Modeling of Massive Gas Injection Triggered Disruptions in Tokamak Plasmas PDF Download
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Author: Alexandre Fil
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Book Description
Plasma disruptions are events occuring in tokamaks which result in the total loss of the plasma confinement and the end of the discharge. These disruptions are rapid and violent events and they can damage the tokamak walls and its structure if they are not controlled. A Disruption Mitigation System (DMS) is thus mandatory in ITER in order to reduce electromagnetic forces, mitigate heat loads and avoid Runaway Electrons (RE) generated by plasma disruptions. These combined objectives make the design of the DMS a complex and challenging task, for which substantial input from both experiments and modeling is needed. We present here modeling results on disruption mitigation by Massive Gas Injection (MGI), which is one of the main methods considered for the DMS of ITER. First, a model which stems from first principles is given for the tranport of neutrals in a plasma and applied to the study of the interaction of the MGI with the plasma. Main mechanisms responsible for the penetration of the neutral gas are described and studied. Charge-exchange processes between the neutrals and the ions of the plasma is found to play a major role. Then, the 3D non linear MHD code JOREK is applied to the study of MGI-triggered disruptions with a particular focus on the thermal quench phase and the MHD events which are responsible for it. The simulation results are compared to experiments done on the JET tokamak.
Author: Alexandre Fil
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Book Description
Plasma disruptions are events occuring in tokamaks which result in the total loss of the plasma confinement and the end of the discharge. These disruptions are rapid and violent events and they can damage the tokamak walls and its structure if they are not controlled. A Disruption Mitigation System (DMS) is thus mandatory in ITER in order to reduce electromagnetic forces, mitigate heat loads and avoid Runaway Electrons (RE) generated by plasma disruptions. These combined objectives make the design of the DMS a complex and challenging task, for which substantial input from both experiments and modeling is needed. We present here modeling results on disruption mitigation by Massive Gas Injection (MGI), which is one of the main methods considered for the DMS of ITER. First, a model which stems from first principles is given for the tranport of neutrals in a plasma and applied to the study of the interaction of the MGI with the plasma. Main mechanisms responsible for the penetration of the neutral gas are described and studied. Charge-exchange processes between the neutrals and the ions of the plasma is found to play a major role. Then, the 3D non linear MHD code JOREK is applied to the study of MGI-triggered disruptions with a particular focus on the thermal quench phase and the MHD events which are responsible for it. The simulation results are compared to experiments done on the JET tokamak.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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High-pressure gas jet injection of neon and argon is used to mitigate the deleterious effects from tokamak disruptions. Thermal loading of the divertor surfaces, vessel stress from poloidal halo currents and the buildup and loss of relativistic electrons to the wall are all greatly reduced or eliminated. The gas jet penetrates through to the central plasma as a neutral species at its sonic velocity[approx] 300-500 m/s. The injected impurity species radiate> 95% of the plasma stored energy, accompanied by a 500-fold increase the total electron inventory in the plasma volume, thus decreasing localized heating at the divertor targets. The poloidal halo currents at the wall are reduced because of the rapid cooling and the slow movement of the plasma toward the wall during the current quench. When a sufficient quantity of gas is injected, the extremely large total (free+ bound) electron density inhibits runaway electrons in the current quench, as predicted. A physical model of radiative cooling has been developed and is validated against DIII-D experiments. The model shows that gas jet mitigation, including runaway suppression, extrapolates favorably to burning plasmas where disruption damage would be more severe. The use of real-time detection of the onset of a disruption to trigger massive gas injection and to mitigate the ensuing damage is demonstrated.
Author: Fedir Savčenko
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Alexei Savtchkov
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Mikhail Koltunov
Publisher: Forschungszentrum Jülich
ISBN: 3893368280
Category :
Languages : en
Pages : 131
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The goal of this research is to establish credible disruption mitigation scenarios based on the technique of massive gas injection. Disruption mitigation seeks to minimize or eliminate damage to internal components that can occur due to the rapid dissipation of thermal and magnetic energy during a tokamak disruption. In particular, the focus of present research is extrapolating mitigation techniques to burning plasma experiments such as ITER, where disruption-caused damage poses a serious threat to the lifetime of internal vessel components. A majority of effort has focused on national and international collaborative research with large tokamaks: DIII-D, Alcator C-Mod, JET, and ASDEX Upgrade. The research was oriented towards empirical trials of gas-jet mitigation on several tokamaks, with the goal of developing and applying cohesive models to the data across devices. Disruption mitigation using gas jet injection has proven to be a viable candidate for avoiding or minimizing damage to internal components in burning plasma experiments like ITER. The physics understanding is progress towards a technological design for the required gas injection system in ITER.
Author: Willem Hundsdorfer
Publisher: Springer Science & Business Media
ISBN: 3662090171
Category : Technology & Engineering
Languages : en
Pages : 479
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Book Description
Unique book on Reaction-Advection-Diffusion problems
Author:
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Category :
Languages : en
Pages :
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Author: D. Biskamp
Publisher: Cambridge University Press
ISBN: 9780521599184
Category : Mathematics
Languages : en
Pages : 400
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Book Description
A self-contained introduction to magnetohydrodynamics with emphasis on nonlinear processes.
Author: Brian Cornille
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This dissertation presents results from two topics in tokamak disruption modeling. The first usessimulation to elucidate the observations from MST tokamak disharge experiments on suppression of runaway electrons (RE) with resonant magnetic perturbations (RMP). When applying RMPs having a single poloidal harmonic, an m = 1 RMP does not suppress RE while and m = 3 RMP achieves full suppression [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. Magnetohydrody- namics (MHD) simulation of the experiment indicates that the m = 3 RMP produces a substantial region of chaotic magnetic fields whereas the m = 1 RMP produces negligible changes in field topology compared to no RMP. Using snapshots of the MHD simulation fields, full-orbit relativis- tic electron test particle computations show [approximately equal to] 50% loss from the m = 3 RMP compared to the 10 -15% loss from the m = 1 RMP. Test particle computations of the m = 3 RMP case in the time-evolving MHD simulation fields show correlation between MHD activity and enhanced particle losses, but finds similar total electron confinement and field snapshots. The second topic presents a novel enhancement to vertical displacement computations in NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. We present development of a quasi-static meshed vacuum region approach for treatment of computations with a resistive wall representation. With this approach a magnetostatic problem is solved for an external vacuum region while coupled through a thin-wall approximation to the implicit time advance of the plasma. Verification of the implementation is presented along with demonstration of its increased robustness in challenging geometries compared to the incumbent implementation.
