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Maximization of ICRF power by SOL density tailoring with local gas injection

(2016) NUCLEAR FUSION. 56(4).
Author
Organization
Abstract
Experiments have been performed under the coordination of the International Tokamak Physics Activity (ITPA) on several tokamaks, including ASDEX Upgrade (AUG), JET and DIII-D, to characterize the increased Ion cyclotron range of frequency (ICRF) antenna loading achieved by optimizing the position of gas injection relative to the RF antennas. On DIII-D, AUG and JET (with the ITER-Like Wall) a 50% increase in the antenna loading was observed when injecting deuterium in ELMy H-mode plasmas using mid-plane inlets close to the powered antennas instead of divertor injection and, with smaller improvement when using gas inlets located at the top of the machine. The gas injection rate required for such improvements (similar to 0.7 x 10(22) el s(-1) in AUG, similar to 1.0 x 10(22) el s(-1) in JET) is compatible with the use of this technique to optimize ICRF heating during the development of plasma scenarios and no degradation of confinement was observed when using the mid-plane or top inlets compared with divertor valves. An increase in the scrape-off layer (SOL) density was measured when switching gas injection from divertor to outer mid-plane or top. On JET and DIII-D, the measured SOL density increase when using main chamber puffing is consistent with the antenna coupling resistance increase provided that the distance between the measurement lines of sight and the injection location is taken into account. Optimized gas injection was also found to be beneficial for reducing tungsten (W) sputtering at the AUG antenna limiters, and also to reduce slightly the W and nickel (Ni) content in JET plasmas. Modeling the specific effects of divertor/top/mid-plane injection on the outer mid-plane density was carried out using both the EDGE2D-EIRENE and EMC3-EIRENE plasma boundary code packages; simulations indeed indicate that outer mid-plane gas injection maximizes the density in the mid-plane close to the injection point with qualitative agreement with the AUG SOL density measurements for EMC3-EIRENE. Field line tracing for ITER in the 15 MA Q(DT) = 10 reference scenario indicates that the planned gas injection system could be used to tailor the density in front the antennas. Benchmarking of EMC3-EIRENE against AUG and JET data is planned as a first step towards the ITER SOL modelling required to quantify the effect of gas injection on the SOL density in front of the antennas.
Keywords
WALL CONDITIONING TECHNIQUE, ASDEX UPGRADE, TORE-SUPRA, ANTENNA, PERFORMANCE, MAGNETIC-FIELD, EDGE DENSITY, PLASMA, JET, WAVES, ICRF power, antenna loading, gas injection, SOL density

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Citation

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MLA
Jacquet, P. et al. “Maximization of ICRF Power by SOL Density Tailoring with Local Gas Injection.” NUCLEAR FUSION 56.4 (2016): n. pag. Print.
APA
Jacquet, P., Goniche, M., Bobkov, V., Lerche, E., Pinsker, R. I., Pitts, A., Zhang, W., et al. (2016). Maximization of ICRF power by SOL density tailoring with local gas injection. NUCLEAR FUSION, 56(4).
Chicago author-date
Jacquet, P., M. Goniche, V. Bobkov, E. Lerche, R. I. Pinsker, A. Pitts, Wei Zhang, et al. 2016. “Maximization of ICRF Power by SOL Density Tailoring with Local Gas Injection.” Nuclear Fusion 56 (4).
Chicago author-date (all authors)
Jacquet, P., M. Goniche, V. Bobkov, E. Lerche, R. I. Pinsker, A. Pitts, Wei Zhang, L. Colas, J. Hosea, S. Moriyama, S-J. Wang, S. Wukitch, X. Zhang, R. Bilato, H. Bufferand, L. Guimarais, H. Faugel, G. R. Hanson, M. Kocan, I. Monakhov, Jean-Marie Noterdaeme, V. Petrzilka, A. Shaw, I. Stepanov, A. C. C. Sips, D. Van Eester, and T. Wauters. 2016. “Maximization of ICRF Power by SOL Density Tailoring with Local Gas Injection.” Nuclear Fusion 56 (4).
Vancouver
1.
Jacquet P, Goniche M, Bobkov V, Lerche E, Pinsker RI, Pitts A, et al. Maximization of ICRF power by SOL density tailoring with local gas injection. NUCLEAR FUSION. Bristol: Iop Publishing Ltd; 2016;56(4).
IEEE
[1]
P. Jacquet et al., “Maximization of ICRF power by SOL density tailoring with local gas injection,” NUCLEAR FUSION, vol. 56, no. 4, 2016.
@article{8519885,
  abstract     = {Experiments have been performed under the coordination of the International Tokamak Physics Activity (ITPA) on several tokamaks, including ASDEX Upgrade (AUG), JET and DIII-D, to characterize the increased Ion cyclotron range of frequency (ICRF) antenna loading achieved by optimizing the position of gas injection relative to the RF antennas. On DIII-D, AUG and JET (with the ITER-Like Wall) a 50% increase in the antenna loading was observed when injecting deuterium in ELMy H-mode plasmas using mid-plane inlets close to the powered antennas instead of divertor injection and, with smaller improvement when using gas inlets located at the top of the machine. The gas injection rate required for such improvements (similar to 0.7 x 10(22) el s(-1) in AUG, similar to 1.0 x 10(22) el s(-1) in JET) is compatible with the use of this technique to optimize ICRF heating during the development of plasma scenarios and no degradation of confinement was observed when using the mid-plane or top inlets compared with divertor valves. An increase in the scrape-off layer (SOL) density was measured when switching gas injection from divertor to outer mid-plane or top. On JET and DIII-D, the measured SOL density increase when using main chamber puffing is consistent with the antenna coupling resistance increase provided that the distance between the measurement lines of sight and the injection location is taken into account. Optimized gas injection was also found to be beneficial for reducing tungsten (W) sputtering at the AUG antenna limiters, and also to reduce slightly the W and nickel (Ni) content in JET plasmas. Modeling the specific effects of divertor/top/mid-plane injection on the outer mid-plane density was carried out using both the EDGE2D-EIRENE and EMC3-EIRENE plasma boundary code packages; simulations indeed indicate that outer mid-plane gas injection maximizes the density in the mid-plane close to the injection point with qualitative agreement with the AUG SOL density measurements for EMC3-EIRENE. Field line tracing for ITER in the 15 MA Q(DT) = 10 reference scenario indicates that the planned gas injection system could be used to tailor the density in front the antennas. Benchmarking of EMC3-EIRENE against AUG and JET data is planned as a first step towards the ITER SOL modelling required to quantify the effect of gas injection on the SOL density in front of the antennas.},
  articleno    = {046001},
  author       = {Jacquet, P. and Goniche, M. and Bobkov, V. and Lerche, E. and Pinsker, R. I. and Pitts, A. and Zhang, Wei and Colas, L. and Hosea, J. and Moriyama, S. and Wang, S-J. and Wukitch, S. and Zhang, X. and Bilato, R. and Bufferand, H. and Guimarais, L. and Faugel, H. and Hanson, G. R. and Kocan, M. and Monakhov, I. and Noterdaeme, Jean-Marie and Petrzilka, V. and Shaw, A. and Stepanov, I. and Sips, A. C. C. and Van Eester, D. and Wauters, T.},
  issn         = {0029-5515},
  journal      = {NUCLEAR FUSION},
  keywords     = {WALL CONDITIONING TECHNIQUE,ASDEX UPGRADE,TORE-SUPRA,ANTENNA,PERFORMANCE,MAGNETIC-FIELD,EDGE DENSITY,PLASMA,JET,WAVES,ICRF power,antenna loading,gas injection,SOL density},
  language     = {eng},
  number       = {4},
  pages        = {14},
  publisher    = {Iop Publishing Ltd},
  title        = {Maximization of ICRF power by SOL density tailoring with local gas injection},
  url          = {http://dx.doi.org/10.1088/0029-5515/56/4/046001},
  volume       = {56},
  year         = {2016},
}

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