Bremsstrahlung spectrum of nonrelativistic electrons scattered in metallic target: Theory and experiment

This work is devoted to theoretical and experimental investigation of the bremsstrahlung (BrS) spectrum of electrons with an energy of 10–30 eV scattered in a copper plate. Modeling of the photon yield from a target has been carried out taking into account the polarization BrS channel, elastic and inelastic electron scattering by medium atoms, photon absorption in the target material, and coherent effects when electrons interact with a polycrystalline structure of metal. An FEI Quanta 200 scanning electron microscope with a supplement for X-ray microanalysis was used. Good agreement between experimental and theoretical results has been obtained.     

Bremsstrahlung of relativistic electrons accelerated in solar flares: The intensity and degree of polarization

The generation of bremsstrahlung by relativistic electrons accelerated in solar flares is considered. The electron distribution function is calculated numerically using the relativistic Fokker-Planck equation. The intensity and degree of polarization of hard X rays are calculated as functions of the energy, observation angle, and electron distributions in pitch angle and energy. The degree of polarization does not exceed 40% and depends most strongly on the observation angle and hardness of the electron energy spectra. The results of model computation are compared with data for solar flares observed July 23, 2002 and October 28, 2003.     

利用韧致辐射诊断激光等离子体相互作用产生的超热电子

超短脉冲强激光与等离子体相互作用时产生的向靶内传输的超热电子在“快点火”方案中起着极其重要的作用.对于这部分向靶内传输的超热电子，韧致辐射方法是一种能有效、全面获得超热电子各方面信息的诊断方法.通过三维蒙特卡罗程序MCNP模拟了超热电子在靶材料中的输运以及它们在靶后方向产生的韧致辐射的性质，论证了韧致辐射诊断方法的可行性. 关键词： 超热电子 韧致辐射 诊断 MCNP程序     

Bremsstrahlung of the free electrons arising in an irradiated specimen

A model of the bremsstrahlung produced by photoelectrons, Auger electrons, and Compton electrons arising in an irradiated specimen is proposed. Calculations have shown that the contribution of the Compton electron bremsstrahlung shows up for monochromatic primary radiation of high-energy photons. For the primary radiation of x-ray tubes, only the bremsstrahlung spectrum of photoelectrons and Auger electrons is significant. The factors affecting the proportions between these components are considered. The bremsstrahlung spectral distribution of the mentioned electrons shows considerable deviations from that predicted by the Kramers theory that are due to the large depth of their occurrence and to the ambiguity of their energy. The region of the spectrum has been determined where the intensity of the electron bremsstrahlung is greater than the intensity of the x-ray tube polychromatic primary radiation scattered by the irradiated object.     

Compton effect in a magnetic field with allowance for polarization effects

A study is made of the scattering of a plane linearly polarized electromagnetic wave by an electron in a magnetic field. The cross section of the process is obtained separately for the and components of the polarization of the incident and scattered waves. The dependence of the cross section on the spin orientation indicates the possibility of self-polarization of the electrons as a result of the scattering of linearly polarized photons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 47–51, August, 1980.We are very grateful to Professor A. A. Sokolov for his interest in the work and to A. V. Borisov for discussing the results.     

Elastic scattering of electrons on nuclei with allowance for the second born approximation

In the framework of the shell model of light nuclei, the contribution to the scattering cross section of the second Born approximation due to the interference between the electric Coulomb interaction and the magnetic-dipole interaction is calculated. The case of backward scattering is considered. For not too high energies of the incident electrons, convenient approximate expressions are obtained for the correction to the cross section.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 12–15, January, 1981.     

Electron polarization in nonrelativistic nondegenerate magnetized electron gas

For a nondegenerate nonrelativistic electron system, taking account of the minimum of its total energy, the population of the Landau electron levels by electrons with intrinsic magnetic moments parallel and antiparallel to the external magnetic field is determined, as a function of the external magnetic field strength H. The results are then compared with analogous data obtained by other authors without taking the minimum of the system’s total energy into account. Brestsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–19, February, 1997.     

Radiation from particles in crystal undulators with allowance for a polarization of the medium

The radiation from relativistic particles channeled in a microscopic undulator created by applying transverse ultrasonic vibrations to a single crystal is investigated. The results of numerical investigations are presented for real crystal undulators. The calculations show the radiation spectra in the particle and photon energy ranges where narrowing of the spectrum occurs when the particle energy is close to a definite threshold energy. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 437–441 (25 September 1998)     

Bremsstrahlung from collisions of low-energy electrons with positive ions in a magnetic field

Bremsstrahlung from electron-ion collisions in a magnetic field is studied for low energies at which the Larmor radius of an electron is smaller than the characteristic impact parameter of close collisions in zero magnetic field. It is shown that the magnetic field does not qualitatively change the bremsstrahlung power at low frequencies smaller than the reciprocal time of electron transit in the vicinity of an ion in close collision in zero magnetic field. At high frequencies, the radiation intensity decreases in accordance with a power law, attains its minimal value, and then increases in accordance with a power law up to frequencies on the order of the electron cyclotron frequency. At such frequencies, the spectral power attains typical power values in zero magnetic field. At frequencies lower than the cyclotron frequency considered here, bremsstrahlung is polarized predominantly linearly in the plane formed by the magnetic field and the direction of radiation.     

Bremsstrahlung production by colliding beams of protons and electrons

The differential cross section of bremsstrahlung emitted in the head-on collision of beams of energetic protons and electrons is calculated in the laboratory frame. The angular distribution of the photons is more isotropic than in the common bremsstrahlung production on stationary target atoms. The total cross section is determined by integration over the photon angles which are allowed kinematically.     

Efficient polarization entanglement concentration for electrons with charge detection

We present an entanglement concentration protocol for electrons based on their spins and their charges. The combination of an electronic polarizing beam splitter and a charge detector functions as a parity check device for two electrons, with which the parties can reconstruct maximally entangled electron pairs from those in a less-entanglement state nonlocally. This protocol has a higher efficiency than those based on linear optics and it does not require the parties to know accurately the information about the less-entanglement state, which makes it more convenient in a practical application of solid quantum computation and communication.     

The inverse Bremsstrahlung absorption in the presence of Maxwellian and non-Maxwellian electrons

Inverse Bremsstrahlung absorption(IBA) of an intense laser field in plasma containing Maxwellian and nonMaxwellian(with Kappa and q-nonextensive distribution functions) electrons is studied analytically. Our results show that IBA decreases with an increase in temperature at high intensities and a decrease in plasma density for all kinds of distribution functions. Another striking result is that IBA is independent of the laser intensity at low intensity but is dependent on it when the intensity is going to rise. Also, it could be find that the behavior of the absorption as the function of laser intensity for the Kappa distribution with κ = 10 at low intensity is close to that for the Maxwellian distribution, but at high intensity it is close to that in the presence of q-nonextensive electrons with q = 0.9. These results provide insights into the inverse Bremsstrahlung absorption in the laser–plasma interactions.     

Depolarization of radiation upon coherent excitation with allowance made for the ground state splitting

It is shown that, if a certain coherence is induced between the low-lying levels of a three-level system, the signal of longitudinal alignment can vanish due to a change in the laser frequency detuning.     

Interaction of the nonrelativistic electrons in the pulsed field of two laser waves

Interaction of two non-relativistic classical electrons in the presence of two strong pulsed laser waves of various frequencies, pulse durations and intensities is theoretically studied. It is shown, that there is a range of wave intensities in which average effective force of the electrons interaction becomes negative in current of the certain interval of time.     

Energy load of a gyrotron collector with allowance for electrons reflected from its surface

We develop a physical model and an algorithm for calculation of the specific density of power scattered by a collector in high-power gyrotrons with allowance for multiple reflections of electrons from the collector surface. Specific features of the angular and energy distributions of reflected electrons in the case of their oblique incidence on the collector surface are taken into account. Electron trajectories and the corresponding power-density distributions for typical collector systems of the gyrotrons are found. Multiple reflections of electrons significantly increase the effective collector surface and reduce the thermal load. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 1, pp. 55–62, January 2009.     

On the self-energy of electrons in metals

The electron self-energy of unoccupied states is investigated taking into account dynamical screening and nonlocal exchange. To obtain agreement with experiment it is crucial to go beyond the framework of the homogeneous electron gas and include the nonlocal exchange with electrons in valence and core shells. This contribution of atomic origin gives rise to a considerable, almost linear energy dependence of the self-energy over a wide energy range in agreement with experimental findings for many substances and in disagreement with the local density approximation. Quantitative results are presented for Ag.     

Thermal conductivity of metals with hot electrons

The action of an ultrashort laser pulse transforms a metal into a two-temperature (2T) state with different temperatures of the electron and ion subsystems (T _e ≫ T _i ). The metal stays in this state in a rather long time interval (from several to several tens of picoseconds depending on the metal). The 2T stage is very important since it includes 2T relaxation, in which laser energy is transferred to ions, and the formation of a heated layer, which plays a key role in the subsequent dynamics. The kinetic coefficients of a condensed medium with hot electrons are poorly known: researchers use phenomenological dependences consisting of asymptotics at low and high temperatures T _e . However, it is impossible to perform a numerical simulation of the interaction of laser radiation with a substance without these coefficients. In this work, the thermal conductivity is calculated using a kinetic equation for the first time. This calculation is valid at low (T _e ≪ T _F = E _F/k _B, where E _F is the Fermi energy and k _B is the Boltzmann constant) and moderate (T _e < T _F) temperatures. The earlier kinetic calculations are related to the case of T _e < T _F, where the calculations of, e.g., the electron-electron collision frequency are significantly simplified due to the reduction of multiple integration to integration in a small neighborhood of the Fermi sphere. In our case, integration at moderate temperatures should be performed over the entire volume of momentum space.     

Spin polarization of electrons in magnetic heterostructures

The scattering of nonspin-polarized electrons on a heterostructure containing a magnetic element (a nonmagnetic barrier adjoining a magnetic one from left or right, or a magnetic well between two nonmagnetic barriers) is considered. The transmission coefficients and degrees of the spin polarization of electrons transmitted through these structures are obtained.