Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus

A. Casati (Corresponding Author), P. Mantica, D. Van Eester, N. Hawkes, F. Imbeaux, E. Joffrin, A. Marinoni, F. Ryter, A. Salmi, Tuomas Tala, P. De Vries

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Abstract

New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented.
The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating a low level of transport and loss of stiffness. In some cases, however, the heat wave is strongly inflated in the region just outside the ITB, showing features of convective-like behavior. In other cases, a second maximum in the perturbation amplitude is generated close to the ITB foot.
Such peculiar types of behavior can be explained on the basis of the existence of a critical temperature gradient length for the onset of turbulent transport. Convective-like features appear close to the threshold (i.e., just outside the ITB foot) when the value of the threshold is sufficiently high, with a good match with the theoretical predictions for the trapped electron mode threshold.
The appearance of a second maximum is due to the oscillation of the temperature profile across the threshold in the case of a weak ITB. Simulations with an empirical critical gradient length model and with the theory based GLF23 [R. E. Waltz et al., Phys. Plasmas, 4, 2482 (1997)] model are presented.
The difference with respect to previous results of cold pulse propagation across JET ITBs is also discussed.
Original languageEnglish
Article number092303
JournalPhysics of Plasmas
Volume14
Issue number9
DOIs
Publication statusPublished - 2007
MoE publication typeA1 Journal article-refereed

Fingerprint

Joint European Torus
wave propagation
temperature gradients
critical temperature
signatures
heat
thresholds
barrier layers
cyclotron resonance
temperature profiles
stiffness
electrons
fusion
damping
modulation
perturbation
gradients
oscillations
heating
propagation

Keywords

  • plasma
  • plasma radiofrequency heating
  • plasma temperature
  • plasma toroidal confinement
  • plasma transport processes
  • plasma turbulence
  • JET
  • internal transport barriers
  • fusion energy
  • fusion reactors

Cite this

Casati, A., Mantica, P., Van Eester, D., Hawkes, N., Imbeaux, F., Joffrin, E., ... De Vries, P. (2007). Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus. Physics of Plasmas, 14(9), [092303]. https://doi.org/10.1063/1.2772618
Casati, A. ; Mantica, P. ; Van Eester, D. ; Hawkes, N. ; Imbeaux, F. ; Joffrin, E. ; Marinoni, A. ; Ryter, F. ; Salmi, A. ; Tala, Tuomas ; De Vries, P. / Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus. In: Physics of Plasmas. 2007 ; Vol. 14, No. 9.
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abstract = "New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented. The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating a low level of transport and loss of stiffness. In some cases, however, the heat wave is strongly inflated in the region just outside the ITB, showing features of convective-like behavior. In other cases, a second maximum in the perturbation amplitude is generated close to the ITB foot. Such peculiar types of behavior can be explained on the basis of the existence of a critical temperature gradient length for the onset of turbulent transport. Convective-like features appear close to the threshold (i.e., just outside the ITB foot) when the value of the threshold is sufficiently high, with a good match with the theoretical predictions for the trapped electron mode threshold. The appearance of a second maximum is due to the oscillation of the temperature profile across the threshold in the case of a weak ITB. Simulations with an empirical critical gradient length model and with the theory based GLF23 [R. E. Waltz et al., Phys. Plasmas, 4, 2482 (1997)] model are presented. The difference with respect to previous results of cold pulse propagation across JET ITBs is also discussed.",
keywords = "plasma, plasma radiofrequency heating, plasma temperature, plasma toroidal confinement, plasma transport processes, plasma turbulence, JET, internal transport barriers, fusion energy, fusion reactors",
author = "A. Casati and P. Mantica and {Van Eester}, D. and N. Hawkes and F. Imbeaux and E. Joffrin and A. Marinoni and F. Ryter and A. Salmi and Tuomas Tala and {De Vries}, P.",
year = "2007",
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Casati, A, Mantica, P, Van Eester, D, Hawkes, N, Imbeaux, F, Joffrin, E, Marinoni, A, Ryter, F, Salmi, A, Tala, T & De Vries, P 2007, 'Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus', Physics of Plasmas, vol. 14, no. 9, 092303. https://doi.org/10.1063/1.2772618

Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus. / Casati, A. (Corresponding Author); Mantica, P.; Van Eester, D.; Hawkes, N.; Imbeaux, F.; Joffrin, E.; Marinoni, A.; Ryter, F.; Salmi, A.; Tala, Tuomas; De Vries, P.

In: Physics of Plasmas, Vol. 14, No. 9, 092303, 2007.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus

AU - Casati, A.

AU - Mantica, P.

AU - Van Eester, D.

AU - Hawkes, N.

AU - Imbeaux, F.

AU - Joffrin, E.

AU - Marinoni, A.

AU - Ryter, F.

AU - Salmi, A.

AU - Tala, Tuomas

AU - De Vries, P.

PY - 2007

Y1 - 2007

N2 - New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented. The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating a low level of transport and loss of stiffness. In some cases, however, the heat wave is strongly inflated in the region just outside the ITB, showing features of convective-like behavior. In other cases, a second maximum in the perturbation amplitude is generated close to the ITB foot. Such peculiar types of behavior can be explained on the basis of the existence of a critical temperature gradient length for the onset of turbulent transport. Convective-like features appear close to the threshold (i.e., just outside the ITB foot) when the value of the threshold is sufficiently high, with a good match with the theoretical predictions for the trapped electron mode threshold. The appearance of a second maximum is due to the oscillation of the temperature profile across the threshold in the case of a weak ITB. Simulations with an empirical critical gradient length model and with the theory based GLF23 [R. E. Waltz et al., Phys. Plasmas, 4, 2482 (1997)] model are presented. The difference with respect to previous results of cold pulse propagation across JET ITBs is also discussed.

AB - New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented. The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating a low level of transport and loss of stiffness. In some cases, however, the heat wave is strongly inflated in the region just outside the ITB, showing features of convective-like behavior. In other cases, a second maximum in the perturbation amplitude is generated close to the ITB foot. Such peculiar types of behavior can be explained on the basis of the existence of a critical temperature gradient length for the onset of turbulent transport. Convective-like features appear close to the threshold (i.e., just outside the ITB foot) when the value of the threshold is sufficiently high, with a good match with the theoretical predictions for the trapped electron mode threshold. The appearance of a second maximum is due to the oscillation of the temperature profile across the threshold in the case of a weak ITB. Simulations with an empirical critical gradient length model and with the theory based GLF23 [R. E. Waltz et al., Phys. Plasmas, 4, 2482 (1997)] model are presented. The difference with respect to previous results of cold pulse propagation across JET ITBs is also discussed.

KW - plasma

KW - plasma radiofrequency heating

KW - plasma temperature

KW - plasma toroidal confinement

KW - plasma transport processes

KW - plasma turbulence

KW - JET

KW - internal transport barriers

KW - fusion energy

KW - fusion reactors

U2 - 10.1063/1.2772618

DO - 10.1063/1.2772618

M3 - Article

VL - 14

JO - Physics of Plasmas

JF - Physics of Plasmas

SN - 1527-2419

IS - 9

M1 - 092303

ER -