Non-self-sustained hollow-cathode glow discharge for large-aperture ion sources

A discharge system is proposed in which an auxiliary gas discharge is used to inject electrons into the cathode cavity of a hollow-cathode glow discharge. A study is made of the region of stable existence of a non-self-sustaining hollow-cathode discharge. It is shown that the injection of electrons permits a reduction to <10⁻² Pa in the minimum pressure at which a discharge can exist. It is shown experimentally that this discharge can be used to generate wide-aperture ion beams. Zh. Tekh. Fiz. 67, 27–31 (June 1997)     

Processes occurring in cluster plasmas and cluster beams

A method of generating a cluster beam of a refractory metal is analyzed. Clusters are formed in a high-pressure arc discharge plasma in which the refractory metal is an additive to the buffer gas. The conditions for cluster formation to occur in the intermediate region of the discharge are found, and the cluster instability, as a result of which all of the refractory metal collects in the form of clusters in this zone of the discharge, is studied. The processes studied are the basis for of a method of generating intense cluster beams. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 741–746 (25 November 1998)     

A Small Isochronous Storage Ring for Spectrometry

The results of a numerical simulation of heavy ion beam motion in a multiturn mass-spectrometer are presented. It consists of a magnet system with an azimuthal variation of magnetic field, two dees and an open type arc discharge ion source. The calculations have shown that the mass resolution of ion beams is above 10⁴. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of directly produce pump,signal, and idler three-color continuous-variable entanglement

Analysis is presented in this paper to directly produce three-color continuous-variable (CV) entanglement by nondegenerate optical parametric oscillator (NOPO) with an injected signal. The quantum entanglement among the pump, signal, and idler beams are calculated by applying sufficient inseparability criteria for CV entanglement which proposed by van Loock and Furusawa [Phys. Rev. A 67, 052315 (2003)]. The results indicates that strong three-color CV entangled beams, i.e. pump, signal, and idler beams, can be generated when the NOPO operating above the threshold. The degree of entanglement dependence on damping rates is also investigated.     

新型毫微秒强流脉冲电子束和离子束发生装置

本文讨论一种新的低气压放电型粒子源,用这种装置可以产生能量达70keV,电流密度超过10⁶A/cm²,电流为几百安培的脉冲电子流和安培级的脉冲离子流,作者建议用“电场递增效应”来解释这种多极板放电室的放电机制,由于它造价低、结构简单、重复频率高、寿命长,可以预期,这一装置将会得到广泛应用。 关键词：     

Sisyphus cooling of rubidium atoms on the line: The role of the neighbouring transitions

We study one-dimensional Sisyphus cooling on the transition of ⁸⁷ Rb atoms in the electric field created by two counter-propagating linearly polarized laser beams with an angle of between the polarization directions. The neighbouring F '=0 and F '=2 excited states are found to play an important role in the cooling mechanism, e.g., by inhibiting a significant population of the velocity-selective dark state. Our experimental data, such as temperatures and probe absorption coefficients, agree well with the results of quantum Monte-Carlo wavefunction simulations. Received 26 November 1998 and Received in final form 20 April 1999     

Ionization mechanism in a liquid-metal ion source. Source for high-melting metals

Investigations have been made of the ionization mechanism in a liquid-metal ion source. At the instant of ion current generation the surface of a liquid metal emitter frozen in a highvoltage field exhibits microprotrusions pulled from the liquid metal by the electric field. A double-focusing mass spectrometer identified two components in the ion beam extracted from the aperture in the extractor. One ion component forms at the tip of the emitter and has an energy spread not exceeding a few tens of electronvolts. The other ion component forms in the cathode plasma at the extractor. On the basis of these investigations, a mechanism is proposed for ion formation in a liquid metal ion source and this mechanism is used to produce a modified source design. The source can produce ion beams from high-melting metals and nonmetals, and beams of Ta, W, Mo, C, and Fe ions were obtained. Zh. Tekh. Fiz. 67, 82–87 (November 1997)     

Range of existence of self-sustained, subcritical microwave streamer discharges

Data are presented from a study of subcritical microwave streamer discharges in air in an electromagnetic beam. It is shown that, depending on the degree of subcriticality, this kind of discharge can have two forms: a self-sustained discharge and a discharge that is attached to the initiating trigger. The range of subcriticality for the initial field is determined as a function of air pressure within which the self-sustained developed discharge form exists. Zh. Tekh. Fiz. 69, 19–24 (November 1999)     

Generation of thin and hollow beams by the axicon with a large open angle

We propose a method to produce diffraction-free thin and hollow beams. The method is based on Laguerre-Gaussian (LG) beams incident on a large open-angle axicon. We use the vector diffraction integrals and stationary phase method to deduce a simple and analytical formula of the propagating field of the linearly polarized LG beams through an axicon. The numerical results show that the hollow beams of whose diameter is in the order of the wavelength can be obtained by using the axicon with the refractive index n = 2 and the open angle α = 25°. These diffraction-free thin and hollow beams may be very useful to accurately trap and manipulate atoms. However, when the open angle is over large, the conversion efficiency from the LG beam to the diffraction-free hollow beam will decrease obviously.     

Investigation of prebreakdown currents flowing in pseudospark gaps

Currents flowing at the prebreakdown stage in a pseudospark-gap switch with an ignition unit based a steady-state glow discharge are studied. The mechanism of operation of the blocking electrodes is explained. An electrode construction that makes it possible to increase substantially the static breakdown voltage of the device is presented. Zh. Tekh. Fiz. 67, 26–29 (October 1997)     

Observation of reflex klystron oscillation phenomena in a plasma

Reflex klystron electron oscillation, occurring in a plasma potential well formed in a system consisting of plasma and two electrodes (filaments and a mesh grid which is at floating potential), was observed in a very simple device with only filaments and a mesh grid. This oscillation mechanism consists of three elements: 1) an acceleration region on the side in which filaments are located, which accelerates primary electron beams emitted from filaments; 2) a deceleration region on the side in which the mesh grid is located, which causes the reflection of the beams; and 3) a plasma region. In addition, the velocity modulation of primary electron beams is given by the electron plasma oscillation at the presheath on the filament side. The maximum amplitude and frequency of an oscillation obtained by this mechanism were V_pp=210 mV 210 mV and f=200 MHz, respectively. These values can be controlled by the discharge potential     

Amplification of monochromatic short-wavelength radiation during the stochastic deceleration of a relativistic electron stream in an incoherent pump field

The use of incoherent multiwave pump radiation or randomly varying magnetostatic fields (stochastic undulators) for improving the energy conversion efficiency in free-electron lasers based on stimulated wave scattering and the stimulated undulator emission of relativistic electron beams is proposed. It is shown within the quasilinear approximation that the electronic efficiency increases in proportion to the width of the pump spectrum due to enrichment of the spectrum of combination waves which are synchronous with the electron beam and realization of a mechanism of stochastic particle deceleration when the signal wave is monochromatic. At the same time, the efficiency scarcely depends on the spread of the beam parameters, making the use of the method promising for improving the efficiency of free-electron lasers powered by intense relativistic electron beams. Zh. Tekh. Fiz. 67, 77–81 (July 1997)     

An intense, slow and cold beam of metastable Ne(3s) 3 P 2 atoms

We employ laser cooling to intensify and cool an atomic beam of metastable Ne(3 s) atoms. Using several collimators, a slower and a compressor we achieve a ²⁰Ne^* flux of 6×10 ¹⁰ atoms/s in an 0.7 mm diameter beam traveling at 100 m/s, and having longitudinal and transverse temperatures of 25 mK and 300μK, respectively. This constitutes the highest flux in a concentrated beam achieved to date with metastable rare gas atoms. We characterize the action of the various cooling stages in terms of their influence on the flux, diameter and divergence of the atomic beam. The brightness and brilliance achieved are 2.1 ×10 ²¹ s^-1m^-2sr^-1 and 5.0 ×10 ²² s^-1m^-2sr^-1, respectively, comparable to the highest values reported for alkali-metal beams. Bright beams of the ²¹Ne and ²²Ne isotopes have also been created. Received 22 June 2001     

Beam-plasma discharge in the propagation of a long-pulse relativistic electron beam in a medium-pressure rarefied gas

A theoretical model is given, along with a numerical analysis of the evolution of beam-plasma discharge in the propagation of a long-pulse relativistic electron beam in a rarefied gas at medium pressure. It is shown that the self-stabilization of beam-plasma discharge as a result of longitudinal inhomogeneity of the density of the discharge plasma makes it possible for the beam to traverse the beam chamber with relatively low total energy losses, including ionization losses and energy losses in the generation of oscillations. During the dissociative recombination of electrons and ions of the discharge-driven plasma, heat is released and spent in raising the temperature of the gas. The investigated collective-discharge mechanism underlying heating of the gas for a relativistic beam can be more efficient than the classical heating mechanism due to ionization losses of the beam in pair collisions of its electrons with gas particles. Zh. Tekh. Fiz. 67, 94–98 (May 1997)     

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)     

Abnormale Energieunschärfe intensiver Elektronenstrahlen aus Plasmakathoden

Intense electron beams extracted from DUOPLASMATRON-plasma cathodes show a high degree of modulation in intensity and an abnormally large energy spread; these facts cannot be explained simply by the temperature of the plasma electrons and the discharge structure. However, an analysis of the discharge stability behaviour and the interaction of source- and extracted beam-plasma leads to an explanation for the observed effects.

     

On the formation of nanosecond volume discharges,subnanosecond runaway electron beams,and x-ray radiation in gases at elevated pressure

Properties of runaway electron beams and x-ray radiation in a nanosecond volume discharge in air at atmospheric pressure are investigated, and results of recent studies in this direction are analyzed. A physical nature of forming runaway electron beams and x-ray radiation in the nanosecond volume discharge is discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 40–51, December, 2005.     

Leader discharge over a water surface in a Lichtenberg figure geometry

A multichannel leader discharge over a water surface is investigated in a Lichtenberg figure geometry. It is established that the Ohmic conductivity of water causes nonlinearity of the R(t)C discharge circuit. A mutual one-to-one correspondence between the channel lengths and the currents flowing in them is established during the discharge, and the discharge has a selfconsistent character. A mechanism is proposed for the initiation of initial channels by maxima which arise in the charge structure of the planar double layer on the water surface during the development of Rayleigh-Bénard instability in the layer after the pulsed corona from the anode reaches the water. Zh. Tekh. Fiz. 68, 63–66 (November 1998)     

Possibility of lowering the effective emittance of neutralized ion beams

Self-similarity conditions are determined for the steady states of a quasineutral beam plasma generated during the transport of ion beams in a gaseous medium. The self-consistent radial distribution of the beam and plasma densities is taken into account. Under the resulting conditions the radial electric field of the beam-plasma system is linear, and it is possible for beams to be transported without nonlinear distortion of their phase response characteristics or an increase in the effective emittance. Zh. Tekh. Fiz. 68, 112–115 (April 1998)     

A DC excited waveguide multibeam CO2 laser using high frequency pre-ionization technique

High power industrial multibeam CO₂ lasers consist of a large number of closely packed parallel glass discharge tubes sharing a common plane parallel resonator. Every discharge tube forms an independent resonator. When discharge tubes of smaller diameter are used and the Fresnel numberN ≪ 1 for all resonators, they operate in waveguide mode. Waveguide modes have excellent discrimination of higher order modes. A DC excited waveguide multibeam CO₂ laser is reported having six glass discharge tubes. Simultaneous excitation of DC discharge in all sections is achieved by producing pre-ionization using an auxiliary high frequency pulsed discharge along with its other advantages. Maximum 170 W output power is obtained with all beams operating in EH₁₁ waveguide mode. The specific power of 28 W/m is much higher as compared to similar AC excited waveguide multibeam CO₂ lasers. Theoretical analysis shows that all resonators of this laser will support only EH₁₁ mode. This laser is successfully used for woodcutting