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Title: ELM frequency enhancement and discharge modification through lithium granule injection into EAST H-modes

Abstract

The injection of impurity granules into fusion research discharges can serve as a catalyst for ELM events. For sufficiently low ELM frequencies, and granule sizes above a threshold, this can result in full control of the ELM cycle, referred to as ELM pacing. For this research, we extend the investigation to conditions where the natural ELM frequency is too high for ELM pacing to be realized. Utilizing multiple sizes of lithium granules and classifying their effects by granule size, we demonstrate that ELM mitigation through frequency multiplication can be used at ELM triggering rates that nominally make ELM pacing unrealizable. We find that above a size threshold, injected granules promptly trigger ELMs and commensurately enhance the ELM frequency. Below this threshold size, injection of an individual granule does not always lead to the prompt triggering of an ELM; however, collective ablation in the edge pedestal region does enhance the ELM frequency. Furthermore, Li granules too small to individually trigger ELMs were injected into EAST H-mode discharges at frequencies up to 2.3 kHz; collectively the granules were observed to enhance the natural ELM frequency up to 620 Hz, resulting in a ~2.4 × multiplication of the natural ELM frequency and amore » 50% decrease of the ELM size.« less

Authors:
ORCiD logo [1];  [2]; ORCiD logo [1];  [1];  [1];  [2];  [2];  [2];  [1];  [3];  [4];  [5];  [6];  [2];  [2];  [2];  [2]
+ Show Author Affiliations
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Chinese Academy of Sciences, Anhui (People's Republic of China)
  3. General Atomics, San Diego, CA (United States)
  4. Johns Hopkins Univ., Baltimore, MD (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. Hunan Univ., Changsha (People's Republic of China)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
The EAST team
OSTI Identifier:
1480326
Grant/Contract Number:  
AC02-09CH11466; FC02-04ER54698; FG02-09ER55012; 11321092; 11405210; 11605246; 11625524; 2013GB114004; 2017YFA0402500; 2017YFE0301100
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELM; pacing; lithium

Citation Formats

Lunsford, R., Hu, J. S., Sun, Z., Maingi, R., Mansfield, D. K., Xu, W., Zuo, G. Z., Huang, M., Diallo, A., Osborne, T., Tritz, K., Canik, J., Meng, X. C., Zang, Q., Gong, X. Z., Wan, B. N., and Li, J. G. ELM frequency enhancement and discharge modification through lithium granule injection into EAST H-modes. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aae2c1.
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Lunsford, R., Hu, J. S., Sun, Z., Maingi, R., Mansfield, D. K., Xu, W., Zuo, G. Z., Huang, M., Diallo, A., Osborne, T., Tritz, K., Canik, J., Meng, X. C., Zang, Q., Gong, X. Z., Wan, B. N., & Li, J. G. ELM frequency enhancement and discharge modification through lithium granule injection into EAST H-modes. United States. https://doi.org/10.1088/1741-4326/aae2c1
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Lunsford, R., Hu, J. S., Sun, Z., Maingi, R., Mansfield, D. K., Xu, W., Zuo, G. Z., Huang, M., Diallo, A., Osborne, T., Tritz, K., Canik, J., Meng, X. C., Zang, Q., Gong, X. Z., Wan, B. N., and Li, J. G. Wed . "ELM frequency enhancement and discharge modification through lithium granule injection into EAST H-modes". United States. https://doi.org/10.1088/1741-4326/aae2c1. https://www.osti.gov/servlets/purl/1480326.
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@article{osti_1480326,
title = {ELM frequency enhancement and discharge modification through lithium granule injection into EAST H-modes},
author = {Lunsford, R. and Hu, J. S. and Sun, Z. and Maingi, R. and Mansfield, D. K. and Xu, W. and Zuo, G. Z. and Huang, M. and Diallo, A. and Osborne, T. and Tritz, K. and Canik, J. and Meng, X. C. and Zang, Q. and Gong, X. Z. and Wan, B. N. and Li, J. G.},
abstractNote = {The injection of impurity granules into fusion research discharges can serve as a catalyst for ELM events. For sufficiently low ELM frequencies, and granule sizes above a threshold, this can result in full control of the ELM cycle, referred to as ELM pacing. For this research, we extend the investigation to conditions where the natural ELM frequency is too high for ELM pacing to be realized. Utilizing multiple sizes of lithium granules and classifying their effects by granule size, we demonstrate that ELM mitigation through frequency multiplication can be used at ELM triggering rates that nominally make ELM pacing unrealizable. We find that above a size threshold, injected granules promptly trigger ELMs and commensurately enhance the ELM frequency. Below this threshold size, injection of an individual granule does not always lead to the prompt triggering of an ELM; however, collective ablation in the edge pedestal region does enhance the ELM frequency. Furthermore, Li granules too small to individually trigger ELMs were injected into EAST H-mode discharges at frequencies up to 2.3 kHz; collectively the granules were observed to enhance the natural ELM frequency up to 620 Hz, resulting in a ~2.4 × multiplication of the natural ELM frequency and a 50% decrease of the ELM size.},
doi = {10.1088/1741-4326/aae2c1},
journal = {Nuclear Fusion},
number = 12,
volume = 58,
place = {United States},
year = {Wed Oct 10 00:00:00 EDT 2018},
month = {Wed Oct 10 00:00:00 EDT 2018}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1088/1741-4326/aae2c1
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Cited by: 10 works
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Figures / Tables:

Table 1 Table 1: Granule injection parameters and resultant effects on ELM frequency. The table displays the size as calculated from impeller camera measurements, duration of ablation as recorded by a plasma viewing camera to a resolution of +/- 50 μs, the frequency of ablation events as recorded by the XUV diodemore » array, and a comparison of the D$α$ resolved ELM frequency both prior to and during granule ablation events. A comparison of the XUV and D$α$ traces results in the prompt ELM triggering efficiency. The elevation of ELM frequency due to granule injection is the granule pacing factor as described in Section 3.4. Notes : a) Ablation camera exposure per frame was 4.5x longer for this set of injections leading to a longer saturated phase where the status of the granule was occulted by a radiative lithium cloud. b) Ablation camera results not recorded during this discharge. c) Granule size was varied over the course of the injection, values in this row represent an average over full injection duration. See section 4.3 for further discussion.« less
All figures and tables (14 total)
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Works referenced in this record:

Characteristics of type I ELM energy and particle losses in existing devices and their extrapolation to ITER
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  • Song, Yun Tao; Wu, Song Tao; Li, Jian Gang
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ELM mitigation by means of supersonic molecular beam and pellet injection on the EAST superconducting tokamak
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10 Hz pellet injection control system integration for EAST
journal, January 2018

First observations of ELM triggering by injected lithium granules in EAST
journal, September 2013

A simple apparatus for the injection of lithium aerosol into the scrape-off layer of fusion research devices
journal, November 2010

First Results of ELM Triggering With a Multichamber Lithium Granule Injector Into EAST Discharges
journal, May 2018

Techniques for injection of pre-characterized dust into the scrape-off layer of fusion plasma
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Anomalous Behavior of the Coefficient of Normal Restitution in Oblique Impact
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Non-linear MHD modelling of ELM triggering by pellet injection in DIII-D and implications for ITER
journal, April 2014

ELM pace making and mitigation by pellet injection in ASDEX Upgrade
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ELM elimination with Li powder injection in EAST discharges using the tungsten upper divertor
journal, January 2018

Active Recycling Control Through Lithium Injection in EAST
journal, May 2018

Fueling efficiency of pellet injection on DIII-D
journal, March 1999

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    Figures / Tables found in this record:

    Table 1 (p. 8)table
    Figure 1 (p. 25)figure
    Figure 2 (p. 26)figure
    Figure 3 (p. 27)figure
    Figure 4 (p. 28)figure
    Figure 5 (p. 29)figure
    Figure 6 (p. 30)figure
    Figure 7 (p. 31)figure
    Figure 8 (p. 32)figure
    Figure 9 (p. 33)figure
    Figure 10 (p. 34)figure
    Figure 11 (p. 35)figure
    Figure 12 (p. 36)figure
    Figure 13 (p. 37)figure
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