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Title: Hollow pellet injection for magnetic fusion

Abstract

The precise delivery of mass to burning plasmas is an area of growing interest in magnetic fusion (MF). The amount of mass that is necessary and sufficient can vary depending on such parameters as the type of atoms involved, the type of applications, plasma conditions, mass injector, and injection timing. Motivated by edge localized mode (ELM) control in H-mode plasmas, disruption mitigation and other applications in MF, we report the progress and new possibilities in mass delivery based on hollow pellets. Here, a hollow pellet refers to a spherical shell mass structure with a hollow core. Based on an empirical model of pellet ablation, coupled with BOUT++ simulations of the ELM triggering threshold, hollow pellets are found to be attractive in comparison with solid spheres for ELM control. By using hollow pellets, it is possible to tailor mass delivery to certain regions of edge plasmas while minimizing core contamination and reducing the total amount of mass needed. We also include the experimental progress in mass delivery experiments, in situ diagnostics and hollow pellet fabrication, and emphasize new experimental possibilities for ELM control based on hollow pellets. A related application is the disruption mitigation scheme using powder encapsulated inside hollow shells.more » Further experiments will also help to resolve known discrepancies between theoretical predictions and experiments in using mass injection for ELM control and leading to better predictive models for ELM stability and triggering.« less

Authors:
ORCiD logo [1];  [1];  [2]; ORCiD logo [3];  [4]; ORCiD logo [5];  [4];  [6]; ORCiD logo [6];  [7]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of California, San Diego, La Jolla, CA (United States)
  3. Chinese Academy of Sciences, Hefei (China); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Chinese Academy of Sciences, Hefei (China)
  5. General Atomics, San Diego, CA (United States)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  7. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Key Research and Development Program of China; National Natural Science Foundation of China (NSFC)
Contributing Org.:
Fusion Energy Sciences long-pulse tokamak program through the Triad National Security, LLC (‘Triad’) contract # 89233218CNA000001; National Key Research Development Program of China (2017YFA0402500) and the National Nature Science Foundation of China (11625524).
OSTI Identifier:
1959464
Alternate Identifier(s):
OSTI ID: 1562483; OSTI ID: 1571597
Report Number(s):
LLNL-JRNL-844699; LA-UR-18-31744
Journal ID: ISSN 0029-5515; 1068126; TRN: US2312867
Grant/Contract Number:  
AC52-07NA27344; 89233218CNA000001; AC02-09CH11466; FC02-04ER54698; 2017YFA0402500; 11625524
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; hollow pellet; ELMs control; boron; Magnetic Fusion Energy

Citation Formats

Wang, Zhehui, Hoffbauer, M. A., Hollmann, E. M., Sun, Zhen, Wang, Y. M., Eidietis, Nicholas W., Hu, Jiansheng, Maingi, R., Menard, Jonathan E., and Xu, X. Q. Hollow pellet injection for magnetic fusion. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab19eb.
Wang, Zhehui, Hoffbauer, M. A., Hollmann, E. M., Sun, Zhen, Wang, Y. M., Eidietis, Nicholas W., Hu, Jiansheng, Maingi, R., Menard, Jonathan E., & Xu, X. Q. Hollow pellet injection for magnetic fusion. United States. https://doi.org/10.1088/1741-4326/ab19eb
Wang, Zhehui, Hoffbauer, M. A., Hollmann, E. M., Sun, Zhen, Wang, Y. M., Eidietis, Nicholas W., Hu, Jiansheng, Maingi, R., Menard, Jonathan E., and Xu, X. Q. Thu . "Hollow pellet injection for magnetic fusion". United States. https://doi.org/10.1088/1741-4326/ab19eb. https://www.osti.gov/servlets/purl/1959464.
@article{osti_1959464,
title = {Hollow pellet injection for magnetic fusion},
author = {Wang, Zhehui and Hoffbauer, M. A. and Hollmann, E. M. and Sun, Zhen and Wang, Y. M. and Eidietis, Nicholas W. and Hu, Jiansheng and Maingi, R. and Menard, Jonathan E. and Xu, X. Q.},
abstractNote = {The precise delivery of mass to burning plasmas is an area of growing interest in magnetic fusion (MF). The amount of mass that is necessary and sufficient can vary depending on such parameters as the type of atoms involved, the type of applications, plasma conditions, mass injector, and injection timing. Motivated by edge localized mode (ELM) control in H-mode plasmas, disruption mitigation and other applications in MF, we report the progress and new possibilities in mass delivery based on hollow pellets. Here, a hollow pellet refers to a spherical shell mass structure with a hollow core. Based on an empirical model of pellet ablation, coupled with BOUT++ simulations of the ELM triggering threshold, hollow pellets are found to be attractive in comparison with solid spheres for ELM control. By using hollow pellets, it is possible to tailor mass delivery to certain regions of edge plasmas while minimizing core contamination and reducing the total amount of mass needed. We also include the experimental progress in mass delivery experiments, in situ diagnostics and hollow pellet fabrication, and emphasize new experimental possibilities for ELM control based on hollow pellets. A related application is the disruption mitigation scheme using powder encapsulated inside hollow shells. Further experiments will also help to resolve known discrepancies between theoretical predictions and experiments in using mass injection for ELM control and leading to better predictive models for ELM stability and triggering.},
doi = {10.1088/1741-4326/ab19eb},
journal = {Nuclear Fusion},
number = 8,
volume = 59,
place = {United States},
year = {Thu Jun 27 00:00:00 EDT 2019},
month = {Thu Jun 27 00:00:00 EDT 2019}
}

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Figures / Tables:

Figure 1 Figure 1: A comparison of various impurity pellet ablation models for $dN/dr$ (in the unit of 1022 m−1) as a function of the normalized minor radius. The fixed plasma temperature and density profiles, normalized to their core values ($T^{max}_{e}$ = 5 keV, $n^{max}_{e}$ = 8×1019 m−3), are shown for amore » H-mode plasma in the bottom frame. In the top and middle frames for Li and B respectively, the plotting symbols are matched for five models and ordered according to the pellet penetration distance from the deepest to the shallowest as: NGS model (a), weak NGS model with a magnetic-field shaping factor of 0.8 (b), weak NGS model (c), bare pellet model without shielding (d) and enhanced pellet ablation model (e). The normalized electron density and temperature profiles (with respect to the peak temperature and density) are shown in the bottom frames. Pellet initial radius is 1 mm, initial velocity 100 m/s. The separatrix density (the vertical line that is not labelled) is 1018 m−3 at a temperature of 30 eV. The pedestal width is 2% of the minor radius.« less

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