| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)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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| 5. |
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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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| 6. |
-
- 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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| 30. |
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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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| 31. |
- 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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| 32. |
- 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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| 33. |
- Reimerdes, H., et al.
(författare)
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Overview of the TCV tokamak experimental programme
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Tidskriftsartikel (refereegranskat)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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| 34. |
- Kazakov, Ye O., et al.
(författare)
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Physics and applications of three-ion ICRF scenarios for fusion research
- 2021
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 28:2
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Forskningsöversikt (refereegranskat)abstract
- This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting the plasma composition to realize three-ion ICRF scenarios, including two equivalent possibilities for the choice of resonant absorbers that have been identified. The theoretical findings have been convincingly confirmed by the proof-of-principle experiments in mixed H–D plasmas on the Alcator C-Mod and JET tokamaks, using thermal 3He and fast D ions from neutral beam injection as resonant absorbers. Since 2018, significant progress has been made on the ASDEX Upgrade and JET tokamaks in H–4He and H–D plasmas, guided by the ITER needs. Furthermore, the scenario was also successfully applied in JET D–3He plasmas as a technique to generate fusion-born alpha particles and study effects of fast ions on plasma confinement under ITER-relevant plasma heating conditions. Tuned for the central deposition of ICRF power in a small region in the plasma core of large devices such as JET, three-ion ICRF scenarios are efficient in generating large populations of passing fast ions and modifying the q-profile. Recent experimental and modeling developments have expanded the use of three-ion scenarios from dedicated ICRF studies to a flexible tool with a broad range of different applications in fusion research.
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| 35. |
- Mantsinen, M. J., et al.
(författare)
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Experiments in high-performance JET plasmas in preparation of second harmonic ICRF heating of tritium in ITER
- 2023
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Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- The reference ion cyclotron resonance frequency (ICRF) heating schemes for ITER deuterium-tritium (D-T) plasmas at the full magnetic field of 5.3 T are second harmonic heating of T and 3He minority heating. The wave-particle resonance location for these schemes coincide and are central at a wave frequency of 53 MHz at 5.3 T. Experiments have been carried out in the second major D-T campaign (DTE2) at JET, and in its prior D campaigns, to integrate these ICRF scenarios in JET high-performance plasmas and to compare their performance with the commonly used hydrogen (H) minority heating. In 50:50 D:T plasmas, up to 35% and 5% larger fusion power and diamagnetic energy content, respectively, were obtained with second harmonic heating of T as compared to H minority heating at comparable total input powers and gas injection rates. The core ion temperature was up to 30% and 20% higher with second harmonic T and 3He minority heating, respectively, with respect to H minority heating. These are favourable results for the use of these scenarios in ITER and future fusion reactors. According to modelling, adding ICRF heating to neutral beam injection using D and T beams resulted in a 10%-20% increase of on-axis bulk ion heating in the D-T plasmas due to its localisation in the plasma core. Central power deposition was confirmed with the break-in-slope and fast Fourier transform analysis of ion and electron temperature in response to ICRF modulation. The tail temperature of fast ICRF-accelerated tritons, their enhancement of the fusion yield and time behaviour as measured by an upgraded magnetic proton recoil spectrometer and neutral particle analyser were found in agreement with theoretical predictions. No losses of ICRF-accelerated ions were observed by fast ion detectors, which was as expected given the high plasma density of n e approximate to 7-8 x 1019 m-3 in the main heating phase that limited the formation of ICRF-accelerated fast ion tails. 3He was introduced in the machine by 3He gas injection, and the 3He concentration was measured by a high-resolution optical penning gauge in the sub-divertor region. The DTE2 experiments with 3He minority heating were carried with a low 3He concentration in the range of 2%-4% given the fact that the highest neutron rates with 3He minority heating in D plasmas were obtained at low 3He concentrations of similar to 2%, which also coincided with the highest plasma diamagnetic energy content. In addition to 3He introduced by 3He gas injection, an intrinsic concentration of 3He of the order of 0.2%-0.4% was measured in D-T plasmas before 3He was introduced in the device, which is attributed to the radioactive decay of tritium to 3He. According to modelling, even such low intrinsic concentrations of 3He lead to significant changes in ICRF power partitioning during second harmonic heating of T due to absorption of up to 30% of the wave power by 3He.
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| 36. |
- Maslov, M., et al.
(författare)
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JET D-T scenario with optimized non-thermal fusion
- 2023
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Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- In JET deuterium-tritium (D-T) plasmas, the fusion power is produced through thermonuclear reactions and reactions between thermal ions and fast particles generated by neutral beam injection (NBI) heating or accelerated by electromagnetic wave heating in the ion cyclotron range of frequencies (ICRFs). To complement the experiments with 50/50 D/T mixtures maximizing thermonuclear reactivity, a scenario with dominant non-thermal reactivity has been developed and successfully demonstrated during the second JET deuterium-tritium campaign DTE2, as it was predicted to generate the highest fusion power in JET with a Be/W wall. It was performed in a 15/85 D/T mixture with pure D-NBI heating combined with ICRF heating at the fundamental deuterium resonance. In steady plasma conditions, a record 59 MJ of fusion energy has been achieved in a single pulse, of which 50.5 MJ were produced in a 5 s time window (P fus = 10.1 MW) with average Q = 0.33, confirming predictive modelling in preparation of the experiment. The highest fusion power in these experiments, P fus = 12.5 MW with average Q = 0.38, was achieved over a shorter 2 s time window, with the period of sustainment limited by high-Z impurity accumulation. This scenario provides unique data for the validation of physics-based models used to predict D-T fusion power.
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| 37. |
- Kirov, K. K., et al.
(författare)
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Analysis of fusion alphas interaction with RF waves in D-T plasma at JET
- 2024
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 64:8
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Tidskriftsartikel (refereegranskat)abstract
- This work studies the influence of radio frequency (RF) waves in the ion cyclotron resonance heating (ICRH) range of frequencies on fusion alphas during the recent JET D-T campaign. Fusion alphas from D-T reactions are created with energies of about 3.5 MeV and therefore have significant Doppler shifts enabling synergistic interactions between them and RF waves at a broad range of frequencies, including the ones foreseen for future fusion machines in ITER (Schneider et al 2021 Nucl. Fusion 61 126058) and SPARC (Creely et al 2020 J. Plasma Phys. 86 865860502). Resonant interactions between RF waves and alphas, also called synergistic effects, will modify the alpha distribution and ultimately will have an impact on alpha orbit losses and heating. Data from JET 3.43 T/2.3 MA pulses based on the hybrid scenario (Hobirk et al 2023 Nucl. Fusion; Hobirk et al 29th IAEA FEC23 Conf. (16-21 October 2023); Challis et al 48th EPS Conf. on Plasma Physics (27 June-1 July 2022) during the DTE2 campaign (Maggi et al 2023 Nucl. Fusion)) were used for the analysis in this study. The impact of synergistic effects on alpha orbit losses and alpha heating are assessed. The conclusions are based on the analysis of experimental data for fast alpha losses, i.e. measurements from neutral particle analyser (NPA), fast ion losses scintillator detector, Faraday cups (FCs), and TRANSP (Hawryluk et al 1980 Physics of Plasmas Close to Thermonuclear Conditions vol 1 (CEC) pp 19-46) simulations. Experimental data and TRANSP analysis indicates that there are indeed changes in the alpha distribution function (DF) due to interaction with RF waves. Data from the NPA show increased 4He flux in the range from a few hundred keV up to 800 keV for pulses with RF power, while TRANSP clearly shows modifications in the fast alpha DF for these energies. Data from the scintillator detector and the FCs were compared for pulses with and without ICRH power and versus cases with enhanced alpha losses due to MHD activity. The trends from these diagnostics consistently show no additional alpha losses due to interaction with RF waves. TRANSP predictions for the impact of ynergistic effects on alpha heating show up to a 42% increase in alpha electron heating and up to a 25% increase in alpha ion heating. These effects, however, become negligibly small, less than 1%, when alpha heating is compared to the total auxiliary heating power in the investigated JET pulses.
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| 38. |
- Kirov, K. K., et al.
(författare)
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Analysis of the fusion performance, beam-target neutrons and synergistic effects of JET's high-performance pulses
- 2021
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Ingår i: Nuclear Fusion. - JET, EUROfus Consortium, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England. [Kirov, K. K.; Belonohy, E.; Challis, C. D.; Garzotti, L.; Keeling, D.; King, D.; Lomas, P. J.; Rimini, F. G.] Culham Sci Ctr, Culham Ctr Fus Energy, United Kingdom Atom Energy Author, Abingdon OX14 3DB, Oxon, England. [Eriksson, J.] Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden. [Frigione, D.] ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy. [Giacomelli, L.] CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy. [Hobirk, J.; Kappatou, A.] Max Planck Inst Plasma Phys, D-85748 Garching, Germany. [Lerche, E.; Van Eester, D.] Lab Plasma Phys, KMS ERM Renaissancelaan,30 Ave Renaissance, B-1000 Brussels, Belgium. [Nocente, M.] Univ Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy. [Reux, C.] CEA, IRFM, F-13108 St Paul Les Durance, France. [Sips, A. C. C.] European Commiss, B-1049 Brussels, Belgium. : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 61:4
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Tidskriftsartikel (refereegranskat)abstract
- Achieving high neutron yields in today's fusion research relies on high-power auxiliary heating in order to attain required core temperatures. This is usually achieved by means of high neutral beam (NB) and radio frequency (RF) power. Application of NB power is accompanied by production of fast beam ions and associated beam-target (BT) reactions. In standard JET operational conditions, deuterium (D) NBs are injected into D plasmas. The injected beams comprise D atoms at full, one-half and one-third injected energy. Typically, the full energy of the injected D beams is between 90 and 120 keV, providing 1.4-2.0 MW of heating, which is about half of the injected power. Half-energy D beams carry about one-third of the injected power and the rest of the power is carried by the third energy fraction of D beams. Under these conditions, thermal fusion reactions, i.e. those between plasma ions, and BT reactions are of the same order of magnitude. This study addresses important issues regarding the impact of density, central electron and ion temperatures and their ratio, T-i(0)/T-e(0), on fusion performance, measured by the total neutron yield and BT neutron counts. NB/RF synergistic effects are discussed as well. It is demonstrated that thermal fusion gain increases linearly with normalised plasma pressure, beta(N), and confinement, B-t tau. The BT neutrons are, however, more difficult to predict and this task in general requires numerical treatment. In this study, BT neutrons in JET's best-performing baseline and hybrid pulses are analysed and the underlying dependencies discussed. Central fast ion densities are found to decrease with increased density and density peaking. This is attributed to poorer beam penetration at high density. The BT reactions however are unchanged and can even increase if operating at higher core temperatures. An increase in the central ion temperature and T-i(0)/T-e(0) ratio leads to higher total and BT reaction rates whilst simultaneously the ratio of the BT to total neutron decreases significantly. NB/RF synergistic effects are found to have a negligible impact on total neutron rate. This can be explained by the reduced beam penetration in high-density conditions leading to lower central fast ion density.
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| 39. |
- Kirov, K. K., et al.
(författare)
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Impact of interaction between RF waves and fast NBI ions on the fusion performance in JET DTE2 campaign
- 2024
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Ingår i: Nuclear Fusion. - : IOP Publishing Ltd. - 0029-5515 .- 1741-4326. ; 64:1
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a study of the interaction between radio frequency (RF) waves used for ion cyclotron resonance heating and the fast deuterium (D) and tritium (T) neutral Beam injected (NBI) ions in DT plasma. The focus is on the effects of this interaction, also referred to as synergistic effects, on the fusion performance in the recent JET DTE2 campaign. Experimental data from dedicated pulses at 3.43 T/2.3 MA heated at (i) 51.4 MHz, giving the central minority H and n = 2 D, and at (ii) 32.2 MHz for the central minority 3He and n = 2 T. Resonances are analysed and conclusions are drawn and supported by modelling of the synergistic effects. Modelling with transport code TRANSP runs with and without the RF kick operator predict a moderate increase, of about 10%, in DT rates for the case of the RF wave-fast D NBI ion interactions at the n = 2 harmonic of ion cyclotron resonance, and a negligible impact due to synergistic interaction between fast T NBI ions and RF waves. JETTO modelling gives a 29% enhancement in fusion rates due to the interction between RF waves and fast D NBI ions, and an 18% enhancement in fast T NBI ions. Analysis of experimental neutron rates compared to TRANSP predictions without synergistic effects and magnetic proton recoil neutron spectrometer indicate an enhancement of approximately 25%-28% in fusion rates due to RF interaction with fast D ions, and an enhancement of approximately 5%-8% when RF waves and fast T NBI ions are interacting. The contributions of various heating and fast ion sources are assessed and discussed.
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| 40. |
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| 41. |
- Garcia, J., et al.
(författare)
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Modelling performed for predictions of fusion power in JET DTE2 : overview and lessons learnt
- 2023
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- For more than a decade, an unprecedented predict-first activity has been carried in order to predict the fusion power and provide guidance to the second Deuterium-Tritium (D-T) campaign performed at JET in 2021 (DTE2). Such an activity has provided a framework for a broad model validation and development towards the D-T operation. It is shown that it is necessary to go beyond projections using scaling laws in order to obtain detailed physics based predictions. Furthermore, mixing different modelling complexity and promoting an extended interplay between modelling and experiment are essential towards reliable predictions of D-T plasmas. The fusion power obtained in this predict-first activity is in broad agreement with the one finally measured in DTE2. Implications for the prediction of fusion power in future devices, such as ITER, are discussed.
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| 42. |
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| 43. |
- Lerche, E., et al.
(författare)
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Optimizing ion-cyclotron resonance frequency heating for ITER : dedicated JET experiments
- 2011
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 53:12, s. 124019-
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Tidskriftsartikel (refereegranskat)abstract
- In the past years, one of the focal points of the JET experimental programme was on ion-cyclotron resonance heating (ICRH) studies in view of the design and exploitation of the ICRH system being developed for ITER. In this brief review, some of the main achievements obtained in JET in this field during the last 5 years will be summarized. The results reported here include important aspects of a more engineering nature, such as (i) the appropriate design of the RF feeding circuits for optimal load resilient operation and (ii) the test of a compact high-power density antenna array, as well as RF physics oriented studies aiming at refining the numerical models used for predicting the performance of the ICRH system in ITER. The latter include (i) experiments designed for improving the modelling of the antenna coupling resistance under various plasma conditions and (ii) the assessment of the heating performance of ICRH scenarios to be used in the non-active operation phase of ITER.
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| 44. |
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| 45. |
- Noterdaeme, J. M., et al.
(författare)
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Heating, current drive and energetic particle studies on JET in preparation of ITER operation
- 2003
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 43:3, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the recent work on JET in the three areas of heating, current drive and energetic particles. The achievements have extended the possibilities of JET, have a direct connection to ITER operation and provide new and interesting physics. Toroidal rotation profiles of plasmas heated far off axis with little or no refuelling or momentum input are hollow with only small differences on whether the power deposition is located on the low field side or on the high field side. With LH current drive the magnetic shear was varied from slightly positive to negative. The improved coupling (through the use of plasma shaping and CD4) allowed up to 3.4 MW of PLH in internal transport barrier (ITB) plasmas with more than 15 MW of combined NBI and ICRF heating. The q-profile with negative magnetic shear and the ITB could be maintained for the duration of the high heating pulse (8 s). Fast ions have been produced in JET with ICRF to simulate alpha particles: by using third harmonic He-4 heating, beam injected He-4 at 120 kV were accelerated to energies above 2 MeV taking advantage of the unique capability of JET to use NBI with 4 He and to confine MeV class ions. ICRF heating was used to replicate the dynamics of alpha heating and the control of an equivalent Q = 10 `burn' was simulated.
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| 46. |
- Ongena, J, et al.
(författare)
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Study and design of the ion cyclotron resonance heating system for the stellarator Wendelstein 7-X
- 2014
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 21:6, s. 061514-
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Tidskriftsartikel (refereegranskat)abstract
- The current status of the mechanical and electromagnetic design for the ICRF antenna system for W7-X is presented. Two antenna plugins are discussed: one consisting of a pair of straps with pre-matching to cover the first frequency band, 25–38 MHz, and a second one consisting of two short strap triplets to cover a frequency band around 76 MHz. This paper focusses on the two strap antenna for the lower frequency band. Power coupling of the antenna to a reference plasma profile is studied with the help of the codes TOPICA and Microwave Studio that deliver the scattering matrix needed for the optimization of the geometric parameters of the straps and antenna box. Radiation power spectra for different phasings of the two straps are obtained using the code ANTITER II and different heating scenario are discussed. The potential for heating, fast particle generation, and current drive is discussed. The problem of RF coupling through the plasma edge and of edge power deposition is summarized. Important elements of the complete ion cyclotron resonance heating system are discussed: a resonator circuit with tap feed to limit the maximum voltage in the system, and a decoupler to counterbalance the large mutual coupling between the 2 straps. The mechanical design highlights the challenges encountered with this antenna: adaptation to a large variety of plasma configurations, the limited space within the port to accommodate the necessary matching components and the watercooling needed for long pulse operation.
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| 47. |
- Pinches, S. D., et al.
(författare)
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Implementation of plasma simulators and plasma reconstruction workflows in ITER’s Integrated Modelling & Analysis Suite (IMAS)
- 2017
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Ingår i: 44th EPS Conference on Plasma Physics, EPS 2017. - : European Physical Society (EPS).
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Konferensbidrag (refereegranskat)abstract
- IMAS has been installed within the majority of the ITER Members and is being used to support ITPA activities including code benchmarking and validation. Sophisticated workflows, such as Plasma Simulators and those describing H&CD systems, have been adapted to IMAS and applied to ITER scenarios. The framework is considered sufficiently flexible to handle all foreseen approaches to the integrated (probabilistic) determination of measurement parameters (and their errors). The inclusion of UDA within the IMAS data Access Layer has allowed the fetching of IDSs directly from experimental databases and the demonstration of the first plasma reconstruction chain. An interactive Live Display in which signals are selected through a web interface has also been demonstrated.
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| 48. |
- Bilato, R., et al.
(författare)
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ICRF-code benchmark activity in the framework of the European task-force on integrated Tokamak Modelling
- 2014
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Ingår i: AIP Conference Proceedings. - : American Institute of Physics. - 9780735412101 ; , s. 291-294
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Konferensbidrag (refereegranskat)abstract
- The grand aim of the Integrated Tokamak Modelling (ITM) task-force is to provide a flexible, modular and reliable plasma simulator in view of planning and analyzing ITER discharges. Since radio-frequency (rf) heating in the ion cyclotron range of frequencies (ICRF) is foreseen as one of the main additional heating systems in ITER, physics modules that simulate ICRF wave propagation and absorption are necessary for the ITM project. Here, we report on the status of the benchmark activity of ICRF codes, already imported in ITM environment platform. We consider various scenarios for ITER, limiting the comparisons to wave propagation and absorption in Maxwellian plasmas.
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| 49. |
- Kim, Hyun-Tae, et al.
(författare)
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Validation of D-T fusion power prediction capability against 2021 JET D-T experiments
- 2023
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Ingår i: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- JET experiments using the fuel mixture envisaged for fusion power plants, deuterium and tritium (D-T), provide a unique opportunity to validate existing D-T fusion power prediction capabilities in support of future device design and operation preparation. The 2021 JET D-T experimental campaign has achieved D-T fusion powers sustained over 5 s in ITER-relevant conditions i.e. operation with the baseline or hybrid scenario in the full metallic wall. In preparation of the 2021 JET D-T experimental campaign, extensive D-T predictive modelling was carried out with several assumptions based on D discharges. To improve the validity of ITER D-T predictive modelling in the future, it is important to use the input data measured from 2021 JET D-T discharges in the present core predictive modelling, and to specify the accuracy of the D-T fusion power prediction in comparison with the experiments. This paper reports on the validation of the core integrated modelling with TRANSP, JINTRAC, and ETS coupled with a quasilinear turbulent transport model (Trapped Gyro Landau Fluid or QualLiKiz) against the measured data in 2021 JET D-T discharges. Detailed simulation settings and the heating and transport models used are described. The D-T fusion power calculated with the interpretive TRANSP runs for 38 D-T discharges (12 baseline and 26 hybrid discharges) reproduced the measured values within 20 % . This indicates the additional uncertainties, that could result from the measurement error bars in kinetic profiles, impurity contents and neutron rates, and also from the beam-thermal fusion reaction modelling, are less than 20 % in total. The good statistical agreement confirms that we have the capability to accurately calculate the D-T fusion power if correct kinetic profiles are predicted, and indicates that any larger deviation of the D-T fusion power prediction from the measured fusion power could be attributed to the deviation of the predicted kinetic profiles from the measured kinetic profiles in these plasma scenarios. Without any posterior adjustment of the simulation settings, the ratio of predicted D-T fusion power to the measured fusion power was found as 65%-96% for the D-T baseline and 81%-97% for D-T hybrid discharge. Possible reasons for the lower D-T prediction are discussed and future works to improve the fusion power prediction capability are suggested. The D-T predictive modelling results have also been compared to the predictive modelling of the counterpart D discharges, where the key engineering parameters are similar. Features in the predicted kinetic profiles of D-T discharges such as underprediction of ne are also found in the prediction results of the counterpart D discharges, and it leads to similar levels of the normalized neutron rate prediction between the modelling results of D-T and the counterpart D discharges. This implies that the credibility of D-T fusion power prediction could be a priori estimated by the prediction quality of the preparatory D discharges, which will be attempted before actual D-T experiments.
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| 50. |
- Lerche, E., et al.
(författare)
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Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET
- 2012
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 54:7, s. 074008-
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Tidskriftsartikel (refereegranskat)abstract
- Two ion cyclotron range of frequencies ( ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas-fundamental H majority and second harmonic He-3 ICRF heating-were recently investigated in JET. Although the same magnetic field and RF frequencies (f approximate to 42 MHz and f approximate to 52 MHz, respectively) were used, the density and particularly the plasma temperature were lower than those expected in the initial phase of ITER. Unlike for the well-performing H minority heating scheme to be used in He-4 plasmas, modest heating efficiencies (n = P-absorbed/P-launched < 40%) with dominant electron heating were found in both H plasma scenarios studied, and enhanced plasma-wall interaction manifested by high radiation losses and relatively large impurity content in the plasma was observed. This effect was stronger in the He-3 ICRF heating case than in the H majority heating experiments and it was verified that concentrations as high as similar to 20% are necessary to observe significant ion heating in this case. The RF acceleration of the heated ions was modest in both cases, although a small fraction of the 3He ions reached about 260 keV in the second harmonic He-3 heating experiments when 5MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the He-3 heating experiments (where both the second and third harmonic ion cyclotron resonance layers of the D ions are inside the plasma) whilst it was practically absent in the majority hydrogen heating scenario. While hints of improved RF heating efficiency as a function of the plasma temperature and plasma dilution (with He-4) were confirmed in the H majority case, the He-3 concentration was the main handle on the heating efficiency in the second harmonic He-3 heating scenario.
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