Shattered pellet injection experiments at JET in support of the ITER disruption mitigation system design

Jachmich, S.; Kruezi, U.; Lehnen, M.; Baruzzo, M.; Baylor, L.R.; Carnevale, D.; Craven, David; Eidietis, N. W.; Ficker, O.; Gebhart, T. E.; Gerasimov, S.; Herfindal, J. L.; Hollmann, E. M.; Huber, A.; Lomas, P.; Lovell, J.; Manzanares, A.; Maslov, M.; Mylnar, J.; Pautasso, G.; Paz-Soldan, C.; Peacock, Alan T.; Plyusnin, V. V.; Reinke, M.L.; Reux, C.; Rimini, F.; Sheikh, U.; Shiraki, D.; Silburn, S.; Sweeney, R.; Wilson, J. R.; Hacquin, S.; Kim, H.-T.; Joffrin, E.

doi:10.1088/1741-4326/ac3c86

Cited by 39 publications

(53 citation statements)

References 21 publications

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“…2016; Jachmich et al. 2021; Vallhagen et al. 2022), to tailor the spatio-temporal properties of dissipating the thermal and magnetic energy content of the plasma.…”

Section: Introductionmentioning

confidence: 99%

Runaway dynamics in tokamak disruptions with current relaxation

2022

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The safe operation of tokamak reactors requires a reliable modelling capability of disruptions, and in particular the spatio-temporal dynamics of associated runaway electron currents. In a disruption, instabilities can break up magnetic surfaces into chaotic field line regions, causing current profile relaxation, as well as a rapid radial transport of heat and particles. Using a mean-field helicity transport model implemented in the disruption runaway modelling framework Dream, we calculate the dynamics of runaway electrons in the presence of current relaxation events. In scenarios where flux surfaces remain intact in parts of the plasma, a skin current is induced at the boundary of the intact magnetic field region. This skin current region becomes an important centre concerning the subsequent dynamics: it may turn into a hot ohmic current channel, or a sizeable radially localized runaway beam, depending on the heat transport. If the intact region is in the plasma edge, runaway generation in the countercurrent direction can occur, which may develop into a sizeable reverse runaway beam. Even when the current relaxation extends to the entire plasma, the final runaway current density profile can be significantly affected, as the induced electric field is reduced in the core and increased in the edge, thereby shifting the centre of runaway generation towards the edge.

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“…2016; Jachmich et al. 2021; Vallhagen et al. 2022), to tailor the spatio-temporal properties of dissipating the thermal and magnetic energy content of the plasma.…”

Section: Introductionmentioning

confidence: 99%

Runaway dynamics in tokamak disruptions with current relaxation

2022

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“…In this perspective, enormous amounts of resources are being devoted to developing tools for the mitigation of disruptions' detrimental effects: electromagnetic forces, thermal loads and runaway electrons [7]. In addition to fast valves for massive gas injection, the technology of the shattered pellets has made very remarkable progress in the last decade [8][9][10][11].…”

Section: A Data-driven Physics-based Approach To Prediction For Proxi...mentioning

confidence: 99%

A hybrid physics/data-driven logic to detect, classify, and predict anomalies and disruptions in tokamak plasmas

Rossi,

Gelfusa,

Craciunescu

et al. 2024

Nucl. Fusion

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Disruptions are abrupt collapses of the configuration that have afflicted all tokamaks ever operated. Reliable observers are a prerequisite to the definition and the deployment of any realistic strategy of countermeasures to avoid or mitigate disruptions. Lacking first principle models of the dynamics leading to disruptions, in the past decades empirical predictors have been extensively studied and some were even installed in JET real-time network. Having been conceived as engineering tools, they were often very abstract. In this work, physics and data-driven methodologies are combined to identify the main macroscopic precursors of disruptions: magnetic instabilities, abnormal kinetic profiles and radiation patterns. Machine learning predictors utilising these observers can not only detect and classify these anomalies but also determine their probability of occurrence and estimate the time remaining before their onset. These tools have been applied to a database of about two thousand JET discharges with various isotopic compositions including DT, in conditions simulating in all respects real time deployment. Their performance would meet ITER requirements, and they are expected to be easily transferrable to larger devices, because they rely only on normalised quantities, form factors, and physical/empirical scaling laws.

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“…As discussed in Section 1, many physical processes could result in a bump or hole on the O-point for the corresponding profiles. For example, the radiative cooling from impurity SPI into the island could result in both current holes and pressure holes on the O-point, [16,40] while the electron cyclotron wave injection (like ECRH) could result in bumps within the island for both profiles. [3][4][5][6] More bizarre cases could exist, for example during hydrogen isotope injections, where the dilution cooling resulted in current expulsion from the island interior but didn't deplete the pressure due to the low radiation power.…”

Section: Quasi-linear Perturbed Equilibrium and Profile Modification ...mentioning

confidence: 99%

“…This is consistent with previous findings in both the ECCD island stabilizing studies and the cooling island destabilizing studies. [3,4,16,40] A positive helical current perturbation on the island O-point tends to stabilize the island, while a negative helical current perturbation on the O-point tends to do the opposite.…”

Section: Impact From Current Density Profile Modification Within the ...mentioning

confidence: 99%

“…[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%

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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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Shattered pellet injection experiments at JET in support of the ITER disruption mitigation system design

Cited by 39 publications

References 21 publications

Runaway dynamics in tokamak disruptions with current relaxation

Runaway dynamics in tokamak disruptions with current relaxation

A hybrid physics/data-driven logic to detect, classify, and predict anomalies and disruptions in tokamak plasmas

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

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