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Title: Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta

Abstract

Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (β t), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate β t up to ~100% with a minimum |B| well spanning up to ~50% of the plasma volume.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1377887
Alternate Identifier(s):
OSTI ID: 1371809
Grant/Contract Number:
FG02-96ER54375
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 119; Journal Issue: 3; Related Information: D.J. Schlossberg, G.M. Bodner, M.W. Bongard, M.G. Burke, R.J. Fonck, J.M. Perry, and J.A. Reusch, "Public Data Set: Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta," DOI: 10.18138/1340695; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; nuclear fusion; equilibrium reconstruction; spherical tokamak; helicity injection; magnetic reconnection

Citation Formats

Schlossberg, David J., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Perry, Justin M., and Reusch, Joshua A. Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta. United States: N. p., 2017. Web. doi:10.1103/PhysRevLett.119.035001.
Schlossberg, David J., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Perry, Justin M., & Reusch, Joshua A. Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta. United States. doi:10.1103/PhysRevLett.119.035001.
Schlossberg, David J., Bodner, Grant M., Bongard, Michael W., Burke, Marcus G., Fonck, Raymond J., Perry, Justin M., and Reusch, Joshua A. Sat . "Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta". United States. doi:10.1103/PhysRevLett.119.035001.
@article{osti_1377887,
title = {Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta},
author = {Schlossberg, David J. and Bodner, Grant M. and Bongard, Michael W. and Burke, Marcus G. and Fonck, Raymond J. and Perry, Justin M. and Reusch, Joshua A.},
abstractNote = {Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (βt), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate βt up to ~100% with a minimum |B| well spanning up to ~50% of the plasma volume.},
doi = {10.1103/PhysRevLett.119.035001},
journal = {Physical Review Letters},
number = 3,
volume = 119,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on July 1, 2018
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  • Amore » 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. « less
  • This public data set contains openly-documented, machine readable digital research data corresponding to figures published in D.J. Schlossberg et al., 'Non-Inductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta,' Phys. Rev. Lett. 119, 035001 (2017).
  • This public data set contains openly-documented, machine readable digital research data corresponding to figures published in J.A. Reusch et al., 'Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment,' Phys. Plasmas 25, 056101 (2018).
  • Local steep pressure gradient generated near an internal transport barrier drives a radially localized magnetohydrodynamic (MHD) instability with low toroidal mode number (n) in the high-{beta}{sub p} mode plasma in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Y. Koide {ital et al.}, Phys. Plasmas {bold 4}, 1623 (1997)]. The instability occurs in the {beta}{sub p} regime lower than that for the {beta}{sub p}-collapse and its growth rate is of the order of the ideal MHD instability. By a linear analysis of ideal MHD stability, low n modes localized near the internal transport barrier are found to be destabilizedmore » in the situation that the bootstrap current driven by the steep pressure gradient reduces the local magnetic shear (s{approx_lt}0) where the safety factor is right close to an integer value. {copyright} {ital 1997 American Institute of Physics.}« less