Benign termination of runaway electron beams on ASDEX Upgrade and TCV

MST1 Team; TCV team; ASDEX-Upgrade team; U. Sheikh; T. Wijkamp

doi:10.1088/1361-6587/ad1e31

Benign termination of runaway electron beams on ASDEX Upgrade and TCV

MST1 Team
, TCV team
, ASDEX-Upgrade team
, U. Sheikh (Corresponding author)
, T. Wijkamp

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

27 Citations (Scopus)

Abstract

This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that a low electron density (n _e) companion plasma was required to achieve a large MHD instability, which expelled the confined REs over a large wetted area and allowed for the conversion of magnetic energy to radiation. Control of the companion plasma n_e was achieved via neutral pressure regulation and was agnostic to material injection method. The neutral pressure required for recombination was found to be dependent on impurity species, quantity and RE current. On TCV, n _e increased at neutral pressures above 1 Pa, indicating that higher collisionality between the REs and neutrals may lead to an upper pressure limit. The conversion of magnetic energy to radiated energy was measured on both machines and a decrease in efficiency was observed at high neutral pressure on TCV. The benign termination technique was able to prevent any significant increase in maximum heat flux on AUG from 200 to 600 kA of RE current, highlighting the ability of this approach to handle fully formed RE beams.

Original language	English
Article number	035003
Number of pages	8
Journal	Plasma Physics and Controlled Fusion
Volume	66
Issue number	3
DOIs	https://doi.org/10.1088/1361-6587/ad1e31
Publication status	Published - Mar 2024
Externally published	Yes
Event	49th European Conference on Plasma Physics, EPS 2023 - Bordeaux Congress Centre, Bordeaux, France Duration: 3 Jul 2023 → 7 Jul 2023 Conference number: 49

Funding

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. C Paz-Soldan acknowledges support from US DOE under DE-SC0022270.

Funders	Funder number
U.S. Department of Energy	DE-SC0022270

Keywords

benign termination
disruptions
runaways

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10.1088/1361-6587/ad1e31

Cite this

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title = "Benign termination of runaway electron beams on ASDEX Upgrade and TCV",

abstract = "This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that a low electron density (n e) companion plasma was required to achieve a large MHD instability, which expelled the confined REs over a large wetted area and allowed for the conversion of magnetic energy to radiation. Control of the companion plasma ne was achieved via neutral pressure regulation and was agnostic to material injection method. The neutral pressure required for recombination was found to be dependent on impurity species, quantity and RE current. On TCV, n e increased at neutral pressures above 1 Pa, indicating that higher collisionality between the REs and neutrals may lead to an upper pressure limit. The conversion of magnetic energy to radiated energy was measured on both machines and a decrease in efficiency was observed at high neutral pressure on TCV. The benign termination technique was able to prevent any significant increase in maximum heat flux on AUG from 200 to 600 kA of RE current, highlighting the ability of this approach to handle fully formed RE beams.",

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author = "\{MST1 Team\} and \{TCV team\} and \{ASDEX-Upgrade team\} and U. Sheikh and J. Decker and M. Hoppe and M. Pedrini and B. Sieglin and L. Simons and J. Cazabonne and J. Caloud and J. Cerovsky and S. Coda and C. Colandrea and \{Dal Molin\}, A. and B. Duval and O. Ficker and M. Griener and G. Papp and G. Pautasso and C. Paz-Soldan and C. Reux and E. Tomesova and T. Wijkamp",

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AU - MST1 Team

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AU - Sheikh, U.

AU - Decker, J.

AU - Hoppe, M.

AU - Pedrini, M.

AU - Sieglin, B.

AU - Simons, L.

AU - Cazabonne, J.

AU - Caloud, J.

AU - Cerovsky, J.

AU - Coda, S.

AU - Colandrea, C.

AU - Dal Molin, A.

AU - Duval, B.

AU - Ficker, O.

AU - Griener, M.

AU - Papp, G.

AU - Pautasso, G.

AU - Paz-Soldan, C.

AU - Reux, C.

AU - Tomesova, E.

AU - Wijkamp, T.

N1 - Conference code: 49

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N2 - This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that a low electron density (n e) companion plasma was required to achieve a large MHD instability, which expelled the confined REs over a large wetted area and allowed for the conversion of magnetic energy to radiation. Control of the companion plasma ne was achieved via neutral pressure regulation and was agnostic to material injection method. The neutral pressure required for recombination was found to be dependent on impurity species, quantity and RE current. On TCV, n e increased at neutral pressures above 1 Pa, indicating that higher collisionality between the REs and neutrals may lead to an upper pressure limit. The conversion of magnetic energy to radiated energy was measured on both machines and a decrease in efficiency was observed at high neutral pressure on TCV. The benign termination technique was able to prevent any significant increase in maximum heat flux on AUG from 200 to 600 kA of RE current, highlighting the ability of this approach to handle fully formed RE beams.

AB - This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that a low electron density (n e) companion plasma was required to achieve a large MHD instability, which expelled the confined REs over a large wetted area and allowed for the conversion of magnetic energy to radiation. Control of the companion plasma ne was achieved via neutral pressure regulation and was agnostic to material injection method. The neutral pressure required for recombination was found to be dependent on impurity species, quantity and RE current. On TCV, n e increased at neutral pressures above 1 Pa, indicating that higher collisionality between the REs and neutrals may lead to an upper pressure limit. The conversion of magnetic energy to radiated energy was measured on both machines and a decrease in efficiency was observed at high neutral pressure on TCV. The benign termination technique was able to prevent any significant increase in maximum heat flux on AUG from 200 to 600 kA of RE current, highlighting the ability of this approach to handle fully formed RE beams.

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T2 - 49th European Conference on Plasma Physics, EPS 2023

Y2 - 3 July 2023 through 7 July 2023

ER -

Benign termination of runaway electron beams on ASDEX Upgrade and TCV

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