arXiv subjects

A. A. Stepanenko

Publications and source records attributed to A. A. Stepanenko.

5 recordsLinked to original sources

arXiv2026

Gas release from metals under irradiation with elliptic Gaussian laser beam during LID-QMS analysis

Laser-induced-desorption quadrupole-mass-spectrometry (LID-QMS) diagnostics is considered as one of the candidate methods for the remote control of tritium inventory in the ITER first wall. Studies involving LID-QMS generally assume the circular shape of the laser spot on the analyzed surface. At the same time, the diagnostics laser source cannot be always positioned so as to irradiate tokamak tiles under normal angles, which results in the laser spot shape differing from the circular one. In this contribution, we analyze the tritium removal process under sample irradiation by an elliptic Gaussian laser beam, extending the results of our previous analysis [Stepanenko, Gasparyan, Physica Scripta 99 (8), 085604 (2025)]. The thermal desorption model governing the heat transport and tritium removal from the solid is formulated. The new analytical expression describing the sample temperature dynamics is derived. The developed model is used to examine the impact of the laser beam/spot ellipticity on the tritium desorption process from a tungsten sample. The conditions, under which the elliptic beam can be approximated with the circular one for the rapid assessment of the amount of desorbed tritium, are assessed.

physics.plasm-ph↗

arXiv2023

Analysis of sample temperature dynamics under pulsed laser irradiation during laser-induced-desorption diagnostic

The accurate assessment of the local tritium concentration in the tokamak first wall by means of the laser-induced desorption (LID) diagnostic is sought as one the key solutions to monitoring the local radioactive tritium content in the first wall of the fusion reactor ITER. Numerical models of gas desorption from solids used for LID simulation are usually closed with the one-dimensional heat transport models. In this study, the temperature dynamics of a target irradiated by a short laser pulse during LID are analyzed by means of the two-dimensional heat transport model to assess the validity of using one-dimensional approximation for recovering the diagnostic signal. The quantitative estimates for the parameters governing the heat transfer are presented. The analytical expressions for the sample temperature distribution resolved both in time and space are derived. The sensitivity analysis of the obtained relations to uncertainties in the experimental parameters is performed. It is shown that, depending of the ratio between the laser spot radius and heat diffusion length, the one-dimensional approach can noticeably overestimate the sample temperature in the limit of small laser spot radius, resulting in more than 100 % larger amounts of tritium desorbed from the irradiated target, compared to the two-dimensional approximation. In the limit of large laser spot radius, both approaches yield comparable amounts of desorbed tritium.

physics.plasm-ph↗

arXiv2022

Impact of the improved parallel kinetic coefficients on the helium and neon transport in SOLPS-ITER for ITER

New Grad's-Zhdanov module is implemented in the SOLPS-ITER code and applied to ITER impurity transport simulations. Significant difference appears in the helium transport due to improved parallel kinetic coefficients. As a result 30\% decrease of the separatrix-averaged helium relative concentration is observed for the constant helium source and pumping speed. Change of the impurity behaviour is discussed. For the neon changes are less pronounced. For the first time the ion distribution functions are studied in the ITER Scrape-off layer conditions to reveal the origin of the kinetic coefficient improvements and theory limitations.

physics.plasm-ph↗

arXiv2021

Higher-order topological phase of interacting photon pairs

Topological phases open a door to such intriguing phenomena as unidirectional propagation and disorder-resilient localization at a stable frequency. Recently discovered higher-order topological phases further extend the concept of topological protection enabling versatile control over localization in multiple dimensions. Motivated by the recent advances in quantum technologies such as large coherently operating qubit ensembles, we predict and investigate the higher-order topological phase of entangled photon pairs emerging due to the effective photon-photon interaction. Being feasible for state-of-the-art experimental capabilities, the designed model provides an interesting example of interaction-induced topological transitions in the few-particle two-dimensional system.

cond-mat.mes-hall↗

arXiv2017

Kohn anomalies in momentum dependence of magnetic susceptibility of some three-dimensional systems

We study a question of presence of Kohn points, yielding at low temperatures non-analytic momentum dependence of magnetic susceptibility near its maximum, in electronic spectum of some three-dimensional systems. In particular, we consider one-band model on face centered cubic lattice with hopping between nearest and next-nearest neighbors, which models some aspects of the dispersion of ZrZn$_2$, and the two-band model on body centered cubic lattice, modeling the dispersion of chromium. For the former model it is shown that Kohn points yielding maxima of susceptibility exist in a certain (sufficiently wide) region of electronic concentrations; the dependence of the wave vectors, corresponding to the maxima, on the chemical potential is investigated. For the two-band model we show existence of the lines of Kohn points, yielding maximum of the susceptibility, which position agrees with the results of band structure calculations and experimental data on the wave vector of antiferromagnetism of chromium.

cond-mat.str-el↗