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31.
This article presents a model of damage accumulation in irradiated crystals. This model is based on the assumption that the
damage accumulation occurs through a series of structural transformations triggered by the destabilization of the current
structure of crystals. Formal equations describing the damage accumulation build-up and experimental assessment of the model
are presented and discussed in the framework of the actual knowledge of radiation effects in oxide crystals (yttria-stabilized
zirconia (YSZ) and magnesium-aluminate spinel (MAS)), silicon carbide crystals and zirconia implanted nickel crystals. 相似文献
32.
We study the existence and linear stability of the zone boundary mode in a nonlinear electrical lattice consisting of N inductors and N voltage-dependent capacitors with periodic boundary conditions. The inductances are allowed to alternate, while the capacitors are identical and each have a quadratic dependence on voltage. By block-diagonalizing a 2N×2N Floquet problem, we reduce the question of the stability of the mode to a single Hill’s equation that is analyzed using methods of perturbation theory and averaging. We show that periodicity of the lattice inductances degrades stability, and also show that the instability threshold is proportional to N−2. Numerical computations validate the perturbative results. 相似文献
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Patrick F. Conforti Manish Prasad Barbara J. Garrison 《Applied Physics A: Materials Science & Processing》2008,92(4):1037-1041
Molecular dynamics (MD) simulations are used to study the interactions of photons with a poly(methyl methacrylate), or PMMA,
substrate and point thermal absorbers. The point thermal absorbers are embedded within the polymer matrix which can be excited
and transfer energy to the surrounding particles through an internal vibrational mode. Using a fluence above the ablation
threshold, two excitation channels are studied—one includes a direct heating of the polymer and the other includes the excitation
of the thermal absorbers. Although the yield of ejected particles is similar for both simulations, the plume composition differs.
For the simulation of the excitation of the point thermal absorbers, the plume consists of a greater number of smaller substrate
fragments due to local high temperature regions. 相似文献
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36.
Abstract We simulated the bombardment of Si(100)(2 × 1) by Si atoms using molecular dynamics. The kinetic energies of the projectiles were 100 and 50 eV. To model the Si–Si-interactions the empirical potential of Stillinger and Weber with the two body part of the potential splined to the universal potential was used. A geometric criterion based on the Lindemann radius was defined to study damage in the Si target. We observed clusters of disordered Si atoms in the target induced by the bombardment. Large clusters of about 50 atoms are formed in the beginning of the bombardment; they shrink and decay into smaller clusters until and equilibrium cluster size of about 10 atoms is reached. Upon annealing at elevated temperature the disordered zones dissolve into point defects. 相似文献
37.
Mikhail E. Povarnitsyn Konstantin V. Khishchenko Pavel R. Levashov 《Applied Surface Science》2009,255(10):5120-5124
In this study we simulate an interaction of femtosecond laser pulses (100 fs, 800 nm, 0.1-10 J/cm2) with metal targets of Al, Au, Cu, and Ni. For analysis of laser-induced phase transitions, melting and shock waves propagation as well as material decomposition we use an Eulerian hydrocode in conjunction with a thermodynamically complete two-temperature equation of state with stable and metastable phases. Isochoric heating, material evaporation from the free surface of the target and fast propagation of the melting and shock waves are observed. On rarefaction the liquid phase becomes metastable and its lifetime is estimated using the theory of homogeneous nucleation. Mechanical spallation of the target material at high strain rates is also possible as a result of void growth and confluence. In our simulation several ablation mechanisms are taken into account but the main issue of the material is found to originate from the metastable liquid state. It can be decomposed either into a liquid-gas mixture in the vicinity of the critical point, or into droplets at high strain rates and negative pressure. The simulation results are in agreement with available experimental findings. 相似文献
38.
Experimental Test of 7.8GHz Power Extractor Using Dielectric Loaded Rectangular Waveguide Structures 下载免费PDF全文
We report on experimental test of a 7.8 GHz power extractor using a dielectric loaded rectangular waveguide structure. This work is conducted at the Argonne wakefield accelerator (AWA) facility. The wakefield is excited by an electron beam travelling through a dielectric loaded rectangular waveguide, and the generated rf power is then subsequently extracted with a properly designed rf coupler. In the experiment, 30 MW of output power is excited by a 66nC single electron bunch, and wakefield superposition by a train consisting of four bunches is also demonstrated. Both the results agree well with theoretical predictions. 相似文献
39.
M. V. Sorokin R. M. Papaleo K. Schwartz 《Applied Physics A: Materials Science & Processing》2009,97(1):143-146
Creation of color centers in LiF under irradiation with 3–12-MeV Au ions was studied. Comparison of experimental data of color
center creation with computer simulation of the energy deposition and elastic atomic displacements reveals the role of elastic
collisions in defect creation by these ions, which have comparable magnitudes of electronic and elastic stopping. The experimentally
measured efficiency of color center creation and that predicted by the simulation of elastic displacements have a similar
dependence on the projectile energy. Thus, the color center creation is mainly associated with the elastic collisions, despite
the relatively large values of the electronic stopping power for these ions. 相似文献
40.
Short-laser-pulse-driven emission of energetic ions into a solid target from a surface layer spalled by a laser prepulse 总被引:1,自引:0,他引:1
A.G. Zhidkov L.V. Zhigilei A. Sasaki T. Tajima 《Applied Physics A: Materials Science & Processing》2001,73(6):741-747
An efficient emission of picosecond bunches of energetic protons and carbon ions from a thin layer spalled from a organic
solid by a laser prepulse is demonstrated numerically. We combine the molecular dynamics technique and multi-component collisional
particle-in-cell method with plasma ionization to simulate the laser spallation and ejection of a thin (∼20–30 nm) solid layer
from an organic target and its further interaction with an intense femtosecond laser pulse. In spite of its small thickness,
a layer produced by laser spallation efficiently absorbs ultrashort laser pulses with the generation of hot electrons that
convert their energy to ion energy. The efficiency of the conversion of the laser energy to ions can be as high as 20%, and
10% to MeV ions. A transient electrostatic field created between the layer and surface of the target is up to 10 GV/cm.
Received: 13 March 2001 / Accepted: 20 March 2001 / Published online: 20 June 2001 相似文献