Projectile System Research Articles

Ballistic Projectile Tracking Using CW Doppler Radar

The theory of operation is presented, together with experimental results, of a projectile target scoring system that determines highly accurate hit locations of small arms fire by processing constant frequency CW radar Doppler phase content into a trajectory estimate. We describe a new algorithm for extracting trajectory parameters from Doppler time series to obtain time, distance, and velocity at closest approach. Vector trajectories are derived by combining multiple scalar trajectories from three radar units. Live fire test results from a local range and Aberdeen Proving Ground are provided to show that a hit location accuracy of 4 cm can be achieved reliably on small arms.

The Lunar rayed-crater population — Characteristics of the spatial distribution and ray retention

The global statistics for young impact craters on the Moon is used to unravel potential spatial asymmetries, that may have been introduced by the particular orbital configuration of a synchronously rotating satellite. Only craters that exhibit bright ejecta rays extending for several crater radii were considered in this study. This crater population is younger than about 750Ma. The shape of the crater size-frequency distribution does not show strong dependence on the target properties (mare vs. highlands). However, slightly lower frequencies indicate a shorter retention of the visibility of rays in mare units when their visibility is purely due to immaturity and not due to composition. Rays of small craters fade away much faster. Large, old, rayed craters sustain their visibility longer than the average crater population because of the compositional contrast between rays and mare material, and thus obscure the cratering record when investigated for spatial variations. Using the existence of rays purely based on optical maturity instead of visibility as marker horizon for the Copernican–Eratosthenian boundary, suggests a shift from 1.1Ga to 750Ma.The spatial distribution of lunar rayed craters, namely the latitudinal and longitudinal frequency variations, does not agree with previous analytical and numerical studies. Although there is an apparent hemispherical asymmetry centred close to the apex, the density distribution is patchy and no predicted spatial pattern could be confirmed. Spatial distribution corrections accounting for the lower frequencies in the mare areas did not result in a better agreement with the analytical estimates. Density variations are less than 15% over vast parts of the lunar surface, and the uncertainties for absolute surface ages are similar. However, variations of up to 50% are found even for the more numerous small craters. These extreme values are located at high latitudes. A combination of crater-forming projectile flux distribution and micrometeorite bombardment, which acts on maturation of the ray systems, could prove as an explanation for the contradicting observed rayed crater distribution.An analysis of the older craters is more challenging (on the Moon) because earlier geological processes complicate the setting, and the orbital configuration of the Moon–Earth–Sun–projectile system altered with time.

Forces and moments affecting underwater projectile mobility

The forces and moments affecting an underwater projectile under conditions of static and dynamic stability are presented and the equations of movement are derived. The models for calculating the forces and moments expressed in the body - fixed coordinate system of the underwater projectile are given as well.

Explanation of anomalous shock temperatures in shock-loaded Mo samples measured using neutron resonance spectroscopy

Neutron resonance spectrometry (NRS) has been used to measure the temperature inside Mo samples during shock loading. The temperatures obtained were significantly higher than predicted assuming ideal hydrodynamic loading, a discrepancy which we now explain. The effects of plastic flow and nonideal projectile behavior were assessed. Plastic flow was calculated self-consistently with the shock jump conditions: this is necessary for a rigorous estimate of the locus of shock states accessible. Plastic flow was estimated to contribute a temperature rise of $53\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ compared with hydrodynamic flow. Simulations were performed of the operation of the explosively driven projectile system used to induce the shock in the Mo sample. The simulations, and related experiments, indicated that the projectile was significantly curved on impact, and still accelerating. The resulting spatial variations in load, including radial components of velocity, should increase the apparent temperature that would be deduced from the width of the neutron resonance by $160\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. These corrections are sufficient to reconcile the apparent temperatures deduced using NRS with the accepted properties of Mo, in particular, its equation of state.

Laser-based projectile speed measurement system

The design and construction of a system to accurately determine the speed of a projectile (bullet) by measuring the time of flight between two parallel laser screens is described. Each screen is formed by a laser source and a set of prisms. At the detection end of each of the screens, a collector lens focuses the incident laser light beam onto a photodetector. The collector lens and detector are kept in a recess so that no stray or ambient light falls on the photodetector. Whenever a projectile crosses either of the screens, the corresponding photodetector senses the event, due to partial or full obscuration of the incident energy. An electronic circuit is used to accurately record the time when the projectile crosses each screen, and the time interval gives the time of flight. The distance between the screens being known, the velocity is displayed on a computer screen. Because a single collimated beam of light generates the entire optical curtain, the reduction in incident energy at the photodetector plane is independent of the entry point of the projectile into the screen. Due to the baffling of the photodetector from ambient light, the optical screens can be used at indoor or outdoor ranges equally effectively.

Isotopic production cross sections of spallation-evaporation residues from reactions ofU238(1AGeV) with deuterium

Isotopic production cross sections and momentum distributions of 602 residual nuclei produced in the collision of $^{238}\mathrm{U}$($1A$ GeV) with deuterium have been measured. These data are relevant for a better understanding of spallation reactions for use as neutron sources for accelerator-driven systems or to produce radioactive nuclear beams. Access to primary residue production makes it possible to study the main reaction mechanisms involved: intranuclear cascade, particle evaporation, and fission. The characteristics of the reaction investigated and the high fissility of the $^{238}\mathrm{U}$ and the dinucleon projectile system are discussed and compared with other available experimental data.

Secondary Electron Emission from Graphite Induced by MeV/atom Carbon Cluster Impacts

Based on the three-step model, we theoretically studied the energy distribution of low-energy (less than 50 eV) secondary electrons emitted from highly-oriented pyrolytic graphite (HOPG), induced by the 0.24 MeV/atom carbon-cluster C n + ( n =1,2,4,8) ions. Here we treated the kinetic excitation process of an electron gas, described by the dynamical dielectric function. In the projectile system, we took into account the charge state, the spatial structure of the cluster and the size of the electron cloud on the constituent atoms. The numerical results show that the intensity of energy spectra per carbon ion is less than that induced by a single carbon ion at the equivalent speed. This sub-linear effect was supported by a recent experimental result. We concluded that this effect could be explained to a considerable extent by the screening effect and the vicinage effect of the incident cluster.

SEARCH FOR POSSIBLE WAY OF PRODUCING SUPER-HEAVY ELEMENTS: DYNAMIC STUDY ON DAMPED REACTIONS OF 244Pu+244Pu, 238U+238U and 197Au+197Au

By using the Improved Quantum Molecular Dynamics model, the 244 Pu +244 Pu , 238 U +238 U and 197 Au +197 Au reactions at the energy range of E c.m. =800 MeV to 2000 MeV are studied. We find that the production probability of superheavy fragments (SHFs) with Z≥114 for the 244 Pu +244 Pu reaction is much higher compared with that for the 238 U +238 U reaction and no product of SHF is found for the 197 Au +197 Au . The production probability of SHFs strongly depends on the incident energy and a narrowly peaked energy dependence of production probability is found. The decay mechanism of the composite system of projectile and target is studied and the time scale of decay process is explored. The binding energies and the shapes of SHFs are studied. The binding energies of SHFs are broadly distributed and the shapes of SHFs are strongly deformed.

Dynamical core deformation effects on single-nucleon knockout reactions at fragmentation beam energies

The effects of core deformation and of its dynamical reorientation and rotational excitation on the inclusive single-neutron knockout reaction cross sections on light spherical nuclei are examined. The projectile nuclei are modeled within the framework of a weak-coupling, quadrupole-deformed core-plus-neutron two-body model. We formulate the inclusion of this non-spectator-core degree of freedom within the nonperturbative eikonal model and calculate the diffractive break up and stripping neutron-removal cross sections. We apply the methods to model the single-neutron removal reactions induced by 11Be and 17C and secondary fragmentation beams incident on a 9Be target. Our calculations indicate that dynamical deformation effects on the diffractive break up component of the knockout cross section can be significant. For the two reactions studied here, the diffractive break up cross section is significantly enhanced. This effect is found to be very surface localised, thus the importance of core deformation is increased the more tightly bound the projectile system. The quadrupole deformation parameter and excitation energy of the core also influence the magnitude of this enhancement of the diffractive cross section, which is relatively insensitive to the projectile energy. The stripping cross section is found to be virtually unchanged by the inclusion of the deformed core degree of freedom.

Electron-electron interaction studied in strong central fields by resonant transfer and excitation with H-like U ions

Electron-electron interaction is studied in the strongest possible atomic fields $(Z\ensuremath{\alpha}\ensuremath{\Rightarrow}1)$ in the presence of only two electrons. A quasifree electron from a hydrogen gas target is resonantly captured into an ${L}_{j}$ subshell of a fast H-like ${\mathrm{U}}^{91+}$ ion by simultaneous excitation of the strongly bound $K$ electron also into an ${L}_{{j}^{\ensuremath{'}}}$ subshell of the projectile, with $j$ and ${j}^{\ensuremath{'}}$ the total angular momenta of 1/2 or 3/2 for the electron of concern. This resonant transfer and excitation process (RTE) ${\mathrm{KL}}_{j}{L}_{{j}^{\ensuremath{'}}}$ is mediated by electron-electron interaction. It is equivalent to dielectronic recombination in ion-electron collisions and leads to a doubly excited He-like ${\mathrm{U}}^{90+**}$ ion, which stabilizes---almost exclusively---via the emission of two successive $K$ x rays, first a $K$ hypersatellite $(K{\ensuremath{\alpha}}_{i}\ensuremath{-}H)$ and then a $K$ satellite $(K{\ensuremath{\alpha}}_{{i}^{\ensuremath{'}}}\ensuremath{-}S)$ transition. The $K$ x-ray emission characteristics associated with one-electron capture in collisions of ${\mathrm{U}}^{91+}$ ions with a hydrogen target are studied for the three resonance groups of the ${\mathrm{KL}}_{j}{L}_{{j}^{\ensuremath{'}}}$ RTE and one off-resonance energy, i.e., in the energy range between 100 and 135 MeV/u. The total cross section for the first resonance group ${\mathrm{KL}}_{1/2}{L}_{1/2}$ confirms the importance of the Breit contribution to the interaction. The angular distribution for the $K{\ensuremath{\alpha}}_{2}\ensuremath{-}H$ transition $(j=1/2)$ is isotropic in the projectile system, whereas the $K{\ensuremath{\alpha}}_{1}\ensuremath{-}H$ transition $(j=3/2)$ indicates a strong alignment for the 3/2 electrons in the doubly excited states for the second resonance group ${\mathrm{KL}}_{1/2}{L}_{3/2}.$ The experimental results are in agreement with fully relativistic calculations including the generalized Breit interaction.

Predicting the fragmentation onset velocity for different metallic projectiles using numerical simulations

For cubes and spheres under high velocity impact there exists for each system of projectile and target, a threshold velocity that is just sufficient to shatter the projectile. This velocity, usually above 2km/s for metallic projectiles, is known as the fragmentation onset velocity. To determine the fragmentation onset velocity experimentally, a number of experiments in which the impact velocity of the projectile is varied in a controlled manner needs to be conducted [1]. In the work described in this paper, the numerical analysis code AUTODYN was used to simulate the impact of stainless steel and tantalum projectiles onto transparent targets in an attempt to simulate the onset of fragmentation. Using the meshfree SPH method for discretizing the spatial domain of the projectile and a simple failure model that allows the critical spall stress of the material to vary with the local material and loading conditions, encouraging results were obtained, with the fragmentation onset velocity for both projectile/target configurations being reasonably well predicted. In addition, further experiments conducted at TNO-PML, to determine the fragmentation onset velocity for tungsten projectiles, will be reported.

Sub-barrier fusion of deformed nuclei in60Ni+154Smand32S+182Wreactions

We have investigated the sub-barrier fusion between spherical projectiles and well-deformed targets in ${}^{60}\mathrm{Ni}{+}^{154}\mathrm{Sm}$ and ${}^{32}\mathrm{S}{+}^{182}\mathrm{W}$ reactions, and both lead to the same compound nucleus ${}^{214}\mathrm{Th}.$ In order to get direct evidence that the projectile really fuses with the deformed target, the fusion evaporation residues emitted to the beam direction were measured by using the JAERI recoil mass separator and identified on the basis of time- and position-correlated $\ensuremath{\alpha}$ decays. The angular distributions of fission fragments were also measured to obtain the total fusion cross section. The measured cross sections of the fusion fission and the fusion evaporation were compared with the results of the coupled channel calculation and the statistical model calculation, respectively. In the ${}^{32}\mathrm{S}{+}^{182}\mathrm{W}$ system, a good agreement between them was obtained for $xn,$ $pxn,$ and $\ensuremath{\alpha}\mathrm{xn}$ channels. In the heavy projectile system of ${}^{60}\mathrm{Ni}{+}^{154}\mathrm{Sm},$ on the other hand, the observed evaporation residue cross sections below the Bass barrier were much less than the calculated results whereas they were well reproduced above the barrier. It was found that this large hindrance could be reproduced by assuming an extra-extra push energy of around 20 MeV in the tip collision of the deformed target and nearly zero in the side collision.

A study of the equations of motion for a plasma-armature railgun

The two derivations of the equation of motion for the plasma armature - projectile system in a railgun are reviewed. Although they describe the same kinematical system, it is shown that they yield conflicting descriptions for the action - reaction forces over the plasma armature. The two inductances per unit length for the equations of motion are then given for the case in which the rail and current distributions are in the form of infinitesimally thin sheets and are shown to be different, although for a RAPID railgun this difference is not significant. Next, the lumped-parameter version of the railgun equation of motion is shown to be incapable of explaining anomalous effects occurring in the plasma armature, which have been observed in railgun firings, whereas no such problem arises with the MHD version. Finally, sufficient conditions under which the equations yield equivalent results are given, though these may not be realized in most railgun applications. .

Revisiting the performance of a plasma armature railgun

Some experimental results obtained from a series of firings using a small-bore two-stage plasma armature railgun are presented which contradict assumptions employed in more recent attempts to model plasma armatures in railgun firings. By introducing the current - time behaviour into the equation of motion for the plasma - projectile system, an expression for a limiting exit velocity is obtained. This general expression is dependent upon the rail inductance per unit length when no anomalous effects occur in a firing. Since current diffusion is not significant close to the plasma - projectile system during a firing, the current distribution can be assumed to be in the form of thin sheets along the inner rail surfaces, thereby enabling the rail inductance per unit length to be evaluated. Different values for the height of the current sheets are then used to evaluate the rail inductance per unit length. When introduced into the expression for the limiting exit velocity, all yield significantly higher exit velocities than those recorded in railgun firings. These results explain the relatively poor performance of a railgun without the need to incorporate relativistic effects as in recent work.

On isotopic yield ratios of complex fragments from heavy ion induced reactions

It is shown that the observed behaviour of the isotope yield ratios of complex fragments as a function of the neutron to proton ratio of the combined system of target and projectile can be understood by multifragmentation including evaporation processes of the originally hot primordial fragments.

Absolute cross sections for projectile-charge-state-correlated multiple-ionisation processes in Ne-Ne collisions

In the collision system Nen++Ne0+ to Nen'++neq++(n'-n+q)e-, absolute cross sections sigma (n,n',q) for the production of recoil ions were determined by a coincidence technique, in which the final charge states of the projectile (n') and the recoil ion (q) were measured simultaneously. This method permitted the investigation of the velocity dependence (at energies of 75-360 keV u-1) of different reaction channels, such as pure multiple ionisation of the target, and multiple ionisation accompanied by both capture of one or more target electrons into the projectile system and loss of projectile electrons. In the velocity range investigated here direct multiple ionisation at large impact parameters is the dominant process in creating recoil ions with low charge states (q=1,2,3), whereas highly charged ions are mainly produced in close collisions. In these symmetric collisions multiple ionisation of the projectile and the target behave quite similarly.

Light fragments produced in40Ar+natAg reactions at 27MeV/u

Angular and energy distributions have been measured for products of 4≦Z≦12 from reaction of 1,095 MeV40Ar+natAg. In addition to sources located near the projectile and fusion system velocities, the data show the presence of a source located aroundVbeam/2 which cannot be explained by any existing model. A possible interpretation is proposed.

Electron capture from hydrogen atoms by fastLi+1(1s2),Li+2(1s), andLi+3ions

The continuum intermediate-states approximation has been used in the evaluation of cross sections for electron capture by ${\mathrm{Li}}^{+1}$ ($1{s}^{2}$), ${\mathrm{Li}}^{+2}$ ($1s$), and ${\mathrm{Li}}^{+3}$ ions from hydrogen atoms within an ionic energy range of $200\mathrm{keV}<~E<~10000\mathrm{keV}$. For each projectile system, the total capture cross sections were compared with the results of Shah, Goffe, and Gilbody [J. Phys. B 11, L233 (1978)] over a quoted experimental range $65\mathrm{keV}<~E<~1500\mathrm{keV}$.

Excitation of a dibaryon ( I = 0, J = 3) state in relativistic [formula omitted] scattering

The dibaryon with J = S = 3 and I = 0 has a chance to be “bound”, m ∗( d 03) < 2m Δ , in the quark model with QCD residual interaction. We calculate a peripheral reaction mechanism whereby an incoming relativistic deuteron is excited to this dibaryon resonance via the (scalar) mean field of the target nucleus (e.g. 16O). In the projectile system the target nucleus corresponds to an effective number of isoscalar (σ) mesons which produce the (ΔΔ) component via 2π intermediate states. At very high energies we calculate the diffraction excitation via pomeron exchange.

Elastic and deeply inelastic reactions in theKr86+La139system at 505, 610, and 710 MeV

Angular and energy distributions were measured for the reaction products from the $^{86}\mathrm{Kr}$ + $^{139}\mathrm{La}$ reaction at 505, 610, and 710 MeV bombarding energies. The elastic scattering data were analyzed to extract information about the conservative potential. The strength of the potential for separations close to the strong absorption radius is in agreement with a number of theoretical potentials including the proximity potential. Contour plots of the cross section for nonelastic reaction products as a function of angle and exit channel total kinetic energy for the 505 and 610 MeV bombardments exhibit two branches, similar to the behavior previously observed at 710 MeV. These results reveal no sharp energy dependence of the character of the deflection function, implying that the ${Z}_{1}{Z}_{2}$ product of the target and projectile system is more important than the bombarding energy in determining the orbits of the reacting nuclei. Upper limits to the fusion cross sections at all energies are less than 25% of the total reaction cross section. Calculations of the energy loss expected on the basis of a one-body proximity friction arising from particle exchange give an energy loss which is less than one-half of the observed energy loss.NUCLEAR REACTIONS $^{139}\mathrm{La}(^{86}\mathrm{Kr},X)$, $E=505, 610, \mathrm{and} 710$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$ for elastic, quasielastic, and deeply inelastic scattering. Also measured $\ensuremath{\sigma}(E,\ensuremath{\theta})$ for nonelastic products. Optical model analysis of elastic scattering. Comparison of energy losses in quasielastic reactions with predictions on one-body proximity friction.