High frequency pacing of edge localized modes by injection of lithium granules in DIII-D H-mode discharges

Journal Article · Fri Apr 08 00:00:00 EDT 2016 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/56/5/056008· OSTI ID:1254013

Bortolon, A.  ^[1]; Maingi, R. ^[1]; Mansfield, D. K. ^[1]; Nagy, A. ^[1]; Roquemore, A. L. ^[1]; Baylor, L. R. ^[2]; Commaux, N. ^[2]; Jackson, G. L. ^[3]; Gilson, E. P. ^[1]; Lunsford, R.  ^[1]; Parks, P. B. ^[3]; Chrystal, C. ^[4]; Grierson, B. A. ^[1]; Groebner, R. ^[3]; Haskey, S. R.  ^[1]; Makowski, M. J. ^[5]; Lasnier, C. J. ^[5]; Nazikian, R. ^[1]; Osborne, T. ^[3]; Shiraki, D. ^[2] ; Van Zeeland, M. A. ^[3]

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1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. General Atomics, San Diego, CA (United States)
4. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

A newly installed Lithium Granule Injector (LGI) was used to pace edge localized modes (ELM) in DIII-D. ELM pacing efficiency was studied injecting lithium granules of nominal diameter 0.3-0.9 mm, speed of 50-120 m/s and average injection rates up to 100 Hz for 0.9 mm granules and up to 700 Hz for 0.3 mm granules. The efficiency of ELM triggering was found to depend strongly on size of the injected granules, with triggering efficiency close to 100% obtained with 0.9 mm diameter granules, lower with smaller sizes, and weakly depending on granule velocity. Robust ELM pacing was demonstrated in ITER-like plasmas for the entire shot length, at ELM frequencies 3-5 times larger than the \natural" ELM frequency observed in reference discharges. Within the range of ELM frequencies obtained, the peak ELM heat flux at the outer strike point was reduced with increasing pacing frequency. The peak heat flux reduction at the inner strike point appears to saturate at high pacing frequency. Lithium wasfound in the plasma core, with a concurrent reduction of metallic impurities and carbon. Overall, high frequency ELM pacing using the lithium granule injection appears to be compatible with both H-mode energy con nement and attractive H-mode pedestal characteristics, but further assessment is needed to determine whether the projected heat flux reduction required for ITER can be met.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Contributing Organization: Princeton Plasma Physics Laboratory, Princeton, NJ; Oak Ridge National Laboratory, Oak Ridge, TN; General Atomics, San Diego, CA; Oak Ridge Associated Universities, Oak Ridge, TN; Lawrence Livermore National Laboratory, CA
• Grant/Contract Number: AC02-09CH11466; FC02-04ER54698; AC52-07NA27344; AC05-00OR22725
• OSTI ID: 1254013
• Alternate ID(s): OSTI ID: 1246536; OSTI ID: 1459511; OSTI ID: 1542718
• Report Number(s): PPPL-5251; LLNL-JRNL-752101
• Journal Information: Nuclear Fusion, Vol. 56, Issue 5; ISSN 0029-5515
• Publisher: IOP Science
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
tokamak
ELM
pacing
pellet
mitigation
head load
control
Physics - Plasma physics