Персона: Крат, Степан Андреевич
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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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Руководитель научной группы "Исследования и разработки в области управляемого термоядерного синтеза на токамаках ITER, Т-15 МД, MEPHIST"
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Степан Андреевич
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Теперь показываю 1 - 10 из 53
- ПубликацияОткрытый доступElastic backscattering as a method for the measurement of the integral lithium content in thin films on fusion-relevant substrates(2019) Mayer, M.; Krat, S.; Vasina, Y.; Prishvitsyn, A.; Gasparyan, Y.; Pisarev, A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович© 2019 Elsevier B.V.Different ion beam analysis techniques for the study of thin lithium-containing layers on top of fusion relevant materials are discussed and compared to each other. Elastic backscattering analysis (EBS) with protons is determined to be one of the most promising techniques and allows measurements of Li layers with thicknesses from ∼100 nm up to ∼600 μm, as shown by SIMNRA simulations. The best sensitivity for thin films (∼100 nm) can be achieved using 4 MeV protons with 170° scattering detection angle for layers on Mo and W substrates, and 2 MeV for C substrates. Experimentally EBS measurements were successfully tested for Li films with thicknesses from ∼50 nm up to ∼400 nm after air exposure. The Li films become strongly inhomogeneous and require averaging over multiple measurements in nearby areas. This necessitates averaging over multiple nearby measurement points, and limits the overall precision of the measurement.
- ПубликацияОткрытый доступPost-mortem analyses of gap facing surfaces of tungsten tiles of T-10 ring limiter(2021) Arkhipov, I.; Grashin, S.; Zibrov, M.; Pisarev, A.; Babich, Y.; Berdnikova, M.; Gasparyan, Y.; Gutorov, K.; Efimov, V.; Isaenkova, M.; Krat, S.; Krymskaya, O.; Kurnaev, V.; Stepanova, T.; Vovchenko, E.; Vizgalov, I.; Писарев, Александр Александрович; Бердникова, Мария Михайловна; Гаспарян, Юрий Микаэлович; Гуторов, Константин Михайлович; Ефимов, Виталий Сергеевич; Исаенкова, Маргарита Геннадьевна; Крат, Степан Андреевич; Крымская, Ольга Александровна; Степанова, Татьяна Владимировна; Вовченко, Евгений Дмитриевич© 2020 Elsevier B.V.Surfaces facing the gap between W tiles of the ring limiter of tokamak T-10 were analyzed after T-10 decommissioning using LIBS, SEM/EDA, XRD, TDS, and NRA techniques. Gaps with the width of 5 mm and 0.1 mm were nearly completely covered to their full depths of 22 and 15 mm, respectively, by a deposited film. The film was formed mainly by deposition of lithium that came from Li limiter and transformed in air to Li2CO3 and Li2O. Carbon was deposited from volatile hydrocarbons sputtered from the tokamak walls. Besides, carbon appeared due to chemical reaction with lithium in air. Chemical interactions of W with C, O, and Li led to formation W2C, WC, WO2, and Li2WO4. Carbides formed in W over the entire surface to the full depth of the gaps. Trapping of deuterium and helium in tiles was demonstrated. Possible influence of auto-oscillating discharges on ionization and ion trapping of C,D, and He in gaps is discussed.
- ПубликацияОткрытый доступAnalytical approach for description of deuterium content in deuterium-beryllium co-deposited layers(2021) De, Temmerman, G.; Krat, S.; Gasparyan, Y.; Vasina, Y.; Prishvitcyn, A. S.; Pisarev, A.; Крат, Степан Андреевич; Гаспарян, Юрий Микаэлович; Пришвицын, Александр Сергеевич; Писарев, Александр Александрович© 2021 The Author(s)Available literature data for beryllium content in D-Be co-deposited layers was modeled using newly developed model. It was shown that the model adequately describes the experimental results. An empirical scaling for the available trap concentrations as a function of deuteron energy was introduced in order to improve the agreement between the experimental data and model predictions. The limited recombination rate describes the co-deposition better than the unlimited one. Assuming two types of traps in the film with detrapping energies of 0.8–0.9 and 1.2–1.3 eV and trap concentrations of 10 at. % and 1 at. %, respectively, and the deuterium implantation energy of 15.6 eV, the average relative deviation between experimental and predicted D/Be values of 1.9 was observed, which is better than the empirical D/Be scalings.
- ПубликацияОткрытый доступCOMPARISON OF EROSION AND DEPOSITION IN JET DURING CARBON AND ITER-LIKE CAMPAIGNS(НИЯУ МИФИ, 2015) Krat, S.; Gasparyan, Yu.; Pisarev, A.; Mayer, M.; de Saint-Aubin, G.; Bykov, I.; Coad, P.; Likonen, J.; van Renterghem, W.; Ruset, C.; Widdowson, A.; JET-EFDA, contributors; Гаспарян, Юрий Микаэлович; Крат, Степан Андреевич; Писарев, Александр АлександровичErosion of plasma facing elements in fusion devices is an important question affecting their lifetimes. Redeposition of eroded materials may lead to accumulation of hydrogen isotopes, which makes it an important problem from the perspective of radiological safety. Redeposition in layers with carbon and beryllium could be a channel for hydrogen isotope accumulation.
- ПубликацияОткрытый доступINTERACTION OF LITHUM-DEUTERIUM FILMS WITH ATMOSPHERIC GASES(НИЯУ МИФИ, 2015) Popkov,A. S.; Krat, S. A.; Gasparyan, Yu. M.; Pisarev, A. A.; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович; Крат, Степан АндреевичA choice of plasma-facing materials is one of the key issues in thermonuclear fusion reactor design. Lithium as an element with the low atomic number is a promising material for plasma-facing components (PFC) in fusion installations and a number of experiments at tokamaks already demonstrated many positive effects on plasma operation [1,2]. Lithium can be used for conditioning, PFC on the base of of capillary porous system with liquid lithium are also considered. In any way, one can expect lithium co-deposition with hydrogen isotopes at the surface of PFC and at remote areas. Lithium as a good getter can accumulate high amount of hydrogen isotopes (deuterium, tritium) that can be a problem from the safety reason. Deuterium retention and thermal desorption from lithium films formed in plasma discharge were investigated in this work.
- ПубликацияОткрытый доступИЗОТОПНЫЙ ЭФФЕКТ В НАКОПЛЕНИИ ВОДОРОДА В ОСАЖДЁННЫХ ИЗ ПЛАЗМЫ ВОЛЬФРАМОВЫХ СЛОЯХ(НИЯУ МИФИ, 2024) КРАТ, С. А.; ПРИШВИЦЫН, А. С.; ГАСПАРЯН, Ю. М.; ПИСАРЕВ, А. А.; Писарев, Александр Александрович; Пришвицын, Александр Сергеевич; Крат, Степан Андреевич; Гаспарян, Юрий МикаэловичВажность изучения накопления водорода в соосаждённых из плазмы металлических слоях во многом обусловлена опасностью избыточного накопления радиоактивного изотопа трития в термоядерных установках, где со-осаждение материалов стенки с частицами работчего газа – один из основных каналов накопления водорода в установке. Так как эксперименты с использованием трития крайне затруднены технически, опасны и дороги, подавляющее большинство работ в данной области проводится с использованием дейтерия как симулятора трития. При этом предполагается, что накопление трития будет происходить идентично накоплению дейтерия. В связи со сложностью проведения экспериментов с тритием, возможно провести опыты по сравнению свойств протия и дейтерия и сделать некоторые оценки в части трития на основе полученных данных.
- ПубликацияОткрытый доступComparison of erosion and deposition in JET divertor during the first three ITER-like wall campaigns(2020) Krat, S.; Mayer, M.; Baron-Wiechec, A.; Brezinsek, S.; Gasparyan, Y.; Крат, Степан Андреевич; Гаспарян, Юрий МикаэловичThe manuscript presents an overview of the erosion and deposition data in the inner and outer JET divertor observed during the first three ITER-like wall campaigns (JET-ILW1, JET-ILW2, JET-ILW3). Erosion and deposition were studied using core samples cut out from divertor tiles. For the studied samples a similar general deposition pattern was observed in all three campaigns: More than 60% of the total deposition occurred in the upper region of the inner divertor on tiles 0 and 1, where Be was transported and deposited from the scrape-off layer. High erosion was observed only on tile 5. In JET-ILW2 and 3, erosion together with high power fluxes was observed in the outer divertor at the bottom of tile 7. Additionally, deposition peaks were observed on the sloping parts of tiles 4 and 6, which were more pronounced in JET-ILW2 and 3 due to placing the strike point more often on these tiles. The deposits consisted primarily of Be, with some additional D and C. Deposition rates were observed to decrease from campaign to campaign, with the C deposition rate decreasing the most, more than 2 times from JET-ILW1 to JET-ILW3. D retention up to levels of similar to 1 at% was observed up to large depths in the W protective coatings in all campaigns.
- ПубликацияОткрытый доступModel for hydrogen accumulation in co-deposited layers(2020) Krat, S. A.; Prishvitsyn, A. S.; Vasina, Y. A.; Gasparyan, Y. M.; Pisarev, A. A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович© 2020 The Author(s)An improved diffusion based model for prediction of the hydrogen content in co-deposited layers depending on the deposition conditions (the properties of the material which is co-deposited with hydrogen, rate of deposition, hydrogen flux and particle energy, substrate temperature) is presented. The model is validated using experimental data for W, Mo and Al, and is compared to empirical scaling equations currently in use. It is shown that a good agreement is observed in regards to hydrogen content vs substrate temperature experimental data, and no disagreement with scaling equations can be seen in regards to the role of hydrogen flux and the rate of deposition. It is shown that the influence of hydrogen particle energy on the hydrogen content requires further investigation. In addition to hydrogen, models for other mobile impurities both in co-deposited layers and in layers under steady-state net erosion conditions are given.
- ПубликацияОткрытый доступHelium accumulation in tungsten layers deposited in Ar-He magnetron discharge(2020) Krat, S.; Fefelova, E.; Prishvitsyn, A. S.; Vasina, Y.; Harutyunyan, Z.; Gasparyan, Y. u.; Pisarev, A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Арутюнян, Зорий Робертович; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович© Published under licence by IOP Publishing Ltd.W-He co-deposition was studied by means of in-vacuo thermal desorption spectroscopy. W-He co-deposited layers were produced at substrate temperatures varied from 400 K to 800 K with a 50 K temperature step. It was found that the He content decreases from ~1.7 at. % at 400 K to ~0.17 at. % at 750 K. At 800 K, an increase in the He content was observed, that should be caused by significant changes in the film structure. Helium TDS spectra had two main peaks with maxima in the 500-600 K range and at ~960 K; the peaks observed are similar to those previously seen for He ion implantation in W. Several scaling expressions are proposed for He/W vs. T.
- ПубликацияТолько метаданныеA setup for study of co-deposited films(2020) Krat, S. A.; Popkov, A. S.; Gasparyan, Y. M.; Vasina, Y. A.; Prishvitsyn, A. S.; Pisarev, A. A.; Крат, Степан Андреевич; Гаспарян, Юрий Микаэлович; Пришвицын, Александр Сергеевич; Писарев, Александр Александрович© 2020 IOP Publishing Ltd and Sissa Medialab.A setup for investigation of thermal desorption spectra of gases accumulated in thin films deposited by plasma sputtering of solid targets is described. Deposition and thermal desorption spectroscopy (TDS) are performed in two different vacuum chambers separated by a gate valve with the sample transferred between the chambers in-vacuo. The temperature of the substrate for deposited films can be varied in the range of 300-800 K; and the deposition rate is controlled by a quartz microbalance. Thermal desorption of co-deposited gases is analyzed by a quadrupole mass spectrometer. Sputtering rate and evaporation of the film during TDS are measured by quartz microbalances. Three experiments are described 1) trapping of deuterium by the growing chemically active Li film with subsequent decomposition and evaporation of the film, 2) temperature dependent deuterium trapping in the growing W film resulting in trapping with several binding energies, and 3) chemical interaction of D-Li layer with water vapor leading to isotopic H-D exchange and chemical transformation of the deposited film.