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Title: Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D

Abstract

The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary driver of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency in the core for advanced tokamak (AT) operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.

Authors:
 [1];  [2];  [2];  [2];  [1];  [3];  [4];  [4];  [5]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of Texas, Austin, TX (United States)
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of Plasma Physics
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1390611
Grant/Contract Number:  
FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Covele, Brent, Kotschenreuther, M., Mahajan, S., Valanju, P., Leonard, Anthony W., Watkins, Jonathan G., Makowski, Michael A., Fenstermacher, Max E., and Si, H. Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa7644.
Covele, Brent, Kotschenreuther, M., Mahajan, S., Valanju, P., Leonard, Anthony W., Watkins, Jonathan G., Makowski, Michael A., Fenstermacher, Max E., & Si, H. Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D. United States. doi:10.1088/1741-4326/aa7644.
Covele, Brent, Kotschenreuther, M., Mahajan, S., Valanju, P., Leonard, Anthony W., Watkins, Jonathan G., Makowski, Michael A., Fenstermacher, Max E., and Si, H. Fri . "Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D". United States. doi:10.1088/1741-4326/aa7644. https://www.osti.gov/servlets/purl/1390611.
@article{osti_1390611,
title = {Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D},
author = {Covele, Brent and Kotschenreuther, M. and Mahajan, S. and Valanju, P. and Leonard, Anthony W. and Watkins, Jonathan G. and Makowski, Michael A. and Fenstermacher, Max E. and Si, H.},
abstractNote = {The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary driver of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency in the core for advanced tokamak (AT) operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.},
doi = {10.1088/1741-4326/aa7644},
journal = {Nuclear Fusion},
number = 8,
volume = 57,
place = {United States},
year = {Fri Jun 23 00:00:00 EDT 2017},
month = {Fri Jun 23 00:00:00 EDT 2017}
}

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