| 1. |
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| 2. |
- Glazunov, G.P., et al.
(författare)
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Vacuum-plasma properties of stainless steel after impact of combined glow-microwave discharges in argon atmosphere
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Problems of Atomic Science and Technology. ; 27:1, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- The experiments were carried out to determine the vacuum-plasma characteristics (mainly erosion and outgassing rate in a vacuum) of the stainless steel 12X18H10T before and after processing the walls of the vacuum chamber with the glow discharge and combined, glow-microwave plasma discharges in argon atmosphere. The current-voltage characteristics, the electron density and electron temperature were measured. It was observed that the discharge voltage in the combined regime is significantly lower than in glow discharges. In some modes, this voltage decrease can be up to 200 V. It was shown that erosion of stainless steel 12X18H10T in the combined discharges is 70 %, less than in the glow discharges. Measurements were made of the outgassing rate of 12X18H10T stainless steel with the thermal desorption probe in situ in the DSM-1 vacuum chamber. It was shown that cleaning the chamber wall by the glow discharge during 5 h leads to a decrease in the outgassing rate from 5.5·10-5 to 1·10-5 (Torr.l)/(s.cm2) . When the chamber wall is treated with GM discharge starting from nearly the same initial conditions the outgassing rate decreased to 3·10-6 (Torr.l)/(s.cm2). Spectral measurements of the plasma radiation of a glow and combined discharges show a decrease in the ratio of the peaks of argon ions and neutrals during the transition from a glow discharge to a combined one.
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| 3. |
- Kamio, S., et al.
(författare)
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First experiments on plasma production using field-aligned ICRF fast wave antennas in the large helical device
- 2021
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Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 61:11
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Tidskriftsartikel (refereegranskat)abstract
- The results of the first experimental series to produce a plasma using the ion cyclotron range of frequency (ICRF) in the large helical device (LHD) within the minority scenario developed at Uragan-2M (U-2M) are presented. The motivation of this study is to provide plasma creation in conditions when an electron cyclotron resonance heating start-up is not possible, and in this way widen the operational frame of helical machines. The major constraint of the experiments is the low RF power to reduce the possibility of arcing. No dangerous voltage increase at the radio-frequency (RF) system elements and no arcing has been detected. As a result, a low plasma density is obtained and the antenna-plasma coupling is not optimal. However, such plasmas are sufficient to be used as targets for further neutral beam injection (NBI) heating. This will open possibilities to explore new regimes of operation at LHD and Wendelstein 7-X (W7-X) stellarator. The successful RF plasma production in LHD in this experimental series stimulates the planning of further studies of ICRF plasma production aimed at increasing plasma density and temperature within the ICRF minority scenario as well as investigating the plasma prolongation by NBI heating.
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| 4. |
- Kotenko, V.G., et al.
(författare)
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Heliotron magnetic system of a fusion neutron source
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Problems of Atomic Science and Technology. ; 27:1, s. 15-18
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Tidskriftsartikel (refereegranskat)abstract
- Numerical calculations have been carried out on magnetic field of heliotron magnetic system with a region of stellarator and mirror-type magnetic field superposition. Formation of a region of magnetic field superposition takes place in the gap between two helical coil sections which have reduced pitch length L in comparison with pitch length L0 of the heliotron helical coils, L=L0/3.
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| 5. |
- Kovtun, Yurii, et al.
(författare)
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Development of Technology for Vacuum Surface Conditioning by RF Plasma Discharge Combined With DC Discharge
- 2021
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Ingår i: Science and Innovation. - : National Academy of Sciences of Ukraine. - 2409-9066 .- 2413-4996. ; 17:4, s. 33-43
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: It is important to decrease light and heavy impurities influxes towards the plasma volume during the high temperature plasma experiments in fusion devices. This is why the conditioning of the wall inner vacuum surfaces is a basic part of the fusion device operation.Problem Statement: The conventional inner vacuum chamber surface conditioning methods has a significant drawback: sputtering materials in a vacuum chamber. The inner vacuum surfaces can be also conditioned with radio-frequency (RF) discharge plasma, but the conditioning effectiveness is limited by low ion energy.Purpose: The purpose of this research is to develop vacuum surface conditioning technology by the radio frequency plasma combined with DC discharge.Materials and Methods: The noncontact passive method of optical plasma spectroscopy has been used to estimate ion plasma composition. The stainless steel outgassing has been determined in situ with the thermodesorption probe method. The sputtering of the samples has been measured with the weight loss method.Results: The studies of combined discharge have shown that: the anode voltage of combined discharge is lower than in case of the glow discharge; the stainless steel 12Kh18N10T erosion coefficient is about 1.5 times less in the case of combined discharge than in the glow one; the thermal desorption diagnostic of wall conditions in the DSM-1 experimental device has shown better efficiency with the combined discharge as compared with the glow discharge. The proposed technology is an original one and has no analogs.Conclusions: The reported research results have shown good prospects for the combined discharge usage for plasma walls conditioning and opportunities for using the combined discharge technology for big fusion machines.
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| 6. |
- Kovtun, Yu.V., et al.
(författare)
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Design and application of glow discharge cleaning at Uragan-2M stellarator
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Charkov Institute of Physics and Technology. ; 27:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- For the Uragan-2M stellarator, a glow discharge cleaning (GDC) system is developed. An overview of the GDC system design is presented. The first experimental studies of GDC in an argon atmosphere have been carried out. The dependence of the breakdown voltage on the argon pressure is determined. The current-voltage characteristics of the gas discharge were measured as a function of the working gas pressure also in presence of a magnetic field.
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| 7. |
- Kulyk, Yu.S., et al.
(författare)
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Modelling of radio-frequency wall conditioning in short pulses in a stellarator
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Problems of Atomic Science and Technology. ; 27:1, s. 9-14
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Tidskriftsartikel (refereegranskat)abstract
- Results of numerical modelling of electron cyclotron (EC) short pulse wall conditioning discharge are presented. The analysis carried out with the usage of a self-consistent model that simulates radio-frequency (RF) plasma production in stellarator type machines in the ion cyclotron and EC frequency ranges. The discussion of the results of the calculations is presented.
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| 8. |
- Lozin, A.V., et al.
(författare)
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Uragan-2m gas mixing system
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Problems of Atomic Science and Technology. ; 134:4, s. 195-199
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Tidskriftsartikel (refereegranskat)abstract
- Gas mixture system (GMS) was developed, created and installed at Uragan-2M (U-2M) device. GMS is based on already known gas mixing method successive puffing. It is implemented through successive puffing of several gases from separate high pressure cylinders into working volume. A number of experiments were carried out to create a He+H2 gas mixture with different percentages. The results of measurements of the He+H2 percentage in the GMS and the U-2M vacuum chamber are in good agreement each to other. This system allows you to change the pressure of the mixture in the U-2M chamber at a constant percentage of gases in the mixture.
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| 9. |
- Marchuk, Yu.M., et al.
(författare)
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Computer calculation of probability for binary collisions of electrons with ions and molecules
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : National Science Center, Kharkov Institute of Physics and Technology. - 1562-6016. ; 134:4, s. 154-156
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Tidskriftsartikel (refereegranskat)abstract
- Computer calculation of rate coefficient for binary collision as a function of temperature is presented, and the Maxwell electron velocity distribution function is chosen. The finite elements of the fifth order made it possible to significantly speed up the process of calculation . The result of the approximation is a smooth function and the values of this function, its first and second derivatives, have no jumps at the mesh nodes and the accuracy of calculation is within the limits of statistical errors for the source data. These advantages and the results will be used in future tasks.
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| 10. |
- Moiseyenko, Volodymyr, et al.
(författare)
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Americium and Curium Burnup in a Fusion Reactor
- 2021
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Ingår i: Problems of Atomic Science and Technology, Ser. Thermonuclear Fusion. - : NRC Kurchatov Institute. - 0202-3822. ; 44:2, s. 133-138
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Tidskriftsartikel (refereegranskat)abstract
- A large amount of spent nuclear fuel (SNF) from nuclear power plants has been accumulated globally to date, and there is still no established strategy for handling it. While SNF can be partitioned, the predominant isotope Uranium-238 can be used to produce secondary fuel in fast nuclear reactors, and plutonium be burned in thermal nuclear reactors as a part of MOX fuel. Fission products can be disposed in geological repositories, as they decay in 200—300 years — much sooner than SNF. A major challenge is to handle minor actinides (MAs), particularly americium and curium, which are long-lived elements and are currently not recycled. They have different nuclear properties and cannot be treated like plutonium. It is possible to have americium and curium effectively burned up (fissioned) through irradiation with fusion neutrons. This paper explores the idea of employing fusion power plants for recycling those elements. An appropriate model was generated, which used americium and curium quantities small enough to avoid any strong impact on the reactor systems and operation. At the same time, the model allowed for high MA burnup rates. Nuclear facility used in the model was a torus-shaped thermonuclear reactor with plasma major and minor radii of 1000 and 300 cm, respectively. Such facility could take up additional 10 t of fuel (americium plus curium) with no significant impact on its physical characteristics. The americium and curium burnup rates, calculated with the MNCPX code, were within acceptable limits. Fission neutrons were found to contribute to the production of tritium, which may be important from the standpoint of the reactor’s self-sufficiency in tritium supply. Calculations proved that the reactivity of the reactor as a fission burner was low, enabling a safe operation. In addition to the MA incineration and tritium breeding capacities, fission reactions provided for a moderate (tens of percent) power gain.
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| 11. |
- Moiseyenko, Volodymyr, et al.
(författare)
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Developments for stellarator-mirror fusion-fission hybrid concept
- 2021
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Ingår i: Problems of Atomic Science and Technology, Ser. Thermonuclear Fusion. - : NRC Kurchatov Institute. - 0202-3822. ; 44:2, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- Conceptual development activities on a stellarator-mirror-based fission-fusion hybrid system (SM hybrid) are reviewed. Intended fortransmutation of spent nuclear fuel and safe fission energy production, SM hybrid consists of a fusion neutron source and a powerful subcritical fast fission reactor core. Its fusion component is a stellarator with an embedded magnetic mirror. The stellarator allows for theconfinement of a moderately hot (1—2 keV) deuterium plasma. In the magnetic mirror, the hot sloshing tritium ions are trapped andfusion neutrons are generated. The magnetic mirror is surrounded by a fission mantle, where transmutation of minor actinides and energygeneration take place. One candidate magnetic confinement device for the SM hybrid is the advanced DRACON magnetic trap system,which, unlike the «classical» DRACON version, has one short, rather than two longer mirrors with a relatively short size of 3—6 m. Acomparative numerical analysis of collisionless losses occurring in the magnetic trap part of the single-mirror DRACON leads to a conclusion about the possibility for high-energy tritium ions to be fairly well confined in the magnetic trap area. The Uragan-2M (U-2M)stellarator is used to test the SM hybrid concept with experiment. To fit a magnetic trap into U-2M system, one of the toroidal coils hadto be switched off. A radial escape of charged particles may spontaneously give rise to a weak radial electric field, which may result inclosing the particles’ drift trajectories and thereby substantially improve their confinement. Background plasma confinement withoutdestructive instabilities is demonstrated in the stellarator-mirror regime of U-2M) operation. The sloshing ions driven by radio-frequencyheating are detected in the mirror part of the device with NPA diagnostics. A novel fission mantle design for the SM hybrid is proposed.
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| 12. |
- Moiseyenko, Volodymyr, et al.
(författare)
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Status and prospects in stellarator research at ipp kipt
- 2021
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Ingår i: Problems of Atomic Science and Technology. - : Problems of Atomic Science and Technology. ; 27:1, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- A review of works performed at the Stellarator Department of KIPT is presented. It includes radio frequency (RF) plasma start-up, RF wall conditioning, RF plasma heating and diagnostics improvements at Uragan stellarators, studies of discharges for wall conditioning at Wendelstein 7-X Helias and some theoretical studies on magnetic configurations and tritium breeding. The prospects for the studies are associated with deeper involvement in EUROfusion activities
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| 13. |
- Ågren, Olov, et al.
(författare)
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3d coils for a compact min B mirror field with minimal flux tube ellipticity
- 2021
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Ingår i: Problems of Atomic Science and Technology, Ser. Thermonuclear Fusion. - : NRC Kurchatov Institute. - 0202-3822. ; 44:2, s. 118-123
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Tidskriftsartikel (refereegranskat)abstract
- We determine coil arrangements for reproducing a minimum-B mirror magnetic field, optimized with respect to plasma stability, plasma cross-section ellipticity and particle drift surfaces. The reproduction has to be done with precision, as field errors may give rise to plasma instabilities or collisionless plasma losses due to the guiding centres’ drift away from the confinement region. We have developed a set of twisted «fishbone» coils to allow an array of coils to be flexibly stacked, as required for a precise magnetic field reproduction. Results suggest that high mirror ratios of around 10 can be obtained using a fishbone coil arrangement. The mirror ratio can be further increased by finite plasma beta. Parameters representative of a compact 10 MW fusion neutron source have been derived.
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