the projectile and target fragments produced from the interaction of 8 4 Kr with nuclear emulsion at 1 A GeV. We have studied the variation of the fragmentation parameter for singly charged (Z = 1) , doubly charged (Z = 2) , lower multiple-charged (Z = 3 – 5) , medium multiple-charged (Z = 6 – 9) and higher multiple-charged (Z > 9) , projectile fragments with respect to mass of the projectile and found that they are showing the different behaviors for different projectile fragments. We have also studied the emission behavior of shower particles, with respect to the black and gray particles. The present studies show that the production of shower particles strongly depends on the incident kinetic energy of the projectile and also depending on the interaction of the different types of target nuclei of nuclear emulsion. [ABSTRACT FROM AUTHOR]

The presented new methodology for full numerical simulating performances of casing rupture integrates the finite element method and the stochastic failure theory in the solvers for 2D and 3D axis-symmetric analyses of the projectile fragmentation. This paper focuses on the effects of the type of casing on the fragmentation characteristics. In this way, the selected specimen considers three specific types of high explosive (HE) items: 105 mm HE projectile M1, 120 mm HE mortar shell M62 and 128 mm HE missile warhead M63. As well, the presented technique makes it possible to consider the effects of the mechanical properties of the casing material and explosive type on the fragmentation. The results of numerical simulation and some relevant experimental data are used for their comparative analysis and evaluation of the numerical approach, confirming the computed parameters of fragmentation predict properly the characteristics of the natural casing disruption.

Ballistic tests with plate and stiffened targets impacted by cylindrical and blade-like projectiles were conducted using compressed gas gun to investigate the perforation-resistance performance of aero-engine fan casing during a blade-out event. It was observed that for the plate target impacted by the blade-like projectile, fragmentation on the projectile nose occurred and the targets were failed by petaling; but for the other combinations, the main failure mode of the targets was plugging and the projectiles were intact except in cases when the blade-like projectile hit the stiffeners. Due to the distinct failure mode, ballistic limit for the plate target impacted by the blade-like projectile was much higher. To analyze the perforation resistance of the target, the energy absorption modes were classified and described with analytical models. A new dishing energy calculating method was proposed for a plate normally impacted by an arbitrary cross-section projectile. The energy absorbed by each mode and the ballistic limits for the plate target were calculated using these analytical models. It was found that fragmentation of the projectile led to a larger amount of dishing energy. The formation conditions of the fragmentation on projectile nose were theoretically analyzed, and the influencing factors for the fragmentation such as the critical thickness of the target and the critical impact velocity of the projectile were derived with established formulas. The theoretical analysis agreed well with the test results. It is argued that if the target is thicker than the critical thickness and the initial velocity of the projectile is larger than the critical impact velocity, fragmentation on projectile nose will occur, failure mode of the target will change to petaling, and the perforation resistance of the target will be significantly enhanced. [ABSTRACT FROM AUTHOR]

• Cross sections for charge changing of 40Ar on elemental targets were studied. • Comparison with different empirical formulae and other data were presented. • No obvious odd-even effect was observed in present investigation. The total and the partial charge-changing cross sections of 40Ar fragmentation on CH 2 , C, Al, Cu and Pb targets at the highest energy of 495 A MeV were investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target was calculated based on the results of polyethylene and carbon targets. It was found that the total charge-changing cross sections for fragmentation of 40Ar on H, C, Al, Cu and Pb targets were independent on the beam energy in our studied energies, and were consistent with the predictions of Bradt-Peters semi-empirical formula. Nilsen semi-empirical formula, NUCFRG2 and PHITS simulation codes given an underestimation of experimental data. The partial cross sections for projectile fragment production were independent on the beam energy in our studied energies for each target and do not show a significant odd-even effect. The partial cross sections for projectile fragment production were also compared with different empirical parametrization formulas, such as different version of Cummings, Nilsen, FRACS and EPAX3. Generally, EPAX3 and FRACS empirical parametrization can give a reasonable estimation of data within 25% relative errors. [ABSTRACT FROM AUTHOR]

This paper presents numerical simulations of hypervelocity impacts of 0.5-mm steel spheres into graphite, for velocities ranging between 1100 and 4500 m/s. Experiments have evidenced a non-monotonic evolution of the projectile penetration depth, along with the trapping of the projectile below the crater surface. Using numerical simulations and simple constitutive relations, we show how our experimental results can be related to both materials mechanical properties. We take advantage of the succession of physical mechanisms to build a step by step procedure and identify thresholds of yield and spall strength that allow a first restitution of the experimental results. These threshold values for the steel projectile were found to be consistent with the literature. As regards the graphite target, the yield strength has also been identified, and we propose to model its dependence with pressure through a linear relation. Comparisons between experiments and simulations are presented and discussed. Despite some difference at the highest impact velocities, the overall trend is well reproduced, which suggests that our results could be used as a starting point for further studies with more complex models. [ABSTRACT FROM AUTHOR]

By means of 3D numerical simulations, we study the statistical properties of the fragments cloud formed during high-velocity impact of a spherical projectile on a mesh bumper. We present a quantitative description of the projectile fragmentation, and study the nature of the transition from the damage to the fragmentation of the projectile when the impact velocity varies. A distinctive feature of the present work is that the calculations are carried out by smoothed particle hydrodynamics (SPH) method applied to the equations of mechanics of deformable solids (MDS). We describe the materials behavior by the Mie-Grüneisen equation of state and the Johnson-Cook model for the yield strength. The maximum principal stress spall model is used as the fracture model. It is shown that the simulation results of fragmentation based on the MDS equations by the SPH method are qualitatively consistent with the results obtained earlier on the basis of the molecular dynamics and discrete element models. It is found that the power-law distribution exponent does not depend on energy imparted to the projectile during the high-velocity impact. At the same time, our calculations show that the critical impact velocity, the power-law exponent and other critical exponents depend on the fracture criterion. [ABSTRACT FROM AUTHOR]

We present a brief overview of nuclear multifragmentation reaction. Basic formalism of canonical thermodynamical model based on equilibrium statistical mechanics is described. This model is used to calculate basic observables of nuclear multifragmentation like mass distribution, fragment multiplicity, isotopic distribution and isoscaling. Extension of canonical thermodynamical model to a projectile fragmentation model is outlined. Application of the projectile fragmentation model for calculating average number of intermediate mass fragments and the average size of the largest cluster at different Z, differential charge distribution and cross-section of neutron-rich nuclei of different projectile fragmentation reactions at different energies are described. Application of nuclear multifragmentation reaction in basic research as well as in other domains is outlined. [ABSTRACT FROM AUTHOR]

Graphical abstract: Display Omitted Highlights: [•] Projectile fragmentation extends the reach of Penning trap mass spectrometry of rare isotopes. [•] Gas stopping techniques are used to thermalize high-energy beams for precision experiments. [•] Measurements performed at LEBIT have contributed to several areas of nuclear science. [ABSTRACT FROM AUTHOR]

Abstract: Frangible projectiles for firearms, which break apart on impact, are mainly used by law enforcement agencies for training purposes, but can also be used for police interventions. Apart from the usual absence of lead in the projectiles, the main advantage of using frangible projectiles is the reduced risk of ricochet after impact with a hard target. This article describes the design and function of frangible projectiles, and describes gunshot wounds caused by ultra-frangible projectiles which fragment after penetration of soft tissues. Shooting experiments performed by the authors confirmed that differences in the geometry and technology of frangible projectiles can significantly modify their wounding effects. Some frangible projectiles have minimal wounding effects because they remain compact after penetration of soft tissues, comparable to standard fully jacketed projectiles. However, a number of ultra-frangible projectiles disintegrate into very small fragments after impact with a soft tissue substitute. In shooting experiments, we found that the terminal behavior of selected ultra-frangible projectiles was similar in a block of ballistic gel and the soft tissues of the hind leg of a pig, except that the degree of disintegration was less in the gel. [Copyright &y& Elsevier]

Abstract: Multiplicity, projected angular and transverse momentum distributions of helium projectile fragment (HPF) produced from 1.7 A GeV 84Kr induced different type of emulsion targets (H, CNO and AgBr) interactions are studied. It is found that the distributions of HPF from 84Kr–H, CNO, AgBr and emulsion interactions can be well explained by two Gaussian distributions. These imply the existence of two distinct emission sources (cold and hot source) of HPF in 84Kr–H, CNO, AgBr and emulsion interactions. The dominant source is the cold one (projectile spectator source) with lower temperature and the other is hot one (projectile participant source) with higher temperature. The temperature parameters of cold and hot source are obtained from distribution fitting using two Rayleigh distribution, which is independent of the target size within experimental errors. [Copyright &y& Elsevier]

Abstract: The present study deals with the determinations of symmetry energy and compressibilities of nuclear matter () at intermediate energies. The observables, available from GSI, namely the multiplicity of neutrons () and the multiplicity of intermediate mass fragments (), are compared with theoretical results of an isospin quantum molecular dynamics (IQMD) model. The soft symmetry energy with soft equation of state reproduces the data of symmetry energy sensitive observable , while hard equation of state is true in the presence of symmetry energy independent observable . The correlation between the multiplicity of free neutrons from the projectile spectator fragmentation (PSF) and the reduced multiplicity of bound neutrons within the IMFs (bound neutron number scaled by the multiplicities of intermediate mass fragments) from the projectile fragmentation (PF) is established. [Copyright &y& Elsevier]

A projectile (Kr) having kinetic energy around 1 A GeV has been used to expose NIKFI BR-2 emulsion target at GSI, Darmstadt, Germany. A total of 700 inelastic events has been identified and used in the present studies on projectile fragments. The emission angle of the projectile fragments are strongly affected by charge of the other projectile fragments emitted at same time with different emission angle is observed. The angular distribution studies show symmetrical nature for lighter charge projectile fragments. The symmetrical nature decreased with the charge of projectile fragments. We have observed at ~4 of emission angle for double charge projectile fragments, the momentum transfer during interaction is similar for various target species of emulsion. We have also observed a small but significant amplitude peaks on both side of the big peak for almost all light charge projectile fragments having different delta angle values. It reflects that there are a few percent of projectile fragments that are coming from the decay of heavy projectile fragments or any other process. [ABSTRACT FROM AUTHOR]