High precision methods for solving a system of cold plasma equations taking into account electron–ion collisions

High precision simulation algorithms are proposed and justified for modelling cold plasma oscillations taking into account electron–ion collisions in the non-relativistic case. The specific feature of the approach is the use of Lagrangian variables for approximate solution of the problem formulated initially in Eulerian variables. High accuracy is achieved both through the use of analytical solutions on trajectories of particles and due to sufficient smoothness of the solution in numerical integration of Cauchy problems. Numerical experiments clearly illustrate the obtained theoretical results. As a practical application, a simulation of the well-known breaking effect of multi-period relativistic oscillations is carried out. It is shown that with an increase in the collision coefficient one can observe that the breaking process slows down until it is completely eliminated.

Ionosonde Total Electron Content Evaluation Using IGS Data

In this work, a period of two years (2016–2017) of vertical total electron content (VTEC) from ionosondes operating in Brazil is compared to the International GNSS Service (IGS) data. Sounding instruments from National Institute for Space Research (INPE) provided the ionograms used, which were filtered based on confidence score (CS) and C-level flags evaluation. Differences between TEC from IGS maps and ionograms were accumulated in terms of root mean square error (RMSE). It has been noticed the TEC values provided by ionograms are systematically underestimated, which is attributed to a limitation in the electron density modeled for the ionogram topside that considers maximum height only around 800–900 Km, while IGS takes in account electron density from GNSS stations up to the satellite network orbits. The ionogram topside profiles covering the plasmasphere were re-modeled using an adaptive alpha-Chapman exponential decay that includes a transition function between the F2 layer and plasmasphere, and electron density integration height was extended to compute TEC. Chapman parameters for the F2 layer were extracted from each ionogram, and plasmaspheric scale height was set to 10,000 Km. Our analysis has shown the plasmaspheric basis electron density, assumed to be proportional to the electron peak density, plays an important role to reduce the RMSE values. Depending on the proportionality coefficient choice, mean RMSE reached a minimum of 5.32 TECU, that is 23 % lower than initial ionograms TEC errors.

Резонансное поглощение электромагнитного излучения в монослое фосфорена

The absorption coefficient of the electromagnetic radiation in a phosphorene single layer placed in a magnetic field is found. A degenerate and nondegenerate electron gas is considered. The resonant dependences of the absorptance on the radiation frequency and applied magnetic field are found. Taking into account electron scattering at an ionized impurity leads to oscillation dependences of the absorption coefficient on the radiation frequency and external magnetic field. The resonance character of the absorption curve is shown. The conditions of resonances and position of resonance peaks are found.

Оценка соотношения энергий излучения Вавилова--Черенкова и катодолюминесценции, возбуждаемых электронным пучком в алмазе

The ratio between energies of Vavilov–Cherenkov radiation and cathodoluminescence excited by an electron beam in diamond samples is determined taking into account electron scattering in these samples, energy distribution of beam electrons, ionization losses of the electron energy, and dispersion of the diamond refractive index. Experimental results on measuring spectral characteristics of the glow of natural and synthetic diamond samples under the action of a subnanosecond electron beam with electron energy of up to 200 keV are presented. It is shown that most of the radiation of the diamond samples in the region of 240–750 nm under the action of an electron beam with electron energy of up to 200 keV belongs to cathodoluminescence.

On accurate high-order numerical derivatives computations for quantum chemistry purposes

Various molecular parameters in quantum chemistry could be computed as derivatives of energy over different arguments. Unfortunately, it is quite complicated to obtain analytical expression for characteristics that are of interest in the framework of methods that account electron correlation. Especially it relates to the coupled cluster (CC) theory. In such cases, numerical differentiation comes to rescue. This approach, like any other numerical method has empirical parameters and restrictions that require investigation. Current work is called to clarify the details of Finite-Field method usage for high-order derivatives calculation in CC approaches. General approach to the parameter choice and corresponding recommendations about numerical steadiness verification are proposed. As an example of Finite-Field approach implementation characterization of optical properties of fullerene passing process through the aperture of carbon nanotorus is given.

Модель накопления зарядов в n- и p-МОП-транзисторах при туннельной инжекции электронов из затвора

A quantitative model for charge accumulation in an undergate dielectric during tunneling electron injection from a gate according to the Fowler–Nordheim mechanism is developed. The model takes into account electron and hole capture at hydrogen-free and hydrogen-related traps as well as the generation of surface states during the interaction of holes with hydrogen-related centers. The experimental dependences of the threshold voltage shift and gate voltage shift of n - and p -channel MOS (metal–oxide–semiconductor) transistors on the injected charge in the constant current mode are analyzed based on the model.

A new optical scheme for large-extraction small-aberration vacuum-ultraviolet synchrotron radiation beamlines

Vacuum-ultraviolet radiation delivered by bending-magnet sources is used at numerous synchrotron radiation facilities worldwide. As bending-magnet radiation is inherently much less collimated compared with undulator sources, the generation of high-quality intense bending-magnet vacuum-ultraviolet photon beams is extremely demanding in terms of the optical layout due to the necessary larger collection apertures. In this article, an optimized optical layout which takes into account both the optical and electron beam properties is proposed. This layout delivers an improved beam emittance of over one order of magnitude compared with existing vacuum-ultraviolet bending-magnet beamlines that, up to now, do not take into account electron beam effects. The arrangement is made of two dedicated mirrors, a cylindrical and a cone-shaped one, that focus independently both the horizontal and the vertical emission of a bending-magnet source, respectively, and has been already successfully applied in the construction of the infrared beamline at the Brazilian synchrotron. Using this scheme, two vacuum-ultraviolet beamline designs based on a SOLEIL synchrotron bending-magnet source are proposed and analysed. They would be useful for future upgrades to the DISCO beamline at SOLEIL and could be readily implemented at other synchrotron radiation facilities.