| 1. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)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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| 2. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 3. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 4. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Krasilnikov, A., et al.
(författare)
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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
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Tidskriftsartikel (refereegranskat)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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| 12. |
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Overview of the JET results
- 2015
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 55:10
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Tidskriftsartikel (refereegranskat)
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| 13. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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| 28. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Tidskriftsartikel (refereegranskat)
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| 29. |
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| 30. |
- Labit, B., et al.
(författare)
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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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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:8
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Tidskriftsartikel (refereegranskat)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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| 31. |
- Bécoulet, A., et al.
(författare)
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Science and technology research and development in support to ITER and the Broader Approach at CEA
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10
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Tidskriftsartikel (refereegranskat)abstract
- In parallel to the direct contribution to the procurement phase of ITER and Broader Approach, CEA has initiated research & development programmes, accompanied by experiments together with a significant modelling effort, aimed at ensuring robust operation, plasma performance, as well as mitigating the risks of the procurement phase. This overview reports the latest progress in both fusion science and technology including many areas, namely the mitigation of superconducting magnet quenches, disruption-generated runaway electrons, edge-localized modes (ELMs), the development of imaging surveillance, and heating and current drive systems for steady-state operation. The WEST (W Environment for Steady-state Tokamaks) project, turning Tore Supra into an actively cooled W-divertor platform open to the ITER partners and industries, is presented.
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| 32. |
- Meyer, H., et al.
(författare)
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Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
- 2017
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 57:10
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Tidskriftsartikel (refereegranskat)abstract
- Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement H-H(98,H-y2) approximate to 0.95. Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes.
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| 33. |
- Meyer, H., et al.
(författare)
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Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
- 2017
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 57:10
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Tidskriftsartikel (refereegranskat)abstract
- Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement H-H(98,H-y2) approximate to 0.95. Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes.
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| 34. |
- Mayoral, M. -L, et al.
(författare)
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Overview of Recent Results on Heating and Current Drive in the JET tokamak
- 2009
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Ingår i: RADIO FREQUENCY POWER IN PLASMAS. - : AIP. - 9780735407534 ; , s. 39-46
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Konferensbidrag (refereegranskat)abstract
- In this paper, significant results in the heating and current drive domains obtained at JET in the past few years following systems upgrade and dedicated experimental time, will be reviewed. Firstly, an overview of the new Ion Cyclotron Resonance Frequency (ICRF) heating capabilities will be presented i.e. results from the ITER-Like ICRF antenna (ILA), the use of External Conjugate-T and 3dB hybrid couplers to increase the ICRF power during ELMy H-mode, Furthermore, experiments to study the influence of the phasing of the ICRF antenna on power absorption and coupling will be described. Looking at Low Hybrid (I-H) issues for ITER, the effect of the location of gas injection on the LH coupling improvement at large launcher-separatrix distances will be discussed as the possibility to operate at ITER-relevant power densities. Experiments to characterise the LH power losses in the Scrape-Off-Layer (SOL) and to determine the LH wave absorption and current drive using power modulation will be shown. Finally, plasma rotation studies in the presence of ICRF heating with standard and enhanced JET toroidal field ripple will be presented.
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| 35. |
- Lerche, E., et al.
(författare)
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Optimization of ICRH for core impurity control in JET-ILW
- 2016
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Ingår i: Nuclear Fusion. - JET, Culham Sci Ctr, EUROfus Consortium, Abingdon OX14 3DB, Oxon, England. [Lerche, E.; Van Eester, D.; Crombe, K.; Kazakov, Y.; Krivska, A.; Ongena, J.] TEC Partner, Assoc EUROFUS Belgian State, LPP ERM KMS, Brussels, Belgium. [Lerche, E.; Jacquet, P.; Giroud, C.; Monakhov, I.; Casson, F. J.; Rimini, F.; Blackman, T.; Brix, M.; Challis, C.; Graham, M.; Kiptily, V.; Lennholm, M.; Lomas, P.; Maggi, C.; Mathews, G.; Mayoral, M. -L.; Santala, M.; Shaw, A.; Stamp, M.] Euratom CCFE Fus Assoc, Culham Sci Ctr, Abingdon, Oxon, England. [Goniche, M.; Colas, L.; Fedorczak, N.; Joffrin, E.; Monier-Garbet, P.] Assoc EUROFUS CEA, IRFM, St Paul Les Durance, France. [Bobkov, V.; Angioni, C.; Hobirk, J.; Puetterich, T.; Reich, M.] EUROFUS Assoziat, Max Planck Inst Plasmaphys, Garching, Germany. [Baruzzo, M.] EUROFUS ENEA Assoc, Consorzio RFX, Padua, Italy. [Brezinsek, S.] TEC Partner, EUROFUS Assoziat, Forschungszentrum Juelich, Julich, Germany. [Czarnecka, A.] EUROFUS Assoc, IPPLM, Warsaw, Poland. [Eriksson, J.] Uppsala Univ, Dept Phys & Astron, Assoc EUROFUS VR, Uppsala, Sweden. [Graves, J. P.] Assoc EUROFUS Confederat Suisse, CRPP EPFL, Lausanne, Switzerland. [Gorini, G.; Mantica, P.; Nocente, M.; Tardocchi, M.; Valisa, M.] EUROFUS ENEA CNR Assoc, Inst Fis Plasma, Milan, Italy. [Johnson, T.] KTH, EES, Fus Plasma Phys, Assoc EUROFUS VR, Stockholm, Sweden. [Meneses, L.; Nave, M. F.; Nunes, I.] EUROFUS IST Assoc, Inst Plasmas & Fusao Nucl, Lisbon, Portugal. [Mlynar, J.; Petrzilka, V.] EUROFUS IPP CR Assoc, Inst Plasma Phys, Prague, Czech Republic. [Petravich, G.] EUROFUS Assoc, MTA Wigner FK RMI, Budapest, Hungary. [Solano, E. R.] EUROFUS Assoc, LNF CIEMAT, Madrid, Spain. [Solano, E. R.] Culham Sci Ctr, EUROfus PMU, Abingdon OX14 3DB, Oxon, England. [Sips, G.] Culham Sci Ctr, JET Exploitat Unit, Abingdon OX14 3DB, Oxon, England. [Tsalas, M.] EUROFUS Assoc, FOM Inst DIFFER, Nieuwegein, Netherlands. : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 56:3
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Tidskriftsartikel (refereegranskat)abstract
- Ion cyclotron resonance frequency (ICRF) heating has been an essential component in the development of high power H-mode scenarios in the Jet European Torus ITER-like wall (JET-ILW). The ICRF performance was improved by enhancing the antenna-plasma coupling with dedicated main chamber gas injection, including the preliminary minimization of RF-induced plasma-wall interactions, while the RF heating scenarios where optimized for core impurity screening in terms of the ion cyclotron resonance position and the minority hydrogen concentration. The impact of ICRF heating on core impurity content in a variety of 2.5 MA JET-ILW H-mode plasmas will be presented, and the steps that were taken for optimizing ICRF heating in these experiments will be reviewed.
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| 36. |
- Ongena, J., et al.
(författare)
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Overview of recent results on Heating and Current Drive in JET
- 2007
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Ingår i: RADIO FREQUENCY POWER IN PLASMAS. - : AIP. ; , s. 249-256
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Konferensbidrag (refereegranskat)abstract
- Recent progress on heating and current drive on JET is reported. Topics discussed are: high power coupling of ICRF/LH at ITER relevant antenna/launcher-separatrix distances, succesfull demonstration of 3 dB couplers for ELM tolerance of the ICRF system, influence of ICRF on LH operation, rotation studies in plasma without external momentum with standard and enhanced JET toriodal field ripple, studies of different ICRF heating schemes and of NTM avoidance schemes using Ion Cyclotron Current Drive. A brief outlook on future plans for experiments at JET is given.
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| 37. |
- Krlin, L., et al.
(författare)
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Anomalous impurity diffusion in models of tokamak edge plasma turbulence
- 2004
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Ingår i: Czechoslovak Journal of Physics. - 0011-4626 .- 1572-9486. ; 54:1-3, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- Using a simple spatially periodical and stationary potential as a model of electrostatic tokamak edge plasma turbulence, we have found recently [1, 2] an anomalous impurity diffusion in this regime. In this contribution, we estimate this diffusion for a more general and realistic form of the potential, which is close to the Hasegawa-Wakatani (HW) potential. As an interesting consequence of the discussed dynamics, we present, possibility of radial electric field generation in the edge turbulence regime. This effect. might play a role in tokamak scenarios with transport barriers.
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| 38. |
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| 39. |
- Panek, R., et al.
(författare)
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Anomalous ion diffusion and radial-electric-field generation in a turbulent edge plasma potential weakly correlated in time and space
- 2005
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; 72:4, s. 327-332
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Tidskriftsartikel (refereegranskat)abstract
- Using a simple model of tokamak-edge-plasma turbulence in the form of a spatially periodic and time-independent electrostatic potential, we have found recently a new type of anomalous impurity diffusion in this regime [1], [2]. In the present contribution, we estimate this diffusion in the test-particle approach for a real turbulent potential obtained in an experiment. A significant difference in the impurity dynannics between the Hamiltonian and drift approaches is observed. As an interesting consequence of these dynamics, the possibility of radial-electric-field generation in the turbulence regimes appears. This effect can be of importance in scenarios related to transport barriers.
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| 40. |
- Rantamäki, K., et al.
(författare)
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LH wave coupling over ITER-like distances at JET
- 2007
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Ingår i: Radio Frequency Power in Plasmas. - : American Institute of Physics (AIP). - 0735404445 - 9780735404441 ; , s. 261-264
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Konferensbidrag (refereegranskat)abstract
- Good coupling of LH power at plasma-launcher distance of 15 cm has been obtained at JET. Near-gas injection is used to increase the density in front of the grill. The role of LH power in the density increase at constant gas level is demonstrated. For the first time at JET the temperature of the hot spots caused by parasitic absorption of LH power has been measured.
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| 41. |
- Ekedahl, A., et al.
(författare)
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Influence of gas puff location on the coupling of lower hybrid waves in JET ELMy H-mode plasmas
- 2012
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 54:7, s. 074004-
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Tidskriftsartikel (refereegranskat)abstract
- Reliable coupling of the lower hybrid current drive (LHCD) to H-mode plasmas in JET is made feasible through a dedicated gas injection system, located at the outer wall and magnetically connected to the antenna (Pericoli Ridolfini et al 2004 Plasma Phys. Control. Fusion 46 349, Ekedahl et al 2005 Nucl. Fusion 45 351, Ekedahl et al 2009 Plasma Phys. Control. Fusion 51 044001). An experiment was carried out in JET in order to investigate whether a gas injection from the top of the torus, as is foreseen for the main gas injection in ITER, could also provide good coupling of the LH waves if magnetically connected to the antenna. The results show that a top gas injection was not efficient for providing a reliable LHCD power injection, in spite of being magnetically connected and in spite of using almost twice the amount of gas flow compared with the dedicated outer mid-plane gas puffing system. A dedicated gas injection system, set in the outer wall and magnetically connected to the LHCD antenna, is therefore recommended in order to provide the reliable coupling conditions for an LHCD antenna in ITER.
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