Analysis of the elastic wave excitation in solid plates by phase velocity scanning of a laser beam

1991 ◽  
Vol 59 (19) ◽  
pp. 2384-2385 ◽  
Author(s):  
Yusuke Tsukahara
Keyword(s):  
Laser Beam ◽  
Phase Velocity ◽  
Elastic Wave ◽  
Wave Excitation

Effect of relativistic self-focusing on plasma wave excitation by a hollow Gaussian beam

2011 ◽  
Vol 77 (6) ◽  
pp. 777-784 ◽  
Author(s):  
RUCHIKA GUPTA ◽  
M. RAFAT ◽  
R. P. SHARMA
Keyword(s):  
Laser Beam ◽  
Gaussian Beam ◽  
Plasma Wave ◽  
Radial Distance ◽  
Laser Frequency ◽  
Pump Laser ◽  
Wave Excitation ◽  
Paraxial Ray Approximation ◽  
Self Focusing ◽  
Paraxial Ray

AbstractA paraxial-like approach has been invoked to understand the nature of propagation of a hollow Gaussian beam (HGB) propagating in plasma under the influence of relativistic non-linearity. In this approach, the parameters are expanded in terms of the radial distance from the maximum of irradiance rather than that from the axis. This paper investigates the excitation of plasma wave in a hot collision less plasma by HGB. On account of the × force, a plasma wave at 2ω0 (here, ω0 is the pump laser frequency) is generated. The solution of the HGB has been obtained within the paraxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic non-linearity.

The Curved Plate Flaw's Location and Direction Detecting Based on the Transducer Array

2013 ◽  
Vol 389 ◽  
pp. 223-230
Author(s):  
Xi Peng Li ◽  
Chun Guang Xu ◽  
Zhao Liu ◽  
Han Hui Xu
Keyword(s):  
Phase Velocity ◽  
Elastic Wave ◽  
Wave Equations ◽  
Velocity Dispersion ◽  
Imaging Method ◽  
Finite Element Software ◽  
Phase Velocity Dispersion ◽  
Elastic Wave Equations ◽  
The Relationship ◽  
Detecting Method

The curved structural plate components have been widely used in petroleum, natural gas, chemical industry, and other industries fields, monitoring and detecting the curved structural plate components flaw has a great significance for improving the components integrity, reliability and lifespan in service. Based on the elastic wave fundamental theory, elastic wave equations, and phase velocity dispersion characteristic curves in curved plate component, the article gives the phase velocity practical detecting method. By using thecomsolfinite element software, the author proposed a wave propagating forward modeling analytical method, which gives a guidance to study the relationship between the wave and the flaw. By adopting the ellipse algorithm, the article proposed a positioning and imaging method which was used to locate the flaws position and distinguish the flaws direction. Based on the theoretical and technical analysis above, a number of experiments has been done, and the results shows that the detecting and imaging method can locate and image the flaws position and its geometrical morphology precisely for the curved plates flaw detecting.

Modeling of frequency-domain elastic-wave equation with an average-derivative optimal method

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. T339-T356 ◽  
Author(s):  
Jing-Bo Chen ◽  
Jian Cao
Keyword(s):  
Wave Equation ◽  
Phase Velocity ◽  
Elastic Wave ◽  
Frequency Domain ◽  
S Wave ◽  
Elastic Wave Equation ◽  
Classical Scheme ◽  
Wave Phase Velocity ◽  
Grid Points ◽  
Average Derivative

Based on an average-derivative method, we developed a new nine-point numerical scheme for a frequency-domain elastic-wave equation. Compared with the classic nine-point scheme, this scheme reduces the required number of grid points per wavelength for equal and unequal directional spacings. The reduction in the number of grid points increases as the Poisson’s ratio becomes larger. In particular, as the Poisson’s ratio reaches 0.5, the numerical S-wave phase velocity of this new scheme becomes zero, whereas the classical scheme produces spurious numerical S-wave phase velocity. Numerical examples demonstrate that this new scheme produces more accurate results than the classical scheme at approximately the same computational cost.

Relativistic cross-focusing of two coaxial Gaussian laser beams in a plasma

1998 ◽  
Vol 60 (4) ◽  
pp. 811-818 ◽  
Author(s):  
RAJ KUMAR ◽  
H. D. PANDEY ◽  
R. P. SHARMA ◽  
M. KUMAR
Keyword(s):  
Laser Beam ◽  
Relativistic Effect ◽  
Laser Pulses ◽  
The Self ◽  
Laser Beams ◽  
Particle Accelerators ◽  
Wave Excitation ◽  
Homogeneous Plasma ◽  
Self Focusing ◽  
Ponderomotive Nonlinearity

The paper presents a paraxial theory of the relativistic cross-focusing of two coaxial Gaussian laser beams of different frequencies in a homogeneous plasma. We discuss the self-focusing of a weaker laser beam in the plasma due to the optical inhomogeneities introduced by another stronger copropagating laser beam. In the presence of the second stronger beam (Pcr21<P2<Pcr22), the plasma behaves as an oscillatory waveguide for the first, weaker, beam (P1<Pcr11) as it propagates in the plasma. When both the beams are strong (Pcr11,21<P1,2<Pcr12,22), the nonlinearities introduced by the relativistic effect are additive in nature, such that one beam can undergo oscillatory self-focusing and the other simultaneously defocusing, and vice versa. A comparison reveals that cross-focusing due to relativistic nonlinearity is possible for a wider range of powers of the laser pulses than is cross-focusing due to ponderomotive nonlinearity. Relativistic cross-focusing is important in plasma beat-wave excitation and collective laser particle accelerators.

scholarly journals Elastic wave excitation in a layer by piezoceramic patch actuators

2006 ◽  
Vol 52 (4) ◽  
pp. 398-407 ◽  
Author(s):  
E. V. Glushkov ◽  
N. V. Glushkova ◽  
W. Seemann ◽  
O. V. Kvasha
Keyword(s):  
Elastic Wave ◽  
Wave Excitation

scholarly journals Beat wave excitation of electron plasma wave by coaxial cosh-Gaussian laser beams in collisional plasma

2015 ◽  
Vol 33 (4) ◽  
pp. 621-632 ◽  
Author(s):  
Arvinder Singh ◽  
Naveen Gupta
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Electron Plasma ◽  
Spot Size ◽  
Collisional Plasma ◽  
Laser Beams ◽  
Theory Approach ◽  
Wave Excitation ◽  
Plasma Parameters ◽  
Electron Plasma Wave

AbstractThis paper presents a scheme for beat wave excitation of an electron plasma wave (EPW) by cross-focusing of two intense cosh-Gaussian (ChG) laser beams in an under dense collisional plasma. The plasma wave is generated on account of beating of two ChG laser beams of frequencies ω1 and ω2. Starting from Maxwell's equations, coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived by using Moment theory approach in Wentzel–Kramers–Brillouin approximation. The collisional nonlinearity depends not only on the intensity of first laser beam, but also on that of second laser beam. Therefore, dynamics of first laser beam affects that of other and hence cross-focusing of the two laser beams takes place. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW. It has been found that decentered parameters of the two laser beams have significant effect on power of EPW.

Selective excitation of single‐mode acoustic waves by phase velocity scanning of a laser beam

1991 ◽  
Vol 58 (15) ◽  
pp. 1591-1593 ◽  
Author(s):  
Kazushi Yamanaka ◽  
Yoshihiko Nagata ◽  
Toshio Koda
Keyword(s):  
Laser Beam ◽  
Phase Velocity ◽  
Acoustic Waves ◽  
Single Mode ◽  
Selective Excitation
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