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

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 0.3–0.9mm, speed of 50–120 m s-1 and average injection rates up to 100 Hz for 0.9mm granules and up to 700 Hz for 0.3mm 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 0.9mm 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 was found in the plasma core, with a concurrent reduction of metallic impurities and carbon. Altogether, high frequency ELM pacing using the lithium granule injection appears to be compatible with both H-mode energy confinement and attractive H-mode pedestal characteristics, but furthermore » assessment is need« less
Authors:
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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)
Publication Date:
OSTI Identifier:
1254013
Report Number(s):
PPPL--5251
Journal ID: ISSN 0029-5515
Grant/Contract Number:
AC02-09CH11466; FC02-04ER54698; AC52-07NA27344; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 5; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
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
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING tokamak; ELM; pacing; pellet; mitigation; head load; control