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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- 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.
- ПубликацияТолько метаданныеSubstitution of heavy hydrogen isotopes in tungsten layers during gas exposure ЗАМЕЩЕНИЕ ТЯЖЕЛЫХ ИЗОТОПОВ ВОДОРОДА В ВОЛЬФРАМОВЫХ СЛОЯХ ПРИ ВЫДЕРЖКЕ В ГАЗЕ(2020) Krat, S. A.; Vasina, Ya. A.; Prishvitcyn, A. S.; Fefelova, E. A.; Popova, M. A.; Gasparyan, Yu. M.; Pisarev, A. A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович© 2020 National Research Center Kurchatov Institute. All rights reserved.Efficiency of deuterium removal from tungsten co-deposited layers was studied by means of thermal desorption spectroscopy in the 30 to 200 °С temperature range in vacuum and hydrogen atmosphere (8 104 Pa). Tungsten layers 100 nm and 500 nm thick were deposited in magnetron discharge in argon-deuterium environment and contained ~2% at. of deuterium. Presence of hydrogen (protium) during sample degassing increases the rate of deuterium removal. Simultaneously, an additional amount of protium is captured in the co-deposited layers. The rate of deuterium removal increases with temperature. Exposure at a temperature of 473 K in a hydrogen atmosphere for 18 hours allowed 99% of the captured deuterium to be removed.
- ПубликацияОткрытый доступSURFACE HYDROGEN ISOTOPES DETECTION BY LOW ANGLE ION SCATTERING SPECTROSCOPY(НИЯУ МИФИ, 2023) Sinelnikov, D. N.; Gasparyan, Y. M.; Grishaev, M. V.; Efimov, N. E.; Krat, S. A.; Nikitin, I. A.; Крат, Степан Андреевич; Гаспарян, Юрий Микаэлович; Синельников, Дмитрий Николаевич; Никитин, Иван Андреевич; Ефимов, Никита Евгеньевич; Гришаев, Максим ВалерьевичHydrogen isotopes retention in thermonuclear fusion reactors is limited due to safety regulations and should be well controlled. Surface conditions can strongly affect accumulation rates of hydrogen isotopes in the bulk of plasma facing materials. Therefore, in vacuo methods of surface composition control may help to investigate mechanisms of this effects.
- ПубликацияОткрытый доступDeuterium trapping in co-deposited layers of ITER-relevant materials(НИЯУ МИФИ, 2021) Krat, S. A.; Prishvitsyn, A. S.; Vasina, Ya. A.; Fefelova, E. A.; Gasparyan, Yu. M.; Pisarev, A. A.; Писарев, Александр Александрович; Гаспарян, Юрий Микаэлович; Крат, Степан Андреевич; Пришвицын, Александр СергеевичHydrogen isotope accumulation in fusion devices is a serious problem. Because deuterium-tritium mixture will be a working gas in future fusion devices, including ITER tokamak, tritium accumulation is an issue from the perspective of radiation safety. In total, only 700 grams of tritium are allowed to be present in ITER vessel at any time, with additional 120 in the cryopumps, and 180 grams allocated to measurement error, to the total of 1000 grams.
- ПубликацияОткрытый доступHYDROGEN CO-DEPOSITION WITH METALS IN PLASMA DISCHARGE(НИЯУ МИФИ, 2017) Krat, S. A.; Gasparyan, Yu. M.; Vasina, Ya. A.; Pisarev, A. A.; Писарев, Александр Александрович; Крат, Степан Андреевич; Гаспарян, Юрий МикаэловичDeposition of a single element film is always accompanied by co-deposition of a certain amount of other elements. This can be done properly to improve properties of the coating or due to contamination by impurities. In the field of thermonuclear fusion research, where hydrogen isotopes are used as a fuel, co-deposition with sputtered material from the wall is one of major mechanisms of hydrogen isotopes accumulation in the installation. Since D-T fuel will be used in ITER and future fusion reactors, accumulation of radioactive tritium will limit the lifespan of the installations due to safety concerns. For example, tritium accumulation in ITER is limited by 1 kg. This is why carbon materials were not accepted for the use in ITER. Basing on experiments, it was predicted that the safety limit could be reached after 100 of shots with tritium. Recent experiments in JET [1] demonstrated in the case of “ITER-like” wall (first wall – Be, divertor area - tungsten) accumulation of deuterium fuel in the co-deposits was 20 times lower than in the full-carbon wall campaign. This is both due to smaller amount of co-deposits and smaller concentration of deuterium in them.
- ПубликацияТолько метаданныеAnalysis of the Near-Surface Layers of Lithium Coatings Using Laser Induced Breakdown Spectroscopy(2019) Vovchenko, E. D.; Krat, S. A.; Kostyushin, V. A.; Khar'kov, M. M.; Bulgadaryan, D. G.; Prishvitsyn, A. S.; Stepanova, T. V.; Kurnaev, V. A.; Zakharov, L. E.; Вовченко, Евгений Дмитриевич; Крат, Степан Андреевич; Харьков, Максим Михайлович; Пришвицын, Александр Сергеевич; Степанова, Татьяна Владимировна© 2019, Pleiades Publishing, Ltd.The paper reports results of studying the geometry of craters formed by the action of laser pulses on solid-state targets of aluminum and lithium films at a power density on the target of (1–5) × 1010 W/cm2 and variation of the number of pulses in the range of 1–150, as well as the results of ex situ layer-by-layer analysis of lithium films on quartz coatings carried out using the method laser induced breakdown spectroscopy to determine the thickness of the films.
- ПубликацияТолько метаданныеSystems of In Situ Diagnostics of Plasma-Surface Interaction in a Mephist-1 Tokamak(2021) Kurnaev, V. A.; Nikolaeva, V. E.; Krat, S. A.; Vovchenko, E. D.; Kaziev, A. V.; Prishvitcyn, A. S.; Vorobiev, G. M.; Stepanova, T. V.; Gvozdevskaya, D. S.; Крат, Степан Андреевич; Вовченко, Евгений Дмитриевич; Казиев, Андрей Викторович; Пришвицын, Александр Сергеевич; Степанова, Татьяна Владимировна© 2021, Springer Science+Business Media, LLC, part of Springer Nature.At the Institute for Laser and Plasma Technologies of NRNU MEPhI, a compact spherical tokamak MEPhIST (MEPhI-Spherical Tokamak) has been developed and constructed for educational, demonstrational and research purposes. The creation of plasma diagnostic systems involves several stages, determined by a successive complication of the plasma research tasks, the device upgrading and the development of educational and methodological materials for the laboratory works to be performed at the tokamak. Testing of the in situ methods for analyzing the plasma-surface interaction is one of the main scientific and technological goals set for this tokamak. The diagnostic complex described in the paper provides cumulative information on the processes occurring after the plasma-surface contact; it represents a set of very informative and well-tested diagnostic tools that allow the students to obtain visual reliable information on the processes occurring in the tokamak vacuum vessel.
- ПубликацияТолько метаданныеMEPHIST-0 Tokamak Toroidal Magnetic Field System(2021) Krat, S. A.; Prishvitcyn, A. S.; Alieva, A. I.; Efimov, N. E.; Vinitskiy, E. A.; Bulgadaryan, D. G.; Vorobyov, G. M.; Kurnaev, V. A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Ефимов, Никита Евгеньевич; Виницкий, Егор Александрович© 2021, Pleiades Publishing, Ltd.Abstract: A system for creating a toroidal magnetic field in the MEPHIST tokamak is described. The system is a single toroidal solenoid consisting of 12 copper loops made from a copper strip of variable width. The shape of the poloidal cross section is selected based on the zero torque condition. The distribution of the angle of inclination of the loops in the toroidal direction along their length was selected empirically by means of numerical modeling designed to minimize the scattered fields. The expected corrugation of the magnetic field at the large radius of the tokamak is ~0.6%. The inductance of the solenoid and the current supply lines is ~ 37 μH, the ohmic resistance is ~12 mΩ. When the toroidal field was raised, the loop voltage of ~ 3 V was observed.
- ПубликацияТолько метаданныеThe Project of MEPhIST Tokamak(2019) Kurnaev, V. A.; Vorobyov, G. M.; Nikolaeva, V. E.; Krat, S. A.; Melnikov, A. V.; Ivanov, D. P.; Gasparyan, Y. M.; Крат, Степан Андреевич; Мельников, Александр Владимирович; Гаспарян, Юрий Микаэлович© 2019, Pleiades Publishing, Ltd.The concept of the small spherical tokamak project is described, the main objectives of the project are to increase competencies at the University in the training of personnel in the field of physics and technologies of controlled thermonuclear fusion, as well as attracting young people to this area. The implementation of the project also implies giving impetus and new opportunities for improving the methods of plasma diagnostics developed at the University, studies on the plasma surface interactions and computer simulation of processes in the plasma and on the plasma facing surfaces. The installation has a large radius of 25 cm, an aspect ratio of less than 2, and a vertical elongation of ∼ 3, which allows, in principle, for small sizes and costs of the installation, taking into account the subsequent increase in the toroidal field to ∼ 2 T, to carry out important studies for progress in plasma performance in tokamaks. Namely, research on physics of plasma confinement, current drive with RF power and plasma interaction with materials. The project includes a phased implementation with a multiple increase in the magnetic field and plasma current, as well as the possibility of quick and convenient access to the internal elements of the discharge chamber and the simultaneous use of a large number of diagnostics.
- ПубликацияТолько метаданныеAccumulation of Deuterium and Helium in Co-Deposited W Layers Formed in He-Seeded Deuterium Plasma(2022) Krat, S. A.; Fefelova, E. A.; Prishvitcyn, A. S.; Khomyakov, A. K.; Gasparyan, Y. M.; Pisarev, A. A.; Крат, Степан Андреевич; Пришвицын, Александр Сергеевич; Гаспарян, Юрий Микаэлович; Писарев, Александр Александрович© 2022, Allerton Press, Inc.Abstract: The effect He in plasma has on the co-deposition of D–W films is investigated for the room–800 K range of substrate temperatures and two He/D2 ratios of 5 and 20%. He can both raise and lower the content of D in a film, and a mechanism is proposed for this effect. The ratio of He/D in the film is higher than in gas, due to the stronger diffusivity and bonding energy of He. A similarity is observed between the dependences of D and He content on temperature, and it is suggested that the low temperature release of D and He during TDS could be due to annealing-induced relaxation of stresses in the film structure. It is expected that the desorption of He above 1300 K could lead to underestimates of the He content.
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