skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Changes in divertor conditions in response to changing core density with RMPs

Abstract

The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertor by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed nomore » evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [2];  [1];  [4];  [2];  [2];  [2];  [3];  [1];  [1];  [5];  [6]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of Wisconsin, Madison, WI (United States)
  4. General Atomics, San Diego, CA (United States)
  5. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  6. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1374849
Grant/Contract Number:
FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; RMP; divertor; SOL

Citation Formats

Briesemeister, Alexis R., Ahn, Joon -Wook, Canik, John M., Fenstermacher, Max E., Frerichs, Heinke, Lasnier, Charles J., Lore, John D., Leonard, Anthony W., Makowski, Michael A., McLean, Adam G., Meyer, William H., Schmitz, Oliver, Shafer, Morgan W., Unterberg, Ezekial A., Wang, H. Q., and Watkins, Jonathan G. Changes in divertor conditions in response to changing core density with RMPs. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa70bd.
Briesemeister, Alexis R., Ahn, Joon -Wook, Canik, John M., Fenstermacher, Max E., Frerichs, Heinke, Lasnier, Charles J., Lore, John D., Leonard, Anthony W., Makowski, Michael A., McLean, Adam G., Meyer, William H., Schmitz, Oliver, Shafer, Morgan W., Unterberg, Ezekial A., Wang, H. Q., & Watkins, Jonathan G. Changes in divertor conditions in response to changing core density with RMPs. United States. doi:10.1088/1741-4326/aa70bd.
Briesemeister, Alexis R., Ahn, Joon -Wook, Canik, John M., Fenstermacher, Max E., Frerichs, Heinke, Lasnier, Charles J., Lore, John D., Leonard, Anthony W., Makowski, Michael A., McLean, Adam G., Meyer, William H., Schmitz, Oliver, Shafer, Morgan W., Unterberg, Ezekial A., Wang, H. Q., and Watkins, Jonathan G. 2017. "Changes in divertor conditions in response to changing core density with RMPs". United States. doi:10.1088/1741-4326/aa70bd.
@article{osti_1374849,
title = {Changes in divertor conditions in response to changing core density with RMPs},
author = {Briesemeister, Alexis R. and Ahn, Joon -Wook and Canik, John M. and Fenstermacher, Max E. and Frerichs, Heinke and Lasnier, Charles J. and Lore, John D. and Leonard, Anthony W. and Makowski, Michael A. and McLean, Adam G. and Meyer, William H. and Schmitz, Oliver and Shafer, Morgan W. and Unterberg, Ezekial A. and Wang, H. Q. and Watkins, Jonathan G.},
abstractNote = {The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertor by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed no evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.},
doi = {10.1088/1741-4326/aa70bd},
journal = {Nuclear Fusion},
number = 7,
volume = 57,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 7, 2018
Publisher's Version of Record

Save / Share:
  • Here in this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to n = 3 magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C 1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant differencemore » between the SN and SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.« less
  • Non-axisymmetric control coils and the so-called snow ake divertor con guration are two potential solutions proposed to solve two separate outstanding issues on the path towards self-sustained burning plasma operations, namely the transient energy bursts caused by edge localized modes and the steady state heat exhaust problem. In a reactor, these two proposed solutions would have to operate simultaneously and it is, therefore, important to investigate their compatibility and to identify possible con icts that could prevent them from operating simultaneously. In this work, single- and two- uid resistive magnetohydrodynamic calculations are used to investigate the e ect of externallymore » applied n = 3 magnetic perturbations on the snow ake divertor con guration. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. The results show that additional and longer magnetic lobes are created in the null-point region of the snow ake con guration, compared to those in the conventional single-null. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat ux target pro les. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snow ake con gurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations. The results also suggest that lower values of current in nonaxisymmetric control coils closer to the null-point region would be required to suppress edge localized modes. This e ect is expected to be enhanced in plasmas with the snow ake con guration.« less
  • In this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to $n=3$ magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant difference between the SN andmore » SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. Additionally, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.« less