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@ARTICLE{Lunsford:904062,
      author       = {Lunsford, R. and Killer, C. and Nagy, A. and Gates, D. A.
                      and Klinger, T. and Dinklage, A. and Satheeswaran, G. and
                      Kocsis, G. and Lazerson, S. A. and Nespoli, F. and Pablant,
                      N. A. and von Stechow, A. and Alonso, A. and Andreeva, T.
                      and Beurskens, M. and Biedermann, C. and Brezinsek, S. and
                      Brunner, K. J. and Buttenschön, B. and Carralero, D. and
                      Cseh, G. and Drewelow, P. and Effenberg, F. and Estrada, T.
                      and Ford, O. P. and Grulke, O. and Hergenhahn, U. and
                      Höfel, U. and Knauer, J. and Krause, M. and Krychowiak, M.
                      and Kwak, S. and Langenberg, A. and Neuner, U. and Nicolai,
                      D. and Pavone, A. and Puig Sitjes, A. and Rahbarnia, K. and
                      Schilling, J. and Svensson, J. and Szepesi, T. and Thomsen,
                      H. and Wauters, T. and Windisch, T. and Winters, V. and
                      Zhang, D. and Zsuga, L.},
      title        = {{C}haracterization of injection and confinement improvement
                      through impurity induced profile modifications on the
                      {W}endelstein 7-{X} stellarator},
      journal      = {Physics of plasmas},
      volume       = {28},
      number       = {8},
      issn         = {1070-664X},
      address      = {[S.l.]},
      publisher    = {American Institute of Physics},
      reportid     = {FZJ-2021-05632},
      pages        = {082506 -},
      year         = {2021},
      abstract     = {Pulsed injections of boron carbide granules into
                      Wendelstein 7-X stellarator (W7-X) plasmas transiently
                      increase the plasma stored energy and core ion temperatures
                      above the reference W7-X experimental programs by up to
                      $30\%.$ In a series of 4 MW electron cyclotron resonance
                      heating experiments, the PPPL Probe Mounted Powder Injector
                      provided 50 ms bursts of 100 μm granules every 350 ms
                      at estimated quantities ranging from approximately
                      1 mg/pulse to over 30 mg/pulse. For each injection, the
                      stored energy was observed to initially drop and the
                      radiated power transiently increased, while the radial
                      electron density profile rose at the edge as material was
                      assimilated. Once the injected boron carbide was fully
                      absorbed, the density rise transitioned to the core while
                      the stored energy increased above the previous baseline
                      level by an amount linearly correlated with the injection
                      quantity. During the injection, the ion temperature gradient
                      steepened with peak core ion temperatures observed to
                      increase from a nominal 1.7 keV to over 2.6 keV for the
                      largest injection amounts. Enhanced performance is
                      accompanied by a reversal of the radial electric field at ρ
                      < 0.3, indicating that the core transport has switched to
                      the ion root. These observations are suggestive of a change
                      in transport and provide further evidence that externally
                      induced profile modifications provide a possible path to
                      enhanced W7-X performance metrics.I. INTRODUCTIO},
      cin          = {IEK-4},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IEK-4-20101013},
      pnm          = {134 - Plasma-Wand-Wechselwirkung (POF4-134)},
      pid          = {G:(DE-HGF)POF4-134},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000683519000002},
      doi          = {10.1063/5.0047274},
      url          = {https://juser.fz-juelich.de/record/904062},
}