SOL characterization and LH coupling measurements on JET in ITER-relevant conditions

M. Goniche, A. Ekedahl, J. Mailloux, V. Petrzilka, Karin Rantamäki, JET-EFDA collaborators

Research output: Contribution to journalArticleScientificpeer-review

21 Citations (Scopus)

Abstract

Lower hybrid (LH) current drive experiments have been carried out on JET with an antenna–plasma separatrix distance varying between 0.09 and 0.15 m, and LH power in the range 0–3.2 MW. For different plasma configurations, the electron density ne of the scrape-off layer has been studied by the mean of a reciprocating Langmuir probe magnetically connected to the LH antenna. For pulses in the high confinement regime (H mode) characterized by strong particle bursts in the plasma edge, the edge localized modes (ELMs), profiles of the saturation current (Jsat) are obtained with a sufficient time resolution to distinguish 'between ELMs' and during the rise and decay of the ELMs.

It is found that gas injection from a valve located near the LH launcher and magnetically connected to it allows one to raise the density and improve the LH coupling. The Jsat profiles indicate quite clearly that this density rise affects mainly the plasma layer in front of the antenna with a typical thickness of 5 cm. The resulting profile can be extremely flat in this region. The effect of the near-launcher gas injection but also of the LH power and the total gas injection on the density at the wall is quantitatively documented. It is shown in particular that with increasing LH power, the required gas injection for obtaining good LH coupling is decreasing, with no saturation obtained so far. Effect of the ELMs on the LH coupling is also discussed. Modelling with the EDGE2D code indicates that such flat profiles of Jsat/ne can be obtained when LH power dissipation is taken into account. Detailed analysis of the heat flux carried by electrons accelerated in the near-field of the antenna confirms the increase in density with gas puff during high LH power coupling.
Original languageEnglish
Article number044002
Number of pages18
JournalPlasma Physics and Controlled Fusion
Volume51
Issue number4
DOIs
Publication statusPublished - 2009
MoE publication typeA1 Journal article-refereed

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gas injection
Antennas
Plasmas
antennas
launchers
Langmuir probes
profiles
Carrier concentration
Heat flux
Energy dissipation
saturation
plasma layers
electrostatic probes
Electrons
heat flux
bursts
near fields
Gases
dissipation
Experiments

Cite this

Goniche, M., Ekedahl, A., Mailloux, J., Petrzilka, V., Rantamäki, K., & JET-EFDA collaborators (2009). SOL characterization and LH coupling measurements on JET in ITER-relevant conditions. Plasma Physics and Controlled Fusion, 51(4), [044002]. https://doi.org/10.1088/0741-3335/51/4/044002
Goniche, M. ; Ekedahl, A. ; Mailloux, J. ; Petrzilka, V. ; Rantamäki, Karin ; JET-EFDA collaborators. / SOL characterization and LH coupling measurements on JET in ITER-relevant conditions. In: Plasma Physics and Controlled Fusion. 2009 ; Vol. 51, No. 4.
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title = "SOL characterization and LH coupling measurements on JET in ITER-relevant conditions",
abstract = "Lower hybrid (LH) current drive experiments have been carried out on JET with an antenna–plasma separatrix distance varying between 0.09 and 0.15 m, and LH power in the range 0–3.2 MW. For different plasma configurations, the electron density ne of the scrape-off layer has been studied by the mean of a reciprocating Langmuir probe magnetically connected to the LH antenna. For pulses in the high confinement regime (H mode) characterized by strong particle bursts in the plasma edge, the edge localized modes (ELMs), profiles of the saturation current (Jsat) are obtained with a sufficient time resolution to distinguish 'between ELMs' and during the rise and decay of the ELMs.It is found that gas injection from a valve located near the LH launcher and magnetically connected to it allows one to raise the density and improve the LH coupling. The Jsat profiles indicate quite clearly that this density rise affects mainly the plasma layer in front of the antenna with a typical thickness of 5 cm. The resulting profile can be extremely flat in this region. The effect of the near-launcher gas injection but also of the LH power and the total gas injection on the density at the wall is quantitatively documented. It is shown in particular that with increasing LH power, the required gas injection for obtaining good LH coupling is decreasing, with no saturation obtained so far. Effect of the ELMs on the LH coupling is also discussed. Modelling with the EDGE2D code indicates that such flat profiles of Jsat/ne can be obtained when LH power dissipation is taken into account. Detailed analysis of the heat flux carried by electrons accelerated in the near-field of the antenna confirms the increase in density with gas puff during high LH power coupling.",
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Goniche, M, Ekedahl, A, Mailloux, J, Petrzilka, V, Rantamäki, K & JET-EFDA collaborators 2009, 'SOL characterization and LH coupling measurements on JET in ITER-relevant conditions', Plasma Physics and Controlled Fusion, vol. 51, no. 4, 044002. https://doi.org/10.1088/0741-3335/51/4/044002

SOL characterization and LH coupling measurements on JET in ITER-relevant conditions. / Goniche, M.; Ekedahl, A.; Mailloux, J.; Petrzilka, V.; Rantamäki, Karin; JET-EFDA collaborators.

In: Plasma Physics and Controlled Fusion, Vol. 51, No. 4, 044002, 2009.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - SOL characterization and LH coupling measurements on JET in ITER-relevant conditions

AU - Goniche, M.

AU - Ekedahl, A.

AU - Mailloux, J.

AU - Petrzilka, V.

AU - Rantamäki, Karin

AU - JET-EFDA collaborators

PY - 2009

Y1 - 2009

N2 - Lower hybrid (LH) current drive experiments have been carried out on JET with an antenna–plasma separatrix distance varying between 0.09 and 0.15 m, and LH power in the range 0–3.2 MW. For different plasma configurations, the electron density ne of the scrape-off layer has been studied by the mean of a reciprocating Langmuir probe magnetically connected to the LH antenna. For pulses in the high confinement regime (H mode) characterized by strong particle bursts in the plasma edge, the edge localized modes (ELMs), profiles of the saturation current (Jsat) are obtained with a sufficient time resolution to distinguish 'between ELMs' and during the rise and decay of the ELMs.It is found that gas injection from a valve located near the LH launcher and magnetically connected to it allows one to raise the density and improve the LH coupling. The Jsat profiles indicate quite clearly that this density rise affects mainly the plasma layer in front of the antenna with a typical thickness of 5 cm. The resulting profile can be extremely flat in this region. The effect of the near-launcher gas injection but also of the LH power and the total gas injection on the density at the wall is quantitatively documented. It is shown in particular that with increasing LH power, the required gas injection for obtaining good LH coupling is decreasing, with no saturation obtained so far. Effect of the ELMs on the LH coupling is also discussed. Modelling with the EDGE2D code indicates that such flat profiles of Jsat/ne can be obtained when LH power dissipation is taken into account. Detailed analysis of the heat flux carried by electrons accelerated in the near-field of the antenna confirms the increase in density with gas puff during high LH power coupling.

AB - Lower hybrid (LH) current drive experiments have been carried out on JET with an antenna–plasma separatrix distance varying between 0.09 and 0.15 m, and LH power in the range 0–3.2 MW. For different plasma configurations, the electron density ne of the scrape-off layer has been studied by the mean of a reciprocating Langmuir probe magnetically connected to the LH antenna. For pulses in the high confinement regime (H mode) characterized by strong particle bursts in the plasma edge, the edge localized modes (ELMs), profiles of the saturation current (Jsat) are obtained with a sufficient time resolution to distinguish 'between ELMs' and during the rise and decay of the ELMs.It is found that gas injection from a valve located near the LH launcher and magnetically connected to it allows one to raise the density and improve the LH coupling. The Jsat profiles indicate quite clearly that this density rise affects mainly the plasma layer in front of the antenna with a typical thickness of 5 cm. The resulting profile can be extremely flat in this region. The effect of the near-launcher gas injection but also of the LH power and the total gas injection on the density at the wall is quantitatively documented. It is shown in particular that with increasing LH power, the required gas injection for obtaining good LH coupling is decreasing, with no saturation obtained so far. Effect of the ELMs on the LH coupling is also discussed. Modelling with the EDGE2D code indicates that such flat profiles of Jsat/ne can be obtained when LH power dissipation is taken into account. Detailed analysis of the heat flux carried by electrons accelerated in the near-field of the antenna confirms the increase in density with gas puff during high LH power coupling.

U2 - 10.1088/0741-3335/51/4/044002

DO - 10.1088/0741-3335/51/4/044002

M3 - Article

VL - 51

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 4

M1 - 044002

ER -