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A theoretical study is performed for the single-photon creation of an electron–positron pair in an external magnetic field. We present general expressions for process rates that are valid for arbitrarily high field strengths. Simple analytical expressions are obtained in the limiting cases of weak and strong fields. The emphasis is placed on the investigation of the spin alignment of the created particles as a function of the incident photon polarization and magnetic field strength. The obtained results show that the maximum value of the polarization degree of electrons (positrons) decreases in supercritical magnetic field. [ABSTRACT FROM AUTHOR]

This work is devoted to the investigation of the nonstationary problem of the thermal conductivity of a nanoemitter on the surface of a massive copper cathode when a field electron emission current passes through it. At the same time, the dependence of volume resistivity, thermal conductivity on temperature, and size effects have been taken into account. The influence of the Nottingham effect has been considered. The dependence of the equilibrium temperature of the emitter apex on the field enhancement factor for different values of the electric field strength has been found. Based on the assumption that the initial stage of the breakdown begins when the emitter apex melts, the conditions for the occurrence of a vacuum breakdown and the influence of the Nottingham effect have been analyzed. [ABSTRACT FROM AUTHOR]

Elementary interaction processes of charged particles in an electron beam with a current of about 1 A are studied numerically concerning the electron cooling problem. A one-dimensional particle-in-cell code is used to consider the following processes: expansion of the free electron gas, temperature equalization in the electron gas, natural oscillations in quasi electron-positron and electron-proton gases. In this method, the free electron gas expands due to electrostatic repulsion between electrons at a constant total energy. The model of a free electron gas represented by computational particles in the form of endless plates is also solved analytically. In this case, the velocity deviation as a function of time and the distance between the charge centers of the two halves of the electron gas are found analytically. And this is compared with the result of the numerical calculation. If the electron gas is represented as two subsystems with different temperatures, this leads to temperature equalization in the simulation. The paper considers several cases with different initial temperature conditions and finds the relaxation time. The simulation result of electron- positron and electron-proton gases shows that their oscillations are accompanied by Landau damping. The spectral frequency distribution of these oscillations shows the maxima that correspond to theoretical estimates. [ABSTRACT FROM AUTHOR]

Quantum-mechanical problem on electron motion through the model potential barrier of metal-vacuum system with an additional near-surface dipole layer is considered. An analytical generalization of the Fowler-Nordheim formula was done in the case of this potential barrier. The introduction of such a layer is used as a way of taking into account the effect of vacancies and pores that appear during irradiation in the surface metal layer on the field emission current density. Taking into consideration the continuity conditions of wave functions and their derivatives at the interface between two media, general expressions of the transmission coefficient of potential barrier and the field emission current density are obtained. The influence of effective thickness of an additional near-surface dipole layer on value of field emission current is shown. Thus, the method is used to take into account the influence of vacancies and pores that appear during irradiation of metal surface on field emission current density. It was found that field emission current, considering the influence of vacancies and pores, that emerge during irradiation of copper surface with Cu2+ ions with energy of 300 keV during the processing time of 5·103 s by dose of 1.6·10 21 m − 2, is 1.3 times less than the value of the Fowler-Nordheim current density. The approximations related to the Fowler- Nordheim formula for current density are given in this paper. The considered approach has more visual mathematical proofs than previous theoretical treatments of the phenomenon of field emission. This research can be a useful basis for studying the transmission of electrons through potential barriers for which there is no an exact analytical theory. [ABSTRACT FROM AUTHOR]

As the title implies the article describes the possibility of taking into account the relativistic correction to the field current density of the field emission of electrons from the metal. The article provides the reader with some analytic generalization of the Fowler-Nordheim equation with the relativistic correction. The relativistic correction to the Fowler-Nordheim equation makes it possible to take into account the influence of the relativism on the field emission current. It is especially noted that the consideration of this correction is necessary in the case of sufficiently strong electric fields and relatively large interelectrode distances. It should be stressed that this correction is valid for fixed interelectrode distances that decrease with increasing electric field strength. It means that for the electric field strength of 0.1 to 1 GV/m the interelectrode distance should not exceed values of 1 to 0.1 cm. First in the article it is spoken in detail about finding of the electron wave function. Next the field emission current calculations are given. As a result the transmission coefficient of the potential step from the Klein-Gordon equation within the framework of the Fowler-Nordheim approximation is found. It is shown that in the case of the interelectrode distance less than 1 cm, an analytical expression for the field electron emission current density is obtained. The conclusion that usually relativistic correction does not exceed a tenth of a percent is made. But in the case of the field electron emission from pulsars (where the work function and electric field strength are much higher) the contribution of the relativistic correction about 10 % has been established. [ABSTRACT FROM AUTHOR]

A heavy charged particle propagation through electron gas has been studied using combination of non-relativistic quantum mechanics and the Green's functions method. The energy loss of a charged particle has been found in the case of large transferred momentum taking into account the interference term in the expression for the rate. The dependence of the energy loss of a charged particles in electron gas with nonzero temperature on the sign of the charge has been obtained. [ABSTRACT FROM AUTHOR]

A general theory of motion of a heavy charged particle in the electron gas with an anisotropic velocity distribution is developed within the quantum-field method. The analytical expressions for the dielectric susceptibility and the stopping power of the electron gas differs in no way from well-known classic formulas in the approximation of large and small velocities. Stopping power of the electron gas with anisotropic temperature in the framework of the quantum-field method is numerically calculated for an arbitrary angle between directions of the motion of the projectile particle and the electron beam. The results of the numerical calculations are compared with the dielectric model approach. [ABSTRACT FROM AUTHOR]

In this paper one- and two-photon pair production in a subcritical magnetic field have been considered. Two-photon production has been studied in the resonant case, when the cross-section considerably increases compared to the non-resonant case. While one-photon pair production is considered to be the main mechanism of plasma generation in a pulsar magnetosphere, we suggest the existence of another one, which is resonant two-photon production process. [ABSTRACT FROM AUTHOR]

The computer experiment for study of the relaxation time of the beam particles with an anisotropic velocity distribution is performed by the molecular dynamics. Obtained results agree with the characteristic times of thermal relaxation in plasma for the electronic coolers in modern storage rings. [ABSTRACT FROM AUTHOR]