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Dive into the research topics where Brent Covele is active.

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Featured researches published by Brent Covele.


Physics of Plasmas | 2013

Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake

M. Kotschenreuther; Prashant M. Valanju; Brent Covele; S. M. Mahajan

Advanced divertors are magnetic geometries where a second X-point is added in the divertor region to address the serious challenges of burning plasma power exhaust. Invoking physical arguments, numerical work, and detailed model magnetic field analysis, we investigate the magnetic field structure of advanced divertors in the physically relevant region for power exhaust—the scrape-off layer. A primary result of our analysis is the emergence of a physical “metric,” the Divertor Index DI, which quantifies the flux expansion increase as one goes from the main X-point to the strike point. It clearly separates three geometries with distinct consequences for divertor physics—the Standard Divertor (DI = 1), and two advanced geometries—the X-Divertor (XD, DI > 1) and the Snowflake (DI < 1). The XD, therefore, cannot be classified as one variant of the Snowflake. By this measure, recent National Spherical Torus Experiment and DIIID experiments are X-Divertors, not Snowflakes.


Nuclear Fusion | 2016

Fusion nuclear science facilities and pilot plants based on the spherical tokamak

J. Menard; T. Brown; L. El-Guebaly; Mark D. Boyer; J.M. Canik; B. Colling; R. Raman; Z.R. Wang; Yuhu Zhai; P. Buxton; Brent Covele; C. D’Angelo; A. Davis; S.P. Gerhardt; M. Gryaznevich; M. Harb; T.C. Hender; S.M. Kaye; D. Kingham; M. Kotschenreuther; S. M. Mahajan; R. Maingi; E. Marriott; E.T. Meier; L. Mynsberge; C. Neumeyer; M. Ono; J.-K. Park; S.A. Sabbagh; V. Soukhanovskii

A fusion nuclear science facility (FNSF) could play an important role in the development of fusion energy by providing the nuclear environment needed to develop fusion materials and components. The spherical torus/tokamak (ST) is a leading candidate for an FNSF due to its potentially high neutron wall loading and modular configuration. A key consideration for the choice of FNSF configuration is the range of achievable missions as a function of device size. Possible missions include: providing high neutron wall loading and fluence, demonstrating tritium self-sufficiency, and demonstrating electrical self-sufficiency. All of these missions must also be compatible with a viable divertor, first-wall, and blanket solution. ST-FNSF configurations have been developed simultaneously incorporating for the first time: (1) a blanket system capable of tritium breeding ratio TBR ≈ 1, (2) a poloidal field coil set supporting high elongation and triangularity for a range of internal inductance and normalized beta values consistent with NSTX/NSTX-U previous/planned operation, (3) a long-legged divertor analogous to the MAST-U divertor which substantially reduces projected peak divertor heat-flux and has all outboard poloidal field coils outside the vacuum chamber and superconducting to reduce power consumption, and (4) a vertical maintenance scheme in which blanket structures and the centerstack can be removed independently. Progress in these ST-FNSF missions versus configuration studies including dependence on plasma major radius R0 for a range 1 m–2.2 m are described. In particular, it is found the threshold major radius for TBR = 1 is ⩾ R 1.7 0 m, and a smaller R0 = 1 m ST device has TBR ≈ 0.9 which is below unity but substantially reduces T consumption relative to not breeding. Calculations of neutral beam heating and current drive for non-inductive ramp-up and sustainment are described. An A = 2, R0 = 3 m device incorporating high-temperature superconductor toroidal field coil magnets capable of high neutron fluence and both tritium and electrical self-sufficiency is also presented following systematic aspect ratio studies. J.E. Menard et al Fusion nuclear science facilities and pilot plants based on the spherical tokamak Printed in the UK 106023 NUFUAU


Nuclear Fusion | 2014

An exploration of advanced X-divertor scenarios on ITER

Brent Covele; Prashant M. Valanju; M. Kotschenreuther; S. M. Mahajan

It is found that the X-divertor (XD) configuration (Kotschenreuther et al 2004 Proc. 20th Int. Conf. on Fusion Energy (Vilamoura, Portugal, 2004) (Vienna: IAEA) CD-ROM file [IC/P6-43] www-naweb.iaea.org/napc/physics/fec/fec2004/datasets/index.html, Kotschenreuther et al 2006 Proc. 21st Int. Conf. on Fusion Energy 2006 (Chengdu, China, 2006) (Vienna: IAEA), CD-ROM file [IC/P7-12] www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/index.htm, Kotschenreuther et al 2007 Phys. Plasmas 14 072502) can be made with the conventional poloidal field (PF) coil set on ITER (Tomabechi et al and Team 1991 Nucl. Fusion 31 1135), where all PF coils are outside the TF coils. Starting from the standard divertor, a sequence of desirable XD configurations are possible where the PF currents are below the present maximum design limits on ITER, and where the baseline divertor cassette is used. This opens the possibility that the XD could be tested and used to assist in high-power operation on ITER, but some further issues need examination. Note that the increased major radius of the super-X-divertor (Kotschenreuther et al 2007 Bull. Am. Phys. Soc. 53 11, Valanju et al 2009 Phys. Plasmas 16 5, Kotschenreuther et al 2010 Nucl. Fusion 50 035003, Valanju et al 2010 Fusion Eng. Des. 85 46) is not a feature of the XD geometry. In addition, we present an XD configuration for K-DEMO (Kim et al 2013 Fusion Eng. Des. 88 123) to demonstrate that it is also possible to attain the XD configuration in advanced tokamak reactors with all PF coils outside the TF coils. The results given here for the XD are far more encouraging than recent calculations by Lackner and Zohm (2012 Fusion Sci. Technol. 63 43) for the Snowflake (Ryutov 2007 Phys. Plasmas 14 064502, Ryutov et al 2008 Phys. Plasmas 15 092501), where the required high PF currents represent a major technological challenge. The magnetic field structure in the outboard divertor SOL (Kotschenreuther 2013 Phys. Plasmas 20 102507) in the recently created XD configurations reproduces what was presented in the earlier XD papers (Kotschenreuther et al 2004 Proc. 20th Int. Conf. on Fusion Energy (Vilamoura, Portugal, 2004) (Vienna: IAEA) CD-ROM file [IC/P6-43] www-naweb.iaea.org/napc/physics/fec/fec2004/datasets/index.html, Kotschenreuther et al 2006 Proc. 21st Int. Conf. on Fusion Energy 2006 (Chengdu, China, 2006) (Vienna: IAEA) CD-ROM file [IC/P7-12] www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/index.htm, Kotschenreuther et al 2007 Phys. Plasmas 14 072502). Consequently, the same advantages accrue, but no close-in PF coils are employed.


Physics of Plasmas | 2014

Response to “Comment on ‘Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake’ ” [Phys. Plasmas 21, 054701 (2014)]

M. Kotschenreuther; Prashant M. Valanju; Brent Covele; S. M. Mahajan

Relying on coil positions relative to the plasma, the “Comment on ‘Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake’ ” [Phys. Plasmas 21, 054701 (2014)], emphasizes a criterion for divertor characterization that was critiqued to be ill posed [M. Kotschenreuther et al., Phys. Plasmas 20, 102507 (2013)]. We find that no substantive physical differences flow from this criteria. However, using these criteria, the successful NSTX experiment by Ryutov et al. [Phys. Plasmas 21, 054701 (2014)] has the coil configuration of an X-divertor (XD), rather than a snowflake (SF). On completing the divertor index (DI) versus distance graph for this NSTX shot (which had an inexplicably missing region), we find that the DI is like an XD for most of the outboard wetted divertor plate. Further, the “proximity condition,” used to define an SF [M. Kotschenreuther et al., Phys. Plasmas 20, 102507 (2013)], does not have a substantive physics basis to override metrics based on flux expansion and line length. Finally, if the criteria of the comment are important, then the results of NSTX-like experiments could have questionable applicability to reactors.


Nuclear Fusion | 2016

Developing and validating advanced divertor solutions on DIII-D for next-step fusion devices

H.Y. Guo; David N. Hill; A.W. Leonard; S.L. Allen; P.C. Stangeby; D. M. Thomas; E.A. Unterberg; T. Abrams; J.A. Boedo; A.R. Briesemeister; Dean A. Buchenauer; I. Bykov; J.M. Canik; C. Chrobak; Brent Covele; R. Ding; R.P. Doerner; D. Donovan; Hailong Du; D. Elder; David Eldon; A. Lasa; M. Groth; J. Guterl; A. Jarvinen; E. T. Hinson; E. Kolemen; C.J. Lasnier; J. Lore; M. A. Makowski


Journal of Fusion Energy | 2016

Taming the Heat Flux Problem: Advanced Divertors Towards Fusion Power

M. Kotschenreuther; S. M. Mahajan; Prashant M. Valanju; Brent Covele; F. L. Waelbroeck; John M. Canik; B. LaBombard


Nuclear Fusion | 2018

Numerical exploration of non-axisymmetric divertor closure in the small angle slot (SAS) divertor at DIII-D

H. Frerichs; O. Schmitz; Brent Covele; Y. Feng; Houyang Guo; David N Hill


Bulletin of the American Physical Society | 2017

Modelling the detachment dependence on strike point location in the small angle slot divertor (SAS) with SOLPS

Livia Casali; Brent Covele; Houyang Guo


Bulletin of the American Physical Society | 2017

Maximizing Heat Dissipation via Target Optimization of the Small-Angle Slot Divertor

Brent Covele; Federico David Halpern; Livia Casali; John M. Canik; D. M. Thomas; Houyang Guo


Bulletin of the American Physical Society | 2016

SOLPS modeling of an innovative small-angle slot divertor concept for low-density detachment

Brent Covele; Chaofeng Sang; H.Y. Guo; L. L. Lao; P.C. Stangeby; D. M. Thomas

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M. Kotschenreuther

University of Texas at Austin

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Prashant M. Valanju

University of Texas at Austin

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S. M. Mahajan

University of Texas at Austin

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John M. Canik

Oak Ridge National Laboratory

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B. LaBombard

Massachusetts Institute of Technology

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J.M. Canik

Oak Ridge National Laboratory

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