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Title: First experimental tests of a new small angle slot divertor on DIII-D

Abstract

A new small angle slot (SAS) divertor concept has been developed to enhance neutral cooling across the divertor target by coupling a closed slot structure with appropriate target shaping. Initial tests on DIII-D find a strong interplay between such anticipated ‘SAS’ effects and cross-field drifts, favouring operation with the ion B×∇B drift away from the X-point, as currently employed for advanced tokamaks. This offers the following key improvements relative to DIII-D’s open lower divertor or partially-closed upper divertor: (i) SAS allows for transition to low temperature moderately detached divertor conditions with T_e≲10eV at very low main plasma densities, lower than are usually attainable at all in DIII-D high confinement (H-mode) plasmas as used in these tests; (ii) Pedestal performance and core confinement are significantly improved with SAS. The final confinement collapse associated with the onset of X-point MARFE (multifaceted asymmetric radiation from the edge) following deep detachment occurs at significantly higher pedestal densities, thus widening the window of H-mode operation compatible with a dissipative divertor. For operation with the ion B×∇B drift toward the X-point, the divertor plasma transitions to a bifurcative detached state at much higher densities, similar to other divertor configurations in DIII-D. These results highlight the strongmore » interplay between divertor closure and drifts, and point to an interesting divertor optimization path to explore that offers potential for future fusion reactors.« less

Authors:
 [1]; ; ; ; ; ; ; ; ; ORCiD logo; ; ORCiD logo; ; ; ; ; ; ; ; more »; ; ORCiD logo; ; ; ORCiD logo; ORCiD logo; « less
  1. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
U.S. Dept. of Energy
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Org.:
the DIII-D Team
OSTI Identifier:
1561847
Alternate Identifier(s):
OSTI ID: 1561958
Grant/Contract Number:  
FC02-04ER54698
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; 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; advanced divertor; plasma-material interactions; tokamak; DIII-D; divertor concept, plasma-material interactions, advanced tokamak, DIII-D, fusion reactor

Citation Formats

Guo, H. Y., Wang, H. Q., Watkins, J. G., Casali, L., Covele, B., Moser, A. L., Osborne, T., Samuell, C. M., Shafer, M. W., Stangeby, P. C., Thomas, D. M., Boedo, J., Buttery, R. J., Groebner, R., Hill, D. N., Holland, L., Hyatt, A. W., Jaervinen, A. E., Kellman, A., Lao, L. L., Lasnier, C. J., Leonard, A. W., Murphy, C., Ren, J., Sang, C. F., Sontag, A. C., and Taylor, T. S. First experimental tests of a new small angle slot divertor on DIII-D. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab26ee.
Guo, H. Y., Wang, H. Q., Watkins, J. G., Casali, L., Covele, B., Moser, A. L., Osborne, T., Samuell, C. M., Shafer, M. W., Stangeby, P. C., Thomas, D. M., Boedo, J., Buttery, R. J., Groebner, R., Hill, D. N., Holland, L., Hyatt, A. W., Jaervinen, A. E., Kellman, A., Lao, L. L., Lasnier, C. J., Leonard, A. W., Murphy, C., Ren, J., Sang, C. F., Sontag, A. C., & Taylor, T. S. First experimental tests of a new small angle slot divertor on DIII-D. United States. doi:10.1088/1741-4326/ab26ee.
Guo, H. Y., Wang, H. Q., Watkins, J. G., Casali, L., Covele, B., Moser, A. L., Osborne, T., Samuell, C. M., Shafer, M. W., Stangeby, P. C., Thomas, D. M., Boedo, J., Buttery, R. J., Groebner, R., Hill, D. N., Holland, L., Hyatt, A. W., Jaervinen, A. E., Kellman, A., Lao, L. L., Lasnier, C. J., Leonard, A. W., Murphy, C., Ren, J., Sang, C. F., Sontag, A. C., and Taylor, T. S. Tue . "First experimental tests of a new small angle slot divertor on DIII-D". United States. doi:10.1088/1741-4326/ab26ee.
@article{osti_1561847,
title = {First experimental tests of a new small angle slot divertor on DIII-D},
author = {Guo, H. Y. and Wang, H. Q. and Watkins, J. G. and Casali, L. and Covele, B. and Moser, A. L. and Osborne, T. and Samuell, C. M. and Shafer, M. W. and Stangeby, P. C. and Thomas, D. M. and Boedo, J. and Buttery, R. J. and Groebner, R. and Hill, D. N. and Holland, L. and Hyatt, A. W. and Jaervinen, A. E. and Kellman, A. and Lao, L. L. and Lasnier, C. J. and Leonard, A. W. and Murphy, C. and Ren, J. and Sang, C. F. and Sontag, A. C. and Taylor, T. S.},
abstractNote = {A new small angle slot (SAS) divertor concept has been developed to enhance neutral cooling across the divertor target by coupling a closed slot structure with appropriate target shaping. Initial tests on DIII-D find a strong interplay between such anticipated ‘SAS’ effects and cross-field drifts, favouring operation with the ion B×∇B drift away from the X-point, as currently employed for advanced tokamaks. This offers the following key improvements relative to DIII-D’s open lower divertor or partially-closed upper divertor: (i) SAS allows for transition to low temperature moderately detached divertor conditions with T_e≲10eV at very low main plasma densities, lower than are usually attainable at all in DIII-D high confinement (H-mode) plasmas as used in these tests; (ii) Pedestal performance and core confinement are significantly improved with SAS. The final confinement collapse associated with the onset of X-point MARFE (multifaceted asymmetric radiation from the edge) following deep detachment occurs at significantly higher pedestal densities, thus widening the window of H-mode operation compatible with a dissipative divertor. For operation with the ion B×∇B drift toward the X-point, the divertor plasma transitions to a bifurcative detached state at much higher densities, similar to other divertor configurations in DIII-D. These results highlight the strong interplay between divertor closure and drifts, and point to an interesting divertor optimization path to explore that offers potential for future fusion reactors.},
doi = {10.1088/1741-4326/ab26ee},
journal = {Nuclear Fusion},
number = 8,
volume = 59,
place = {United States},
year = {2019},
month = {7}
}

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