Divertor regimes: attached case
stable operation at
high density ne = 2.5 10 20 m3
Te,0 = 450 eV, Te,s = 90 eV
P. Grigull, Plasma Phys. Contr. Fus., submitted (2001)
thermal target load pattern frad 50 %, Te,d = 20 eV
watershed
from thermography
deposition stripes consistent with island topology
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Divertor regimes: transition to (partial) detachment
stable operation at
very high density ne = 3.5 10 20 m3
Te,0 = 390 eV, Te,s = 20 eV
P. Grigull, Plasma Phys. Contr. Fus., submitted (2001)
thermal target load pattern frad ~ 90 %, Te,d ~ 10 eV
watershed
residual heat load
from thermography
cool divertor plasma
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Confinement at high density
|
P. Grigull, Plasma Phys. Contr. Fus., submitted (2001) |
energy confinement |
reverse scaling of |
impurity confinement !!! |
|
|
Al XII decay time |
|
after LBO-injection |
good energy confinement above ISS95-level
favourable density scaling of energy ( E ) and impurity ( imp ) confinement
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Resumee on longpulse / divertor operation
steady state operation is proven with low performance (ATF)
long pulse operation extended to 2 min with moderate performance (LHD)
first island divertor operates succesfull (W7AS)
improved density control (Tipumps not yet operating !)
access to very high densities
with favourable scaling of E and imp
stable (partial) detachment
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Achievements
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Summary of experimental results from stellarators
stellarators can be accurately build to provide the expected vacuum field properties
the technical feasibility of the modular stellarator concept is proven
the plasma equilibrium accords with theory
the limit is at least as high as predicted
transport at low collisionality accords with neoclassical theory (including electric fields)
first HSX results confirm the quasisymmetric stellarator approach
at higher collisionality transport is anomalous as in tokamaks
anomalous transport can be reduced by transport barriers
the island divertor gives stable access to extremely high densities
The results confirm the physics basis of large scale steady state devices having just started operation (LHD) or under construction (W7X)
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