Installation for studying the plasma of Z-pinch initiated by an electron beam

An installation is developed for studying the dynamics of Z-pinch plasma with the discharge initiation by an electron beam. Research and commissioning works are performed for creating a system of electron beam formation using the adiabatic plasma lens. The study results are presented.     

Specific features of the formation of a uniform ribbon electron beam by a plasma source in the forevacuum pressure range

Results are presented from experimental studies of the formation of a ribbon electron beam during the extraction of electrons from the plasma of a steady-state hollow-cathode discharge in the forevacuum pressure range. It is shown that the main reason for the nonuniformity of the current density is the increase in the local nonuniformity of the emission plasma density caused by the return flow of ions from the accelerating gap. Taking this feature into account when developing a system of beam extraction provides for the generation of a ribbon beam with a nonuniformity of the current density along the beam of less than 10%.     

Radiative characteristics of nitrogen upon excitation by volume discharge initiated by runaway electron beam

The amplitude, time, spectral, and energetic characteristics of a volume (diffuse) discharge at an elevated pressure (up to 5 atm) in a gap with an inhomogeneous electric field without an additional preionization source are studied. The concentration and temperature of electrons in the discharge plasma are mea-sured by spectral methods. The effective lifetime of the C ³Π _u state of the nitrogen molecule at the trailing edge of the radiation pulse is shown to be determined by radiative and collisional quenchings. For transitions of the second positive system of nitrogen, a plasma discharge radiation power into the complete solid angle is obtained to be ～120 kW, with a specific radiation power of up to ～50 kW/cm³.     

Characteristics and efficiency of a compact HF laser initiated by an electron beam

A compact hydrogen fluoride laser is described and its efficiency is evaluated. The HF laser is initiated by injecting a 150 kV electron beam into a mixture of SF₆ and H₂ transversely to the laser cell axis. The optimum laser energy characteristics are determined as a function of the beam energy and gas pressure.     

Energy lost by an electron beam in interaction with a plasma

Measurements of the electron beam distribution function after the beam has interacted with a plasma, indicate that a large fraction of the energy lost by the beam has been absorbed by the plasma. Only a small fraction is in the wave field.     

Level inversion by excitation with a monoenergetic electron beam

The efficiency of level excitation with a monoenergetic electronic beam has been studied and compared with plasma excitation. The ratio of the 3s₂ and 2p₄ level populations of neon excited by a monokinetic beam was found to be three times higher than for plasma excitation. This result is in satisfactory agreement with theory.     

Terahertz surface plasmon excitation over a bismuth thin film by an electron beam

The excitation of terahertz surface plasma wave (SPW) over bismuth thin film-glass structure by a parallel propagating electron beam is studied. The SPW phase velocity is sensitive to the thickness of bismuth film and it is driven via the Cerenkov resonance. The growth rate for terahertz radiation generation by an electron beam is obtained under small signal approximation.     

Gas laser excitation by an electron beam formed at open discharge

The method of formation of powerful electron beams (EBs) with nanosecond duration has been described (electron energyu10 to 20 keV and beam currentl _EB>1 kA) in the medium pressure gas which is simultaneously the laser active medium. The value ofl _EB=7 kA has been achieved atU=22 kV, =20 ns andp _Ne=300 Pa in a coaxial cell 330 mm long and 99 mm in diameter. The 3 kA current from the cathode with 60 cm² square in the shape of a segment of a sphere 140 mm in diameter has been achieved atU=23 kV, =15 ns andp _Ne=300 Pa. With the help of a magnetic field this beam has been transported to a distance of up to 100 cm.Applications of the beams for pumping various lasers were broadened. Lasing in He + Cd⁺ mixtures at the optimal He pressure of 10 to 12 kPa and in the triple mixture He-Cd-Kr has been obtained. Using the method of doubled excitation pulses it has been shown that EB pumping provides preservation of the lasing pulse parameters in the Eu atom laser in comparison with glowing discharge, the sequential frequency being an order of magnitude greater. Lasing at a significantly greater ion concentration than in gas discharge has been obtained in the ion laser on the self-terminating transition of Ca⁺,=866 nm. Quasicontinuous lasing has been realized in the mixture He + Sr + Kr in the plasma laser on Sr⁺,=430.6 nm.     

Neutron-scattering investigation of the excitation spectrum of liquid helium

The results of the investigation of the temperature evolution of the scattering law S(Q, ω) of superfluid helium measured in the wave-vector range 0.3 < Q < 0.8 Å^?1 and helium temperatures from 1.0 to 2.2 K are reported. The investigations have been performed on the high-flux reactor at the Institut Laue-Langevin (France) with the IN6 neutron inelastic-scattering spectrometer. The deviation of the experimental scattering law of liquid helium from the damping harmonic oscillator model, which was previously observed independently in the experiments with the IN6 spectrometer [1] and with the DIN-2PI spectrometer (at the IBR-2 reactor, Dubna, Russia) [2, 3] and were more recently called extrapeak, has been corroborated. The temperature dependence of the extrapeak parameters has been determined. This dependence makes it possible to propose hypotheses on the nature of the extrapeak.     

Electron excitation by a multi passage laser beam in a plasma

The limits put by optical guiding, and channel guiding mechanisms on the Laser Wakefield Acceleration (LWFA) technique are imposed on the Resonant Laser Wakefield Acceleration (RLWFA) scheme. Energy gained by the electrons in both schemes are calculated and compared. It has presented that in the RLWFA case, the electrons gain more and more energy after each traversal of the laser pulse and the electrons in a plasma gain about 3 GeV after 10 passages of the laser pulse. They gain 13 GeV when the laser light makes 50 passages and 26 GeV after the laser beam traverses the plasma 100 times. Moreover, the channel guiding mechanism is integrated to the RLWFA scheme and together with diffraction guiding a model for electron acceleration is proposed. Received 13 September 2000 and Received in final form 27 October 2000     

绝对测量He原子快电子碰撞双激发的电子关联动力学

应用高分辨快电子能量损失谱仪 ,绝对测量了He原子各种光学允许和光学禁戒的双电子激发过程的动量转移依赖特性 ,报道了作为动量转移函数的以内禀关联量子数K ,T和A表征的电子态 2(0 ,1 ) 2 1 Po,2 (1 ,0 ) 2 1 Se和 2(1 ,0 ) 2 1 De的Fano参数q ,fa,ρ2 ,f和S ,同时对 2(- 1 ,0 ) 2 1 Se和 2(1 ,0 ) 2 的波函数作出定性检验 .从而在实验上通过激发动力学过程研究了电子关联效应     

Ion spectrum under excitation of a cluster beam by a laser pulse

A model describing the decay dynamics of large charged clusters formed during the interaction of a short laser pulse with a cluster beam is constructed. It is shown that the dynamics of the evolution of the cluster plasma and the energy spectrum of ions are affected by the presence of the decay products from neighboring clusters and the electron background due to ionization. The parameters of the plasma being formed are determined as functions of the cluster beam and laser pulse parameters.