Bulk changes in the microhardness of a solid WC-110G13 steel alloy exposed to a low-energy, high-current electron beam

Bulk changes in the microhardness of a solid WC-110G13 steel alloy are studied as a function of the energy density of a low-energy, high-current electron beam, the number of pulses, and the target thickness. It is established that the beam energy density has a threshold at which quasiperiodic changes in the microhardness occur in the bulk of the alloy. Pis’ma Zh. Tekh. Fiz. 25, 54–59 (October 26, 1999)     

Pair production in counterpropagating electron and laser beams

An analysis is made of the collision between a high-energy electron beam and laser radiation. It is shown that when the electron energy is 800 GeV and the laser pulse has an intensity of 10²⁰ W/cm², a wavelength of 248 nm, and a duration of 300 fs, a single seed electron produces 60 electrons and positrons. Pis’ma Zh. Tekh. Fiz. 23, 72–75 (July 26, 1997)     

Removal of acrolein vapor from air by a nanosecond electron beam

Results are presented of an experimental investigation of the decomposition of small quantities of acrolein vapor in air irradiated by a pulsed electron beam. It is shown that the reduction in the impurity concentration as a function of the energy deposited in the gas is satisfactorily approximated by an exponential law. An empirical expression is derived to predict the energy consumption for a given initial acrolein concentration and required degree of purification. Pis’ma Zh. Tekh. Fiz. 24, 35–39 (August 26, 1998)     

Removal of nitrogen oxides from the air under the action of a microsecond electron beam

The oxidation of nitrogen oxides in a model mixture ionized by a microsecond pulsed electron beam has been investigated experimentally and results are presented. It is shown that when the mixture has a high impurity content, the energy dissipated in the removal of a single toxic molecule is substantially lower than the dissociation energies of nitrogen monoxide and molecular oxygen, being ∼2 eV. Pis’ma Zh. Tekh. Fiz. 24, 52–56 (February 26, 1998)     

High-power HF laser pumped by an electron-beam-initiated chemical nonchain reaction

The development of a high-power HF laser pumped by a chemical nonchain reaction initiated by a radially converging electron beam is reported. A radiation energy of ∼ 115 J with an efficiency of ∼ 8% in terms of deposited energy has been achieved in a mixture with an active volume of ∼ 30 liters. It is shown that because of the high SF₆ density, the total pressure jump in SF₆–H₂(D₂) mixtures caused by the electron beam injection and the chemical reactions is several times smaller than that in the active mixtures of exciplex lasers for the same input energies. This factor considerably facilitates the development of wide-aperture HF and DF lasers with an SF₆ fluorine donor pumped by an electron-beam-initiated chemical nonchain reaction. Pis’ma Zh. Tekh. Fiz. 23, 58–64 (March 12, 997)     

Structure of a picosecond electron beam inside a vacuum diode

The structure of a picosecond (∼150 ps) electron beam in the cathode-anode gap of a vacuum diode is determined. The electron beam is modeled in the form of flat quasiparticles with a definite charge density which follow one after another in equal time intervals. It is shown that the expansion of concentric layers of the beam under the action of the electric and magnetic self-fields strongly depends on the current strength. The experimental confirmation of the computed estimates is illustrated by recording the structure of the electron beam at the anode using a film which is sensitive to electron radiation. Pis’ma Zh. Tekh. Fiz. 25, 39–45 (September 26, 1999)     

Influence of the parameters of a pulsed electron beam on the removal of nitrogen oxides from flue gases

Results are presented of an experimental investigation of the oxidation of small quantities of nitrogen oxides in air irradiated by a pulsed electron beam. It is shown that the impurity removal process is strongly influenced by the pulse length and current density of the electron beam. It is noted that an adequate model is needed to describe the plasma-chemical oxidation processes of nitrogen oxides involving charged and excited particles. Pis’ma Zh. Tekh. Fiz. 24, 47–50 (August 12, 1998)     

Possible emission of supermodes in a free electron laser with a transversely developed interaction space

A theoretical analysis is made of the formation of the transverse field profile in a free electron laser with an oversize planar-geometry Bragg cavity driven by a ribbon electron beam. It is shown that cw spatially coherent lasing may be achieved with an oversize parameter of the order of 50 with the excitation of supermodes comprising a set of “ cold” waveguide modes. Pis’ma Zh. Tekh. Fiz. 25, 28–34 (March 12, 1999)     

Possible use of two-dimensional Bragg structures in an FEL amplifier powered by a sheet electron beam

It is shown that two-dimensional doubly-periodic Bragg structures can be used effectively in the amplification schemes of free electron lasers powered by sheet relativistic electron beams. The presence of such a structure ensures spatial coherence of radiation from different parts of the electron beam when the input signal propagates across the electron flux. Theoretical analysis shows that the gain in the regenerative scheme can reach 50 dB. Pis’ma Zh. Tekh. Fiz. 25, 87–95 (October 12, 1999)     

Influence of the shock wave pressure gradient in α-Fe irradiated by a high-power ion beam on the occurence of a microhardness maximum at large depths

The defect structure and microhardness of α-Fe irradiated by a high-power pulsed beam have been studied using positron annihilation, transmission electron spectroscopy, and a nanoindenter, and results are presented. It is shown that in α-Fe exposed to a high-power pulsed beam, the pressure gradient and depth of formation of the shock wave front influence the formation and location of the dislocation density maximum and the microhardness maximum in the modified layer. Pis’ma Zh. Tekh. Fiz. 24, 47–53 (February 12, 1998)     

Electron entrainment current in gases bombarded with beams of fast highly-charged ions

It is shown that asymmetry in the ejection of electrons in an elementary collision event between an atom and a fast highly-charged ion may lead to a macroscopic effect, the electron entrainment current, when a gas target is bombarded by a beam of fast highly-charged ions. The entrainment current is calculated for the bombardment of a helium target by a 25 MeV/u Mo⁴⁰⁺ beam. Pis’ma Zh. Tekh. Fiz. 24, 62–65 (September 26, 1998)     

Interaction between relativistic charged particles and an extended strong rf field

An investigation is made of the interaction between relativistic charged particles and a high-intensity microwave electric field over long interaction lengths. The microwave field has no magnetic component over the entire interaction length. It is shown that the interaction of the relativistic particles has features which depend on the relation between the incoming particle energy and the field strength. In particular, part of a monoenergetic particle beam may be accelerated by the beam’s own energy with some of the energy being transferred from the beam to the field. Pis’ma Zh. Tekh. Fiz. 24, 80–86 (May 26, 1998)     

Experimental study of the transient process in a pulsed relativistic backward-wave tube for the millimeter range

The influence of the rise time of the current pulse of a nanosecond high-current electron beam on the self-oscillation regime that is established in a relativistic backward-wave tube for the 38 GHz range is investigated experimentally. It is shown that a peak power of more than 50 MW is attained in a time of ∼300 ps. Pis’ma Zh. Tekh. Fiz. 25, 19–23 (May 26, 1999)     

Influence of a shock-wave pressure gradient on the appearance of a microhardness maximum in α-Fe irradiated by a high-power ion beam

The results of research on the defect structure and microhardness in α-Fe irradiated by a pulsed high-power ion beam are presented. The results are obtained with the use of positron annihilation, electron microscopy, and a nanoindenter. It is shown that the pressure gradient and the depth of formation of the shock wave front in α-Fe irradiated by a high-power ion beam have an influence on the formation and location of the maximum of the dislocation density and microhardness in the modified layer. Pis’ma Zh. Tekh. Fiz. 24, 72–77 (October 26, 1998)     

Scenario for the establishment of an electron beam “squeezed state” in a magnetically insulated vircator

A 2.5-dimensional particle-in-cell code was used to simulate different scenarios for the establishment of an electron beam “squeezed state” in a magnetically insulated vircator. Vircators with and without anode foils were compared. It was found that the squeezed state is established in both cases but the dynamics of establishment differ. Pis’ma Zh. Tekh. Fiz. 23, 29–33 (November 26, 1997)     

Change in the properties of BT-23 titanium alloy induced by implantation of iron and zirconium ions followed by exposure to a low-energy high-current electron beam

Atomic physics methods, atomic force microscopy, and testing of microhardness, wear resistance, and friction coefficient were used to investigate Ti₄₁-V₄₁-Al₁₈ samples implanted with iron (60 kV) and zirconium (40 kV) ions, and then exposed to a high-current electron beam with energy fluxes of 2.7 and 5.5 J/cm². The maximum concentration of iron ions is 16.5 at.% at a depth of 85 nm and that of zirconium ions 0.85 at.% at 56 nm. After double implantation, the friction coefficient decreases and the wear resistance increases. After implantation and high-current electron beam treatment, the depth of the hardened layer and the wear resistance increase. Pis’ma Zh. Tekh. Fiz. 25, 66–73 (August 12, 1999)     

Spin splitting in longitudinal carrier transport in quantum structures

The role of spin effects in electron waveguides is analyzed. It is shown that in noncentrosymmetric structures where the spin splitting is odd in the wave vector the phase velocity of the electron waves depends on the spin orientation. On the one hand this destroys the conditions for interference and degrades the characteristics of the device; but on the other hand it allows one in principle to obtain a beam of completely spin-polarized electrons from the exit. Pis’ma Zh. Tekh. Fiz. 23, 83–89 (February 26, 1997) Deceased     

Fabrication of InAs quantum dots on silicon

Reflection high-energy electron diffraction and scanning tunneling microscopy have been used to demonstrate for the first time that InAs quantum dots may be fabricated directly on Si(100) by molecular beam epitaxy. It is shown that heteroepitaxial growth in an InAs/Si system takes place by the Stranski-Krastanow mechanism and the surface morphology depends strongly on the substrate temperature. Pis’ma Zh. Tekh. Fiz. 24, 10–15 (April 26, 1998)     

Electron energy balance in an ionization-unstable plasma in a magnetogasdynamic channel

An experimental investigation was made of the evolution of ionization instability in a model of a disk-shaped Faraday magnetogasdynamic channel connected to a shock tube in a pure rare gas (xenon) with an alkaline additive. The main components of the average electron energy balance were determined: the Joule heating power, the average rate of energy transport of the heavy component by elastic collisions, and the average rate of energy lost through ionization. It was found that the electron energy defect which includes losses not taken into account, increases abruptly at supercritical values of the magnetic induction and accounts for approximately half of the Joule heating power. It is concluded that some of the electron energy is transferred to pulsations. Pis’ma Zh. Tekh. Fiz. 24, 48–53 (July 26, 1998)     

Induction self-acceleration of a high-current electron beam

Computer modeling using the particle-in-cell method confirmed that self-acceleration by induction of a high-current relativistic electron beam predicted by G. A. Askar’yan [At. énerg. 6, 658 (1959)] may occur when this beam passes through a thick diaphragm containing an aperture. Pis’ma Zh. Tekh. Fiz. 25, 52–56 (July 26, 1999)