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SUMMARY:On the non-stiffness of edge transport in L-modes
DTSTART:20131202T103000
DTEND:20131202T113000
DTSTAMP:20260924T215414Z
UID:68f3336bf4ee9fcfb600484a0d77c3be6cfdc1dc6b0ce24ff59e799c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Olivier Sauter\, CRPP-EPFL\nTransport analyses using first
  principle turbulence codes as well as 1½-D transport codes often study t
 ransport properties between the plasma axis and a normalized radius around
  0.8. In this region\, heat transport shows significant stiffness properti
 es leading to R/LTe values that are relatively independent of auxiliary in
 put power. In this work\, we study experimentally in the TCV tokamak\, the
  transport properties of the edge region\, close to the last closed flux s
 urface\, namely between ρV=0.8 and 1 (ρψ≥0.9). It is shown that elect
 ron transport is not stiff in this region and extremely high R/LTe values 
 can be attained even for L-mode confinement. These results bring a new per
 spective to several "accepted" understandings. In particular a specific st
 udy related to the Ip scaling of ohmic and ECH L-mode discharges shows tha
 t the strong Ip scaling is in fact related in a large part to this non-sti
 ff edge region. The Te scale length is shown to be proportional to Ip in t
 he edge region and constant (independent of Ip) in the core region. The re
 lation with L-H transition and the I-modes will also be discussed\, since 
 it shows that the edge gradient can be continuously increased\, by increas
 ing the input power\, even in the L-mode phase. It is also proposed that t
 he pedestal width is related to the width over which the transport is non-
 stiff\, and can be studied in detail already in L-mode. The present study 
 also explains the large improved confinemet obtain with negative triangula
 rity and a new model is proposed including non-stiff edge local transport 
 which can recover the experimental observations.
LOCATION:PPB 017
STATUS:CONFIRMED
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