- 标题
- 摘要
- 关键词
- 实验方案
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Relativistic Self Focusing and Frequency Shift of super-Gaussian Laser Beam in Plasma
摘要： Relativistic self focusing and frequency shift of laser beam having super-Gaussian profile in space and Gaussian profile in time is studied in a plasma. The relativistic mass nonlinearity is found to cause time dependent self focusing of the laser pulse and the saturation effect of nonlinearity avoids point focusing of the beam. For ultrashort laser pulse, the front of the pulse undergoes frequency down shift while that of the tail undergoes up shift. Frequency shift increases and self focusing becomes stronger for higher intensity of the laser. The self focusing is also stronger for the laser beam carrying larger wavelength.
关键词： Beam width parameter,Self focusing,Frequency shift,super-Gaussian laser,Moment Theory,Relativistic nonlinearity
更新于2025-09-23 15:21:01
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Quantum Particle Swarm Optimization for Synthesis of Non-uniformly Spaced Linear Arrays with Broadband Frequency Invariant Pattern
摘要： This paper describes a method using Quantum Particle Swarm Optimization to obtain a broadband frequency invariant pattern for synthesis of nonuniformly spaced linear array of isotropic antennas. Two cases related to this work using QPSO have been studied, namely, in the first case, the generated frequency invariant far-field pattern is broadside in the vertical plane and in the second case, the far-field frequency invariant pattern is scanned in a particular direction. An effort is made such that the side lobe level and first null beam widths of the patterns are made similar to their related desired values. The two cases are presented in this paper to show the effectiveness of the proposed method in achieving the desired specifications. Even though, the developed method is utilized here for a linear array of isotropic antennas; it can be extended to other type of arrays. The performance of this algorithm is validated by duly comparing it with firefly algorithm.
关键词： firefly algorithm,quantum particle swarm optimization,frequency invariant pattern,side lobe level,first null beam width,Broadband array
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - A Circularly Polarized Antenna Element Based on Open-ended Waveguide
摘要： Based on the open-ended rectangular waveguide structure, we proposed a circularly polarized antenna element with wide axial-ratio (AR) beam-width in this communication. Two rectangular notches are distributed on the wide sides of a rectangular waveguide in a 180° rotational symmetry to excite circular polarization. The simulated RHCP gain of the antenna is about 3.2 dBic at 11.5 GHz and the 3-dB AR beam-width is more than 120°. In addition, Owing to its simple configuration, the compact size (12(cid:2)(cid:2)6 mm2), this antenna element lays a good foundation for circularly polarized array antennas in wireless communication applications.
关键词： Circular polarization,End-fire antennas,Waveguide antennas,Wide beam-width
更新于2025-09-23 15:19:57
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Role of magnetic field on self focusing of super-Gaussian laser beam under relativistic effect
摘要： Considering an external magnetic field along the direction of propagation of laser, the self focusing of a super-Gaussian laser beam is studied when it propagates through the plasma at relativistic intensities. We consider the cyclotron motion of the electrons and use the tensor form of the plasma dielectric constant obtained based on the direction of the external magnetic field. For completeness, relativistic mass effect is incorporated in both the plasma frequency and electron cyclotron frequency. Using appropriate conditions, an equation for the beam width parameter is derived and solved. The equilibrium beam radius for a self trapped laser beam is also derived. Self focusing is better when cyclotron effects are taken into account. At higher intensity and higher spot size of the laser beam, self focusing becomes better.
关键词： Super-Gaussian laser,Moment theory,Beam width parameter,Self focusing,Relativistic nonlinearity
更新于2025-09-23 15:19:57
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Electron Cyclotron interaction in the early stage of EC-assisted plasma breakdown
摘要： Electron Cyclotron (EC) wave interaction with very low temperature electrons in conditions like those occurring for EC-assisted plasma breakdown is investigated via the Hamiltonian adiabatic formalism. Estimates of interest for applications to present tokamak experiments are derived. The analysis allows ultimately to derive analytically the particle energy gain per single beam crossing and to characterize the dependency of the maximum possible energy variation as a function of the wave frequency, harmonics and polarization and EC power and beam width. The investigation confirms that electrons can easily gain energies well above the ionization energy in most conditions, as observed in experiments.
关键词： tokamak experiments,beam width,Hamiltonian adiabatic formalism,harmonics,polarization,Electron Cyclotron,wave frequency,EC power,plasma breakdown
更新于2025-09-10 09:29:36