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Title: Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

Abstract

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low i . The low aspect ratio ( R 0 / a ~ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ~100% is achieved. Finally, these high β t discharges disrupt at the ideal no-wall β limit at β N ~ 7.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1433090
Grant/Contract Number:  
FG02-96ER54375; SC0006928
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; spherical tokamaks; helicity injection; equilibrium reconstruction; beta limit; magnetic reconnection

Citation Formats

Reusch, Joshua A., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Pachicano, Jessica L., Perry, Justin M., Pierren, Christopher, Rhodes, Alexander T., Richner, Nathan J., Rodriguez Sanchez, Cuauhtemoc, Schlossberg, David J., and Weberski, Justin D. Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment. United States: N. p., 2018. Web. doi:10.1063/1.5017966.
Reusch, Joshua A., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Pachicano, Jessica L., Perry, Justin M., Pierren, Christopher, Rhodes, Alexander T., Richner, Nathan J., Rodriguez Sanchez, Cuauhtemoc, Schlossberg, David J., & Weberski, Justin D. Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment. United States. https://doi.org/10.1063/1.5017966
Reusch, Joshua A., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Pachicano, Jessica L., Perry, Justin M., Pierren, Christopher, Rhodes, Alexander T., Richner, Nathan J., Rodriguez Sanchez, Cuauhtemoc, Schlossberg, David J., and Weberski, Justin D. Wed . "Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment". United States. https://doi.org/10.1063/1.5017966. https://www.osti.gov/servlets/purl/1433090.
@article{osti_1433090,
title = {Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment},
author = {Reusch, Joshua A. and Bodner, Grant M. and Bongard, Michael W. and Burke, Marcus G. and Fonck, Raymond J. and Pachicano, Jessica L. and Perry, Justin M. and Pierren, Christopher and Rhodes, Alexander T. and Richner, Nathan J. and Rodriguez Sanchez, Cuauhtemoc and Schlossberg, David J. and Weberski, Justin D.},
abstractNote = {A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ , and high toroidal and normalized beta (βt and βN ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio (R0/a~1.2) of Pegasus allows access to high κ and high normalized plasma currents IN=Ip/aBT>14). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ~100% is achieved. Finally, these high βt discharges disrupt at the ideal no-wall β limit at βN~7.},
doi = {10.1063/1.5017966},
journal = {Physics of Plasmas},
number = 5,
volume = 25,
place = {United States},
year = {2018},
month = {3}
}

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