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ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (982 download)
Download or read book Non-linear MHD Modelling of ELM Triggering by Pellet Injection in DIII-D and Implications for ITER. written by and published by . This book was released on 2012 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : C Wendell Horton, Jr
Publisher : World Scientific
ISBN 13 : 9814678686
Total Pages : 248 pages
Book Rating : 4.8/5 (146 download)
Download or read book Iter Physics written by C Wendell Horton, Jr and published by World Scientific. This book was released on 2015-06-25 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: The promise of a vast and clean source of thermal power drove physics research for over fifty years and has finally come to collimation with the international consortium led by the European Union and Japan, with an agreement from seven countries to build a definitive test of fusion power in ITER. It happened because scientists since the Manhattan project have envisioned controlled nuclear fusion in obtaining energy with no carbon dioxide emissions and no toxic nuclear waste products.This large toroidal magnetic confinement ITER machine is described from confinement process to advanced physics of plasma-wall interactions, where pulses erupt from core plasma blistering the machine walls. Emissions from the walls reduce the core temperature which must remain ten times hotter than the 15 million degree core solar temperature to maintain ITER fusion power. The huge temperature gradient from core to wall that drives intense plasma turbulence is described in detail.Also explained are the methods designed to limit the growth of small magnetic islands, the growth of edge localized plasma plumes and the solid state physics limits of the stainless steel walls of the confinement vessel from the burning plasma. Designs of the wall coatings and the special 'exhaust pipe' for spent hot plasma are provided in two chapters. And the issues associated with high-energy neutrons — about 10 times higher than in fission reactions — and how they are managed in ITER, are detailed.
Download or read book DIII-D Research to Address Key Challenges for ITER and Fusion Energy written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: DIII-D has made significant advances in the scientific basis for fusion energy. The physics mechanism of resonant magnetic perturbation (RMP) edge localized mode (ELM) suppression is revealed as field penetration at the pedestal top, and reduced coil set operation was demonstrated. Disruption runaway electrons were effectively quenched by shattered pellets; runaway dissipation is explained by pitch angle scattering. Modest thermal quench radiation asymmetries are well described NIMROD modeling. With good pedestal regulation and error field correction, low torque ITER baselines have been demonstrated and shown to be compatible with an ITER test blanket module simulator. However performance and long wavelength turbulence degrade as low rotation and electron heating are approached. The alternative QH mode scenario is shown to be compatible with high Greenwald density fraction, with an edge harmonic oscillation demonstrating good impurity flushing. Discharge optimization guided by the EPED model has discovered a new super H-mode with doubled pedestal height. Lithium injection also led to wider, higher pedestals. On the path to steady state, 1 MA has been sustained fully non inductively with [beta]N = 4 and RMP ELM suppression, while a peaked current profile scenario provides attractive options for ITER and a [beta]N = 5 future reactor. Energetic particle transport is found to exhibit a critical gradient behavior. Scenarios are shown to be compatible with radiative and snowflake diverter techniques. Physics studies reveal that the transition to H mode is locked in by a rise in ion diamagnetic flows. Intrinsic rotation in the plasma edge is demonstrated to arise from kinetic losses. New 3D magnetic sensors validate linear ideal MHD, but identify issues in nonlinear simulations. Detachment, characterized in 2D with sub-eV resolution, reveals a radiation shortfall in simulations. As a result, future facility development targets burning plasma physics with torque free electron heating, the path to steady state with increased off axis currents, and a new divertor solution for fusion reactors.
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ISBN 13 :
Total Pages : 714 pages
Book Rating : 4.:/5 (7 download)
Download or read book Fusion Nucléaire written by and published by . This book was released on 2005 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : T. Onjun
Publisher :
ISBN 13 :
Total Pages : 19 pages
Book Rating : 4.:/5 (5 download)
Download or read book MHD-callibrated ELM Model in Simulations of ITER written by T. Onjun and published by . This book was released on 2005* with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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Download or read book Nonlinear Fluid Simulation of Particle and Heat Fluxes During Burst of ELMs on DIII-D with BOUT++ Code [Fluid Simulation of Particle and Heat Fluxes During Burst of ELMs on DIID with BOUT++ Code]. written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to study the distribution and evolution of the transient particle and heat fluxes during edge-localized mode (ELM) bursts, a BOUT++ six-field two-fluid model based on the Braginskii equations with non-ideal physics effects is used to simulate pedestal collapse in divertor geometry. We used the profiles from the DIII-D H-mode discharge #144382 with fast target heat flux measurements as the initial conditions for the simulations. Moreover, a flux-limited parallel thermal conduction is used with three values of the flux-limiting coefficient ${{\alpha}_{j}}$, free streaming model with ${{\alpha}_{j}}=1$, sheath-limit with ${{\alpha}_{j}}=0.05$, and one value in between. The studies show that a 20 times increase in ${{\alpha}_{j}}$ leads to ~6 times increase in the heat flux amplitude to both the inner and outer targets, and the widths of the fluxes are also expanded. The sheath-limit model of flux-limiting coefficient is found to be the most appropriate one, which shows ELM sizes close to the measurements. The evolution of the density profile during the burst of ELMs of DIII-D discharge #144382 is simulated, and the collapse in width and depth of ${{n}_{\text{e}}}$ are reproduced at different time steps. The growing process of the profiles for the heat flux at divertor targets during the burst of ELMs measured by IRTV (infrared television) is also reproduced by this model. The widths of heat fluxes towards targets are a little narrower, and the peak amplitudes are twice the measurements possibly due to the lack of a model of divertor radiation which can effectively reduce the heat fluxes. The magnetic flutter combined with parallel thermal conduction is found to be able to increase the total heat loss by around 33% since the magnetic flutter terms provide the additional conductive heat transport in the radial direction. Finally, the heat flux profile at both the inner and outer targets is obviously broadened by magnetic flutter. The lobe structures near the X-point at LFS are both broadened and elongated due to the magnetic flutter.
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ISBN 13 :
Total Pages : 24 pages
Book Rating : 4.:/5 (684 download)
Download or read book The Impact of ELMs on the ITER Divertor written by and published by . This book was released on 1998 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge-Localized-Modes (ELMs) are expected to present a significant transient flux of energy and particles to the ITER divertor. The threshold for ablation of the graphite target will be reached if the ELM transient exceeds Q/t12 (approximately) 45 MJ-m−2-s−12 where Q is the ELM deposition energy density and t is the ELM deposition time. The ablation parameter in ITER can be determined by scaling four factors from present experiments: the ELM energy loss from the core plasma, the fraction of ELM energy deposited on the divertor target, the area of the ELM profile onto the target, and finally the time for the ELM deposition. Review of the ELM energy loss of Type 1 ELM data suggests an ITER ELM energy loss of 2--6% of the stored energy or 25--80 MJ. The fraction of heating power crossing the separatrix due to ELMs is nearly constant (20--40%) resulting in an inverse relationship between ELM amplitude and frequency. Measurements on DIII-D and ASDEX-Upgrade indicate that 50--80% of the ELM energy is deposited on the target. There is currently no evidence for a large fraction of the ELM energy being dissipated through radiation. Profiles of the ELM heat flux are typically 1--2 times the width of steady heat flux between ELMs, with the ELM amplitude usually larger on the inboard target. The ELM deposition time varies from about 0.1 ms in JET to as high as 1.0 ms in ASDEX-Upgrade and DIII-D. The ELM deposition time for ITER will depend upon the level of conductive versus convective transport determined by the ratio of energy to particles released by the ELM. Preliminary analysis suggests that large Type 1 ELMs for low recycling H-mode may exceed the ablation parameter by a factor of 5. Promising regimes with smaller ELMS have been found at other edge operational regimes, including high density with gas puffing, use of rf heating and operation with Type 3 ELMs.
Author : Martin Greenwald
Publisher :
ISBN 13 :
Total Pages : 22 pages
Book Rating : 4.:/5 (197 download)
Download or read book Current Profile Modification and MHD Activity Following Pellet Injection in Alcator C written by Martin Greenwald and published by . This book was released on 1988 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (727 download)
Download or read book Non-linear Instability of DIII-D to Error Fields written by and published by . This book was released on 1991 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Otherwise stable DIII-D discharges can become nonlinearly unstable to locked modes and disrupt when subjected to resonant m = 2, n = 1 error field caused by irregular poloidal field coils, i.e. intrinsic field errors. Instability is observed in DIII-D when the magnitude of the radial component of the m = 2, n = 1 error field with respect to the toroidal field is B{sub r21}/B{sub T} of about 1.7 x 10−4. The locked modes triggered by an external error field are aligned with the static error field and the plasma fluid rotation ceases as a result of the growth of the mode. The triggered locked modes are the precursors of the subsequent plasma disruption. The use of an n = 1 coil'' to partially cancel intrinsic errors, or to increase them, results in a significantly expanded, or reduced, stable operating parameter space. Precise error field measurements have allowed the design of an improved correction coil for DIII-D, the C-coil'', which could further cancel error fields and help to avoid disruptive locked modes. 6 refs., 4 figs.
Download or read book Exploration of the Super H-mode Regime on DIII-D and Potential Advantages for Burning Plasma Devices written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a new high pedestal regime ("Super H-mode") we predicted and accessed DIII-D. Super H-mode was first achieved on DIII-D using a quiescent H-mode edge, enabling a smooth trajectory through pedestal parameter space. By exploiting Super H-mode, it has been possible to access high pedestal pressures at high normalized densities. And while elimination of Edge localized modes (ELMs) is beneficial for Super H-mode, it may not be a requirement, as recent experiments have maintained high pedestals with ELMs triggered by lithium granule injection. Simulations using TGLF for core transport and the EPED model for the pedestal find that ITER can benefit from the improved performance associated with Super H-mode, with increased values of fusion power and gain possible. In similar studies demonstrate that the Super H-mode pedestal can be advantageous for a steady-state power plant, by providing a path to increasing the bootstrap current while simultaneously reducing the demands on the core physics performance.
Download or read book PROGRESS IN THE PEELING-BALLOONING MODEL OF ELMS written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonlinear simulations with the 3D electromagnetic two-fluid BOUT code are employed to study the dynamics of edge localized modes (ELMs) driven by intermediate wavelength peeling-ballooning modes. It is found that the early behavior of the modes is similar to expectations from linear, ideal peeling-ballooning mode theory, with the modes growing linearly at a fraction of the Alfven frequency. In the nonlinear phase, the modes grow explosively, forming a number of extended filaments which propagate rapidly from the outer closed flux region into the open flux region toward the outboard wall. Similarities to non-linear ballooning theory, as well as additional complexities are observed. Comparison to observations reveals a number of similarities. Implications of the simulations and proposals for the dynamics of the full ELM crash are discussed.
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ISBN 13 :
Total Pages : 658 pages
Book Rating : 4.:/5 (413 download)
Download or read book Plasma Surface Interactions in Controlled Fusion Devices written by and published by . This book was released on 1978 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ELM Heat Flux in the ITER Divertor written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge-Localized-Modes (ELMs) have the potential to produce unacceptable levels of erosion of the ITER divertor. Ablation of the carbon divertor target will occur if the surface temperature rises above about 2,500 C. Because a large number of ELMs, [ge]1000, are expected in each discharge it is important that the surface temperature rise due to an individual ELM remain below this threshold. Calculations that have been carried out for the ITER carbon divertor target indicate ablation will occur for ELM energy[ge]0.5MJ/m[sup 2] if it is deposited in 0.1 ms, or 1.2 MJ/m[sup 2] if the deposition time is 1.0 ms. Since[Delta]T[proportional-to]Q[Delta]t[sup[minus]1/2], an ablation threshold can be estimated at Q[Delta]t[sup[minus]1/2][approx]45 MJm[sup[minus]2] s[sup[minus]1/2] where Q is the divertor ELM energy density in J-m[sup[minus]2] and[Delta]t is the time in seconds for that deposition. If a significant fraction of ELMs exceed this threshold then an unacceptable level of erosion may take place. The ablation parameter in ITER can be determined by scaling four factors from present experiments: the ELM energy loss from the core plasma, the fraction of ELM energy deposited on the divertor target, the area of the ELM profile onto the target, and the time for the ELM deposition. ELM data from JET, ASDEX-Upgrade, JT-60U, DIII-D and Compass-D have been assembled by the ITER Divertor Modeling and Database expert group into a database for the purpose of predicting these factors for ELMs in the ITER divertor.
Author : D. Gray
Publisher :
ISBN 13 :
Total Pages : 22 pages
Book Rating : 4.:/5 (316 download)
Download or read book Effect of B-Field Dependent Particle Drifts on ELM Behavior in the DIII-D Boundary Plasma written by D. Gray and published by . This book was released on 2004 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: ELM effects in the DIII-D pedestal and boundary plasmas were measured with multiple fast diagnostics in matched, lower single null, ELMing H-mode discharges with the ion Bx{gradient}B drift toward and away from the divertor. Data show a strong dependence of the delay in inner vs. outer divertor ELM D{sub alpha} emission on drift direction, and a weaker drift dependence of the inner vs. outer delay of the total radiated power, in addition to the strong density dependence seen in previous work [1]. Time dependent modeling of the boundary plasma during an ELM was done with the UEDGE code including a six-species fluid carbon model and the effect of B-field induced particle drifts [2]. The ELM perturbation was modeled as an instantaneous, outer midplane peaked, increase of diffusion coefficients from the top of the pedestal to the outer SOL. The simulations show delays in the ELM perturbation at the inner vs. outer divertor targets that are similar to the measured delays.
Download or read book Characterization of MHD Activity and Its Influence on Radiation Asymmetries During Massive Gas Injection in DIII-D. written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements from the DIII-D tokamak show that toroidal radiation asymmetries during fast shutdown by massive gas injection (MGI) are largely driven by n = 1 magnetohydrodynamic modes during the thermal quench. The phenomenology of these modes, which are driven unstable by pro le changes as the thermal energy is quenched, is described based on detailed magnetic measurements. Here, the toroidal evolution of the dominantly n = 1 perturbation is understood to be a function of three parameters: the location of the MGI port, pre-MGI plasma rotation, and n = 1 error elds. Here, the resulting level of radiation asymmetry in these DIII-D plasmas is modest, with a toroidal peaking factor (TPF) of 1:2 ± 0:1 for the total thermal quench energy and 1:4 ± 0:3 for the peak radiated power, both of which are below the estimated limit for ITER (TPF ≈ 2).
Download or read book Energetic/alpha Particle Effects on MHD Modes and Transport written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A nonvariational kinetic-MHD stability code (NOVA-K) has been employed to study TAE stability in TFRR D-T and DIII-D experiments and to achieve understanding of TAE instability drive and damping mechanism. Reasonably good agreement between theory and experiment has been obtained. In these experiments the dominant damping mechanism is due to both the thermal ion Landau damping and/or the beam ion Landau damping. Based on ITER EDA parameters, the TAE modes are expected to be unstable in normal ITER operations. Energetic particle transport has been studied using a test particle code (ORBIT). Energetic particle loss scales linearly with the TAE mode amplitude and can be large for TFRR and DIII-D for [delta]B[sub r]/B> 10[sup [minus]4] due to large banana orbit. From quasi-linear (ORBIT) and nonlinear kinetic-MHD (MH3D-K) simulations the saturation of TAE modes is due to nonlinear wave particle trapping and energetic particle profile modification in both radial and energy space. Finally, a convective bucket transport mechanism by MHD waves with time-dependent frequency is presented. Based on the energy-selective characteristics of the bucket transport mechanism, undesirable particles such as helium ash can be removed from the plasma core efficiently.
Author : Olivier Sauter
Publisher : American Institute of Physics
ISBN 13 : 9780735406001
Total Pages : 400 pages
Book Rating : 4.4/5 (6 download)
Download or read book Theory of Fusion Plasmas written by Olivier Sauter and published by American Institute of Physics. This book was released on 2008-12-02 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Joint Varenna-Lausanne International Workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favorable for informal and in depth discussions. Invited and contributed papers present state-of-the art researches in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always allows a fruitful mix of experienced researchers and students, to allow for a better understanding of the key theoretical physics models and applications, such as: Theoretical issues related to burning plasmas; Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive; Macroinstabilities; Plasma-Edge Physics and Divertors; Fast particles instabilities.
