3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

JET Contributors

doi:10.1088/1741-4326/ad1d10

3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

JET Contributors

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power (P _rad) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess and check’) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ ² statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98 + 0.03 / − 0.29 and 1.01 + 0.02 / − 0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.

Original language	English
Article number	036020
Journal	Nuclear Fusion
Volume	64
Issue number	3
DOIs	https://doi.org/10.1088/1741-4326/ad1d10
State	Published - Mar 2024

Funding

This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Awards DE-SC0014264. The views and opinions expressed herein do not necessarily reflect those of the Department of Energy. This work has been carried out within the framework of the EUROfusion Consortium, partially funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion). The Swiss contribution to this work has been funded by the Swiss State Secretariat for Education, Research and Innovation (SERI). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union, the European Commission or SERI. Neither the European Union nor the European Commission nor SERI can be held responsible for them. The JET SPI project is a collaborative effort of EURATOM, the ITER Organization, and the US Department of Energy. It received funding from the ITER Organization. The views and opinions expressed herein do not necessarily reflect those of the of the ITER Organization. This work has been carried out within the framework of the EUROfusion Consortium, partially funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion). The Swiss contribution to this work has been funded by the Swiss State Secretariat for Education, Research and Innovation (SERI). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union, the European Commission or SERI. Neither the European Union nor the European Commission nor SERI can be held responsible for them.

Funders	Funder number
European Commission or SERI
ITER Organization
U.S. Department of Energy
Spine Education and Research Institute
Office of Science
Fusion Energy Sciences	DE-SC0014264
European Commission	101052200—EUROfusion
Staatssekretariat für Bildung, Forschung und Innovation

Keywords

Cherab
JET
bolometry
disruption
mitigation
shattered pellet injection
tokamak

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1088/1741-4326/ad1d10

Cite this

@article{5384b396dfbc4cfca92f37a41a861e1c,

title = "3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool",

abstract = "Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power (P rad) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling ({\textquoteleft}guess and check{\textquoteright}) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ 2 statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98 + 0.03 / − 0.29 and 1.01 + 0.02 / − 0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.",

keywords = "Cherab, JET, bolometry, disruption, mitigation, shattered pellet injection, tokamak",

author = "{JET Contributors} and B. Stein-Lubrano and R. Sweeney and D. Bonfiglio and J. Lovell and P. Carvalho and L. Baylor and Granetz, {R. S.} and S. Jachmich and E. Joffrin and M. Kong and M. Lehnen and C. Maggi and E. Marmar and E. Nardon and P. Puglia and U. Sheikh and D. Shiraki and S. Silburn",

year = "2024",

month = mar,

doi = "10.1088/1741-4326/ad1d10",

language = "English",

volume = "64",

journal = "Nuclear Fusion",

issn = "0029-5515",

publisher = "IOP Publishing",

number = "3",

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T1 - 3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

AU - JET Contributors

AU - Stein-Lubrano, B.

AU - Sweeney, R.

AU - Bonfiglio, D.

AU - Lovell, J.

AU - Carvalho, P.

AU - Baylor, L.

AU - Granetz, R. S.

AU - Jachmich, S.

AU - Joffrin, E.

AU - Kong, M.

AU - Lehnen, M.

AU - Maggi, C.

AU - Marmar, E.

AU - Nardon, E.

AU - Puglia, P.

AU - Sheikh, U.

AU - Shiraki, D.

AU - Silburn, S.

PY - 2024/3

Y1 - 2024/3

N2 - Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power (P rad) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess and check’) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ 2 statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98 + 0.03 / − 0.29 and 1.01 + 0.02 / − 0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.

AB - Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power (P rad) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess and check’) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ 2 statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98 + 0.03 / − 0.29 and 1.01 + 0.02 / − 0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.

KW - Cherab

KW - JET

KW - bolometry

KW - disruption

KW - mitigation

KW - shattered pellet injection

KW - tokamak

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U2 - 10.1088/1741-4326/ad1d10

DO - 10.1088/1741-4326/ad1d10

M3 - Article

AN - SCOPUS:85184852752

SN - 0029-5515

VL - 64

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 3

M1 - 036020

ER -

3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

Abstract

Funding

Keywords

UN SDGs

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