Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas

S. K. Hansen*, S. K. Nielsen, J. Stober, J. Rasmussen, Mirko Salewski, M. Stejner, ASDEX Upgrade Team

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Parametric decay instabilities (PDIs) occur for large-amplitude waves in quadratically nonlinear media, where they provide a limit of validity of linear theories and allow efficient coupling between different, well-defined wave modes. We investigate PDIs near the upper hybrid resonance in plasmas by injection of high-power electron cyclotron (EC) waves at the ASDEX Upgrade tokamak. Our measurements of PDIs have an unprecedented frequency resolution, far below the ion cyclotron frequency, allowing the first observations of secondary and tertiary PDIs during the saturation phase in a controlled laboratory setting. Furthermore, we are for the first time able to systematically compare theoretical predictions of the EC wave power thresholds, which must be exceeded to excite such PDIs, with experimental observations, validating the theory. Our findings are relevant for EC wave heating and current drive in tokamaks and stellarators, including future fusion power plants, as well as in low-temperature laboratory and industrial plasmas, inertial confinement fusion, and ionospheric modification experiments.
Original languageEnglish
Article number062102
JournalPhysics of Plasmas
Volume26
Issue number6
Number of pages7
ISSN1070-664X
DOIs
Publication statusPublished - 2019

Cite this

@article{8f0d2acb299d446e9a2a13f5f62be512,
title = "Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas",
abstract = "Parametric decay instabilities (PDIs) occur for large-amplitude waves in quadratically nonlinear media, where they provide a limit of validity of linear theories and allow efficient coupling between different, well-defined wave modes. We investigate PDIs near the upper hybrid resonance in plasmas by injection of high-power electron cyclotron (EC) waves at the ASDEX Upgrade tokamak. Our measurements of PDIs have an unprecedented frequency resolution, far below the ion cyclotron frequency, allowing the first observations of secondary and tertiary PDIs during the saturation phase in a controlled laboratory setting. Furthermore, we are for the first time able to systematically compare theoretical predictions of the EC wave power thresholds, which must be exceeded to excite such PDIs, with experimental observations, validating the theory. Our findings are relevant for EC wave heating and current drive in tokamaks and stellarators, including future fusion power plants, as well as in low-temperature laboratory and industrial plasmas, inertial confinement fusion, and ionospheric modification experiments.",
author = "Hansen, {S. K.} and Nielsen, {S. K.} and J. Stober and J. Rasmussen and Mirko Salewski and M. Stejner and {ASDEX Upgrade Team}",
year = "2019",
doi = "10.1063/1.5091659",
language = "English",
volume = "26",
journal = "Physics of Plasmas",
issn = "1070-664X",
publisher = "American Institute of Physics",
number = "6",

}

Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas. / Hansen, S. K.; Nielsen, S. K.; Stober, J.; Rasmussen, J.; Salewski, Mirko; Stejner, M.; ASDEX Upgrade Team.

In: Physics of Plasmas, Vol. 26, No. 6, 062102, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas

AU - Hansen, S. K.

AU - Nielsen, S. K.

AU - Stober, J.

AU - Rasmussen, J.

AU - Salewski, Mirko

AU - Stejner, M.

AU - ASDEX Upgrade Team

PY - 2019

Y1 - 2019

N2 - Parametric decay instabilities (PDIs) occur for large-amplitude waves in quadratically nonlinear media, where they provide a limit of validity of linear theories and allow efficient coupling between different, well-defined wave modes. We investigate PDIs near the upper hybrid resonance in plasmas by injection of high-power electron cyclotron (EC) waves at the ASDEX Upgrade tokamak. Our measurements of PDIs have an unprecedented frequency resolution, far below the ion cyclotron frequency, allowing the first observations of secondary and tertiary PDIs during the saturation phase in a controlled laboratory setting. Furthermore, we are for the first time able to systematically compare theoretical predictions of the EC wave power thresholds, which must be exceeded to excite such PDIs, with experimental observations, validating the theory. Our findings are relevant for EC wave heating and current drive in tokamaks and stellarators, including future fusion power plants, as well as in low-temperature laboratory and industrial plasmas, inertial confinement fusion, and ionospheric modification experiments.

AB - Parametric decay instabilities (PDIs) occur for large-amplitude waves in quadratically nonlinear media, where they provide a limit of validity of linear theories and allow efficient coupling between different, well-defined wave modes. We investigate PDIs near the upper hybrid resonance in plasmas by injection of high-power electron cyclotron (EC) waves at the ASDEX Upgrade tokamak. Our measurements of PDIs have an unprecedented frequency resolution, far below the ion cyclotron frequency, allowing the first observations of secondary and tertiary PDIs during the saturation phase in a controlled laboratory setting. Furthermore, we are for the first time able to systematically compare theoretical predictions of the EC wave power thresholds, which must be exceeded to excite such PDIs, with experimental observations, validating the theory. Our findings are relevant for EC wave heating and current drive in tokamaks and stellarators, including future fusion power plants, as well as in low-temperature laboratory and industrial plasmas, inertial confinement fusion, and ionospheric modification experiments.

U2 - 10.1063/1.5091659

DO - 10.1063/1.5091659

M3 - Journal article

VL - 26

JO - Physics of Plasmas

JF - Physics of Plasmas

SN - 1070-664X

IS - 6

M1 - 062102

ER -