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Лисица, Валерий Степанович

Организационные подразделения

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Институт лазерных и плазменных технологий

Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.

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Валерий Степанович

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Interaction of ultra-short electromagnetic pulses with ions in hot dense plasmas
(2019) Astapenko, V. A.; Calisti, A.; Lisitsa, V. S.; Лисица, Валерий Степанович
© 2019 Elsevier B.V. The general properties of ultra-short electromagnetic pulse (USP) interactions with highly charge ions in dense and high temperature plasmas are considered. The application of USP in X-ray spectral range provided by modern technology including free-electron laser machines opens up new opportunities for investigations of dense plasmas. They are based on the possibility of USP penetration into optically dense media due to their broad spectral distribution. In the framework of the use of USP for active spectroscopy in high energy density plasmas, new expressions of the transition probabilities are proposed. An aluminum plasma at local thermodynamic equilibrium is considered. The interaction of USP with hydrogen-like ions at N e = 2⋅10 22 cm −3 and T = 1 keV is analyzed in details by taking into account both the specificity of the USP and the plasma effects, such as Stark and Doppler effects on the line profile of the excited radiative transitions. The results are applied for demonstration of optical depth and pulse duration effects on excitation probabilities of the n = 1–n = 3 radiative transition, which is the simplest atomic scheme to observe fluorescence signal.
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From the vector to scalar perturbations addition in the stark broadening theory of spectral lines
(2021) Astapenko, V.; Letunov, A.; Lisitsa, V.; Лисица, Валерий Степанович
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.The effect of plasma Coulomb microfied dynamics on spectral line shapes is under consideration. The analytical solution of the problem is unachievable with famous Chandrasekhar–Von-Neumann results up to the present time. The alternative methods are connected with modeling of a real ion Coulomb field dynamics by approximate models. One of the most accurate theories of ions dynamics effect on line shapes in plasmas is the Frequency Fluctuation Model (FFM) tested by the comparison with plasma microfield numerical simulations. The goal of the present paper is to make a detailed comparison of the FFM results with analytical ones for the linear and quadratic Stark effects in different limiting cases. The main problem is connected with perturbation additions laws known to be vector for small particle velocities (static line shapes) and scalar for large velocities (the impact limit). The general solutions for line shapes known in the frame of scalar perturbation additions are used to test the FFM procedure. The difference between “scalar” and “vector” models is demonstrated both for linear and quadratic Stark effects. It is shown that correct transition from static to impact limits for linear Stark-effect needs in account of the dependence of electric field jumping frequency in FFM on the field strengths. However, the constant jumping frequency is quite satisfactory for description of the quadratic Stark-effect. The detailed numerical comparison for spectral line shapes in the frame of both scalar and vector perturbation additions with and without jumping frequency field dependence for the linear and quadratic Stark effects is presented.
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Kinetics of dense plasma in the field of short laser pulses: A generalized approach
(2024) Astapenko, V. A.; Lisitsa, V. S.; Лисица, Валерий Степанович
A generalized kinetic model of atomic level populations in an optically dense plasma excited by laser pulses of arbitrary duration is formulated and studied. This model is based on a nonstationary expression for the probability of excitation of an atomic transition and takes into account the effects of laser pulse penetration into an optically dense medium. A universal formula for the excitation probability as a function of time and propagation length is derived and applied to the case of a Lorentzian spectral profile of an atomic transition excited by a laser pulse with a Gaussian envelope. The features of nonstationary excitation probabilities are presented for different optical depths of the plasma, laser pulse durations, and carrier frequencies. The formulas derived here will be useful for the description of atomic populations excited by laser pulses under realistic conditions of dense plasmas.
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The coulomb symmetry and a universal representation of rydberg spectral line shapes in magnetized plasmas
(2020) Letunov, A.; Lisitsa, V.; Лисица, Валерий Степанович
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.A new method of line shape calculations of hydrogen-like atoms in magnetized plasmas is presented. This algorithm makes it possible to solve two fundamental problems in the broadening theory: the analytical description of the radiation transition array between excited atomic states and an account of a thermal ion motion effect on the line shapes formation. The solution to the first problem is based on the semiclassical approach to dipole matrix elements calculations and the usage of the specific symmetry properties of the Coulomb field. The second one is considered in terms of the kinetic treatment of the frequency fluctuation model (FFM). As the result, one has a universal description of line shapes under the action of the dynamic of ion’s microfield. The final line shape is obtained by the convolution of the ionic line shape with the Voigt electron Doppler profile. The method is applicable formally for large values of principal quantum numbers. However, the efficiency of the results is demonstrated even for well known first members of the hydrogen Balmer series Dα and Dβ lines. The comparison of obtained results with accurate quantum calculations is presented. The new method may be of interest for investigations of spectral line shapes of hydrogen-like ions presented in different kinds of hot ionized environments with the presence of a magnetic field, including So L and divertor tokamak plasmas.
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Statistical and quantum photoionization cross sections in plasmas: Analytical approaches for any configurations including inner shells
(2020) Vainshtein, L. A.; Astapenko, V. A.; Rosmej, F. B.; Lisitsa, V. S.; Лисица, Валерий Степанович
© 2020 Author(s).Statistical models combined with the local plasma frequency approach applied to the atomic electron density are employed to study the photoionization cross-section for complex atoms. It is demonstrated that the Thomas-Fermi atom provides surprisingly good overall agreement even for complex outer-shell configurations, where quantum mechanical approaches that include electron correlations are exceedingly difficult. Quantum mechanical photoionization calculations are studied with respect to energy and nl quantum number for hydrogen-like and non-hydrogen-like atoms and ions. A generalized scaled photoionization model (GSPM) based on the simultaneous introduction of effective charges for non-H-like energies and scaling charges for the reduced energy scale allows the development of analytical formulas for all states nl. Explicit expressions for nl = 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, and 5s are obtained. Application to H-like and non-H-like atoms and ions and to neutral atoms demonstrates the universality of the scaled analytical approach including inner-shell photoionization. Likewise, GSPM describes the near-threshold behavior and high-energy asymptotes well. Finally, we discuss the various models and the correspondence principle along with experimental data and with respect to a good compromise between generality and precision. The results are also relevant to large-scale integrated light-matter interaction simulations, e.g., X-ray free-electron laser interactions with matter or photoionization driven by a broadband radiation field such as Planckian radiation.
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Dielectronic recombination in non-LTE plasmas
(2020) Rosmej, F. B.; Astapenko, V. A.; Lisitsa, V. S.; Vainshtein, L. A.; Лисица, Валерий Степанович
Novel phenomena and methods related to dielectronic capture and dielectronic recombination are studied for non-local thermodynamic equilibrium (LTE) plasmas and for applications to non-LTE ionization balance. It is demonstrated that multichannel autoionization and radiative decay strongly suppress higher-order contributions to the total dielectronic recombination rates, which are overestimated by standard approaches by orders of magnitude. Excited-state coupling of dielectronic capture is shown to be much more important than ground-state contributions, and electron collisional excitation is also identified as a mechanism driving effective dielectronic recombination. A theoretical description of the effect of angular-momentum-changing collisions on dielectronic recombination is developed from an atomic kinetic point of view and is visualized with a simple analytical model. The perturbation of the autoionizing states due to electric fields is discussed with respect to ionization potential depression and perturbation of symmetry properties of autoionization matrix elements. The first steps in the development of statistical methods are presented and are realized in the framework of a local plasma frequency approach. Finally, the impact of collisional-radiative processes and atomic population kinetics on dielectronic recombination is critically discussed, and simple analytical formulas are presented. (C) 2020 Author(s).
Только метаданные
Absorption of ultrashort electromagnetic pulses in plasma with inhomogeneous distribution of density and temperature
(2020) Astapenko, ValeriyA.; Sakhno, Sergey, V.; Lisitsa, ValeryS.; Лисица, Валерий Степанович
The analysis of influence of the inhomogeneous distribution of temperature and density of atoms on the probability of absorption of ultrashort electromagnetic pulses in plasma is carried out. A specific example of divertor plasma of tokamaks and absorption in the Lyman series (at the Ly-alpha line) is considered. It is shown that the absorption probability may exceed relative populations of excited levels in divertor plasma by several orders of magnitude. The influence of the pulse duration on the probability of excitation of an atomic level is considered. The results suggest a possibility of a sharp increase in a fluorescence signal under the action of an ultrashort pulse.
Только метаданные
Stark-Zeeman and Blokhintsev Spectra of Rydberg Atoms
(2020) Letunov, A. Y.; Lisitsa, V. S.; Лисица, Валерий Степанович
The problem of Rydberg atomic spectra in crossed electric F and magnetic B fields (combined Stark-Zeeman effects), as well as an oscillating electric field are under consideration. The main problem is the great array of radiative transitions between the Rydberg atomic states. The different versions of semiclassical approaches are applied for the solution of the problem. New approximate selection rules are established to simplify the matrix elements of radiative transitions, making it possible to reduce the complex expressions of Gordon's hypergeometric series to the trivial trigonometric functions. Simple analytical formulas for the dipole matrix elements of a Rydberg hydrogen-like atom in external crossed electric and magnetic fields for H-n alpha are obtained. The specific calculations are presented for n = 10 to 9 transition both for parallel and perpendicular orientations of F-B fields. The result of Blokhintsev for a single Stark component in oscillating field is generalized for the array of radiative transitions between Rydberg atomic states. Such spectra with large values of modulation index are compared with static ones.
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Simulation of passive charge exchange signals of hydrogenlike beryllium ions for cxrs edge diagnostics in iter
(2020) Sdvizhenskii, P. A.; Levashova, M. G.; Neverov, V. S.; Romazanov, Y. A.; Kukushkin, A. B.; Lisitsa, V. S.; Кукушкин, Александр Борисович; Лисица, Валерий Степанович
© 2020 National Research Center Kurchatov Institute. All rights reserved.For one of the divertor's operation scenarios in ITER, the background radiation from passive charge exchange was calculated for one of the beryllium (Be IV) spectral lines used for Charge eXchange Recombination Spectroscopy (CXRS) diagnostics. The contribution of the charge exchange of beryllium ions Be V on neutral deuterium atoms in the ground and first excited states is calculated. The cross sections for the charge exchange reaction calculated by the numerical code ARSENY and other codes are used. The data from the ITER edge plasma modeling database is used based on the SOLPS numerical code: Calculations of the kinetics of deuterium recycling by the EIRENE code and the erosion of the beryllium first wall by the ERO2.0 code.
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Thomson scattering in plasmas: Theory generalization for ultrashort laser pulse effects
(2020) Astapenko, V. A.; Khramov, E. S.; Rosmej, F. B.; Lisitsa, V. S.; Лисица, Валерий Степанович
© 2020 Author(s).The standard approach to calculate the Thomson scattering probability is reconsidered for the case of ultrashort incident laser pulses (USLPs). We established a new model for the interaction of USLP with plasmas that is based on Fermi's equivalent photon conception to calculate the spectral-angular differential Thomson scattering probability. The simulations demonstrate that the scattering probability for USLP is a non-monotonic function of pulse duration in contrast to the standard long-pulse model showing linear dependence. An analytical approach is developed to study the nonlinear behavior of the scattering probability as a function of pulse duration and other parameters.