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CATEGORIES:Conferences/Seminars/Lectures
DESCRIPTION:Pellet injection and record performance in the W7-X stellarator
 \n\nPer Helander\, Max Planck Institute for Plasma Physics\n\nAbstract: In 
 most stellarators\, the neoclassical energy losses are very large\, and for
  this reason the magnetic field in Wendelstein 7-X was optimised to reduce 
 such losses. As a result\, the experimentally observed transport is mostly 
 turbulent\, but in certain plasmas fueled by cryogenic pellets the net ener
 gy transport is comparable to the neoclassical prediction. These plasmas of
 fer an opportunity to experimentally verify the efficacy of the optimisatio
 n. By comparing with other stellarators\, it is possible to conclude that t
 he confinement in W7-X exceeds that achievable in other magnetic configurat
 ions\, even if the turbulence is completely suppressed. \n\nIn most W7-X pl
 asmas the electrons are heated by ECRH\, and the ions only acquire energy i
 ndirectly from the electrons. In addition to ordinary collisional energy ex
 change\, there is another mechanism by which ions are heated in plasmas wit
 h pellet injection. The pellet ablation cloud expands along the magnetic fi
 eld and an electric field accelerates the ions in the cloud. These ions sub
 sequently share their energy with the bulk-plasma ions through Coulomb coll
 isions. Pellet injection is thus accompanied by a net transfer of thermal e
 nergy from electrons to ions. In W7-X\, this mechanism can account for a su
 bstantial fraction of the ion heating power during pellet injection. \n\nBi
 o: Professor Per Helander is Head of the Stellarator Theory Division at the
  Max Planck Institute for Plasma Physics in Greifswald Germany. He is a Sci
 entific Member of the Max Planck Society and a Professor for Theoretical Ph
 ysics at the University of Greifswald\, where he teaches plasma physics\, h
 ydrodynamics and general relativity. His research interests include most ar
 eas of stellarator and tokamak physics. He received his PhD from Chalmers U
 niversity of Technology in 1994\, worked at MIT 1994-1995 and at the United
  Kingdom Atomic Energy Authority 1996-2006 before coming to  Greifswald in 
 2006.
DTEND:20190920T200000Z
DTSTAMP:20260308T133539Z
DTSTART:20190920T190000Z
GEO:42.359858;-71.099164
LOCATION:Plasma Science and Fusion Center\, NW17-218
SEQUENCE:0
SUMMARY:PSFC Seminar: Per Helander
UID:tag:localist.com\,2008:EventInstance_31316274612886
URL:https://calendar.mit.edu/event/psfc_seminar_per_helander
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