| 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. |
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| 3. |
- 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
-
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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| 4. |
- Krasilnikov, A., et al.
(author)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
-
Journal article (peer-reviewed)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Schneider, M., et al.
(author)
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Modelling third harmonic ion cyclotron acceleration of deuterium beams for JET fusion product studies experiments
- 2016
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In: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 56:11, s. 112022-
-
Journal article (peer-reviewed)abstract
- Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (He-3) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail enhancing DD and (DHe)-He-3 fusion reactions. Modelling and measuring the fast deuterium tail accurately is essential for quantifying the fusion products. This paper presents the modelling of the D distribution function resulting from the NBI+ICRF heating scheme, reinforced by a comparison with dedicated JET fast ion diagnostics, showing an overall good agreement. Finally, a sawtooth activity for these experiments has been observed and interpreted using SPOT/RFOF simulations in the framework of Porcelli's theoretical model, where NBI+ICRH accelerated ions are found to have a strong stabilizing effect, leading to monster sawteeth.
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| 9. |
- Aad, G., et al.
(author)
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- 2011
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Journal article (peer-reviewed)
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| 10. |
- Aad, G., et al.
(author)
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- 2012
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Journal article (peer-reviewed)
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| 11. |
- Aad, G., et al.
(author)
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- 2012
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Journal article (peer-reviewed)
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| 12. |
- Aad, G., et al.
(author)
-
- 2012
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Journal article (peer-reviewed)
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| 13. |
- Aad, G., et al.
(author)
-
- 2012
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Journal article (peer-reviewed)
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| 14. |
- Aad, G., et al.
(author)
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- 2012
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In: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :7
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Journal article (peer-reviewed)
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| 15. |
- Aad, G., et al.
(author)
-
- 2012
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368 .- 1550-7998. ; 86:7
-
Journal article (peer-reviewed)
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| 16. |
- Aad, G., et al.
(author)
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- 2012
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In: Physical Review Letters. - : American Physical Society. - 1079-7114 .- 0031-9007. ; 108:26
-
Journal article (peer-reviewed)
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| 17. |
- Aad, G., et al.
(author)
-
- 2012
-
In: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :6
-
Journal article (peer-reviewed)
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| 18. |
- Abata, E., et al.
(author)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
-
Journal article (peer-reviewed)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 19. |
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| 20. |
- becoulet, A, et al.
(author)
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The way towards thermonuclear fusion simulators
- 2007
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In: Computer Physics Communications. - : Elsevier BV. - 0010-4655. ; 177:1, s. 55-59
-
Journal article (peer-reviewed)abstract
- AbstractIn parallel to the ITER project itself, many initiatives address complementary technological issues relevant to a fusion reactor, as well as many remaining scientific issues. One of the next decade's scientific challenges consists of merging the scientific knowledge accumulated during the past 40 years into a reliable set of validated simulation tools, accessible and useful for ITER prediction and interpretation activity, as well as for the conceptual design of the future reactors. Obviously such simulators involve a high degree of “integration” in several respects: integration of multi-space, multi-scale (time and space) physics, integration of physics and technology models, inter-discipline integration etc. This very distinctive feature, in the framework of a rather long term and world-wide activity, constrains strongly the choices to be made at all levels of developments. A European task force on integrated tokamak modelling has been activated with the long-term aim of providing the EU with a set of codes necessary for preparing and analysing future ITER discharges, with the highest degree of flexibility and reliability. In parallel with the development of simulation tools and software environment, the long term evolution of hardware needs is also discussed at several levels (EU, EU–Japan broader approach, high performance computing, grid technology, data access, etc.), and progress in this domain is reported. Finally, the ITM task force is also working out the worldwide compatibility through regular collaboration with the similar integrated modelling structures which already exist or are being put in place by the other ITER partners.
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| 21. |
- Chapman, I. T., et al.
(author)
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The physics of sawtooth stabilization
- 2007
-
In: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 49:12B, s. B385-B394
-
Journal article (peer-reviewed)abstract
- Long period sawteeth have been observed to result in low-beta triggering of neo-classical tearing modes, which can significantly degrade plasma confinement. Consequently, a detailed physical understanding of sawtooth behaviour is critical, especially for ITER where fusion-born a particles are likely to lead to very long sawtooth periods. Many techniques have been developed to control, and in particular to destabilize the sawteeth. The application of counter-current neutral beam injection (NBI) in JET has resulted in shorter sawtooth periods than in Ohmic plasmas. This result has been explained because, firstly, the counter-passing fast ions give a destabilizing contribution to the n=1 internal kink mode-which is accepted to be related to sawtooth oscillations-and secondly, the flow shear strongly influences the stabilizing trapped particles. A similar experimental result has been observed in counter-NBI heated plasmas in MAST. However, the strong toroidal flows in spherical tokamaks mean that the sawtooth behaviour is determined by the gyroscopic flow stabilization of the kink mode rather than kinetic effects. In NBI heated plasmas in smaller conventional aspect-ratio tokamaks, such as TEXTOR, the flow and kinetic effects compete to give different sawtooth behaviour. Other techniques applied to destabilize sawteeth are the application of electron cyclotron current drive (ECCD) or ion cyclotron resonance heating (ICRH). In JET, it has been observed that localized ICRH is able to destabilize sawteeth which were otherwise stabilized by a co-existing population of energetic trapped ions in the core. This is explained through the dual role of the ICRH in reducing the critical magnetic shear required to trigger a sawtooth crash, and the increase in the local magnetic shear which results from driving current near the q=1 rational surface. Sawtooth control in ITER could be provided by a combination of ECCD and co-passing off-axis negative-NBI fast ions.
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| 22. |
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| 23. |
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| 24. |
- Coster, D. P., et al.
(author)
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Simulations of the edge plasma: the role of atomic, molecular and surface physics
- 2009
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In: ICAMDATA-2008. - 9780735406612 ; 1125, s. 113-122
-
Conference paper (peer-reviewed)abstract
- Atomic, molecular and surface physics plays an important role in simulations of the edge plasma in present day tokamaks, and in the predictive simulations of new devices. The edge plasma-in this context, the Scrape-Off Layer (SOL), the Private Flux Region (PFR) and core region close to the separatrix (or Last Closed Flux Surface, LCFS)-provides the boundary conditions for the main plasma, and is the region where much of the power and all of the particle exhaust occurs. It is also the region where the plasma interacts with solid surfaces, puffed gases and gas arising from recycling. The results of plasma edge simulations can depend strongly on the availability and quality of the atomic, molecular and surface data (the peak plasma temperature at the divertor was found to vary by a factor of five dependent on the choice of atomic physics data in a recent sensitivity analysis). The current material choice for ITER with Plasma Facing Components (PFCs) consisting of C, Be and W also presents challenges, both in the availability of the necessary data for W, and in the plethora of charge states for W. Another challenge presented by the material choice is the likely presence of mixed materials formed by the migration of material from one surface to another. These introduce effects like alloying and preferential sputtering as well as new (much longer) time-scales in the problem. Efforts to incorporate a bundled charge state model within one of the present edge simulation codes, SOLPS, will he described, as well as efforts to address some of the questions raised by mixed materials. Some issues related to data consistency and traceability within the context of the European effort on Integrated Tokamak Modelling will also be addressed.
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| 25. |
- Eriksson, L.G.
(author)
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A sampler with a new type of shutter
- 1981
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In: Soil mechanics and foundation engineering. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9061912121 ; , s. 471-474
-
Conference paper (peer-reviewed)abstract
- Describes a sampler provided with a new type of shutter, which holds the sample during withdrawal. Some results from a comparative test series, where this new sampler, and the Swedish standard piston sampler were used are presented.
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| 26. |
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| 27. |
- Eriksson, L-G, et al.
(author)
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Destabilization of fast-ion-induced long sawteeth by localized current drive in the JET tokamak.
- 2004
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:23
-
Journal article (peer-reviewed)abstract
- In a tokamak fusion reactor the energetic alpha particles will transiently stabilize the magnetohydrodynamic activity causing sawtooth oscillations. The crash events terminating long sawtooth free periods can provide seed islands for neoclassical tearing modes [Phys. Rev. Lett. 88, 105001 (2002)]]. To shorten the sawtooth periods localized current drive near the q=1 surface is a possibility. This Letter provides the first experimental evidence for the effectiveness of this method in the different physics regime associated with fast-ion-induced long sawteeth on the JET tokamak.
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| 28. |
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| 29. |
- Eriksson, L. G., et al.
(author)
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Modelling of ripple losses in tokamak plasmas heated by ICRF waves
- 2001
-
In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 43:10, s. 1291-1302
-
Journal article (peer-reviewed)abstract
- A model for treating ripple induced fast ion losses during ion cyclotron resonance frequency heating is presented. It is suitable for codes solving an orbit averaged three-dimensional Fokker-Planck equation with a Monte Carlo method, and has been implemented in such a code. The resulting code has been used for a comparison with experimental data form Tore Supra and for assessing the ripple induced losses in different ICRF heating scenarios.
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| 30. |
- Eriksson, L. G., et al.
(author)
-
On ion cyclotron current drive for sawtooth control
- 2006
-
In: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 46:10, s. S951-S964
-
Journal article (peer-reviewed)abstract
- Experiments using ion cyclotron current drive (ICCD) to control sawteeth are presented. In particular, discharges demonstrating shortening of fast ion induced long sawteeth reported in (Eriksson et al 2004 Phys. Rev. Lett. 92 235004) by ICCD have been analysed in detail. Numerical simulations of the ICCD driven currents are shown to be consistent with the experimental observations. They support the hypothesis that an increase in the magnetic shear, due to the driven current, at the surface where the safety factor is unity was the critical factor for the shortening of the sawteeth. In view of the potential utility of ICCD, the mechanisms for the current drive have been further investigated experimentally. This includes the influence of the averaged energy of the resonating ions carrying the current and the spectrum of the launched waves. The results of these experiments are discussed in the light of theoretical considerations.
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| 31. |
- Eriksson, L-G, et al.
(author)
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Plasma rotation induced by directed waves in the ion-cyclotron range of frequencies
- 2004
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:23
-
Journal article (peer-reviewed)abstract
- Changes of the toroidal plasma rotation induced by directed waves in the ion-cyclotron range of frequencies (ICRF) have been identified experimentally for the first time on the JET tokamak. The momentum carried by the waves is initially absorbed by fast resonating ions, which subsequently transfer it to the bulk plasma. Thus, the results provide evidence for the influence of ICRF heated fast ions on plasma rotation.
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| 32. |
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| 33. |
- Eriksson, L.G.
(author)
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Temperature effects on consolidation properties of sulphide clays
- 1989
-
In: Proceedings of the twelfth international conference on soil mechanics and foundation engineering. Technical papers / 3. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9061918936 ; , s. 2087-2090
-
Conference paper (peer-reviewed)abstract
- When heat energy is stored in clay, the geotechnical properties will change as a result of changing temperature. This paper presents results from laboratory tests on sulphide rich silty clays. The tests are ordinary oedometer tests and creep tests in the temperature range 5 to 55°C. It is shown that even a small deviation of the testing temperature from the in situ temperature is of importance for the results. Based on the test results, a creep-temperature equation is proposed
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| 34. |
- Eriksson, L. -G, et al.
(author)
-
Toroidal rotation in RF heated JET plasmas
- 2007
-
In: RADIO FREQUENCY POWER IN PLASMAS. - : AIP. - 9780735404441 ; , s. 59-62
-
Conference paper (peer-reviewed)abstract
- Experiments have been carried out on JET aimed at studying rotation in RF heated plasmas with low external momentum input. Both plasmas with Ion Cyclotron Resonance Frequency (ICRF) heating and Lower Hybrid Current Drive (LHCD) have been investigated. The rotation profiles are measured by Charge Exchange recombination spectroscopy, using short diagnostic Neutral Beam Injection (NBI) pulses. Moreover, the temporal evolution of the central rotation could in some cases be deduced from MHD activity. While most of the measurements were focussed on ICRF heating, the profiles measured in plasmas with LHCD are interesting since they are the first reported from JET in such plasmas. In particular, they allowed for studies of rotation in RF heated plasmas with q>1. The experimental results are presented together with an analysis of the torque from ICRF heated fast ions.
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| 35. |
- Eriksson, L. G., et al.
(author)
-
Toroidal rotation in RF heated JET plasmas
- 2009
-
In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 51:4
-
Journal article (peer-reviewed)abstract
- Observations of bulk plasma rotation in radio frequency (RF) heated JET discharges are reported. This study is concentrated on RF heated L-mode plasmas. In particular, the toroidal rotation profiles in plasmas heated by ion cyclotron resonance frequency (ICRF) waves and lower hybrid (LH) waves have been analysed. It is the first time that rotation profiles in JET plasmas with LH waves have been measured in dedicated discharges. It is found that the toroidal plasma rotation in the outer region of the plasmas is in the co-current direction irrespective of the heating scenario. An interesting feature is that the toroidal rotation profile appears to be hollow in many discharges at low plasma current, but a low current in itself does not seem to be a sufficient condition for finding such profiles. Fast ion transport and finite orbit width effects are mechanisms that could explain hollow rotation profiles. This possibility has been investigated by numerical simulations of the torque on the bulk plasma due to fast ICRF accelerated ions. The obtained torque is used in a transport equation for the toroidal momentum density to estimate the effect on the thermal bulk plasma rotation profile.
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| 36. |
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| 37. |
- Eriksson, Sara, et al.
(author)
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Effect of Ce-doping on Rh/ZrO2 catalysts for partial oxidation of methane
- 2007
-
In: Applied Catalysis A. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 326:1, s. 8-16-
-
Journal article (peer-reviewed)abstract
- The partial oxidation of methane over supported (ZrO2, CeO2-ZrO2) rhodium catalysts was investigated at atmospheric pressure. The effect of temperature, CH4/O-2 ratio, catalyst composition and pre-treatment was studied. Ceria doping of the support material resulted in significant improvements concerning the methane conversion and syngas selectivity, which could be related to a higher noble metal dispersion on the Rh/CeO2-ZrO2 catalyst. In addition, the light-off temperature was decreased by 128 degrees C when using CeO2-ZrO2, as support. X-ray photoelectron spectroscopy revealed the presence of different Rh oxidation states depending on catalyst composition and pre-treatment. A stabilization of partially oxidized (Rh delta+) species by ceria could be detected. An active and stable catalyst behavior could be observed for Rh/CeO2-ZrO2, irrespectively of catalyst pre-treatment, whereas an activation period was required for stabilizing the activity of the Rh/ZrO2 catalyst. The activity tests indicate that the indirect reaction mechanism, consisting of methane combustion followed by steam and dry reforming, prevails under the experimental conditions studied.
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| 38. |
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| 39. |
- Eriksson Sörman, Daniel, et al.
(author)
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Leisure-time activity in old age as predictors of impending dementia: A 15-year prospective study
- 2012
-
Conference paper (peer-reviewed)abstract
- This study examined the relationship between leisure activities and risk of dementia in a sample of healthy older individuals, dementia free at the beginning of the project. Data were drawn from a population-based longitudinal study (the Betula project) and the participants were followed up for 15 years. At baseline, participants were asked about their frequency of participation in 15 selected leisure activities. When age, gender, education, APOE and other potential confounders were controlled for, results revealed quite moderate effects on dementia after analysis of the activities separately. However, by weighting each activity into a mental, social and physical dimension (based on valuation by the participants), and then summarizing into a score for each dimension, we further investigated if level of engagement could predict impending dementia. Preliminary results indicate that the dimensions may have influence on the risk of dementia for certain age groups. The study also showed that the strongest predictor of dementia is being a carrier of the APOE ɛ4 allele. The outcomes are discussed in terms of important methodological difference between studies concerning the effects of leisure activities in preventing dementia diseases.
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| 40. |
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| 41. |
- Fogelberg, J., et al.
(author)
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Kinetic modelling of hydrogen ad/absorption in thin films of hydrogen sensitive field effect devices : Observation of large hydrogen induced dipoles at the Pd/SiO2 interface
- 1995
-
In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 78, s. 988-
-
Journal article (peer-reviewed)abstract
- A kinetic modeling of the hydrogen interaction with a Pd‐SiO2‐Si (Pd‐MOS) device is reported. The model is fitted to a number of experimental results, mainly from mass spectrometric desorption measurements. The new results verify an older description of the energetics of hydrogen adsorption states at the Pd/SiO2 interface in the sense that the adsorption may be described by a so‐called Temkin isotherm; however, several new findings have to be incorporated into the model in order to obtain a consistent picture. The initial heat of adsorption at the interface is around 0.8 eV/hydrogen atom. The number of adsorption sites at the interface is considerably smaller than at the surface, 6×1017 m−2 versus 1.5×1019 m−2. Furthermore, the interface hydrogen atoms are strongly polarized. An average value of 2 Debye is obtained. It is the large hydrogen polarization at the Pd/SiO2 interface and not a large concentration of adsorbed hydrogen atoms per se which accounts for the very high sensitivity of a Pd‐MOS device as hydrogen sensor
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| 42. |
- Gilbert, F., et al.
(author)
-
Sediment reworking by the burrowing polychaete Hediste diversicolor modulated by environmental and biological factors across the temperate North Atlantic. A tribute to Gaston Desrosiers
- 2021
-
In: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 541
-
Journal article (peer-reviewed)abstract
- Particle mixing and irrigation of the seabed by benthic fauna (bioturbation) have major impacts on ecosystem functions such as remineralization of organic matter and sediment-water exchange. As a tribute to Prof. Gaston Desrosiers by the Nereis Park association, eighteen laboratories carried out a collaborative experiment to acquire a global snapshot of particle reworking by the polychaete Hediste diversicolor at 16 sites surrounding the Northern Atlantic. Organisms and soft sediments were collected during May - July at different geographical locations and, using a common laboratory protocol, particulate fluorescent tracers (`luminophores') were used to quantify particle transport over a 10-day period. Particle mixing was quantified using the maximum penetration depth of tracers (MPD), particle diffusive coefficients (D-b), and non-local transport coefficients (r). Non-local coefficients (reflecting centimeter scale transport steps) ranged from 0.4 to 15 yr(-1), and were not correlated across sites with any measured biological (biomass, biovolume) or environmental parameters (temperature, grain size, organic matter). Maximum penetration depths (MPD) averaged similar to 10.7 cm (6.5-14.5 cm), and were similar to the global average bioturbation depth inferred from short-lived radiochemical tracers. MPD was also not correlated with measures of size (individual biomass), but increased with grain size and decreased with temperature. Bio-diffusion (D-b) correlated inversely with individual biomass (size) and directly with temperature over the environmental range (Q(10) similar to 1.7; 5-21 degrees C). The transport data were comparable in magnitude to rates reported for localized H. diversicolor populations of similar size, and confirmed some but not all correlations between sediment reworking and biological and environmental variables found in previous studies. The results imply that measures of particle reworking activities of a species from a single location can be generally extrapolated to different populations at similar conditions.
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| 43. |
- Graves, J. P., et al.
(author)
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Experimental verification of sawtooth control by energetic particles in ion cyclotron resonance heated JET tokamak plasmas
- 2010
-
In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 50:5, s. 052002-
-
Journal article (other academic/artistic)abstract
- Experimental evidence from the JET tokamak is presented supporting the predictions of a recent theory (Graves et al 2009 Phys. Rev. Lett. 102 065005) on sawtooth instability control by toroidally propagating ion cyclotron resonance waves. Novel experimental conditions minimized a possible alternate effect of magnetic shear modification by ion cyclotron current drive, and enabled the dependence of the new energetic ion mechanism to be tested over key variables. The results have favourable implications on sawtooth control by ion cyclotron resonance waves in a fusion reactor.
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| 44. |
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| 45. |
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| 46. |
- Graves, J. P., et al.
(author)
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Sawtooth control mechanism using counter current propagating ICRH in JET
- 2008
-
In: EPS Conf. Plasma Phys., EPS - Europhys. Conf. Abstr.. - 9781622763351 ; , s. 2010-2013
-
Conference paper (peer-reviewed)abstract
- The sawtooth control mechanism in plasmas employing off-axis ICCD is reinvestigated. In particular, for counter propagating waves on the high field side, asymmetrically distributed energetic passing ions destabilise the ideal internal kink mode when the q=1 surface resides within a narrow region centred about the shifted fundamental cyclotron resonance.
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| 47. |
- Graves, J. P., et al.
(author)
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Sawtooth-Control Mechanism using Toroidally Propagating Ion-Cyclotron-Resonance Waves in Tokamaks
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:6
-
Journal article (peer-reviewed)abstract
- The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q=1 surface resides within a narrow region centered about the shifted fundamental cyclotron resonance.
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| 48. |
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| 49. |
- Hedin, J., et al.
(author)
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The influence of finite drift orbit width on ICRF heating in toroidal plasmas
- 2002
-
In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 42:5, s. 527-540
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Journal article (peer-reviewed)abstract
- Ion cyclotron resonance heating in a toroidal plasma not only increases the perpendicular energy of the resonating ions but also results in their spatial transport. Depending on the direction of propagation of the waves, the ions will either drift inwards or outwards giving rise to an RF induced rotation with the toroidal torque component in the co-current or counter-current directions, respectively. It is found that the spatial transport induced by the RF field, the topology of the ion drift orbits and a wave field consistent with ion absorption are important for determining the distribution function of the heated species. Studies of ICRF heating with the self-consistent code SELFO reveal new features such as the formation of non-standard passing orbits residing on the low field side of the magnetic axis. For a symmetric spectrum the drift terms will in general not cancel. Some classes of orbit will be subjected only to an inward drift and others only to an outward drift. The lack of cancellation of the drift terms is further enhanced by the self-consistent coupling, increasing the absorption for waves propagating parallel to the plasma current, but not for waves propagating in the antiparallel direction. This results in a strong inward pinch also for symmetric wave spectra as well as for typical experimental spectra, with the dominant peak in the counter-plasma-direction.
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- Hedin, J., et al.
(author)
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The influence of non-standard orbits on ICRH power deposition in tokamaks
- 2000
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 40:11, s. 1819-1824
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Journal article (peer-reviewed)abstract
- The distribution function and power deposition during ICRH in a tokamak plasma are analysed. The importance of self-consistent calculations and the formation of son-standard drift orbits are addressed. It is found that for high power ICRH, the presence of non-standard orbits are crucial for describing the distribution function. For a standard minority heating scenario with the ion cyclotron resonance located at the high field side, the absorption of the wave power is shifted to the low field side (LFS) because of the orbit topology and the evolving wave field profile. The high energy tail of the distribution function of the resonating ions is found to be dominated by ions in passing orbits, of which some reside completely on the LFS of the tokamak.
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