arXiv subjects

A. Yu. Popov

Publications and source records attributed to A. Yu. Popov.

9 recordsLinked to original sources

arXiv2021

Low-threshold induced side-scattering instability in the edge transport barrier at O-mode ECRH experiments in magnetic fusion devices

The lower hybrid wave trapping in a tokamak edge transport barrier is predicted. This effect makes possible excitation of the low-power-threshold absolute parametric decay instability leading to side-scattering of the ordinary microwave pump in the electron cyclotron resonance heating experiments. The instability can result in broadening of the power deposition profile both in present day machines and in ITER.

physics.plasm-ph↗

arXiv2016

On Novel Mechanism of a Pump Electromagnetic Wave Absolute Two-Plasmon Parametric Decay Instability Excitation in Tokamak ECRH Experiments

Novel mechanism leading to excitation of absolute two plasmon parametric decay instability (TPDI) of a pump extraordinary (X) wave is discussed. It is shown that the upper hybrid (UH) plasmon can be 3D trapped in the presence of both a nonmonotonous density profile and a finite-size pump beam in a plane perpendicular to the plasma inhomogeneity direction. This leads to excitation of the absolute TPDI of the pump X wave, which manifests itself in temporal exponential growth of the trapped daughter UH wave amplitude and is perhaps the most dangerous instability for mm-waves, widely utilized nowadays in tokamak and stellarators for local plasma heating and current drive and being considered for application in ITER.

physics.plasm-ph↗

arXiv2014

ECRH beam broadening in the edge turbulent plasma of fusion machines

Two analytical models for the ordinary mode propagating through inhomogeneous edge plasma layer are developed. Simple analytical expressions for diffusion-like angular and spatial beam width variation are obtained and compared to time-averaged results coming from 2D Maxwell's equations solver for different turbulence k-spectra and plasma conditions. The strong spatial broadening of microwave beam is predicted by the two approaches at realistic turbulent edge parameters for ECRH experiments at ITER.

physics.plasm-ph↗

arXiv2012

Asymptotics of Maxwell time in the plate-ball problem

The problem on rolling of a sphere on a plane without slipping or twisting is considered. One should roll the sphere from one contact configuration to another so that the length of the curve traced by the contact point in the plane was the shortest possible. Asymptotics of Maxwell time for rolling of the sphere along small amplitude sinusoids is studied. Two-sided estimate for this asymptotics is obtained.

math.OC↗

arXiv2012

Generation of optical vortex light beams by volume holograms with embedded phase singularity

Special features of the optical-vortex (OV) beams generated by thick holographic elements (HE) with embedded phase singularity are considered theoretically. The volume HE structure is based on the 3D pattern of interference between an OV beam and a standard reference wave with regular wavefront. The incident beam diffraction is described within the framework of a linear single-scattering model in which the volume HE is represented by a set of parallel thin layers with the "fork" holographic structure. An explicit integral expression is derived for the complex amplitude distribution of the diffracted paraxial beam with OV. The numerical analysis demonstrates that the HE thickness may essentially influence not only selectivity and efficiency of the OV beam generation but also the amplitude and phase profile of the diffracted beam as well as regularities of its propagation. We have studied the generated OV morphology and laws of its evolution; in particular, the possibility of obtaining a circularly symmetric OV beam regardless of the diffraction angle is revealed.

physics.optics↗

arXiv2010

Low Threshold Parametric Decay Instabilities in ECRH experiments at toroidal devices

The experimental conditions leading to substantial reduction of backscattering decay instability threshold in ECRH experiments in toroidal devices are analyzed. It is shown that drastic decrease of threshold is provided by non monotonic behaviour of plasma density, which is often observed due to so-called density-pump-out effect or presence of magnetic islands, and by poloidal magnetic field inhomogeniety making possible localization of ion Bernstein decay waves. The corresponding ion Bernstein wave gain and the parametric decay instability pump power threshold is calculated. The possible experimental consequences of easy backscattering decay instability excitation are discussed.

physics.plasm-ph↗

arXiv2010

Low Threshold Parametric Decay Back Scattering Instability in Tokamak ECRH Experiments

The experimental conditions leading to substantial reduction of backscattering decay instability threshold in ECRH experiments in toroidal devices are analyzed. It is shown that drastic decrease of threshold is provided by non monotonic behavior of plasma density in the vicinity of magnetic island and poloidal magnetic field inhomogeneity making possible localization of ion Bernstein decay waves. The corresponding ion Bernstein wave gain and the parametric decay instability pump power threshold is calculated.

physics.plasm-ph↗

arXiv2004

Electron Bernstein waves in spherical tokamak plasmas with "magnetic wells"

In addition to traditional regimes with monotonously increasing magnetic field, regimes with "magnetic wells" also occur in spherical tokamaks (STs). The magnetic field profile inversion modifies significantly the whole picture of the wave propagation and damping. Since the magnetic wells may become quite common with further improvement of ST performance, analysis of such configurations is of interest for assessment of EBW plasma heating an CD perspectives. In this paper the basic features of the EBWs propagation and damping for the second cyclotron harmonic in a slab model are considered.

physics.plasm-ph↗

arXiv1997

The asymptotical behavior of spectral function of one family of differential operators

Is considered the asymptotical behavior of spectral function $ρ(λ, ε),ε> 0$, of one family of self adjoint differential operators of second order, defined in space $L_2[0,+\infty)$ with potentials, depending on $ε$. Are given evaluations for the derivative of spectral function for negative $λ$ and is proved the weak convergence of $ρ'(λ, ε)$ to $ρ'(λ, 0)$ with $ε\to +0$.

funct-an↗