On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

Nardon, E.; Fil, A.; Chauveau, P.; Tamain, P.; Guirlet, R.; Koslowski, H. R.; Lehnen, M.; Reux, C.; Saint‐Laurent, F.; Contributors, Jet

doi:10.1088/0029-5515/57/1/016027

Cited by 10 publications

(10 citation statements)

References 34 publications

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“…As shown in figure 6 of [31], above a certain pellet velocity, the mass fraction contained in solid fragments drops sharply from > 70% to < 10%. A large gas fraction is clearly not desirable since the gas will not fuel the plasma directly in the core but will instead fuel at the edge [32], with the risk of cooling down the edge too much and triggering MHD modes [29]. This sets a limit on the pellet velocity which depends on the angle of the shattering tube.…”

Section: Discussionmentioning

confidence: 99%

Fast plasma dilution in ITER with pure deuterium shattered pellet injection

Nardon

Hoelzl

et al. 2020

Nucl. Fusion

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JOREK 3D non-linear magnetohydrodynamic (MHD) simulations of pure deuterium shattered pellet injection in ITER are presented. Considering a 15 MA L-mode plasma with a thermal energy content of 36 MJ from the non-activated phase of ITER operation, it is shown that such a scheme could allow diluting the plasma by more than a factor 10 without immediately triggering large MHD activity, provided the background impurity density is low enough. This appears as a promising strategy to reduce the risk of hot tail runaway electron (RE) generation and possibly to avoid RE beams altogether in ITER, motivating further studies in this direction.

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Section: Discussionmentioning

confidence: 99%

Fast plasma dilution in ITER with pure deuterium shattered pellet injection

Nardon

Hoelzl

et al. 2020

Nucl. Fusion

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“…The presented ECE data was digitised with a 200 kHz rate and smoothed with a +/-100 µs triangular filter to reduce noise. The time origin here is the time at which the argon enters the vacuum vessel (22.5282 s in 'JET absolute time'), calculated from the DMV1 opening time (22.5239 s) and the theoretical gas propagation time from DMV1 to the vessel (4.3 ms) [30] [31]. The pre-TQ phase lasts about 6 ms and is characterized by a gradual increase of n el and decrease of I p .…”

Section: Methodsmentioning

confidence: 99%

“…Indeed, as mentioned above, our model does not include gas dynamics. Simulations including gas dynamics [33] [31] find that when the gas front first reaches the plasma edge, only a small fraction of the gas penetrates the plasma. Poloidal cross-section of the electron temperature, with a Poincaré crosssection (white dots) and the q = 2 and LCFS (calculated for the axisymmetric part of the magnetic field, green lines) overlayed, in the injection plane at t = 4.62 (left), 4.91 (middle) and 5.09 ms (right) for Case B (see Table 1).…”

Section: Impact Of the Amount Of Argon Deposited In The 2/1 Island Re...mentioning

confidence: 99%

Thermal quench and current profile relaxation dynamics in massive-material-injection-triggered tokamak disruptions

Nardon

Di²,

Artola

et al. 2021

Plasma Phys. Control. Fusion

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3D non-linear magnetohydrodynamic simulations of a disruption triggered by a massive injection of argon gas in JET are performed with the JOREK code. The key role of the thermal drive of the m = 2, n = 1 tearing mode (i.e. the drive from helical cooling inside the island) in the disruption process is highlighted by varying the amplitude and position of the argon source across simulations, and also during a simulation. In cases where this drive persists in spite of the development of magnetic stochasticity, which is favoured by moving the argon source in an ad hoc way from the plasma edge into the 2/1 island at some point in the simulation, a relaxation in the region q ⩽ 2 (roughly) takes place. This relaxation generates a plasma current spike comparable to the experimental one. Simulations are compared in detail to measurements via synthetic diagnostics, validating the model to some degree.

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“…Ref. [30] developed the 1D radial fluid code IMAGINE to model MGI with comparisons to JET interferometer diagnostics. Ref.…”

Section: Introductionmentioning

confidence: 99%

Spatially-dependent modeling and simulation of runaway electron mitigation in DIII-D

Beidler,

del-Castillo-Negrete,

Baylor

et al. 2020

Preprint

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New simulations with the Kinetic Orbit Runaway electron (RE) Code KORC show RE deconfinement losses to the wall are the primary current dissipation mechanism in DIII-D experiments with high-Z impurity injection, and not collisional slowing down. The majority of simulations also exhibit an increase in the RE beam energy due to acceleration by the induced toroidal electric field, even while the RE beam current is decreasing. In this study, KORC integrates RE orbits using the relativistic guiding center equations of motion, and incorporates time-sequenced, experimental reconstructions of the magnetic and electric fields and line integrated electron density to construct spatiotemporal models of electron and partially-ionized impurity transport in the companion plasma. Simulation results indicate current profile changes due to increased pitch angle scattering of REs by injected impurities lower the rotational transform and lead to the deconfinement of REs. Comparisons of experimental current evolution and KORC results demonstrate the importance of including Coulomb collisions with partially-ionized impurity physics, initial RE energy, pitch angle, and spatial distributions, and spatiotemporal electron and partially-ionized impurity transport. This research provides an initial quantification of the efficacy of RE mitigation via injected impurities, and identification of the critical role played by loss of confinement as compared to the relatively slow collisional damping.

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On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

Cited by 10 publications

References 34 publications

Fast plasma dilution in ITER with pure deuterium shattered pellet injection

Fast plasma dilution in ITER with pure deuterium shattered pellet injection

Thermal quench and current profile relaxation dynamics in massive-material-injection-triggered tokamak disruptions

Spatially-dependent modeling and simulation of runaway electron mitigation in DIII-D

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