On the resonant excitation of plasma oscillations with laser beams

A recent proposal for the resonant excitation of longitudinal plasma oscillations by transverse electromagnetic waves provides an application of non-secular perturbation techniques on the cold plasma equations. The amplitudes and frequencies of the oscillations so excited are calculable in terms of the amplitudes and frequencies of the transverse radiation and the plasma parameters. Some numerical examples are given.     

Radiation of a flow of oscillating electrons in the excitation of parametric oscillations

A study is made of phase modulation of an electron flow and the saturation of coherent radiation in such a flow after parametric excitation in a nonlinear system. Expressions are obtained for the intensity of the radiation of a charged particle and the coherent radiation in a resonator. The dependece of the intensity and frequency of the radiation on the amplitude and frequency of the external source are examined. Scientific Research Institute of Nuclear Physics at Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 103–106, October, 1997.     

Resonance parametric excitation of temperature oscillations in levitating aerosol droplets

The threshold conditions of excitation of temperature oscillations in high-Q water aerosol droplets have been studied under the conditions of slow evaporation. Selection rules have been obtained for interacting modes in a droplet. The threshold intensity of excitation of temperature oscillations has been analyzed in comparison with the threshold intensity of stimulated Brillouin and stimulated Raman scattering in a droplet. It is shown that, in the three-mode regime, the temperature oscillations can be excited at a rather low pumping level (about 10 W/cm²). A method is proposed for the remote measurement of the microphysical parameters of a droplet from the periodic temperature shift of eigenfrequencies of a droplet, the threshold intensity of excitation of temperature oscillations, and the thermal Raman frequency.     

Parametric excitation of Langmuir oscillations in a relativistic electron plasma

A systematic discussion is carried out of the parametric action of an external high-frequency field on a high-temperature plasma. The conditions for the onset of parametric resonance and the corresponding increments, as well as the frequency shift of the Langmuir oscillations under the action of a high-frequency field, are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 58–61, May, 1982.     

Magnetoacoustic resonance for nonlinear excitation in a cold plasma

In magnetoacoustic resonance, amplification of the exciting magnetic field B_z was studied in the region where B_z is not small compared with magnetostatic field B_o. Dependence on the mutual polarity of B_z, B₀ and on the exciting energy was found and excitation of higher harmonics was observed.     

On the parametric transparency of a magnetized plasma slab

This paper suggests a new mechanism for the nonlinear transparency of a dense magnetized plasma slab. It is shown that a significant part of the radiation can penetrate the slab due to parametric excitation of surface waves.     

On the excitation of density oscillations in nuclear matter

The possibility of the exciting small density oscillations in cold nuclear matter is investigated within the frame of the Landau theory, assuming F_l = 0 for l > 2. These excitations may propagate for F₀ ? 1 (K ? 576 MeV and are strongly damped for F₀ which does not fulfill this inequility.     

Modeling of particle motion in a betatron chamber during the excitation of parametric resonance by free radial oscillations

There is a dynamical modeling of the amplitudes and phases of free radial oscillations of electrons at parametric resonance. The solutions obtained are discussed and compared with the solutions found by other methods.Translated from Izvestiya Vysshikh Uchebnykh Zevedenii Fizika, Vol. 12, No. 4, pp. 39–43, April, 1969.     

Micromotion compensation in a surface electrode trap by parametric excitation of trapped ions

We report a surface electrode trap with a relatively large trap depth (0.6–1.0?eV). The trap electrodes are formed by gold plating an alumina substrate. Calcium ions are trapped approximately 400?μm above the trap surface. We demonstrate micromotion compensation based on parametric resonance for surface electrode traps. Unlike the conventional method based on radio-frequency (rf)–photon correlation in which the wave vector of the laser beam must have a component parallel to the micromotion to be detected, the proposed method is independent of the laser propagation direction. This enables the micromotion component normal to the electrode surface to be detected without increasing the scattered light.     

On the injection of a cold relativistic electron beam into a cold plasma

In a one-dimensional model the initial phase of the injection of a relativistic electron beam into a plasma is studied, both analytically and computationally. We find that in a time of a few beam plasma periods the beam obtains a “temperature” which is much higher than expected from the analytic treatment.     

Parametric excitation of relativistic plasma oscillations by strong electromagnetic waves

Parametric interaction of strong waves ($\text{?=}\text{eE}{}_{\mathrm{<mtext>o</mtext>}}\text{m}{}_{\mathrm{<mtext>e</mtext>}}\text{cω}{}_{\mathrm{<mtext>o</mtext>}}\text{～ 1}$) with a cold, two-fluid (ion and electron) plasma is studied in the limits of high frequency (ω_o?ω_Le) and resonance (ω_o ≈ ω_Le). Unstable oscillations of both electrons and ions are found in the resonance limit.     

Optical constants of lithium in the region of 2–3.8 eV determined by the excitation of surface plasma oscillations

Optical constants of lithium thin films, thickness about 500 Å, have been determined in the region of 2–3.8 eV by reflection versus angle of incidence measurements, involving the excitation of nonradiative surface plasmons in the film by a prism method.     

Dispersion relations of the surface plasma oscillations of multilayers

An equation for determining the dispersion relations of the surface plasma oscillations has been derived for the most general case of multilayers. The equation is given in a very simple form of the vanishing of the trace of a product of 2×2 matrices of recursive type.     

Optical-to-THz wave conversion via excitation of plasma oscillations in the tunneling-ionization process

A new ("linear-parametric") mechanism of a direct conversion of an ultrashort laser pulse into terahertz radiation is suggested. The conversion is due to the ionization-induced excitation and the subsequent electromagnetic emission of the superluminous polarization wave created by the axicon-focused laser pulse. For a few-cycle pulse with an optimum carrier-envelope phase, the considered mechanism is found to be much more effective than the alternative one based on the excitation of plasma oscillations in the laser wakefield by the ponderomotive force and able to provide THz radiation of the gigawatt power level with the use of moderate optical intensity (approximately 10(14)-10(15) W/cm2).     

Hysteresis phenomena of the parametric oscillations

Parametric amplifiers have been described which are based on the magnetoelastic interaction of the oscillation of a torsional pendulum and an electrical circuit. When the inverting amplifier is driven overcritically, selfexcitation of the pendulum occurs. Because of the nonlinear magnetoelastic damping, it may happen that the pendulum oscillates only in a certain range of amplitudes. Varying the intensity of the magnetic pumping field, hysteresis effects of the oscillation appear which can be explained by damping measurements. Oscillation measurements of other authors can now be understood.The author thanks Prof. Dr. G.Dietz for many valuable remarks to this paper and Prof. Dr. H.Happ in whose institute the experiments were performed.     

On parametric absorption in laser plasma

A theory for the nonlinear saturation of convective parametric instabilities in inhomogeneous plasmas is proposed. The role of parametric processes in laser light absorption in a dense plasma corona is discussed on the basis of this theory.