Effect of gas injection during LH wave coupling at ITER-relevant plasma-wall distances in JET

Annika Ekedahl, Karin Rantamäki, M. Goniche, JET-EFDA collaborators

Research output: Contribution to journalArticleScientificpeer-review

26 Citations (Scopus)

Abstract

Good coupling of lower hybrid (LH) waves has been demonstrated in different H-mode scenarios in JET, at high triangularity (δ ~ 0.4) and at large distance between the last closed flux surface and the LH launcher (up to 15 cm). Local gas injection of D2 in the region magnetically connected to the LH launcher is used for increasing the local density in the scrape-off layer (SOL). Reciprocating Langmuir probe measurements magnetically connected to the LH launcher indicate that the electron density profile flattens in the far SOL during gas injection and LH power application. Some degradation in normalized H-mode confinement, as given by the H98(y,2)-factor, could be observed at high gas injection rates in these scenarios, but this was rather due to total gas injection and not specifically to the local gas puffing used for LH coupling. Furthermore, experiments carried out in L-mode plasmas in order to evaluate the effect on the LH current drive efficiency, when using local gas injection to improve the coupling, indicate only a small degradation (ΔILH/ILH ~ 15%). This effect is largely compensated by the improvement in coupling and thus increase in coupled power when using gas puffing.
Original languageEnglish
Article number044001
JournalPlasma Physics and Controlled Fusion
Volume51
Issue number4
DOIs
Publication statusPublished - 2009
MoE publication typeA1 Journal article-refereed

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gas injection
launchers
Plasmas
Langmuir probes
Degradation
Gases
Carrier concentration
Fluxes
degradation
electron density profiles
electrostatic probes
gases
Experiments

Cite this

Ekedahl, Annika ; Rantamäki, Karin ; Goniche, M. ; JET-EFDA collaborators. / Effect of gas injection during LH wave coupling at ITER-relevant plasma-wall distances in JET. In: Plasma Physics and Controlled Fusion. 2009 ; Vol. 51, No. 4.
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title = "Effect of gas injection during LH wave coupling at ITER-relevant plasma-wall distances in JET",
abstract = "Good coupling of lower hybrid (LH) waves has been demonstrated in different H-mode scenarios in JET, at high triangularity (δ ~ 0.4) and at large distance between the last closed flux surface and the LH launcher (up to 15 cm). Local gas injection of D2 in the region magnetically connected to the LH launcher is used for increasing the local density in the scrape-off layer (SOL). Reciprocating Langmuir probe measurements magnetically connected to the LH launcher indicate that the electron density profile flattens in the far SOL during gas injection and LH power application. Some degradation in normalized H-mode confinement, as given by the H98(y,2)-factor, could be observed at high gas injection rates in these scenarios, but this was rather due to total gas injection and not specifically to the local gas puffing used for LH coupling. Furthermore, experiments carried out in L-mode plasmas in order to evaluate the effect on the LH current drive efficiency, when using local gas injection to improve the coupling, indicate only a small degradation (ΔILH/ILH ~ 15{\%}). This effect is largely compensated by the improvement in coupling and thus increase in coupled power when using gas puffing.",
author = "Annika Ekedahl and Karin Rantam{\"a}ki and M. Goniche and {JET-EFDA collaborators}",
year = "2009",
doi = "10.1088/0741-3335/51/4/044001",
language = "English",
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Effect of gas injection during LH wave coupling at ITER-relevant plasma-wall distances in JET. / Ekedahl, Annika; Rantamäki, Karin; Goniche, M.; JET-EFDA collaborators.

In: Plasma Physics and Controlled Fusion, Vol. 51, No. 4, 044001, 2009.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Effect of gas injection during LH wave coupling at ITER-relevant plasma-wall distances in JET

AU - Ekedahl, Annika

AU - Rantamäki, Karin

AU - Goniche, M.

AU - JET-EFDA collaborators

PY - 2009

Y1 - 2009

N2 - Good coupling of lower hybrid (LH) waves has been demonstrated in different H-mode scenarios in JET, at high triangularity (δ ~ 0.4) and at large distance between the last closed flux surface and the LH launcher (up to 15 cm). Local gas injection of D2 in the region magnetically connected to the LH launcher is used for increasing the local density in the scrape-off layer (SOL). Reciprocating Langmuir probe measurements magnetically connected to the LH launcher indicate that the electron density profile flattens in the far SOL during gas injection and LH power application. Some degradation in normalized H-mode confinement, as given by the H98(y,2)-factor, could be observed at high gas injection rates in these scenarios, but this was rather due to total gas injection and not specifically to the local gas puffing used for LH coupling. Furthermore, experiments carried out in L-mode plasmas in order to evaluate the effect on the LH current drive efficiency, when using local gas injection to improve the coupling, indicate only a small degradation (ΔILH/ILH ~ 15%). This effect is largely compensated by the improvement in coupling and thus increase in coupled power when using gas puffing.

AB - Good coupling of lower hybrid (LH) waves has been demonstrated in different H-mode scenarios in JET, at high triangularity (δ ~ 0.4) and at large distance between the last closed flux surface and the LH launcher (up to 15 cm). Local gas injection of D2 in the region magnetically connected to the LH launcher is used for increasing the local density in the scrape-off layer (SOL). Reciprocating Langmuir probe measurements magnetically connected to the LH launcher indicate that the electron density profile flattens in the far SOL during gas injection and LH power application. Some degradation in normalized H-mode confinement, as given by the H98(y,2)-factor, could be observed at high gas injection rates in these scenarios, but this was rather due to total gas injection and not specifically to the local gas puffing used for LH coupling. Furthermore, experiments carried out in L-mode plasmas in order to evaluate the effect on the LH current drive efficiency, when using local gas injection to improve the coupling, indicate only a small degradation (ΔILH/ILH ~ 15%). This effect is largely compensated by the improvement in coupling and thus increase in coupled power when using gas puffing.

U2 - 10.1088/0741-3335/51/4/044001

DO - 10.1088/0741-3335/51/4/044001

M3 - Article

VL - 51

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

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M1 - 044001

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