Wave dynamic processes induced by a supersonic projectile discharging from a shock tube

A numerical study on wave dynamic processes occurring in muzzle blast flows, which are created by a supersonic projectile released from the open-end of a shock tube into ambient air, is described in this paper. The Euler equations, assuming axisymmetric flows, are solved by using a dispersion-controlled scheme implemented with moving boundary conditions. Three test cases are simulated for examining friction effects on the muzzle flow. From numerical simulations, the wave dynamic processes, including two blast waves, two jet flows, the bow shock wave and their interactions in the muzzle blasts, are demonstrated and discussed in detail. The study shows that the major wave dynamic processes developing in the muzzle flow remain similar when the friction varies, but some wave processes, such as shock-shock interactions, shock-jet interactions and the contact surface instability, get more intensive, which result in more complex muzzle blast flows.

Function Innovation in Combined Surface Technologies for Metals

表面技术能够显著提高材料功能而成为工程和产品设计的重要组成部分, 但前提是表面技术必须具有可设计性。为此, 需要开拓和发展表面组合加工技术, 进行创新。该技术的内涵体现了新材料与新技术、基础研究与产业化有机结合的特点, 具有重要的价值和广阔的前景。

Impact of laser-accelerated micron-size projectile on dense plasma

The impact of a laser-accelerated micron-size projectile on a dense plasma target is studied using two-dimensional particle-in-cell simulations. The projectile is first accelerated by an ultraintense laser. It then impinges on the dense plasma target and merges with the latter. Part of the kinetic energy of the laser-accelerated ions in the projectile is deposited in the fused target, and an extremely high concentration of plasma ions with a mean kinetic energy needed for fusion reaction is induced. The interaction is thus useful for laser-driven impact fusion and as a compact neutron source.

Quadratic nonlinear technologies for femtosecond lasers

Quadratic optical nonlinearity chi((2)) can be exploited in femtosecond lasers and regarded as a significant new degree of freedom for the design of short-pulse sources. We will review our recent progress on developing nonlinear quadratic technologies for femtosecond lasers. Our nonlinear laser technology offers new properties for femtosecond lasers, including optical parametric amplifier with novel working regime, efficient second harmonic generation, and time telescope.

The research and progress of micro-fabrication technologies of two-dimensional photonic crystal

The novel material of photonic crystal makes it possible to control a photon, and the photonic integration will have breakthrough progress due to the application of photonic crystal. It is based on the photonic crystal device that the photonic crystal integration could be realized. Therefore, we should first investigate photonic crystal devices based on the active and the passive semiconductor materials, which may have great potential application in photonic integration. The most practical and important method to fabricate two-dimensional photonic crystal is the micro-manufacture method. In this paper, we summarize and evaluate the fabrication methods of two-dimensional photonic crystal in near-infrared region, including electron beam lithography, selection of mask, dry etching, and some works of ours. This will be beneficial to the study of the photonic crystal in China.

Isospin effect of projectile fragment yields

Isospin asymmetry is very important in the nuclear equation of state (EOS), isotope yield from the projectile fragments can give information of the reaction process. In this paper projectile fragment yields are measured in the collision Ar-36,Ar-40 + Ni-64 at incident energy 50 MeV/u with different isospin asymmetry project Ar-36,Ar-40, data analysis, particle identification and event selection are described. Isotope yields are compared in these two reactions, and axe also compared with the empirical parametrization of fragmentation cross-section calculated by EPAX.

Slow isocharged sequence ions with helium collisions: Projectile core dependence

The collisions of the isocharged sequence ions of q=6 (C6+, N6+, O6+, F6+, Ne6+, Ar6+, and Ca6+), q=7 (F7+, Ne7+, S7+, Ar7+, and Ca7+), q=8 (F8+, Ne8+, Ar8+, and Ca8+), q=9 (F9+, Ne9+, Si9+, S9+, Ar9+, and Ca9+) and q=11 (Si11+, Ar11+, and Ca11+) with helium at the same velocities were investigated. The cross-section ratios of the double-electron transfer (DET) to the single-electron capture (SEC) sigma(DET)/sigma(SEC) and the true double-electron capture (TDC) to the double-electron transfer sigma(TDC)/sigma(DET) were measured. It shows that for different ions in an isocharged sequence, the experimental cross-section ratio sigma(DET)/sigma(SEC) varies by a factor of 3. The results confirm that the projectile core is another dominant factor besides the charge state and the collision velocity in slow (0.35-0.49v(0); v(0) denotes the Bohr velocity) highly charged ions (HCIs) with helium collisions. The experimental cross-section ratio sigma(DET)/sigma(SEC) is compared with the extended classical over-barrier model (ECBM) [A. Barany , Nucl. Instrum. Methods Phys. Res. B 9, 397 (1985)], the molecular Coulombic barrier model (MCBM) [A. Niehaus, J. Phys. B 19, 2925 (1986)], and the semiempirical scaling laws (SSL) [N. Selberg , Phys. Rev. A 54, 4127 (1996)]. It also shows that the projectile core properties affect the initial capture probabilities as well as the subsequent relaxation of the projectiles. The experimental cross-section ratio sigma(TDC)/sigma(DET) for those lower isocharged sequences is dramatically affected by the projectile core structure, while for those sufficiently highly isocharged sequences, the autoionization always dominates, hence the cross-section ratio sigma(TDC)/sigma(DET) is always small.

Projectile fragmentation of Kr-86 at 64 MeV/nucleon

We measured fragmentation cross sections produced using the primary beam of Kr-86 at 64 MeV/nucleon on Be-9 and Ta-181 targets. The cross sections were obtained by integrating the momentum distributions of isotopes with 25 <= Z <= 36 measured using the RIPS fragment separator at RIKEN. The cross-section ratios obtained with the Ta-181 and Be-9 targets depend on the fragment masses, contrary to the simple geometrical models. We compared the extracted cross sections to EPAX; an empirical parametrization of fragmentation cross sections. Predictions from current EPAX parametrization severely overestimate the production cross sections of very neutron-rich isotopes. Attempts to obtain another set of EPAX parameters specific to the reaction studied here to extrapolate the neutron-rich nuclei more accurately have not been very successful, suggesting that accurate predictions of production cross sections of nuclei far from the valley of stability require information of nuclear properties that are not present in EPAX.