Electron Bernstein wave research on NSTX and PEGASUS

S. J. Diem; G. Taylor; J. B. Caughman; T. Bigelow; G. D. Garstka; R. W. Harvey; B. P. Leblanc; J. Preinhaelter; S. A. Sabbagh; J. Urban; J. B. Wilgen

doi:10.1063/1.2800504

Electron Bernstein wave research on NSTX and PEGASUS

S. J. Diem, G. Taylor, J. B. Caughman, T. Bigelow, G. D. Garstka, R. W. Harvey, B. P. Leblanc, J. Preinhaelter, S. A. Sabbagh, J. Urban, J. B. Wilgen

Fusion Technology

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

1 Scopus citations

Abstract

Spherical tokamaks (STs) routinely operate in the overdense regime (ω _pe≫ω _ce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees, supporting a launcher placed near the midplane. Current was driven on axis primarily via the Fisch-Boozer mechanism. The PEGASUS experiment provides an attractive opportunity to investigate EBW heating and current drive physics at the fundamental electron cyclotron frequency in an ST plasma, and will complement the EBW research planned for NSTX.

Original language	English
Title of host publication	RADIO FREQUENCY POWER IN PLASMAS
Subtitle of host publication	17th Topical Conference on Radio Frequency Power in Plasmas
Pages	331-338
Number of pages	8
DOIs	https://doi.org/10.1063/1.2800504
State	Published - 2007
Event	17th Topical Conference on Radio Frequency Power in Plasmas - Clearwater, FL, United States Duration: May 7 2007 → May 9 2007

Publication series

Name	AIP Conference Proceedings
Volume	933
ISSN (Print)	0094-243X
ISSN (Electronic)	1551-7616

Conference

Conference	17th Topical Conference on Radio Frequency Power in Plasmas
Country/Territory	United States
City	Clearwater, FL
Period	05/7/07 → 05/9/07

Keywords

Electron Bernstein waves
NSTX
Pegasus
Spherical torus

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1063/1.2800504

Cite this

Diem, S. J., Taylor, G., Caughman, J. B., Bigelow, T., Garstka, G. D., Harvey, R. W., Leblanc, B. P., Preinhaelter, J., Sabbagh, S. A., Urban, J., & Wilgen, J. B. (2007). Electron Bernstein wave research on NSTX and PEGASUS. In RADIO FREQUENCY POWER IN PLASMAS: 17th Topical Conference on Radio Frequency Power in Plasmas (pp. 331-338). (AIP Conference Proceedings; Vol. 933). https://doi.org/10.1063/1.2800504

@inproceedings{b18667612aa848288a4942e49da6fee4,

title = "Electron Bernstein wave research on NSTX and PEGASUS",

abstract = "Spherical tokamaks (STs) routinely operate in the overdense regime (ω pe≫ω ce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees, supporting a launcher placed near the midplane. Current was driven on axis primarily via the Fisch-Boozer mechanism. The PEGASUS experiment provides an attractive opportunity to investigate EBW heating and current drive physics at the fundamental electron cyclotron frequency in an ST plasma, and will complement the EBW research planned for NSTX.",

keywords = "Electron Bernstein waves, NSTX, Pegasus, Spherical torus",

author = "Diem, {S. J.} and G. Taylor and Caughman, {J. B.} and T. Bigelow and Garstka, {G. D.} and Harvey, {R. W.} and Leblanc, {B. P.} and J. Preinhaelter and Sabbagh, {S. A.} and J. Urban and Wilgen, {J. B.}",

year = "2007",

doi = "10.1063/1.2800504",

language = "English",

isbn = "0735404445",

series = "AIP Conference Proceedings",

pages = "331--338",

booktitle = "RADIO FREQUENCY POWER IN PLASMAS",

note = "17th Topical Conference on Radio Frequency Power in Plasmas ; Conference date: 07-05-2007 Through 09-05-2007",

}

Diem, SJ, Taylor, G, Caughman, JB , Bigelow, T, Garstka, GD, Harvey, RW, Leblanc, BP, Preinhaelter, J, Sabbagh, SA, Urban, J & Wilgen, JB 2007, Electron Bernstein wave research on NSTX and PEGASUS. in RADIO FREQUENCY POWER IN PLASMAS: 17th Topical Conference on Radio Frequency Power in Plasmas. AIP Conference Proceedings, vol. 933, pp. 331-338, 17th Topical Conference on Radio Frequency Power in Plasmas, Clearwater, FL, United States, 05/7/07. https://doi.org/10.1063/1.2800504

TY - GEN

T1 - Electron Bernstein wave research on NSTX and PEGASUS

AU - Diem, S. J.

AU - Taylor, G.

AU - Caughman, J. B.

AU - Bigelow, T.

AU - Garstka, G. D.

AU - Harvey, R. W.

AU - Leblanc, B. P.

AU - Preinhaelter, J.

AU - Sabbagh, S. A.

AU - Urban, J.

AU - Wilgen, J. B.

PY - 2007

Y1 - 2007

N2 - Spherical tokamaks (STs) routinely operate in the overdense regime (ω pe≫ω ce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees, supporting a launcher placed near the midplane. Current was driven on axis primarily via the Fisch-Boozer mechanism. The PEGASUS experiment provides an attractive opportunity to investigate EBW heating and current drive physics at the fundamental electron cyclotron frequency in an ST plasma, and will complement the EBW research planned for NSTX.

AB - Spherical tokamaks (STs) routinely operate in the overdense regime (ω pe≫ω ce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees, supporting a launcher placed near the midplane. Current was driven on axis primarily via the Fisch-Boozer mechanism. The PEGASUS experiment provides an attractive opportunity to investigate EBW heating and current drive physics at the fundamental electron cyclotron frequency in an ST plasma, and will complement the EBW research planned for NSTX.

KW - Electron Bernstein waves

KW - NSTX

KW - Pegasus

KW - Spherical torus

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U2 - 10.1063/1.2800504

DO - 10.1063/1.2800504

M3 - Conference contribution

AN - SCOPUS:36849018888

SN - 0735404445

SN - 9780735404441

T3 - AIP Conference Proceedings

SP - 331

EP - 338

BT - RADIO FREQUENCY POWER IN PLASMAS

T2 - 17th Topical Conference on Radio Frequency Power in Plasmas

Y2 - 7 May 2007 through 9 May 2007

ER -

Electron Bernstein wave research on NSTX and PEGASUS

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Keywords

UN SDGs

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