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B. V. Ivanov

Publications and source records attributed to B. V. Ivanov.

At least 19 recordsLinked to original sources
arXiv2020

Detritiation of the electrostatic spectrometer of Troitsk Nu-mass experiment

The paper describes methods and presents results of the Troitsk Nu-mass experiment spectrometer cleanup, which inner volume (40 m3) and surfaces (160 m2) was contaminated by 4.4 GBq of tritium. The Troitsk Nu-mass experiment of Institute for Nuclear Research of Russian Academy of Sciences, Moscow, is designed to measure the spectrum of electrons from tritium decays in order to search for hypothetical particles - sterile neutrinos. As a result of equipment failure, the spectrometer internal volume was contaminated with tritium. The contamination made measurements impossible and the research program stopped. The methods of vacuum extraction, hydrogen soaks, and water vapour soaks were used for cleanup. As a result of detritiation, the background level of the main detector of the Troitsk Nu-mass spectrometer decreased by more than 10 times, which made it possible to resume work. The results are consistent with the data obtained earlier for volumes in normal conditions in the air and can be used for planning work on detritiation of similar installations.

physics.ins-det↗
arXiv2020

Generating solutions for charged stellar models in general relativity

It is shown that the expressions for the tangential pressure, the anisotropy factor and the radial pressure in the Einstein - Maxwell equations may serve as generating functions for charged stellar models. The latter can incorporate an equation of state when the expression for the energy density is also used. Other generating functions are based on the condition for the existence of conformal motion (conformal flatness in particular) and the Karmarkar condition for embedding class one metrics, which do not depend on charge. In all these cases the equations are linear first order differential equations for one of the metric components and Riccati equations for the other. The latter may be always transformed into second order homogenous linear differential equations. These conclusions are illustrated by numerous particular examples from the study of charged stellar models.

gr-qc↗
arXiv2020

Linear and Riccati equations in generating functions for stellar models in general relativity

It is shown that the expressions for the tangential pressure, the anisotropy factor and the radial pressure in the Einstein equations may serve as generating functions for stellar models. The latter can incorporate an equation of state when the expression for the energy density is also used. Other generating functions are based on the condition for the existence of conformal motion (conformal flatness in particular) and the Karmarkar condition for embedding class one metrics. In all these cases the equations are linear first order differential equations for one of the metric components and Riccati equations for the other. The latter may be always transformed into second order homogenous linear differential equations. These conclusions are illustrated by numerous particular examples from the study of stellar models.

gr-qc↗
arXiv2017

Analytical study of anisotropic compact star models

A simple classification is given of the anisotropic relativistic star models, resembling the one of charged isotropic solutions. On the ground of this database, and taking into account the conditions for physically realistic star models, a method is proposed for generating all such solutions. It is based on the energy density and the radial pressure as seeding functions. Numerous relations between the realistic conditions are found and the need for a graphic proof is reduced just to one pair of inequalities. This general formalism is illustrated with an example of a class of solutions with linear equation of state and simple energy density. It is found that the solutions depend on three free constants and concrete examples are given. Some other popular models are studied with the same method.

gr-qc↗
arXiv2016

A different approach to anisotropic spherical collapse with shear and heat radiation

In order to study the type of collapse, mentioned in the title, we introduce a physically meaningful object, called the horizon function. It directly enters the expressions for many of the stellar characteristics. The main junction equation, which governs the collapse, transforms into a Riccati equation with simple coefficients for the horizon function. We integrate this equation in the geodesic case. The same is done in the general case when one or another of the coefficients vanish. It is shown how to build classes of star models in this formulation of the problem and simple solutions are given.

gr-qc↗
arXiv2015

All solutions for geodesic anisotropic spherical collapse with shear and heat radiation

We introduce a physically important object, called the horizon function, in the study of geodesic collapse. It is closely related to the stellar characteristics and satisfies a simple Riccati equation. This equation is integrated and all of its solutions are found in terms of some generating functions. Previous solutions are regained and further investigated.

gr-qc↗
arXiv2015

The effect of anode emitter injection capability on characteristics of hybrid SIT-MOS transistors

The possibility of optimization of high voltage hybrid SIT-MOS transistors (HSMT) by local reduction of the lifetime near anode emitter and/or reduction of the anode emitter injection ability by three different ways has been investigated using two-dimensional numerical simulation. It has been shown that all of these methods proposed previously for optimization of insulated-gate bipolar transistor (IGBT) are physically equivalent and makes it possible to reduce turn-off energy losses $E_{off}$ in HSMT by 30-40%. Importantly that energy $E_{off}$ in optimized HSMT appears to be 15-35% less than in equivalent trench IGBT under other equal conditions.

cond-mat.other↗
arXiv2014

Simulation of Submicrosecond Regimes of High-Voltage Reversibly-Switched Dynistors

Basing on 2D computer simulation of physical processes in high-voltage reversibly-switched dynistors (RSD) important peculiarities of their submicrosecond pulse performance mechanisms have been studied. It is characteristic that on early stages of switching fronts rather great voltage spikes and dangerous delays in current rise are observed. These undesirable manifestations are found to be eliminated due to appropriate reduction of the doping in p-base. Following this way for RSD with blocking voltage of 2.5-5 kV at the value of reversibly pumped charge 5-10 uC/cm^2 one can diminished the switching front duration up to 75-100 ns and lower. As for the current rise rate it can be increased up to (20-30) A/cm^2/ns, i.e., more then the order higher of the similar parameter for the standard RSD. For the switching pulse amplitudes of few unites kA and with the total pulse duration of several hundred nanoseconds the energy transmitted to the load can reach fractions and units of joules per cycle at the power losses in RSD nearly 10% of these values.

cond-mat.other↗
arXiv2014

Comparison of the time-averaged power losses in the insulated-gate bipolar transistors and the hybrid SIT-MOS thyristors

Two-dimensional numerical simulation of switching processes for equivalent silicon insulated gate bipolar transistors of CSTBT-type and hybrid SITh-MOS thyristors (HSMT) has been performed. It is shown that the energy of switching losses during turning on and off periods in HSMT is greater than in totaly equivalent CSTBT. Therefore, the time-averaged power Pav dissipated in HSMT is smaller than in equivalent CSTBT only for rather long total current pulse duration. However, lowering the lifetime of nonequilibrium charge carriers tnp in the SITh can significantly reduce switching losses of the whole HSMT, while maintaining its advantage for the static on state. Therefore, for each set of CSTBT parameters it seams to be possible to select up such tnp in "almost equivalent" HSMT that the averaged power dissipation in HSMT will be less, than in equivalent CSTBT, for any set ranges of current pulse amplitude and duration.

cond-mat.other↗
arXiv2012

Collapsing shear-free perfect fluid spheres with heat flow

A global view is given upon the study of collapsing shear-free perfect fluid spheres with heat flow. We apply a compact formalism, which simplifies the isotropy condition and the condition for conformal flatness. This formalism also presents the simplest possible version of the main junction condition, demonstrated explicitly for conformally flat and geodesic solutions. It gives the right functions to disentangle this condition into well known differential equations like those of Abel, Riccati, Bernoulli and the linear one. It yields an alternative derivation of the general solution with functionally dependent metric components. We bring together the results for static and time- dependent models to describe six generating functions of the general solution to the isotropy equation. Their common features and relations between them are elucidated. A general formula for separable solutions is given, incorporating collapse to a black hole or to a naked singularity.

gr-qc↗
arXiv2011

Self-gravitating spheres of anisotropic fluid in geodesic flow

The fluid models mentioned in the title are classified. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids and dust as particular cases. Many uncharged and charged anisotropic solutions, all conformally flat and some uniform density solutions are found. A number of solutions with linear equation among the two pressures are derived, including the case of vanishing tangential pressure.

gr-qc↗
arXiv2011

Evolving spheres of shear-free anisotropic fluid

The fluid models mentioned in the title are studied in a modified approach, based on two formulas for the mass function. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids as particular cases. All charged anisotropic solutions, all conformally flat and all uniform density solutions are found. A large class of solutions with linear equation among the two pressures is derived, including the case of vanishing tangential pressure. The mechanism responsible for the appearance of equation of state is elucidated.

gr-qc↗
arXiv2009

The fundamental spherically symmetric fluid model

It is shown that an effective anisotropic spherically symmetric fluid model with heat flow can absorb the addition to a perfect fluid of pressure anisotropy, heat flow, bulk and shear viscosity, electric field and null fluid.

gr-qc↗
arXiv2007

Purely electromagnetic spacetimes

Electrovacuum solutions devoid of usual mass sources are classified in the case of one, two and three commuting Killing vectors. Three branches of solutions exist. Electromagnetically induced mass terms appear in some of them.

gr-qc↗
arXiv2004

Strong gravitational force induced by static electromagnetic fields

It is argued that static electric or magnetic fields induce Weyl-Majumdar-Papapetrou solutions for the metric of spacetime. Their gravitational acceleration includes a term many orders of magnitude stronger than usual perturbative terms. It gives rise to a number of effects, which can be detected experimentally. Four electrostatic and four magnetostatic examples of physical set-ups with simple symmetries are proposed. The different ways in which mass sources enter and complicate the pure electromagnetic picture are described.

gr-qc↗
arXiv2003

The general double-dust solution

The gravitational field of two identical rotating and counter-moving dust beams is found in full generality. The solution depends on an arbitrary function and a parameter. Some of its properties are studied. Previous particular solutions are derived as subcases.

gr-qc↗