wendelstein 7x temperatur
Im Buch gefunden – Seite 42Diese Hochtemperaturplasma - schäftigte im Jahr 2001 ( 2001 : letztes Jahr , für das Personalphysik oder auch Fusionsforschung ... Ländern ist das Forschungspersonal in den öffentlich tor - Experiment , der Wendelstein 7 - X aufgebaut . [46]) combined with a 'leave-one-out' (median) filter to deal with outliers. Rainer Wesche Höhere Temperaturen und Dichten des Plasmas, längere Pulse und den weltweiten Stellarator-Rekord für das Fusionsprodukt hat Wendelstein 7-X in der zurückliegenden Experimentierrunde erreicht. By contrast, in combination with the broad electron-to-ion energy-exchange heating profile in ECRH plasmas, ion-turbulent-heat transport leads to clamping of the central ion temperature at Ti ∼ 1.5 keV ± 0.2 keV. Figure 1 shows that virtually the same Ti ∼ 1.5 ± 0.2 keV is achieved in four configurations with various degrees of neoclassical optimization, where one would expect a clear separation on the basis of neoclassical simulations between low and high εeff configurations, as shown by the grey symbols in the figure. In the current conditions, high helium fuel purity can only be achieved after a time-consuming wall-conditioning program with repetitive pulses, for which no experimental time was allocated. Figures 3(c) and (d) show that in this predictive run, the transport is dominated by electron and ion neoclassical heat transport for the core plasma r/a < 0.75. The price to pay is therefore an increased impurity content, with Zeff rising from 1.3 to 3.2. A stationary elevated Ti,0 = 2 keV was achieved (label (3) in figure 10) above the clamped value, a day after standard boronisation (not a powder-dropper) in a steady-state hydrogen-fueled plasma lasting almost 60 s with low power of PECRH = 1 MW during the first 40 s and with an averaged density 〈ne〉 = 4 × 1019 m−3. M.N.A. lines of sight of the CXRS diagnostic [45] and assuming poloidal symmetry. Details of the magnetic configurations. Im Buch gefunden – Seite 27Wendelstein 7 - X als ein großes , hoch komplexes und einzigartiges wissenschaftliches Projekt erfordert bei ... Meilensteine erreicht : Alle 70 supraleitenden Spulen sind bei CEA Saclay bei Tieftemperatur erfolgreich „ auf Herz ... Naturally, the model is for demonstration purposes, and for this reason no sensitivity analysis is provided. Figure 6. The results show that both can help to reduce the turbulent transport, but that in the case of the pellet experiments, the introduction of a strong density gradient is likely to be the main driving mechanism for the (ITG) turbulence suppression [7]. RIS. Im Buch gefunden – Seite 209Farbliche Darstellung der magnetischen Feldstärke im Forschungsreaktor Wendelstein 7-X (Greifswald) Phasenübergänge ... Oxfordshire dalen Tokamakreaktor richten Unterhalb selbe Richtung der Curie-Temperatur aus (links)–oberhalb TC sich. Therefore, characterizing the perturbative ion transport in W7-X configurations requires a different tool than the simple PB analysis presented in this paper. Numerical calculations based on nonlinear two-fluid equations have been carried out to understand the sawtooth-like crashes of electron temperature observed in Wendelstein 7-X stellarator experiments with electron cyclotron current drive (ECCD). The ion and electron heat diffusivities used are shown in ((c) and (d)) for the neoclassical dominant model (neo) and in ((e) and (f)) for the dominant anomalous transport model (ano). (e) Experimental volume-integrated ion heat flux A ⋅ Qi,exp (solid) as calculated from the exchange power, compared to the neoclassical integrated ion heat flux A ⋅ Qi,NC (dashed). Similarly to the situation in the experiment, the plasma performance suffers strongly from anomalous transport, and in these simulations Wth,anom = 0.5 MJ, the normalized pressure 〈βanom〉 ∼ 0.5%, and τE,anom/τISS04 = 0.65, replicating the performance found in the experiment. Since a wider ECRH power range is possible in the helium-fueled plasma, the power steps in this plasma are used to study the temperature-clamping phenomenon, while a comparison of the H and He plasmas at PECRH = 3.9 MW is used to link to the wider post-boronization hydrogen W7-X database in figure 1. Profile comparison of an ECRH power scan in He-fueled plasma from PECRH = 3.9 to 1.2 MW. The improved confinement was lost after relaxation of the density profile over a particle-confinement timescale of several 100 ms, and oftentimes due to an MHD event [8]. Therefore, as the kinetic profiles and their gradients (figure 15(j)) look similar for the two plasmas, the ion heat diffusivity for the hydrogen- and helium-fueled plasmas are also similar (figure 15(i)) and is of the order of 0.5–1 m2 s−1 across the full profiles, i.e. It is designed to achieve enclosure of up to 30 minutes of continuous plasma discharge in 2021, thus demonstrating an essential feature of a future fusion power plant: continuous operation. The neoclassical mono-energetic transport coefficients are calculated using the DKES code [29]. Both linear as well as nonlinear gyro-kinetic calculations were conducted. Wolf1 and the W7-X Team7,1, Published 25 October 2021 • National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan, 4 Operational phase 1 continued (OP1.2) in 2017[23] to test the (uncooled) divertor. More than 2,000 pulses were conducted before shutdown. The residual (or unaccounted-for) power is given by Pres = PECRH − Pdiv − Prad. Figure 4. Figure 2. However, it appears that in tokamaks, linear gyro-kinetic simulations which focus on the strongest growing mode can quantitatively describe the degree of ion transport stiffness enhancement due to Te/Ti. The saturation of the central ion temperature with increasing heating power and increasing density is well captured; however, obtaining the details of the ion temperature gradient response to increasing ion heat flux will require further characteristics of ITG turbulence. The vertical drawn lines indicate the radii of the analyses in figures 8 and 9. Their confinement scaling lies at or is less than the ISS04 scaling, depending on the density in these plasmas[14]. However, even at the highest density achievable by ECRH-O2 heating, 1.6 × 1020 m−3, the ratio Te/Ti is not unity (figure 6(c)). 61st Annual Meeting of the APS Division of Plasma Physics Volume 64, Number 11 Monday-Friday, October 21-25, 2019; Fort Lauderdale, Florida The viability of the stellarator architecture is currently being investigated with the Wendelstein 7-X facility in . Collisions between heated particles cause some to escape the magnetic field. This simulated plasma therefore has a much higher global performance with Wth,NC = 1.6 MJ, 〈βNC〉 ∼ 1.5%, and τE,NC/τISS04 = 2.1. Ion temperature clamping in ECRH heated plasmas in W7-X is likely a result of various factors that lead to a reduction in the local ion temperature gradients and the global plasma performance. Yes: Then connect to the University network via VPN client in order to access the licensed contents. Based on the assumption that neoclassical transport is the dominant transport process, the fear was expressed in [19], that hollow density profiles are inevitable in W7-X centrally heated plasmas, given the recycling properties of the device. As the neutral pressure should, at most, be constant, this gives an upper bound. Close this notification This exceeded the original budget estimate, mainly because the initial development phase was longer than expected, doubling the personnel costs. Also shown are the ECRH deposition and radiated power profiles assumed in both models. The optimised Wendelstein 7-X stellarator, which went into operation five years ago, is intended to demonstrate that stellarator-type fusion plants are suitable for power plants. (d) Total experimental volume integrated heat flux A ⋅ Qtot (solid) compared to the total neoclassical integrated heat flux A ⋅ Qtot,NC (dashed); A is the flux surface area. Energy content exceeded 1 megajoule. [32–34]), the achievable central temperature does not strongly depend on the shape of the heat deposition profile; instead, it is largely determined by the strength of the edge pedestal pressure pped. M.N.A. The Wendelstein 7-X (W7-X) experiment [1–3] is a stellarator with predicted good equilibrium properties and high normalized pressures of up to 〈β〉 ∼ 5%. The shape of the electron density profile is taken from the experiment as an input. As the XICS Ti profiles are the result of an Abel inversion [42, 44] no further fitting of this data was applied, but the plotted error margins are a result of the statistical spread of the profiles inside the averaging time window. post-pellet experiments [7, 8, 56]. As a result, the experimentally achieved Ti-profiles are well below the neoclassical predictions (see e.g. With good plasma values, long-lasting plasmas with long discharge times of 100 seconds were obtained. For the core PB coming up in the next section we derive the ion density profile in the H/He fuel mixes from figure 12(b) as ni/ne = 0.9 and ni/ne = 0.65, respectively. This effect is seen in figure 12(a), which shows the radiative power density profile for each power step. These plasmas feature flat density profiles, and their transport is dominated by anomalous transport. The density profiles in such plasmas are flat to slightly peaked, as can be seen from e.g. Javier has 1 job listed on their profile. The experimental heat fluxes are shown in figures 15(d)–(f) for the sum of the electron and ion fluxes, the electrons, and the ions, respectively. 300 votes, 28 comments. For the highest power level PECRH = 3.9 MW, the Ti and Te profiles as given in figure 15 are similar to that of the H plasma, whereas the electron density is somewhat higher at 〈ne〉= 7 × 1019 m−3. IPP, Wigner RCP. Moreover, the electron heat transport shows only a small configuration dependence and no strong density dependence, and only a weak positive power dependence was found. Revised 30 June 2021 The difference in the power dependence on the saturation level seen in figure 5(a) may be due to the fact that a fixed χe,turb = 0.7 m2 s−1 is chosen, whereas [27] reports a weak power dependence of χe,turb. (d) Total experimental volume-integrated heat flux A ⋅ Qtot (solid) compared to the total neoclassical integrated heat flux A ⋅ Qtot,NC (dashed), (A is the flux surface area). Although in experiments a/{L}_{{T}_{\text{e}}}\geqslant a/{L}_{{T}_{\text{i}}}, the assumption a/{L}_{{T}_{\text{e}}} = 0 is representative, as the impact of a/{L}_{{T}_{\text{e}}} on ITG turbulence is small. The latter is reconstructed from bolometer tomography [47] by assuming toroidal symmetry. The ambipolar radial electric field, as calculated by NTSS, remains in the ion root during the scan (figure 7(c)), as confirmed by CXRS and Doppler reflectometry (DR) measurements of Er. Im Buch gefunden – Seite 512... Alexanvon Wasserstoffplasmen hoher Temperatur der , Andelfinger , Asmussen , Behler , Bosch , in Magnetfeldern , Heizung und ... ASDEX Upgrade besitzt einen X. WENDELSTEIN 7 - X soll mit einem sogenannten offenen Divertor , der dem ... In turbulence simulations, however, these subdominant modes also contribute to the determination of the ion heat flux level. Im Buch gefundenZwei profilgebende Einrichtungen sind dabei das Institut für Niedertemperaturplasmaphysik und das Max-Planck-Institut für Plasmaphysik. Letzteres befasst sich mit der Fusionsforschung am Versuchsreaktor Wendelstein 7X. Now the team says its latest round of experiments have achieved long-lasting plasmas . To enable CXRS Ti measurements, short 10 ms beam blips (compared to τE > 100 ms of neutral beam injection (NBI) heating) are used. The simulation results are shown in figure 5. Also shown in (a) and (b) are the neoclassical simulations for PECRH = 4.5 MW for the 'standard' (grey triangles) and 'high mirror' configurations (grey squares). Hence, electron heating can indirectly intensify ion transport as Te/Ti is increased. [4], The coils (NbTi in aluminium[4]) are arranged around a heat insulating cladding with a diameter of 16 metres, called the cryostat. Now turning to the heat transport, the electron temperature in gas-fueled ECRH plasmas can be varied widely from ∼1 to 10 keV, depending on density and input power, as seen in figure 1. Management Information Systems Tree: publications by Alfred Werner, Universität Zürich [17] On that day the reactor successfully produced helium plasma (with temperatures of about 1 MK) for about 0.1 s. For this initial test with about 1 mg of helium gas injected into the evacuated plasma vessel, microwave heating was applied for a short 1.3 MW pulse. However, for the four configurations shown in figure 1, ion temperature clamping occurs at the same level of Ti ∼ 1.5 ± 0.2 keV. Note that the simulations presented here act as a qualitative comparison to the experimental data and that a quantitative comparison has currently not been conducted. This site uses cookies. Breaking of Ti clamping with up to Ti ∼ 3 keV achieved in selected experiments. As the nonlinear simulations are costly in terms of the required calculation time, fewer steps in a/{L}_{{T}_{\text{i}}} and fewer values of Te/Ti have been used. This agrees with the findings of [29], in which similarly low but not identical levels of turbulent transport were assumed. However, Ti clamping can be broken, as has been shown experimentally. The equilibrium for mapping profiles is obtained using the VMEC code [40] with the kinetic profile information as input for an iterative equilibrium calculation. We first investigate how well the ion temperature clamping as seen in W7-X electron-heated plasmas can be explained by assuming gyro-Bohm-level turbulent transport without the additional ITG features described by the theory above. The linear stability of the ion-temperature-gradient modes (ITG) in the electrostatic limit is examined in the short wavelength region by using a two fluid reactive model in fully three-dimensional Wendelstein 7-X (W7-X) stellarator [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. Im Buch gefunden – Seite 107... in Greifswald einen Teil des Max-Planck-Instituts für Hochtemperatur-Plasmaphysik zu errichten. Die Forschungsstätte sollte rund 300 Mitarbeiter haben, und es sollte auchein kleiner Fusionsexperimentalreaktor vom Typ Wendelstein 7-X ... Assembly began in April 2005. The rest of this paper will address each of these aspects in turn, giving the full details of the simulations and experiments used to reach this conclusion. average temperature Wendelstein. The ion temperature may be increased through the mechanism of density-gradient-aided turbulence suppression. In the twisted coil forms, computational optimization has taken shape. The response of the ion temperature to the decreasing ion heat flux appears curious at first: figure 7(j) shows how the Ti profile changes shape during the power scan: outside r/a ∼ 0.5, the normalized ion temperature gradient a/{L}_{{T}_{\text{i}}} increases, whereas inside this radius it decreases with increasing ion heat flux Qi,turb. It is suggested that a combination of fresh wall conditioning and low power electron heating helped to increase the normalized density gradient from a/Ln In an electron heat transport study using ECRH modulations at density of ne,0 ∼ 4 × 1019 m−3, the PB and HPP transport could be separately identified. As both the density gradient and the ion root radial electric field rise after the pellet injection, a theoretical analysis using nonlinear gyro-kinetic simulations with the GENE code compared the effect of strong density gradients as well as a radial electric field on the turbulent transport. Free shipping for many . First, the exchange power density pe–i is maximized at high densities due to its n2-dependence, but also has an optimum temperature difference (figure 2). (b) and (d) The residual Pres is balanced within ∼200 kW for the phases in which Prad < PECRH up to the time point t = 7 s. The local charge exchange losses are furthermore estimated from the neutral particle density profile for the hydrogen-fueled plasma (figure 14). Im Buch gefunden – Seite 39Er wird durch eine Wärmepumpe ergänzt , die sich bei einer Frischlufttemperatur unter 8 ° C zuschaltet . ... 2003 ( derzeit im Depot ) SEC SECO 25.2500 R Neue Energietechniken STELLARATOR - SPULE » WENDELSTEIN 7 - AS « , 1988 Bei einer ... The magnet system of Wendelstein 7-X. figure 3). For radius reff/amin = 0.3: response of normalized ion temperature gradient a/{L}_{{T}_{\text{i}}} to (a) turbulent ion heat flux Qi,turb times the flux surface area A, in MW, (b) turbulent ion heat diffusivity χi,turb in m2 s−1 as well as (c) turbulent ion heat flux Qi,turb in gyro-Bohm units (equation (3.1)) and (d) turbulent ion heat diffusivity χi,turb in gyro-Bohm units (equation (3.2)). The construction of Wendelstein 7-X", "Magnet tests on Wendelstein 7-X successfully completed", "Wendelstein 7-x stellarator puts new twist on nuclear fusion power", "US narrows fusion research focus, joins German stellarator", "Princeton, Max Planck Society launch new research center plasma physics", "Start of scientific experimentation at the Wendelstein 7-X fusion device", "Preparations for operation of Wendelstein 7-X starting", "Wendelstein 7-X Newsletter No. 2 Wendelsteinstrasse 1, Max-Planck-Institut fur Plasmaphysik Teil The LOWESS filter width, the outlier window used for data-point weighting, was set to r/a = 0.1 for the Thomson Te and CXRS Ti profiles. Labelled reference plasmas (labels 1, 2, 2a) and experiments in which the clamping was broken in standard-configuration plasmas (labels 3-5) are: for labels (1),(2) and (2a),power step experiments used in this paper in helium (1) and hydrogen (2) plasmas, respectively (see e.g. Indeed turbulent transport, and not radiation losses, limit the heat transport and are responsible for the so-called ion temperature clamping observed in these plasmas. P0.6 is the density above which a radiative collapse will occur for a given input power P and is derived from [14]. We therefore ignore the charge exchange losses in the further core PB analysis. Suggested mechanisms that may influence the density profile shape include enhanced wall outgassing by ECRH, causing increased neutral recycling levels, and a possible 'density pump-out' caused by central electron heating that reduces the profile peaking. Im Buch gefunden – Seite 163Das Erreichen einer hohen Temperatur und Energieeinschlusszeit wird einfacher, je größer das Volumen ist. Für den magnetischen Einschluss in einem ... Abb. 5.30b zeigt ein Schema von Wendelstein 7-X, welcher in Greifswald gebaut wird. Citation M.N.A. In [27], where the electron transport was studied, the reverse was done by setting Ti = Te from the point where Ti > Te in the outer region of the plasma. The radiated power Prad is taken from a poloidal averaged polarimeter-tomographic reconstruction and assumes toroidal symmetry. Find 500+ million publication pages, 20+ million researchers, and 900k+ projects. Keeping the overpredictions of the neoclassical transport simulation in figure 3 in mind, we would like to see what the gyro-Bohm model would predict for the higher ECRH levels for a comparison with the results in [29], and to get insight in future performance. [25], In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 1020 particles/m3, and a confinement time of 0.2 second yielded a record fusion product of 6 × 1026 degree-seconds per cubic metre. Wolf https://orcid.org/0000-0002-2606-5289, Received 30 April 2021 Im Buch gefunden – Seite 16519 Jahre nach dem Antrag zur Errichtung der Forschungs-Anlage „Wendelstein 7-X“ starteten in Greifswald die ersten Tests des „KernfusionsExperiments“. Dabei wurde zunächst ein Helium-Plasma erzeugt. ... Sonnen-Temperatur. Im Buch gefunden – Seite xix196 Globale Temperatur-Mittelwerte (1861–1994) . . . . . . . 199 Schwankungen der mittleren Temperatur auf der Nordhalbkugel ... 276 Plasma- und Magnetspulen-Geometrie des Stellarators WENDELSTEIN 7-X . . Moreover, there appears to be only a small density dependence on the Ti saturation, certainly when we take a power-dependent radiative density limit into account following [14]. [8] An ion cyclotron resonance heating (ICRH) system will become available for physics operation in OP1.2. 6 Author to whom any correspondence should be addressed. Are you a member of Bonn University? A cooling device produces enough liquid helium to cool down the magnets and their enclosure (about 425 metric tons of "cold mass") to superconductivity temperature (4 K[5]). The high density of 〈ne〉 = 7 × 1019 m−3 is required to ensure that ion root transport is guaranteed for all power steps. As of 2015[update], the Wendelstein 7-X reactor is the largest stellarator device. Full details of the method are given in [65]. In experiments, fixing Te,0 = 3 keV would require that ne and PECRH are simultaneously increased. [27][28], In 2021 an analysis of X-ray imaging crystal spectrometer data collected in the 2018 experiment substantially reduced troubling neoclassical transport heat loss. Figure 11(b) shows the waveforms achieved with power steps of 3.9, 2.4, 1.8, and 1.2 MW. The latter lifts up the stiff core profile with pped/p0 In the remainder of this paper we will select only the standard configuration with the best NC transport reduction to study the turbulent ion transport in detail. Second panel: central (Thomson) and line-averaged (interferometer) electron densities. The charge exchange QCX loss channel for the ions can be neglected in the analysis. These profiles are explicitly taken as the inputs to the pe–i calculations only, and do not represent any transport analysis, nor indicate whether they are achievable in W7-X. As a result, a predictive transport model that could explain the clamping of the Ti gradients would need to be based on nonlinear gyro-kinetic calculations, which are very costly, and a program such as TGLF will not be readily implementable for W7-X. Although the neutral source is difficult to estimate and forms an uncertain factor in the PB, the effect is only likely to be large near the plasma edge and will not significantly affect the balance at, or inside, the mid radius, as will be shown in this appendix. The impact on the plasma stored energy is less than ΔWdia = 5% (see figure 11). τE,ISS04 ∼ n0.51, whereas, at high densities that approach the radiative density limit, an increase in density no longer scales beneficially following τE ∼ nα For the TS density profiles a broader filter width of r/a = 0.2 was used due to larger statistical and systematic errors. Im Buch gefunden – Seite 286Kürzere Einschlußzeiten , aber dafür höhere Temperaturen ( so daß man auch nur kürzere Zeiten benötigt ) ergeben sich beim Trägheitseinschluß . Hierbei wird eine 1016 Thermonukleares Brennen 1095 WENDELSTEIN 7 - X ITER שב ום כש_ : S ... For this reason, helium plasmas are better suited to probing the ion transport, as a wider variation of the exchange power is possible at a constant high density. Here, n and T represent the species density and temperature, respectively. Using the same model as that used in figure 5, and following the same approach as in [29], figure 6 'predicts' the performance with upgraded ECRH power, in terms of confinement normalized to the ISS04 scaling τE/ In [27] it is therefore concluded that the electron turbulent transport is largely diffusive. In these simulations, the highest temperatures can be achieved in the standard configuration (Ti filled, and Te open symbols), thanks to its better neoclassical optimization and smaller effective magnetic ripple 〈εeff〉. At low densities, the confinement timescales are similar to the ISS04 scaling i.e. As an answer to these questions, it will be shown in this paper that the Ti clamping is the result of a combination of effects: (a) the limited and broad ion heating due to power transfer from electrons in ECRH heated plasmas, (b) the expected increase of heat transport according to the gyro-Bohm scaling and (c) the exacerbated turbulent heat transport due to the effect of an increasing Te/Ti ratio on ITG turbulence in such plasmas. figure 7) to a/Ln [9], A system of sensors and probes based on a variety of complementary technologies will measure key properties of the plasma, including the profiles of the electron density and of the electron and ion temperature, as well as the profiles of important plasma impurities and of the radial electric field resulting from electron and ion particle transport. The upper bound of the ECRH power used in the experiment is limited to 3.9 MW due to the requirement to share the high-voltage power supply between the ECRH system and the NBI system used to provide 10 ms beam blips for the CXRS Ti measurements. where Lx (a) Radiated power density for the H-fueled plasma (dashed) and the He-fueled plasma (solid), for the various ECRH power steps in figure 11. Operational phase 1 (OP1.1) concluded 10 March 2016[17] and an upgrade phase began. This additional driver for turbulence is inherent to electron-heated plasmas: an increase of the ECRH power enhances Te, which simultaneously enhances the exchange power pe–i as well as exacerbating the ITG turbulence and the degree of Ti profile stiffness. A detailed PB analysis shows that the ion heat flux at this point is almost fully dominated by neoclassical transport, whereas the electron transport remains largely turbulence dominated. Im Buch gefunden – Seite 486... siehe Einfach magnetisierter Torus Soliton, 185ff Sonne, 3, 63 Strahlungstemperatur, 3 Sphärischer Tokamak, ... 351 Klassischer, 314, 386 Linearer, 347 Optimierung, 349 Quasi-axisymmetrischer, 350 TJ-II, 351 Wendelstein 7-X, ... The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Project Matterhorn.[3].
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