共查询到20条相似文献,搜索用时 15 毫秒
1.
Modulation instability of quasi-plane-wave optical beams in biased photorefractive-photovoltaic crystals 下载免费PDF全文
We investigate the modulation instability of quasi-plane-wave optical beams in biased photorefractive-photovoltaic crystals by globally treating the space-charge field. The modulation instability growth rate is obtained, which depends on the external bias field, on the bulk photovoltaic effect, and on the ratio of the optical beam's intensity to that of the dark irradiance. Our analysis indicates that this modulation instability growth rate is identical to the modulation instability growth rate studied previously in biased photorefractive-nonphotovoltaic crystals when the bulk photovoltaic effect is negligible for shorted circuits, and predicts the modulation instability growth rate in open- and closed-circuit photorefractive-photovoltaic crystals when the external bias field is absent. 相似文献
2.
The modulation instability of a broad electromagnetic beam in a biased two-photon photovoltaic photorefractive material, due to two-photon-photorefractive effect has been investigated. The one-dimensional modulation instability growth rate has been estimated under the linear stability framework. The behavior of the gain spectrum is different in low and high power regions. It has been predicted that, with the application of external electric field, it is possible to initiate and control growth of the instability in those media, where modulation instability was hitherto prohibited. The influence of different system parameters on the instability growth rate has been examined. 相似文献
3.
黄林 《核聚变与等离子体物理》1987,(1)
本文研究了离子束-等离子体系统的电磁不稳定性,考虑了离子-电子和离子-离子碰撞对维泊耳(Weibel)型电磁不稳定性增长率的影响。结果表明,在离子束-等离子体系统中可以激发维泊耳型电磁不稳定性,离子和电子之间的碰撞将使这类不稳定性的增长率增加。 相似文献
4.
Fatemeh Khodadadi Azadboni 《等离子体物理论文集》2021,61(3):e202000135
The presence of Weibel instability in laser-irradiated fuel could be detrimental to the process of ablative implosion, which is necessary for achieving thermonuclear fusion reactions. In this paper, the effect of the Coulomb collisional within the turbulent plasma on the Weibel instability growth rate has been investigated for linear and circular polarization. The results indicate that the Weibel instability growth rate at circular polarization near the ignition centre of the fuel fusion (collisional plasma) is about 105 times higher than the collisional Weibel instability growth rate at linear polarization. The Weibel instability growth rate is observed near the critical density of the fuel fusion (collisionless plasma) at linear polarization and enhancement near the foot of the heat in front of the fuel fusion. By increasing the steps of the density gradient plasma in the low-density corona, electromagnetic instability occurs at a higher stress flow. Therefore, the deposition condition of electron beam energy in circular polarization of turbulent plasma can be shifted to the fuel core for suitable ignition. 相似文献
5.
Rikanati A Sadot O Ben-Dor G Shvarts D Kuribayashi T Takayama K 《Physical review letters》2006,96(17):174503
Theoretical and experimental research, on the previously unresolved instability occurring along the slip stream of a shock-wave Mach reflection, is presented. Growth rates of the large-scale Kelvin-Helmholtz shear flow instability are used to model the evolution of the slip-stream instability in ideal gas, thus indicating secondary small-scale growth of the Kelvin-Helmholtz instability as the cause for the slip-stream thickening. The model is validated through experiments measuring the instability growth rates for a range of Mach numbers and reflection wedge angles. Good agreement is found for Reynolds numbers of Re 2 x 10(4). This work demonstrates, for the first time, the use of large-scale models of the Kelvin-Helmholtz instability in modeling secondary turbulent mixing in hydrodynamic flows, a methodology which could be further implemented in many important secondary mixing processes. 相似文献
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J. Myslive
ek C. Schelling F. Schffler G. Springholz P.
milauer J. Krug B. Voigtlnder 《Surface science》2002,520(3):193-206
A scanning tunneling microscopy/atomic force microscopy study is presented of a kinetically driven growth instability, which leads to the formation of ripples during Si homoepitaxy on slightly vicinal Si(0 0 1) surfaces miscut in [1 1 0] direction. The instability is identified as step bunching, that occurs under step-flow growth conditions and vanishes both during low-temperature island growth and at high temperatures. We demonstrate, that the growth instability with the same characteristics is observed in two dimensional kinetic Monte Carlo simulation with included Si(0 0 1)-like diffusion anisotropy. The instability is mainly caused by the interplay between diffusion anisotropy and the attachment/detachment kinetics at the different step types on Si(0 0 1) surface. This new instability mechanism does not require any additional step edge barriers to diffusion of adatoms. In addition, the evolution of ripple height and periodicity was analyzed experimentally as a function of layer thickness. A lateral “ripple-zipper” mechanism is proposed for the coarsening of the ripples. 相似文献
8.
We investigate the spatial modulation instability in colloidal suspension based on the nonlinear Schrödinger equation. By a standard linear stability analysis, we obtain the expression for instability gain and identified the relationship between the measurable instability characteristic parameters and the particle radius, the optical beam width. It is shown that the modulation growth rate, the maximum growth rate, cut-off frequency and the fastest growth frequency increase as the particle radius decreases and (or) the beam width increases if the optical intensity is constant. Moreover, the ultimate values of the cut-off frequency and the fastest growth frequency are proportional to the beam width, while are independent of the sphere radius. The results provide a new approach to measure the sphere radius and to control the characteristic parameters of modulation instability through the beam width. 相似文献
9.
We study the step bunching kinetic instability in a growing crystal surface characterized by anisotropic diffusion. The instability is due to the interplay between the elastic interactions and the alternation of step parameters. This instability is predicted to occur on a vicinal semiconductor surface Si(001) or Ge(001) during epitaxial growth. The maximal growth rate of the step bunching increases like F4, where F is the deposition flux. Our results are complemented with numerical simulations which reveal a coarsening behavior in the long time evolution for the nonlinear step dynamics. 相似文献
10.
Tatsuhiro Sakaiya Hidenori Terasaki Kosaku Akimoto Hiroki Kato Taichi Ueda Ryota Hosogi 《高压研究》2019,39(1):150-159
The Rayleigh–Taylor (RT) instability of liquid iron alloys is important for understanding the core formation mechanism in the Earth. Here we first report the measurement of RT instability growth for a liquid iron–silicon (Fe–Si) alloy, which is one of the major candidate for the material of the Earth’s core, using a high power laser. We optimized the measurement setup and analytical technique to observe the growth of perturbation on an Fe–Si sample surface. The growth of perturbation amplitude on the Fe–Si alloy under high pressure and temperature was successfully observed using in situ X-ray radiography. The growth rate of the RT instability for the Fe–Si alloy on about 1000?GPa was estimated to be 0.3 ns?1. 相似文献
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《中国物理 B》2020,(5)
Biological growth is a common phenomenon in nature, and some organisms such as DNA molecules and bacterial filaments grow in viscous media. The growth induced instability of morphoelastic rod in a viscous medium is studied in this paper. Based on the Kirchhoff kinetic analogy method, the mechanical model for growing elastic thin rod in the viscous medium is established. A perturbation analysis is used to analyze the stability of the growing elastic rod in the viscous medium. We apply the results into planar growing ring and get its criterion of instability. Take the criterion into DNA ring to discuss the influence of viscous resistance on its instability. 相似文献
13.
采用洛伦兹变换推导出左旋椭圆偏振强激光在磁化等离子体中的非线性色散关系,根据Karpman方法推导出激光场包络的非线性控制方程,分析了在磁化等离子体中左旋椭圆偏振激光的调制不稳定性,得到了调制不稳定的时间增长率。分析结果表明,磁化等离子体中自调制不稳定的极大增长率较非磁化情况明显减小,且在激光等离子体临界面附近处调制不稳定性的时间增长率显著增大。 相似文献
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采用洛伦兹变换推导出左旋椭圆偏振强激光在磁化等离子体中的非线性色散关系,根据Karpman方法推导出激光场包络的非线性控制方程,分析了在磁化等离子体中左旋椭圆偏振激光的调制不稳定性,得到了调制不稳定的时间增长率。分析结果表明,磁化等离子体中自调制不稳定的极大增长率较非磁化情况明显减小,且在激光等离子体临界面附近处调制不稳定性的时间增长率显著增大。 相似文献
15.
Based on helium atom beam diffraction and scanning tunneling microscopy data, the coexistence of a meandering and a bunching instability during homoepitaxial step flow growth is established in a class of nonreconstructed, metallic vicinal surfaces, Cu (1,1,n), n=5,9,17. Specifically, the meandering instability is shown to act as a precursor to the bunching instability, indicating that a one-dimensional treatment of bunching in step flow growth is not sufficient. Our findings might be generic to step flow growth in kinetically restricted systems. 相似文献
16.
《中国物理 B》2017,(7)
In this paper, the characteristics of magneto-Rayleigh-Taylor(MRT) instability of liner plasmas in Mag LIF is theoretically investigated. A three-region slab model, based on ideal MHD equations, is used to derive the dispersion relation of MRT instability. The effect of compressibility on the development of MRT instability is specially examined. It is shown that the growth rate of MRT instability in compressible condition is generally lower than that in incompressible condition in the presence of magnetic field. In the case of zero magnetic field, the growth rate in compressible assumption is approximately the same as that in incompressible assumption. Generally, MRT instability in(x, y) plane can be remarkably mitigated due to the presence of magnetic field especially for short-wavelength perturbations. Perturbations may be nearly completely mitigated when the magnetic field is increased to over 1000 T during liner implosions. The feedthrough of MRT instability in liner outer surface on inner surface is also discussed. 相似文献
17.
The filamentation instability of a current‐carrying plasma under the diffusion condition is investigated taking into account the Bohm potential and the Fermi electron pressure. Using quantum hydrodynamic equations, the dispersion relation and growth rate of the instability is obtained. It is found that the filamentation instability, in the presence of quantum effects, depends on various characteristic parameters such as: electron Fermi velocity, plasma number density, ion thermal velocity and electron drift velocity. Moreover, the wavelength region in which the instability occurs is more restricted and the minimum size of filaments is larger, in comparison with the classical case. It is also found that the growth rate of the instability is smaller in the presence of quantum effects. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Ajit Kumar Dubey 《Proceedings of the Combustion Institute》2019,37(2):1869-1877
Experiments and theoretical analysis are presented to clarify the effect of geometrical parameters on thermo-acoustic instability of downward propagating flames in tubes. The experiments reveal that the longer tubes have higher instability compared to shorter tubes and the lower diameter tubes have higher instability compared to higher diameter tubes. The secondary instability leading to turbulent burning is found to be more sensitive to change in geometrical parameters compared to primary instability (oscillating flat flame). The secondary instability is re-stabilized for some intermediate burning velocity conditions even though lower and higher burning velocity conditions show secondary instability. The appearance of such re-stabilization is only observed for some specific lengths of the tube. Present experimental observations pertaining to the effect of geometrical parameters is found to be contradicting the theoretical predictions based on pressure coupling mechanism. To clear the underlying mechanism, analytical growth rate is computed considering velocity coupling mechanism. The computed growth rates correctly predict the effect of geometrical parameters on thermo-acoustic instability of downward propagating flames. This work provides further evidence to believe that the flame -acoustic coupling in downward propagating flames is due to flame area modulation (leading to heat release modulation) through action of acoustic acceleration. 相似文献
20.
Differential growth in elastic materials can produce stress either through incompatibility of growth or by interaction with the surrounding medium. In many situations, this stress can be sufficient to induce shape instability in the growing medium. To gain better insight in growth-induced instabilities, the growth of an elastic shell loaded with hydrostatic pressure or embedded in an elastic medium is studied. The residual stress arising from the incompatibility of growth and the contact stress arising from the interaction with the surrounding medium are computed with respect to growth and geometric parameters and critical values for instability are obtained. Depending on these parameters, different modes of instability can be obtained. 相似文献