Dirac particle in Aharonov–Bohm–Coulomb field: Path integral treatment

Exact Green’s function related to a Dirac particle submitted to the combination of Aharonov–Bohm and Coulomb potentials in [Formula: see text]) coordinate space is analytically calculated via path integral formalism. The Pauli matrices which describe the spin dynamics are replaced by two fermionic oscillators via the Schwinger model. The energy spectrum as well as the corresponding normalized wave functions are extracted following this approach. The interesting properties of the spinors are thus deduced after symmetrization. According to the symmetric form for Green’s function, it is shown that the non-relativistic limit of the Dirac particle is undertaken with much ease.

Simulation studies of beam dynamics in 50 MeV linear accelerator with laser-plasma electron gun

Conventionally, electron guns with thermionic cathodes or field-emission cathodes are used for research or technological linear accelerators. RF-photoguns are used to provide the short electron bunches which could be used for FEL’s of compact research facilities to generate monochromatic photons. Low energy of emitted electrons is the key problem for photoguns due to high influence of Coulomb field and difficulties with the first accelerating cell simulation and construction. Contrary, plasma sources, based on the laser-plasma wakefield acceleration, have very high acceleration gradient but rather broad energy spectrum compared with conventional thermoguns or field-emission guns. The beam dynamics in the linear accelerator combines the laser-plasma electron source and conventional RF linear accelerator is discussed in this paper. Method to capture and re-accelerate the short picosecond bunch with extremely broad energy spread (up to 50 %) is presented. Numerical simulation shows that such bunches can be accelerated in RF linear accelerator to the energy of 50 MeV with output energy spread not higher than 1 % .

A novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology

In this study, a novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology was fabricated. Sample transistors of different structures and sizes were constructed. Through measurements, it was found that by changing the width of the opening, the threshold voltage of the device could be easily modulated across a larger range. The open-gate device had two working modes with different transconductance. When the gate-source voltage VGS ≤ − 4.5 V, only the open region was conductive, and a new working mechanism modulated the channel current. Corresponding theoretical analysis and calculations showed that its saturation mechanism was related to a virtual gate formed by electron injection onto the surface. Also, the gate-source voltage modulated the open channel current by changing the channel electron mobility through polarization Coulomb field scattering. When used as class-A voltage amplifiers, open-gate devices can achieve effective voltage amplification with very low power consumption.

Rutherford’s extended formula and optimization of the gravity assists beam modelling in the Solar system

Rutherford’s formula for the scattering of charged α-particles in the Coulomb field can be easily generalized to the case of gravitational scattering. The extended Rutherford formula for the gravitational scattering is presented. One of the types of the gravitational scattering in the Solar system is the gravity assist maneuvers. In this paper, an effective gravitational scattering cross-section is introduced by analogy for them and the generalized Rutherford formula for gravitational scattering is presented out when performing gravity assists. Modern methods of the ballistic design of the interplanetary space flights using gravity assist maneuvers around planets [1-3] are associated with the need to calculate a lot of trajectories (i.e. of the phase beams). For their effective use it is necessary to study the structure of non-linear flyby gravitational scattering using the Rutherford’ formula and to construct the corresponding effective modelling using according regularized phase beams. It is shown that with using of such approach, it is possible to significantly increase the efficiency of the recurrent procedure for the gravity assists chains searching for ballistic scenarios of the modern interplanetary flights.

Gravity assists gravitational scattering and the perturbation rings in the Solar system

One of the types of gravitational scattering in the Solar system within the framework of the model of the restricted three-body problem (R3BP) is gravity assist maneuvers of the “particles of insignificant mass” [1] (spacecraft, asteroids, comets, etc.). For their description, a physical analogy with the beam scattering of charged α particles in a Coulomb field is useful. However, unlike the scattering of charged particles, there are external restrictions for the possibility of gravity assists executing related from the restricted size of planet’s sphere of influence. At the same time, internal restrictions for the gravity assists performance estimated by the effective radii of planets are known from the literature on R3BP [2] (gravitational capture by the planet, falling into it). They depend from the particle asymptotic velocity relative the planet. For obvious reasons, their influence cuts off the possibility of effective gravity assists performance [3]. In this work the generalized estimates of the sizes of the near-planetary regions (“perturbation rings”), falling into which is a necessary condition for the implementation of gravity assists, are presented. The detailed analysis shows that Neptune and Saturn have the characteristic “perturbation rings” of the largest sizes in the Solar system, and Jupiter occupies only the fourth place in this checklist.

Dirac Particle in the Coulomb Field on the Background of Hyperbolic Lobachevsky Model

The known systems of radial equations describing the relativistic hydrogen atom on the base of the Dirac equation in Lobachevsky hyperbolic space is solved. The relevant 2-nd order differential equation has six regular singular points, its solutions of Frobenius type are constructed explicitly. To produce the quantization rule for energy values we have used the known condition for determination of the transcendental Frobenius solutions. This defines the energy spectrum which is physically interpretable and similar to the spectrum arising for the scalar Klein-Fock-Gordon equation in Lobachevsky space. In the present paper, exact analytical solutions referring to this spectrum are constructed. Convergence of the series involved is proved analytically and numerically. Squared integrability of the solutions is demonstrated numerically. It is shown that the spectrum coincides precisely with that previously found within the semi-classical approximation.

A spontaneously sustainable bioinspired interfacial evaporation driven power generation strategy

In nature, liquid evaporation occurs everywhere all the time. This low-grade energy absorption to drive liquid evaporation is greatly potential for sustainable spontaneously power generation. Here, a natural liquid evaporation strategy of interfacial evaporation driven nanogenerator (IENG) is developed in this work. Coupled by the phonon wind and a fluctuating Coulomb field, an induced direct current is generated. Simultaneously, inspired by the light-trapping properties of moth eye, a simple and efficient BLT-IENG including a hierarchical surface of bionic light-trapping and electrospinning perovskite conductivity with an enhanced thermally insulating and water storage capability is designed. This enhancement of the output performance is greatly attributed to the improvement of the interfacial evaporation characteristics driven by natural solar and wind energies. Hence, our BLT-IENG achieves a breakthrough in the unit area open-circuit voltage in the marine environment, which is improved by a factor of 7.6 over the currently reported average value. This work provides an unexplored strategy for multi-energies inspired natural interfacial evaporation driven power generation.