Simulation of experimentally achieved detached plasmas using the UEDGE code Page: 17 of 32
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the inner divertor leg. This suggests we must examine the model used for the low
temperature region to better simulate the experiment.
IV. Conclusions
We have shown exciting new measurements of the plasma density and temperature
in the divertor region of DIII-D. These data have been obtained using a newly
installed divertor Thomson scattering system. We have demonstrated clear evidence
of the existence of two plasma regimes for the SOL, detached and attached. Attached
plasmas are characterized by high temperature (Te >10 eV) at the divertor plate and
relatively low density. On the other hand, the plate density is a factor of 7 higher for
the detached plasma state, and the electron temperature is 2 eV.
We also observe the existence of two plasma regimes in simulation of the DIII-D
SOL plasma using the UEDGE. We find the detached regime is obtained first at the
inner divertor plate then, at lower power, at the outer leg. This is similar to behavior
seen in experiments. The powers at which we achieve detachment in our simulations
are comparable to those found experimentally. The detached state can be achieved
by reducing power; increasing plasma density; gas puffing; and impurity injection in
both simulation and experiment. Our simulations indicate the region of low electron
temperature expands up the separatrix toward the X-point as the power is reduced
below that required to achieve detachment. When the low temperature region
expands far enough to permit neutral penetration to the closed flux surfaces, we
obtain a localized high density region on the closed flux surfaces, similar to MARFEs
seen experimentally. These similarities between experiment and simulation are very
encouraging about our ability to apply the SOL plasma models to the design of
divertors for future devices such as ITER.
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Porter, G. D.; Allen, S. & Fenstermacher, M. Simulation of experimentally achieved detached plasmas using the UEDGE code, article, October 30, 1995; California. (https://digital.library.unt.edu/ark:/67531/metadc667586/m1/17/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.