Experimental results of multiple shattered pellet injection systems in KSTAR

Park, Soo-Hwan; Lee, KunSu; Lee, HyunMyung; Song, J. H.; Yun, Sang‐Won; Baylor, L. R.; Meitner, S. J.; Kim, Jaewook; Kim, KwangPyo; Maruyama, S.; Lehnen, M.; Kruezi, U.; Park, Kaprai; Yoon, S.W.

doi:10.1016/j.fusengdes.2020.112200

Cited by 17 publications

(9 citation statements)

References 5 publications

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“…Shattered pellet injection (SPI) is the current concept for the ITER disruption mitigation system (DMS) to mitigate thermal loads, mechanical forces and effects of runaway electrons (REs) in case of disruptions [1,2]. SPI systems have been installed on various tokamaks around the world such as AUG [3], DIII-D [4][5][6], HL-2A [7], KSTAR [8], JET [2,9,10] and J-TEXT [11]. 3D non-linear MHD codes such as JOREK, M3D-C1 and NIMROD have been applied to predict the thermal quench (TQ) and current quench (CQ) dynamics during SPI [12][13][14][15][16][17][18][19][20], with the knowledge gained from studies on massive gas injection (MGI) [21-25, and references therein].…”

Section: Introductionmentioning

confidence: 99%

Interpretative 3D MHD modelling of deuterium SPI into a JET H-mode plasma

Kong,

Nardon,

Hoelzl

et al. 2024

Nucl. Fusion

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The pre-thermal quench (pre-TQ) dynamics of a pure deuterium (D2) shattered pellet injection (SPI) into a 3MA/7MJ JET H-mode plasma is studied via 3D non-linear MHD modelling with the JOREK code. The interpretative modelling captures the overall evolution of the measured density and radiated power. The simulations also identify the importance of the drifts of ablation plasmoids towards the tokamak low field side (LFS) and the impurities in the background plasma in fragment penetration, assimilation, radiative cooling and MHD activity in D2 SPI experiments. It is found that plasmoid drifts lead to an about 70% reduction of the central line-integrated density (compared to a simulation without drifts) in the JET D2 SPI discharge considered. Impurities that pre-exist before the SPI as well as those from possible impurity influxes related to the SPI are shown to dominate the radiation in the considered discharge. With inputs from JOREK simulations, modelling with the Lagrangian particle-based pellet code PELOTON reproduces the deviation of the SPI fragments in the direction of the major radius as observed by the fast camera. This confirms the role of rocket effects and plasmoid drifts in the considered discharge and reinforces the validity of the JOREK modelling. The limited core density rise due to plasmoid drifts and the strong radiative cooling and MHD activity with impurities (depending on their species and concentration) could limit the effectiveness of LFS D2 SPI in runaway electron avoidance and are worth considering in the design of the ITER disruption mitigation system.

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Section: Introductionmentioning

confidence: 99%

Interpretative 3D MHD modelling of deuterium SPI into a JET H-mode plasma

Kong,

Nardon,

Hoelzl

et al. 2024

Nucl. Fusion

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“…Several devices, such as AUG [8], DIII-D [9], JET [6], KSTAR [10] J-TEXT [11] and HL-2 A [12], have contributed towards the definition of the DMS in ITER thanks to the installation and operation of SPI systems. Useful lessons have been learned in firing of the pellets to remove efficiently the thermal energy and to dissipate REs.…”

Section: Introductionmentioning

confidence: 99%

Radiation asymmetry in JET disruption mitigation experiments with shattered pellet injection

Piron,

Jachmich,

Baylor

et al. 2024

Plasma Phys. Control. Fusion

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In ITER, to mitigate the deleterious effects of plasma disruptions, massive quantities of radiating impurities will be injected into the disrupting plasma by shattered pellet injectors (SPI) to pre-emptively radiate away the stored thermal and magnetic energy (Lehnen et al Proc. 27th IAEA Fusion Energy Conf. (FEC 2018) (Gandhinagar, India) EX/P7-12). However, asymmetries in the radiation pattern could result in intense photon flashes during the thermal quench that could locally damage or erode the stainless steel plasma-facing surface of the diagnostic port plugs (Pitts et al 2015 J. Nucl. Mater. 463 748–75). Experiments have been undertaken at JET to assess the potential dependence of the radiated power asymmetry on plasma energy during SPI mitigated disruptions. Calculations of the toroidal asymmetry in the radiated power indicate that the toroidal peaking factor is largest near the SPI position and decreases with the plasma stored energy, which is a promising result in view of radiation heat loads during mitigated disruptions in ITER.

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“…[2] To avoid such damages and safely guard the continued operation of future high performance devices, various disruption avoidance systems (DAS) are designed, such as the electron cyclotron current drive (ECCD) or Heating (ECRH), [3][4][5][6] to suppress the instability of the dominant magnetic islands by modifying the current and pressure profile within. Facing this, disruption mitigation systems (DMS) such as the shattered pellet injection (SPI) [7][8][9][10][11][12][13][14][15][16][17] or other massive material injection (MMI) [18][19][20][21][22][23][24][25] techniques are used to deplete the majority of thermal energy via radiation loss during the TQ, and raise the density to help with runaway electron suppression during the CQ phase.…”

Section: Introductionmentioning

confidence: 99%

Stability impacts from the current and pressure profile modifications within finite sized island

Sun

2023

Chinese Phys. B

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The stability (or instability) of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics. Especially, various current and pressure profile modifications, such as the current drive and heating caused by electron cyclotron wave, or the radiative cooling and current expulsion caused by the Shattered Pellet Injection could be applied within the island to modify its stability, thus change the ensuing dynamics. In this study, we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach, thus obtain the change of stability criterion ∆′ and assess the corresponding quasi-linear island stability. The positive helical current perturbation is found to always stabilize the island, while the negative one is found to do the opposite, in agreement with previous results. The pressure bump or hole within the island has a more complicated stability impact. In the small island regime, its contribution is monotonic, with pressure bump tends to stabilize the island while pressure hole destabilizes it. This effect is relatively weak, though, due to the cancellation of the pressure term’s odd parity contribution in the second derivatives of the mode structure. In the large island regime, such cancellation is broken due to the island asymmetry, and the pressure contribution to stability is manifested, which is non-monotonic. The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.

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Experimental results of multiple shattered pellet injection systems in KSTAR

Cited by 17 publications

References 5 publications

Interpretative 3D MHD modelling of deuterium SPI into a JET H-mode plasma

Interpretative 3D MHD modelling of deuterium SPI into a JET H-mode plasma

Radiation asymmetry in JET disruption mitigation experiments with shattered pellet injection

Stability impacts from the current and pressure profile modifications within finite sized island

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