Plasma radiation emitted by dense mixtures of rare gases excited by an electron beam and by a discharge

An experimental investigation was made of the radiation emitted from a plasma formed by rare gases (He, Ne, Ar, Kr, Xe) excited by a beam of electrons with different parameters and by discharge pulses (P= 0.1–0.5 atm, I=1 kA, U=10–15 kV, C=0.25 F). An investigation was made of the spectral composition and time characteristics of the radiation, and of their dependences on the excitation conditions. New molecular bands were observed in the near-ultraviolet and visible ranges. The uniquely large widths of these bands could be of interest in the amplification of light in a wide spectral range.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 56–73, January, 1992.     

Two-conductor strips with drift tubes excited by an electron beam in an ion accelerator

Excitation by a heavy-current electron beam in an ion accelerator is studied for a two-conductor strip with drift tubes whose supports on one bar are displaced at half the distance between the supports of another bar. The relations obtained on the basis of harmonic analysis and the equations from TWT theory indicate the potential of constructing such a system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 24–29, June 1986.     

100 MW, 248.4 nm,KrF laser excited by an electron beam

Laser oscillations have been observed at 248.4 nm from excited KrF molecules. The excited KrF molecules were produced by injecting an intense electron beam into mixtures of Ar, Kr and F₂. A peak power of 1.15 × 10⁸ W with a total energy of 5.6 J has been observed. Up to 3% of the deposited e-beam energy was converted to laser-energy.     

Nonuniform distribution of absorbed energy in high-resistance materials excited by an electron beam

Experimental results are presented on the changes in the optical characteristics of lithium fluoride induced by an electron beam with time-varying density and pulse energies close to the threshold for destruction of the material. The spatial distribution of color centers is investigated, especially near breakdown channels. Mechanisms for nonuniform accumulation of defects are discussed, along with the fundamental causes of the inhomogeneous energy distributions induced by the high-current electron beam. Concrete results of calculations of the field intensity distribution in LiF crystals during irradiation are presented, based on models of “uniform” and nonuniform charging of the sample. An abrupt increase in the electric field intensity is predicted near the breakdown channel. Zh. Tekh. Fiz. 68, 53–59 (April 1998)     

Parametric instabilities produced by a relativistic electron beam in a plasma

The parametric instability driven by the primary spectrum of the hydrodynamic two-stream instability produced by a relativistic electron beam in a plasma is investigated. The saturated level of the primary wave electric field is determined by electron trapping in the potential well of the wave or by the quasilinear beam relaxation process. After saturation, the primary wave collapses by way of the oscillating two-stream instability. The cases of the strong and weak primary electric field in comparison with the thermal energy of a plasma are considered. For a strong field the growth rates of the parametric instability and plasma heating due to the latter are found. Ion heating is not significant in comparison with electron heating (approximately as the cube root of the mass ratio). In a weak field the parametric oscillating two-stream spectrum of saturation is found. In the one-dimensional case this spectrum of electric field energy fluctuations varies as k⁻² if the fluctuation field exceeds the threshold pump electric field for the oscillating two-stream instability. For the weak field plasma heating rate is found. Since the energy transfer is via Landau damping, the particle heating is characterized by the formation of high-energy tails on the distribution function.     

Spectrum of light emitted from ZnCdS: Ag screens excited by an electron beam

The emission spectrum of a ZnCdS: Ag phosphor screen excited by an electron beam was measured for different screen's thickness. This spectrum is found to be shifted towards the longer wavelengths when the screen thickness increases. The matching factor a between screen and some commercial photocathodes, which alter because of this shifting, is given as a function of the screen thickness.     

Cherenkov terahertz radiation from Dirac semimetals surface plasmon polaritons excited by an electron beam

We demonstrate a physical mechanism for terahertz(THz) generation from surface plasmon polaritons(SPPs). In a structure with a bulk Dirac semimetals(BDSs) film deposited on a dielectric substrate, the energy of the asymmetric SPP mode can be significantly enhanced to cross the light line of the substrate due to the SPP-coupling between the interfaces of the film. Therefore, the SPPs can be immediately transformed into Cherenkov radiation without removing the wavevector mismatch. Additionally, the symmetric SPP mode can also be dramatically lifted to cross the substrate light line when a buffer layer with low permittivity relative to the substrate is introduced. In this case, dual-frequency THz radiation from the two SPP modes can be generated simultaneously. The radiation intensity is significantly enhanced by over two orders due to the field enhancement of the SPPs. The radiation frequency can be tuned in the THz frequency regime by adjusting the beam energy and the chemical potential of the BDSs. Our results could find potential applications in developing room temperature, tunable, coherent, and intense THz radiation sources to cover the entire THz band.     

Volume discharge excited by an electron beam in an Ar-SF6 mixture I. Beam-controlled discharge

Beam-controlled current flow is investigated in an Ar-SF₆ mixture at atmospheric pressure. It is shown that electron attachment to SF₆ molecules plays an important role in the charge-dparticle balance, and the attachment constant is determined. The discharge energy properties are studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 72–76, July, 1978.     

Long pulse electron beam excited XeF laser

Long pulse operation of the XeF laser has been achieved with a short gain length and medium intensity electron beam excitation for both Ar/Xe/NF₃ and Ne/Xe/NF₃ mixtures. Use of Ne as diluant strongly lower the threshold for lasing and give an important increase in extracted power. For a total mixture pressure of 2 atm about 6 mJ of 3500 Å radiation was obtained in a 400 ns fwhm pulse limited only by e-beam pulse length.     

Volume discharge excited by an electron beam in an Ar-SF6 mixture II. Cascade ionization discharge

The discharge investigated is initiated by an electron beam with a duration of 10^–7 sec under conditions where cascade ionization plays an important role in sustaining the current. The results obtained for the dynamics of the transition from a beam-controlled discharge to the cascade ionization mode are given. Stable discharge regions with a high specific energy input into the gas are identified.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 77–81, July, 1978.     

电子束激发原子对金属蒸发的影响

在原子蒸气激光同位素分离工程(AVLIS)中,金属受电子束的加热而熔化,并向真空蒸发,蒸气原子通过电子束的过程中,可能与电子发生非弹性碰撞,被激发到高能级.在膨胀的过程中,高能级的原子通过与原子的非弹性碰撞消激发,将原子内的电子能量转换为蒸气的平动能.为了分析电子束与原子作用对蒸气的密度、速度和温度等物理特性的影响,采样直接模拟蒙特卡罗法(DSMC)模拟钆原子蒸发过程.模拟结果表明,电子束与原子的作用使得原子蒸气的速度增加,密度减小,温度升高 关键词： 金属蒸发 AVLIS DSMC 电子枪     

Tunable terahertz radiation from arbitrary profile dielectric grating coated with graphene excited by an electron beam

In this paper, the enhanced terahertz radiation transformed from surface plasmon polaritons, excited by a uniformly moving electron bunch, in a structure consisting of a monolayer graphene supported on a dielectric grating with arbitrary profile is investigated. The results show that the grating profile has significant influence on the dispersion curves and radiation characteristics including radiation frequency and intensity. The dependence of dispersion and radiation characteristics on the grating shape for both the symmetric and asymmetric gratings is studied in detail. Moreover, we find that, for an asymmetric grating with certain profile, there exist two different diffraction types, and one of the two types can provide higher radiation intensity comparing to the other one. These results will definitely facilitate the practical application in developing a room-temperature, tunable, coherent and miniature terahertz radiation source.     

On the 1920 Å continuous spectrum of the supersonic argon jet excited by an electron beam

The T₀/?(T₀) dependences (T₀ is the intensity of the 1920 Å continuum at its maximum, ? is the concentration of argon atoms at the intersection of an electron beam and a jet, T₀ is the temperature of argon at the nozzle) for the 1920 Å continuum radiated by a supersonic argon jet excited by an electron beam were investigated at various pressures of argon at the entry to a nozzle. The experiments performed suggested a possible generation mechanism of the 1920 Å continuum emitted by an argon jet.     

Nitrogen oxide conversion in nitrogen-oxygen mixtures excited by a microsecond electron beam

The removal of nitrogen oxides from gas mixtures under the action of an ionizing microsecond pulsed electron beam is studied experimentally. Experiments were carried out with gas mixtures simulating flue gases of thermal power plants. The current density and pulse duration of the electron beam, as well as the concentrations of oxygen and the impurity to be removed, are shown to affect the cleaning characteristics. It is found that the nitrogen oxide conversion initiated by a pulsed electron beam cannot be described by models developed for steady-state electron beams.     

Plasma instabilities in an anisotropically expanding geometry

We study (3+1)D kinetic (Boltzmann-Vlasov) equations for relativistic plasma particles in a one dimensionally expanding geometry motivated by ultrarelativistic heavy-ion collisions. We set up local equations in terms of Yang-Mills potentials and auxiliary fields that allow simulations of hard- (expanding-) loop dynamics on a lattice. We determine numerically the evolution of plasma instabilities in the linear (Abelian) regime and also derive their late-time behavior analytically, which is consistent with recent numerical results on the evolution of the so-called melting color-glass condensate. We also find a significant delay in the onset of growth of plasma instabilities which are triggered by small rapidity fluctuations, even when the initial state is highly anisotropic.     

Simulation of the radiation of a wide-aperture XeCl laser excited with an electron beam

A wide-aperture exciplex XeCl laser (308 nm) based on the Ar:Xe: HCl mixture and pumped with an electron beam is considered as a final unit of a system that generates subpetawatt femtosecond pulses.     

Silicon dioxide modification by an electron beam

The overheating temperature of a microvolume of silicon dioxide produced by bombardment by a high specific-power electron beam has been estimated. Calculations showed that the maximum temperature to which a microvolume of silicon dioxide is overheated can be as high as 1200°C for an electron beam current of 100 nA. The variation in the cathodoluminescence characteristics of amorphous silica with different contents of hydroxyl groups was studied for various electron beam specific-power levels. The impact of a high specific-power electron beam was shown to create additional lattice defects up to the formation of silicon clusters.     

Observation of a backward ion-cyclotron wave parametrically excited by a modulated electron beam

The lower-hybrid parametric resonant decay instability (decay into electrostatic lower-hybrid waves and backward ioncyclotron waves) driven by a modulated electron beam is investigated experimentally. Plasma heating and the possibility of wave-enhanced particle loss associated with this instability are discussed.