| 1. |
- Murari, A., et al.
(author)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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In: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Journal article (peer-reviewed)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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| 2. |
- Joffrin, E., et al.
(author)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Research review (peer-reviewed)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 6. |
- Ruilope, LM, et al.
(author)
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Design and Baseline Characteristics of the Finerenone in Reducing Cardiovascular Mortality and Morbidity in Diabetic Kidney Disease Trial
- 2019
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In: American journal of nephrology. - : S. Karger AG. - 1421-9670 .- 0250-8095. ; 50:5, s. 345-356
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Journal article (peer-reviewed)abstract
- <b><i>Background:</i></b> Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. <b><i>Patients and</i></b> <b><i>Methods:</i></b> The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate ≥25 mL/min/1.73 m<sup>2</sup> and albuminuria (urinary albumin-to-creatinine ratio ≥30 to ≤5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level α = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. <b><i>Conclusions:</i></b> FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049.
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| 7. |
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| 8. |
- Labit, B., et al.
(author)
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Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
- 2019
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:8
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Journal article (peer-reviewed)abstract
- © 2019 Institute of Physics Publishing. All rights reserved. Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (ne,sep/nG ∼ 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.
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| 9. |
- Stroth, U., et al.
(author)
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Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Journal article (peer-reviewed)abstract
- An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts.
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| 10. |
- Coda, S., et al.
(author)
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Physics research on the TCV tokamak facility: From conventional to alternative scenarios and beyond
- 2019
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Journal article (peer-reviewed)abstract
- The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device's unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly non-inductive H-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power 'starvation' reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached L-mode phase, increasing the outer connection length reduces the in-out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable-configuration baffles and possibly divertor pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam injection heating will be added.
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| 11. |
- Reimerdes, H., et al.
(author)
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Overview of the TCV tokamak experimental programme
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Journal article (peer-reviewed)abstract
- The tokamak a configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019-20 campaign its configurational flexibility has been enhanced with the installation of removable divertor gas baffles, its diagnostic capabilities with an extensive set of upgrades and its heating systems with new dual frequency gyrotrons. The gas baffles reduce coupling between the divertor and the main chamber and allow for detailed investigations on the role of fuelling in general and, together with upgraded boundary diagnostics, test divertor and edge models in particular. The increased heating capabilities broaden the operational regime to include T (e)/T (i) similar to 1 and have stimulated refocussing studies from L-mode to H-mode across a range of research topics. ITER baseline parameters were reached in type-I ELMy H-modes and alternative regimes with 'small' (or no) ELMs explored. Most prominently, negative triangularity was investigated in detail and confirmed as an attractive scenario with H-mode level core confinement but an L-mode edge. Emphasis was also placed on control, where an increased number of observers, actuators and control solutions became available and are now integrated into a generic control framework as will be needed in future devices. The quantity and quality of results of the 2019-20 TCV campaign are a testament to its successful integration within the European research effort alongside a vibrant domestic programme and international collaborations.
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| 12. |
- Chellaï, O., et al.
(author)
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Millimeter-wave beam scattering and induced broadening by plasma turbulence in the TCV tokamak
- 2021
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 61:6
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Journal article (peer-reviewed)abstract
- The scattering of millimeter-wave beams from electron density fluctuations and the associated beam broadening are experimentally demonstrated. Using a dedicated setup, instantaneous deflection and (de-)focusing of the beam due to density blobs on the beam path are shown to agree with full-wave simulations. The detected time-averaged wave power transmitted through the turbulent plasma is reproduced by the radiative-transfer model implemented in the WKBeam code, which predicts a ∼50% turbulence-induced broadening of the beam cross-section. The role of core turbulence for the considered geometry is highlighted.
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| 13. |
- Valassi, E., et al.
(author)
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High mortality within 90 days of diagnosis in patients with Cushing's syndrome: results from the ERCUSYN registry
- 2019
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In: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 181:5, s. 461-472
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Journal article (peer-reviewed)abstract
- Objective: Patients with Cushing's syndrome (CS) have increased mortality. The aim of this study was to evaluate the causes and time of death in a large cohort of patients with CS and to establish factors associated with increased mortality. Methods: In this cohort study, we analyzed 1564 patients included in the European Registry on CS (ERCUSYN); 1045 (67%) had pituitary-dependent CS, 385 (25%) adrenal-dependent CS, 89 (5%) had an ectopic source and 45 (3%) other causes. The median (IQR) overall follow-up time in ERCUSYN was 2.7 (1.2-5.5) years. Results: Forty-nine patients had died at the time of the analysis; 23 (47%) with pituitary-dependent CS, 6 (12%) with adrenal-dependent CS, 18 (37%) with ectopic CS and two (4%) with CS due to other causes. Of 42 patients whose cause of death was known, 15 (36%) died due to progression of the underlying disease, 13 (31%) due to infections, 7 (17%) due to cardiovascular or cerebrovascular disease and 2 due to pulmonary embolism. The commonest cause of death in patients with pituitary-dependent CS and adrenal-dependent CS were infectious diseases (n = 8) and progression of the underlying tumor (n = 10) in patients with ectopic CS. Patients who had died were older and more often males, and had more frequently muscle weakness, diabetes mellitus and ectopic CS, compared to survivors. Of 49 deceased patients, 22 (45%) died within 90 days from start of treatment and 5 (10%) before any treatment was given. The commonest cause of deaths in these 27 patients were infections (n = 10; 37%). In a regression analysis, age, ectopic CS and active disease were independently associated with overall death before and within 90 days from the start of treatment. Conclusion: Mortality rate was highest in patients with ectopic CS. Infectious diseases the commonest cause of death soon after diagnosis, emphasizing the need for careful vigilance at that time, especially in patients presenting with concomitant diabetes mellitus.
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| 14. |
- Moiseenko, V. E., et al.
(author)
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Stellator research at IPP KIPT : Status and prospects
- 2019
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In: PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. - : KHARKOV INST PHYSICS & TECHNOLOGY. - 1562-6016. ; :1, s. 3-8
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Journal article (peer-reviewed)abstract
- Features of the recent Uragan-2M campaign are reviewed together with some theoretical advances. They include experiments with B4C limiter, studies of various 1. . . 20 kHz oscillations, development of a new in-situ diagnostics for wall conditions, i.e. the thermal desorption probe, the improved numerical model of RF plasma production in stellarators in the ion cyclotron and electron-cyclotron frequency ranges, a new positive-definite form of time-harmonic Maxwell's equations and plasma start-up studies.
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| 15. |
- van Laarhoven, Cjhcm, et al.
(author)
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Delayed Development of Aneurysmal Dilatations in Patients with Extracranial Carotid Artery Dissections
- 2022
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In: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884. ; 64:6, s. 595-601
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Journal article (peer-reviewed)abstract
- Objective: Dissection of the carotid artery (CaAD) may result in aneurysm formation. The present study was undertaken to evaluate the time of onset of post-dissection extracranial carotid artery aneurysms (ECAA) following CaAD, and to analyse independent risk factors for the development of these aneurysms. Methods: From four European stroke centres, 360 patients with extracranial CaAD were included. The time between the estimated dissection onset and aneurysm formation was analysed, and the clinical risk factors increasing the probability of aneurysm were assessed. Results: The median duration of follow up was 5.2 months (range 0 - 24 months). A total of 75 post-dissection ECAAs were identified in 70 patients (19.4%, 95% confidence interval [CI] 15.7 - 23.8). In 52 of 70 (74%) patients, the ECAA was diagnosed at the initial clinical work up of CaAD diagnosis, with the median estimated time of dissection onset to ECAA diagnosis being six days (interquartile range [IQR] 0 - 25). In the remaining 18 (26%) patients who had normal carotid arteries at the initial imaging, the aneurysm diagnosis was made a median of 6.2 months (189 days) from the original imaging (IQR 128 - 198). A Cox proportional hazards model showed that both multiple artery dissections (hazard ratio [HR] 2.58, 95% CI 1.54 - 4.33) and arterial tortuosity (HR 1.79, 95% CI 1.08 - 2.95) were associated with presence of ipsilateral ECAA. Conclusion: This post hoc cohort analysis showed substantially delayed development of ipsilateral ECAA in patients with CaAD, months after baseline. Multiple dissections and arterial tortuosity are associated with the presence of ECAA and can be used in future prediction models of ECAA development in patients with CaAD.
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| 16. |
- Moiseyenko, Volodymyr, et al.
(author)
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Developments for stellarator-mirror fusion-fission hybrid concept
- 2021
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In: Problems of Atomic Science and Technology, Ser. Thermonuclear Fusion. - : NRC Kurchatov Institute. - 0202-3822. ; 44:2, s. 111-117
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Journal article (peer-reviewed)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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| 17. |
- Moiseyenko, Volodymyr, et al.
(author)
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FUSION RESEARCH IN STELLARATOR DEPARTMENT OF IPP NSC KIPT
- 2022
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In: PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. - : Problems of Atomic Science and Technology. - 1562-6016. ; :6, s. 3-8, s. 3-8
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Journal article (peer-reviewed)abstract
- This paper briefly describes intrinsic and collaborative scientific activities in the Stellarator Department of the Institute of Plasma Physics of the National Science Center "Kharkov Institute of Physics and Technology" in last two years. These activities include experiments on JET tokamak, stellarators Wendelstein 7-X and Uragan-2M, TOMAS toroidal device and theoretical studies related to modeling of radio-frequency fields in plasma and conceptual development of the stellarator-mirror fission-fusion hybrid.
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