| 1. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Kanai, M, et al.
(författare)
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- 2023
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swepub:Mat__t
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| 3. |
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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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| 6. |
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| 7. |
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| 8. |
- Hobirk, J., et al.
(författare)
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The JET hybrid scenario in Deuterium, Tritium and Deuterium-Tritium
- 2023
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- The JET hybrid scenario has been developed from low plasma current carbon wall discharges to the record-breaking Deuterium-Tritium plasmas obtained in 2021 with the ITER-like Be/W wall. The development started in pure Deuterium with refinement of the plasma current, and toroidal magnetic field choices and succeeded in solving the heat load challenges arising from 37 MW of injected power in the ITER like wall environment, keeping the radiation in the edge and core controlled, avoiding MHD instabilities and reaching high neutron rates. The Deuterium hybrid plasmas have been re-run in Tritium and methods have been found to keep the radiation controlled but not at high fusion performance probably due to time constraints. For the first time this scenario has been run in Deuterium-Tritium (50:50). These plasmas were re-optimised to have a radiation-stable H-mode entry phase, good impurity control through edge Ti gradient screening and optimised performance with fusion power exceeding 10 MW for longer than three alpha particle slow down times, 8.3 MW averaged over 5 s and fusion energy of 45.8 MJ.
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| 9. |
- 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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| 10. |
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| 11. |
- Van Eester, D., et al.
(författare)
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Maximising D - T fusion power by optimising the plasma composition and beam choice in JET
- 2022
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 64:5
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Tidskriftsartikel (refereegranskat)abstract
- JET has a neutral beam injection as well as a radio frequency (RF) system for bringing plasmas to fusion-relevant temperatures. The former allows D as well as T birth energies of the order of 100-120 keV while the latter has the flexibility to heat a variety of populations by adjusting the antenna frequency. In this paper it is illustrated that-when the JET plasma is heated-the power harvested from D - T fusion reactions favours operating away from the 50-50 D - T balance and that exploiting pure D beams is more beneficial than combined D and T beams as well as pure T beams. Although beam heating dominates the overall behaviour in JET-as much more beam power than wave power can be coupled to the plasma-RF heating allows efficient heating of the very core.
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| 12. |
- de la Luna, E., et al.
(författare)
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Exploring the physics of a high-performance H-mode scenario with small ELMs at low collisionality in JET with Be/W wall
- 2024
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 64:9
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Tidskriftsartikel (refereegranskat)abstract
- A new H-mode regime at low density and low edge safety factor (q 95 = 3.2, with Ip = 3 MA) that combines high energy confinement, stationary conditions for density and radiation and small Edge Localized Modes (ELMs) have been found in JET with Be/W wall. Such a regime is achieved by operating without external gas puffing, leading to a decrease in the edge density and a substantial increase in rotation and ion temperature in both the pedestal and the core region. Transport modelling shows a reduction of the turbulence, which starts in the pedestal region and extends into the plasma core, and outward impurity convection, consistent with the improved energy confinement and the lack of W accumulation observed in those conditions. In addition, large type I ELMs, typically found in gas-fuelled plasmas, are replaced by smaller and more frequent ELMs, whose appearance is correlated with a substantial reduction of the pedestal density and its gradient. Pedestals in this operating regime are stable to peeling-ballooning modes, consistent with the lack of large ELMs. This is in contrast to results in unfuelled JET-C plasmas that typically operated at higher pedestal densities and developed low frequency, large type I ELMs, thus pointing to the low density as one of the critical parameters for accessing this small ELMs regime in JET. This small ELMs regime exhibits the same low pedestal collisionality ( nu e,ped & lowast;similar to 0.1 ) expected in ITER and operates at low q 95, thus making it different from other small ELMs regimes that are typically obtained at higher q 95 and higher pedestal collisionality. These features make this newly developed H-mode regime in JET with Be/W wall a valuable tool for exploring the underlying transport, the different mechanisms of turbulence stabilization, as well as the physics associated with the appearance of small ELMs in high-temperature plasmas at ITER relevant pedestal collisionality.
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| 13. |
- Edney, Laura C., et al.
(författare)
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Empirical Estimates of the Marginal Cost of Health Produced by a Healthcare System: Methodological Considerations from Country-Level Estimates
- 2022
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Ingår i: PharmacoEconomics (Auckland). - : ADIS INT LTD. - 1170-7690 .- 1179-2027. ; 40:1, s. 31-43
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Forskningsöversikt (refereegranskat)abstract
- Many health technology assessment committees have an explicit or implicit reference value (often referred to as a threshold) below which new health technologies or interventions are considered value for money. The basis for these reference values is unclear but one argument is that it should be based on the health opportunity costs of funding decisions. Empirical estimates of the marginal cost per unit of health produced by a healthcare system have been proposed to capture the health opportunity costs of new funding decisions. Based on a systematic search, we identified eight studies that have sought to estimate a reference value through empirical estimation of the marginal cost per unit of health produced by a healthcare system for England, Spain, Australia, The Netherlands, Sweden, South Africa and China. We review these eight studies to provide an overview of the key methodological approaches taken to estimate the marginal cost per unit of health produced by the healthcare system with the aim to help inform future estimates for additional countries. The lead author for each of these papers was invited to contribute to the current paper to ensure all the key methodological issues encountered were appropriately captured. These included consideration of the key variables required and their measurement, accounting for endogeneity of spending to health outcomes, the inclusion of lagged spending, discounting and future costs, the use of analytical weights, level of disease aggregation, expected duration of health gains, and modelling approaches to estimating mortality and morbidity effects of health spending. Subsequent research estimates for additional countries should (1) carefully consider the specific context and data available, (2) clearly and transparently report the assumptions made and include stakeholder perspectives on their appropriateness and acceptability, and (3) assess the sensitivity of the preferred central estimate to these assumptions.
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| 14. |
- Garcia, J., et al.
(författare)
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New H-mode regimes with small ELMs and high thermal confinement in the Joint European Torus
- 2022
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 29:3
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Tidskriftsartikel (refereegranskat)abstract
- New H-mode regimes with high confinement, low core impurity accumulation, and small edge-localized mode perturbations have been obtained in magnetically confined plasmas at the Joint European Torus tokamak. Such regimes are achieved by means of optimized particle fueling conditions at high input power, current, and magnetic field, which lead to a self-organized state with a strong increase in rotation and ion temperature and a decrease in the edge density. An interplay between core and edge plasma regions leads to reduced turbulence levels and outward impurity convection. These results pave the way to an attractive alternative to the standard plasmas considered for fusion energy generation in a tokamak with a metallic wall environment such as the ones expected in ITER.
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| 15. |
- 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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| 16. |
- Wong, Paul T.P., et al.
(författare)
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Self-Transcendence as a Buffer Against COVID-19 Suffering : The Development and Validation of the Self-Transcendence Measure-B
- 2021
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The age of COVID-19 calls for a different approach toward global well-being and flourishing through the transcendence suffering as advocated by existential positive psychology. In the present study, we primarily explained what self-transcendence is and why it represents the most promising path for human beings to flourish through the transformation of suffering in a difficult and uncertain world. After reviewing the literature on self-transcendence experiences, we concluded that the model of self-transcendence presented by Frankl is able to integrate both of the characteristics associated with self-transcendence. Afterward, we discussed how the self-transcendence paradigm proposed by Wong, an extension of the model by Frankl, may help awaken our innate capacity for connections with the true self, with others, and with God or something larger than oneself. We presented self-transcendence as a less-traveled but more promising route to achieve personal growth and mental health in troubled times. Finally, we presented the history of the development and psychometrics of the Self-Transcendence Measure-Brief (STM-B) and reported the empirical evidence that self-transcendence served as a buffer against COVID-19 suffering. The presented data in the current study suggested that the best way to overcome pandemic suffering and mental health crises is to cultivate self-transcendence.
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