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W7-X DCD Colloquium
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7.2-001 (IPP-HGW)
7.2-001
IPP-HGW
Description
Meeting Location: 7.2-001
Zoom Raum 2: (ID: 948-1054-7070 / PW: 021741)
Dear colleagues,
Thank you for your continued interest in divertor design!
Please be advised that there is no colloquium next week.
The next colloquium is scheduled for Tuesday 09.04. from 16:30 to 17:30 in Room 7.2-001 and Zoom Raum 2 (ID: 948-1054-7070 / PW: 021741)
https://event.ipp-hgw.mpg.de/event/1327/
On the Agenda is an idealized target design for an incoming plasma flux through D-SOL and PFR, the directed particle release and ionization front control.
Slides and Minutes from the previous colloquia can be found under:
https://event.ipp-hgw.mpg.de/category/63/
Below are the Minutes from this week:
We discussed the multi reservoir model consisting of Core, Edge, P-SOL, D-SOL, PFR, Divertor, and Sub-Divertor.
Efficiencies have been introduced for particle collection, removal, plugging, and screening. The challenging task seems to be the conflict of comprehensiveness vs. overwhelming complexity.
The general consensus was that the presented model was too complex to be shown as one figure. A de-coupling into layers seems like the best strategy to not overload the image.
Based on the function, a separation into D-SOL, PFR, Divertor, and Sub-divertor from the Core, Edge, and P-SOL seems the most practical. Further i.e. an overall screening efficiency can be defined in the first layer, which is then separated into more detailed layers i.e. SOL and Edge Screening on a lower level.
The importance of a systematic approach was stressed to make this model adjustable to other concepts. For example at ASDEX the sub-divertor is split from a pumping volume. A methodical approach ensures that the top layer metrics are still valid and additional reservoirs can be added on lower layers depending on individual machine properties.
Based on the comments, the topic of parallel ion transport through the reservoirs back into the core should not be visualized, but rather mentioned in the text, to keep facilitate access. Alternatively a color code for Neutrals and Ions could be implemented, replacing the color code for the favorable or unfavorable direction of particles.
A few functions are still missing their statistical metric:
Divert Plasma
Neutralize plasma
Survive
For neutralization, I can define a volumetric neutralization efficiency, i.e. what volumetric fraction of the D-SOL is neutralized. A target that reaches into the O-Point would guarantee a neutralization of the entire D-SOL, while i.e. the current W7-X target can only neutralize the layers close to the seperatrix, but allows plasma to be confined around the island o-point, significantly increasing our D-SOL width.
Further I can define the fraction of surface and volume recombination compared to the incoming flux.
For the survival function I can define the fraction of my received heat flux vs. the allowed heat flux. Similarly I can define a statistical value of the sputtering yield.
Where I’m currently lacking ideas, is a statistical metric on the first principle: Divert Plasma. Anyone has any ideas?
We briefly started on the topic for the next colloquium and we jumped into a discussion on the dependence of fluxes on the inclination of flux surfaces with the target.
Amit provided the following reference: https://infoscience.epfl.ch/record/273934?ln=en
While I found this section in Uli Stroths textbook “Plasmaphysik”
Thank you for your continued interest, input and the lively discussion!
Best,
Thierry
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