Nonlinear diffraction in a quantum-dot system with allowance for the Hubbard interaction

The propagation of monochromatic laser radiation in a volume system of quantum dots (QDs) that are tunnel-coupled along one axis is considered. The electron energy spectrum of the QD system is modeled in the tight-binding approximation with allowance for the Coulomb interaction of electrons in the Hubbard model. The electromagnetic field of laser radiation in a QD system is described quasi-classically by Maxwell equations; as applied to this problem, they are reduced to a non-one-dimensional wave equation for the vector potential. As a result of the analysis of the wave equation in the approximation of varying amplitudes and phases, an effective equation describing the electromagnetic field in a QD system is obtained and numerically solved. The influence of the parameters of the system and the amplitude and frequency of the field of incident laser radiation on the character of its propagation is investigated. Nonmonotonic dependences of the factor characterizing the laser beam diffraction spread on the parameters of the electron energy spectrum of the system are obtained.     

Physical mechanisms for transition radiation of electromagnetic pulses

The excitation of electromagnetic pulses is examined in various generation schemes. The physical mechanism for excitation of the radiation is studied and the field from transition radiation by high current relativistic electron beams is analyzed. An analysis of the efficiency of the various generation schemes shows that the electron efficiency of beam radiators based on transition radiation may be quite substantial for beam parameters that are easily realized experimentally. Zh. Tekh. Fiz. 69, 90–95 (October 1999)     

电子在激光驻波场中运动产生的太赫兹及X射线辐射研究

采用单电子模型和经典辐射理论分别对低能和高能电子在线偏振激光驻波场中的运动和辐射过程进行了研究. 结果表明: 垂直于激光电场方向入射的低速电子在激光驻波场中随着光强的增大, 逐渐从一维近周期运动演变为二维折叠运动, 并产生强的微米量级波长的太赫兹辐射; 高能电子垂直或者平行于激光电场方向入射到激光驻波场中, 都会产生波长在几个纳米的高频辐射; 低能电子与激光驻波场作用中, 激光强度影响着电子的运动形式、辐射频率以及辐射强度; 高能电子入射时, 激光强度影响了电子高频辐射的强度, 电子初始能量影响着辐射的频率; 电子能量越高, 产生的辐射频率越大. 研究表明可以由激光加速电子的方式得到不同能量的电子束, 并利用电子束在激光驻波场的辐射使之成为太赫兹和X射线波段的小型辐射源. 研究结果可以为实验研究和利用激光驻波场中的电子辐射提供依据.     

Nonstationary 2D models of the electron-wave interaction

A 2D nonstationary model of induced emission of ribbon-shaped electron beams and clusters in free space is developed in the quasi-optical approximation. On the basis of this model, the problem of enhancement of a short electromagnetic pulse propagating along a quasi-stationary ribbon electron flow, the theory of a BWT-type oscillator with radiation channeling by an electron beam, and the process of collective acceleration of a short electron cluster in the field of an intense cocurrent wave are considered.     

The Electromagnetic Sector of the Evans Field Theory

The equations of the electromagnetic sector of the Evans field theory are given in terms of differential geometry and are based on the well-known structure relations and Bianchi identities. The equations thus complete Einstein’s basic axiom, that physics is derived from geometry, and extend the axiom to electrodynamics. Precise tests are suggested for the theory using the interaction of circularly polarized electromagnetic radiation with a non-relativistic electron beam. These tests include; the inverse Faraday effect (IFE), radiatively induced fermion resonance (RFR), and the electromagnetic Aharonov-Bohm (EMAB) effect.     

W波段同轴静磁波荡器自由电子激光优化设计

基于同轴静磁波荡器的自由电子激光主要利用环形电子束与同轴TE模式的相互作用产生电磁辐射,是一种重要的毫米波辐射源。分析了同轴结构作用区内外半径、工作模式、电子束电压、波荡器周期等参数对辐射频率的影响规律,研究了电子束平均半径的选取原则和束波互作用腔的设计方法,设计了辐射频率在W波段的基于同轴静磁波荡器的自由电子激光,并进行了粒子模拟,在电子束电压为720 kV,电子束流为1 kA的情况下,获得了频率107 GHz、辐射功率35 MW的TE01模,束波转换效率为4.9%,束波作用腔总长度小于200 mm,同轴静磁波荡器的磁场幅度0.34 T。     

To the theory of a free-electron laser

The interaction of an electron beam, moving inside a magnetic lattice, with an electromagnetic wave is considered. It is shown that under certain conditions generation (amplification) of coherent electromagnetic radiation occurs. The gain is calculated.     

The effects of the guide field and tapered wiggler in free-electron laser

The interaction between electromagnetic field and electron beam was investigated numerically in a free-electron laser, using a new simulation code which consist of the three-dimensional electron motion, amplitude and phase of emitted radiation. The maintenance of the quality and stability of electron beam and the resonance condition through the wiggler is important to obtain the high gain and the high efficiency. But the electron orbits diverge and become unstable, and the resonance condition is not preserved because of the three-dimensional effects on the off-axis electron and the conversion of electron energy to electromagnetic field. To prevent those defects and improve the efficiency compared with the conventional case, we used the new methods such as the axial-guide field and tapered wiggler.     

未磁化等离子体介质切连科夫脉塞的线性理论

利用线性自洽场理论，讨论了电子在扰动场作用下的三维扰动．在此基础上，对常用的薄环形相对论电子环束在填充未磁化等离子体的介质筒慢波波导中激励的切连科夫辐射进行了详细的分析，导出了此电子环束与慢波系统中任意波导模互作用的色散方程和波增长率，并对其进行了详细的分析和讨论．分析表明切连科夫辐射是由其波导模与电子注模耦合所致．最后详细计算和分析了等离子体密度对色散特性和波增长率的影响 关键词：     

Side-effects of the space charge field introduced by a hollow electron beam in the electron cooler of CSRm

An electron cooler is used to improve the quality of the ion beam in a synchrotron;however it also introduces a nonlinear electromagnetic field to the accelerator,which causes tune shift,tune spread and may drive resonances leading to ion beam loss.In this paper the tune shift and the tune spread caused by the nonlinear electromagnetic field of a hollow electron beam is investigated,and the resonance driving terms of the nonlinear electromagnetic field are analysed.The differences are presented compared with a solid electron beam.Calculations are performed for ~(238)U~(32+) ion of energy 1.272 MeV stored in the main Cooler Storage Ring(CSRm) at the Institute of Modern Physics,Lanzhou.It is found that in this situation the nonlinear field caused by the hollow electron beam does not lead to serious resonances.     

Non-relativistic quantum theory of stimulated Cherenkov radiation and Compton scattering in plasma

The stimulated processes in electron plasma, i.e., Cherenkov radiation by a nonrelativistic electron beam of longitudinal oscillations and Compton scattering of a transverse electromagnetic wave in plasma with quantum mode excitation (de Broglie wave), are considered in the three-wave approximation. The possibility of the occurrence of quantum oscillations is discussed.     

On the possibility to realize the efficient relativistic Čerenkov microwave generator without an external guiding magnetic field

We consider the preconditions for efficient operation of the relativistic Čerenkov microwave generator in the absence of an external guiding magnetic field. The analytical expression for the length of propagation of a solid cylindrical electron beam along the drift tube is obtained in the framework of the paraxial approximation. The influence of preliminary modulation of the electron beam on the starting current of the generator and its linear efficiency is analyzed. We calculated the geometry of a relativistic Čerenkov microwave generator with an efficiency of about 30%, in which the solid cylindrical electron beam propagates over a short resonance decelerating system (with the length L ≈ 3λ, where λ is the radiation wavelength) in the absence of an external magnetic field. In experiments, the efficiency of power conversion from the high-current electron beam into the electromagnetic radiation of the E₀₁ mode reached 8%, approximately (relative to the total current of the vacuum diode), for a power of 1.2 ± 0.3 GW and a generation frequency of 4.06 GHz. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 829–836, October 2006.     

Chaotic electron trajectories in electromagnetic wiggler free-electron laser with a guide magnetic field

Summary The Hamiltonian for an electron travelling through a large-amplitude backward electromagnetic wave, an axial guide magnetic field and radiation field is formulated. Poincaré surface-of-section plots show that this Hamiltonian is non-integrable, and leads to chaotic trajectories. Equilibrium conditions are derived in the limit where the radiation field approaches zero. Compared to conventional FEL, the total energy of the system at pondermotive resonanceE _c is large, while the electron's critical energy γ_c is low for electromagnetic wiggler FEL. Moreover, the threshold wave amplitude (A _r=A _c) of beam chaoticity is found at lower values of the radiation field amplitude compared to magnetostatic wiggler FEL. Previous features confirmed that electromagnetic wiggler FEL can operate more coherently and more efficiently at moderated particle's energy compared to magnetostatic wiggler FEL.     

Beam instabilities in the collective Cherenkov effect and anomalous Doppler effect in a spatially bounded system near the nontransparency band

Beam instabilities of the type of the collective induced Cherenkov effect and the anomalous Doppler effect, which develop in a longitudinally bounded electrodynamic system near its nontransparency band (i.e., when the electromagnetic wave excited by the beam has zero group velocity), are considered. The dispersion equation is derived, which defines the instability increments taking into account the emission of radiation from the electrodynamic system. The solutions to the dispersion equation are analyzed for various parameters of the electron beam and of the electrodynamic system.     

Superluminal spectral densities of ultra-relativistic electrons in intense electromagnetic wave fields

Superluminal radiation from electrons accelerated in electromagnetic waves is investigated. The radiation field is a Proca field with negative mass-square, minimally coupled to the electron current. The spectrum is continuous in the ultra-relativistic regime, where steepest-descent asymptotics can be used to evaluate the power coefficients. The time averaging of Lissajous orbits in polarized wave fields is discussed, and the tachyonic spectral densities of electrons orbiting in intense laser beams are derived. In the ultra-relativistic limit, realized by high injection energy or high field intensity, the spectral functions are evaluated in closed form in terms of Airy integrals. In contrast to electromagnetic radiation, there is a longitudinal polarization component, and oscillations emerge at high beam intensity in the longitudinal and transversal spectral slopes, generated by the negative mass-square of the tachyonic quanta. The thermal ultra-relativistic electron plasma of two active galactic nuclei is analyzed in this regard, based on TeV spectral maps obtained with imaging air Cherenkov detectors. Specifically, tachyonic cascade fits are performed to γ-ray flares of the TeV blazars RGB J0152+017 and 3C 66A, and the transversal and longitudinal radiation components are disentangled in the spectral maps. The curvature of the spectral slopes is shown to be intrinsic, caused by the Boltzmann factor of the electronic source plasma radiating the tachyonic cascades.     

Calculation of the characteristics of the radiation from a generator with a virtual cathode

A three-dimensional computer model, described by a system of Maxwell-Vlasov equations, for the interaction of a plasma with the electromagnetic field was used to calculate the excitation of a field by a relativistic electron beam with a virtual cathode oscillating in a resonance chamber. The characteristics of the generator radiation are investigated. Zh. Tekh. Fiz. 69, 87–92 (February 1999)     

The Electromagnetic Sector of the Evans Field Theory

No Heading The equations of the electromagnetic sector of the Evans field theory are given in terms of differential geometry and are based on the well-known structure relations and Bianchi identities. The equations thus complete Einsteins basic axiom, that physics is derived from geometry, and extend the axiom to electrodynamics. Precise tests are suggested for the theory using the interaction of circularly polarized electromagnetic radiation with a non-relativistic electron beam. These tests include; the inverse Faraday effect (IFE), radiatively induced fermion resonance (RFR), and the electromagnetic Aharonov-Bohm (EMAB) effect.     

Electromagnetic radiation of quantum systems under conditions of Lorentz-invariance and <Emphasis Type="Italic">CPT</Emphasis> violation

Solutions to the Dirac equation for an electron moving in a central electrostatic and a constant uniform magnetic field are considered within extended electrodynamics (in the presence of Lorentz-invariance violation of the minimal CPT-odd form). On the basis of these solutions, the features of electromagnetic radiation from a hydrogen-like atom and the features of electron synchrotron radiation are calculated, and possible observable effects caused by the assumed Lorentz-invariance violation are described.     

On the diffraction of ultrashort pulses

The diffraction of ultrashort pulses of electromagnetic radiation is considered in terms of the model of an initial Gaussian time pulse and a Gaussian beam. A criterion for the short pulse duration and the average pulse wavelength are introduced, and the diffraction length and angular divergence of radiation are estimated. Along with the general expression for a field, simple expressions for the case of the far zone are derived. The results obtained are compared with the simplified delta pulse model.