Персона: Маренков, Евгений Дмитриевич
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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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Маренков
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Евгений Дмитриевич
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- ПубликацияОткрытый доступAssessment of laser induced breakdown spectroscopy accuracy for determination of hydrogen accumulation in tungsten(2021) Tsygvintsev, I. P.; Marenkov, E. D.; Gasparyan, Y. M.; Stepanenko, A. A.; Маренков, Евгений Дмитриевич; Гаспарян, Юрий Микаэлович; Степаненко, Александр Александрович© 2021 The Author(s)Laser-induced breakdown spectroscopy (LIBS) is an in situ method of determining hydrogen (H) content in plasma-facing materials in tokamak fusion reactors. Observing radiation from the plasma plume produced by a powerful laser pulse during the target exposition characterizes the sample composition. This is typically accomplished using the Saha-Boltzmann (SB) plot technique under local thermodynamic equilibrium (LTE) conditions. Despite many experimental studies dedicated to applying LIBS to determine H isotope retention in fusion reactor materials, the current understanding of this method's intrinsic accuracy remains inadequate. In this report, we use numerical calculations to estimate the relative error of determining H content in a sample using LIBS. As an example. we consider LIBS to study a W sample loaded with H in a vacuum. Under typical LIBS pulse parameters (109 W/cm2 and 12 ns duration), the error can be quite large, approximately 70%. We demonstrate that the error tends to decrease as the laser pulse intensity increases. Various factors contributing to the relative error are examined and their dependence on the LIBS plasma parameters is discussed. The SB plot remains a straight line even when LTE conditions are violated, making it difficult to anticipate the experimental results’ error.
- ПубликацияОткрытый доступABLATION OF HIGH-Z MATERIAL DUST GRAINS IN EDGE PLASMAS(НИЯУ МИФИ, 2015) Marenkov, E.; Krasheninnikov, S.; Маренков, Евгений ДмитриевичNowadays it is well recognized that dust particles can play an important role in fusion plasma performance and material transport [1]. Therefore, it is important to have a good understanding of the most important processes dust grains encounter in the course of the interactions with fusion grade plasmas. Many fundamentals of grain-plasma interactions were developed by dusty-plasma community. However, grain-plasma interactions in fusion devices have some important distinctions. In particular, in hot and dense fusion plasma environment dust grains ablate rather quickly. The effect of the vapor on grain-plasma interactions can only be neglected for relatively small grains (below ~10 microns). Meanwhile, it is important to know how the vapor “shielding” alters grain-plasma interactions for larger (~100 microns) grains, which may pose significant threat for plasma performance and even result in disruption, especially for the case where these are high-Z material grains.
- ПубликацияОткрытый доступVAPOUR SHIELDING OF SOLID TARGETS EXPOSED TO HIGH HEAT FLUX(НИЯУ МИФИ, 2015) Pshenov, A. A.; Eksaeva, A. A.; Krasheninnikov, S. I.; Marenkov, E. D.; Маренков, Евгений ДмитриевичThe thickness of a Tungsten monoblocks composing future ITER divertor is supposed to be 8 mm only. Severe erosion caused by a high heat fluxes during transients, such as Type I ELMs and disruptions, therefore is a limiting factor to PFCs lifespan. Thermal loads over the range of Q = 0.5−2 MJ/m2 on the timescale of τ = 0.3− 0.6 ms are expected during Type I ELMs. Even larger heat fluxes, of the order of = − Q 0.5 5 MJ/m2 are expected during thermal quench stage of disruption lasting approximately τ = 1 −3 ms [1]. Under the influence of the extreme heat fluxes serious surface modification and cracking of the Tungsten monoblocks is anticipated [2]. Moreover, melting of a thin surface layer is likely. Melt motion contributes seriously to the material erosion [3]. The other sources of erosion are melt splashing, in form of a droplet ejection, and stationary evaporation [4]. These mechanics lead to a cold dense secondary plasma region formation near the irradiated surface. Intense re-radiation of the incident plasma flow energy in the secondary plasma layer results in a significant reduction of the heat flux reaching the target surface [5]. Accounting for this vapour shielding effect is essential to estimate the surface erosion properly. Predicting the divertor plates lifespan therefore requires deep understanding of all the processes mentioned and their interplay.
- ПубликацияОткрытый доступВлияние транспорта водорода в первой стенке термоядерных реакторов на рециклинг(НИЯУ МИФИ, 2013) Маренков, Е. Д.; Маренков, Евгений Дмитриевич; Цветков, И. В.
- ПубликацияТолько метаданныеShielding of liquid metal targets in plasma of linear devices(2020) Marenkov, E. D.; Pshenov, A. A.; Kukushkin, A. S.; Маренков, Евгений Дмитриевич© 2020 Author(s).We apply a 0D model of shielding for simulations of liquid Li exposure experiments in He plasma of the Magnum-PSI linear device. The model accounts for all the most essential processes in the vapor cloud and plasma-surface interactions. The simulation results are in good agreement with the target surface temperature measurements. A factor of 10 increase in the erosion flux leads to a 100 °C decrease in the surface temperature, still giving a reasonable agreement with experiments. Therefore, the temperature measurements are inconclusive with respect to determining whether enhanced erosion takes place or not. We observe that only 10% of the eroded material is redeposited, while several other works suggest up to 99% redeposition. We show that low redeposition is a consequence of the low electron temperature, about 0.3 eV, in the vapor cloud and that the ratio of the ionization length to the transverse cloud size is the critical parameter to look at. Hence, the redeposition factor is not a universal quantity and can vary in quite a broad range depending on the plasma parameters and machine geometry.
- ПубликацияОткрытый доступERO-PSI CODE FOR NUMERICAL SIMULATION OF EXPERIMENTS ON TUNGSTEN SPUTTERING IN LINEAR PLASMA DEVICE PSI-2(НИЯУ МИФИ, 2015) Eksaeva, A. A.; Marenkov, E. D.; Borodin, D.; Kirshner, A.; Laenger, M.; Kurnaev, V. A.; Kreter, A.; Маренков, Евгений ДмитриевичPlasma-wall interaction is one of the recognized issues for thermonuclear reactor performance and seems to be a key direction in fusion researches in the framework of the ITER project [1]. Tungsten (W) has been chosen as a main material for construction of ITER divertor due to its low sputtering at edge plasma temperatures, large melting temperature, and small uptake of tritium.
- ПубликацияТолько метаданныеVapor shielding of liquid lithium divertor target during steady state and transient events(2020) Marenkov, E.; Pshenov, A.; Маренков, Евгений ДмитриевичWe develop a 0D model of vapor shielding including a vast variety of processes in the vapor cloud and plasma-surface interactions. The model is applied to a liquid lithium (Li) divertor with targets covered by a self-restoring Li coating. Calculations show that in the steady state, the target heat flux saturates with increasing external heat flux at approximately 7.5 MW m(-2). This value may seem very optimistic. However, we show that a significant part of the external heat is removed with the eroded particles. Hence, the maximum sustainable heat load is restricted by the coating renewal rate. The response of the coating to pulsed loads similar to the ITER-scale type I edge localized modes (ELMs) demonstrates high shielding efficiency. Similar to the steady-state regime, the coating renewal rate is the critical quantity for the target survival under pulsed heat loads. Surviving an ELM with an external heat load of 100 MW m(-2) requires a fast coating recovery rate (10(26) m(-2) s(-1)) or a substantial reservoir of Li on the surface, which may be a concern for some target designs.
- ПубликацияОткрытый доступAPPLICATION OF LIBS, LA-QMS, LA-TOF-MS FOR FUSION RELEVANT MATERIALS ANALYSIS(НИЯУ МИФИ, 2021) Efimov, N. E.; Sinelnikov, D. N.; Bulgadaryan, D. G.; Gasparyan, Y. M.; Vovchenko, E. D.; Marenkov, E. D.; Маренков, Евгений Дмитриевич; Ефимов, Никита Евгеньевич; Вовченко, Евгений Дмитриевич; Синельников, Дмитрий Николаевич; Гаспарян, Юрий МикаэловичOne of the critical issues on the way to controlled nuclear fusion is related to plasma wall interaction. Such interaction leads to co-deposition of hydrogen isotopes together with eroded first wall materials. It is known that the deuterium-tritium (DT) mixture will be used in ITER and future fusion devices as a fuel. So as the accumulation of radioactive tritium in the machines is limited by the nuclear license, there is a need for some remote fuel retention monitoring system. In current devices, the total fuel amount is determined from the gas balance (difference between input and output flows) measurements and from a post mortem analysis of plasmafacing components. One of the most promising techniques which can be applied in situ in tokamaks is based on laser irradiation of the surface of interest followed by mass- or optical spectroscopy. Such a technique was already applied in TEXTOR tokamak to the hydrogenic carbon layers [1], and it is included in the task list of ITER with a high priority.
- ПубликацияОткрытый доступANGULAR DISTRIBUTION OF W SPUTTERED BY LOW ENERGY AR(НИЯУ МИФИ, 2017) Sorokin, I.; Marenkov, E.; Nordlund, K.; Eksaeva, A.; Маренков, Евгений Дмитриевич; Сорокин, Иван АлександровичSputtering of the first wall tokamak materials by low energy of the order of 100 eV but high fluxes, 1020 cm-2s-1 is one of the main mechanisms responsible for steady-state first wall erosion. At such low energies sputtering occurs due to few-collision cascades. The resulting angular and energy distributions of sputtered particles are different from cosine and Thompson distributions predicted by kinetic theory of cascades valid at larger energies. Experimental data on the distributions for materials and energies of interest are scarce [1]. At the same time experiments at linear plasma devices demonstrated that the distributions play a substantial role in comprehension of the sputtered particles transport in plasma [2]. In this work we develop an experimental procedure for direct measurements of the angular distributions of the sputtered particles and a method for molecular dynamics calculation of them. The proposed simulation procedure accurately accounts for polycrystalline structure of the samples.
- ПубликацияТолько метаданныеOn the role of hydrogen radiation absorption in divertor plasma detachment(2019) Krasheninnikov, S. I.; Pshenov, A. A.; Kukushkin, A. S.; Marenkov, E.; Маренков, Евгений ДмитриевичTransition to the detached divertor regime that allows lowering the peak power loads on the divertor targets to a tolerable level requires low plasma temperature T-e similar to 1 eV and high plasma density n(e) similar to 10(21) M-3 in front of the target. Under such conditions, radiation trapping of the Lyman lines of hydrogen isotopes becomes important. It can influence both energy balance and the ionization/recombination rates significantly. Nevertheless, opacity is typically neglected in the 2D edge transport codes used to study the divertor plasma detachment. We report on the first in-depth investigation of radiation opacity effects on transition to detachment. Simulations are performed with the SOLPS 4.3 code package using a DIII-D size tokamak as a particular example. It is found that in pure hydrogen plasma suppression of the neutral hydrogen radiation loss due to the photon absorption makes reaching the detached plasma regime more difficult. A significantly higher average separatrix plasma pressure is required to reach a similar degree of detachment. Adding plasma impurities compensates for the reduced neutral radiation and offsets the effect of opacity. In a carbon device, where the impurity source is due to erosion of the divertor components and is strongly connected to the edge plasma density, the absorbed fraction of the hydrogen radiation is easily compensated with the increasing carbon radiation loss. However, nowadays, in the more relevant case of the full-metal wall and seeded impurity with the feedback-controlled content, the increase of the edge plasma density alone is insufficient to compensate for trapping of the hydrogen radiation. In this case, achievement of the desired degree of detachment requires higher average separatrix plasma pressure or seeded impurity content than those obtained from the transparent plasma model.