The role of plasma-atom/molecule interaction on power, particle and momentum balance during detachment

The role of plasma-atom/molecule interaction on power, particle and momentum balance during detachment

The role of plasma-atom/molecule interaction on power, particle and momentum balance during detachment 150 150 UKAEA Opendata
UKAEA-CCFE-CP(21)04

The role of plasma-atom/molecule interaction on power, particle and momentum balance during detachment

Hi Stuart, Thank you for your comments and for improving some of the text. Regarding the minor edits, I have all applied them to the paper. The larger edits, I have highlighted in the annotated document with comments below. Regarding the localisation of the various processes, I agree this is an important subject and should be addressed in more detail. In fact, the evidence we do have (based on SOLPS simulations as well as toroidally viewing cameras), suggests that the emission regions of the various plasma-molecule interactions and plasma-atom interactions are different (for instance, the Halpha emission near the target is much wider than for other Balmer lines – suggesting that that plasma-molecule interactions occur over a wider regime spatially). Comments of this have now been added to the text. The localisation of the various effects can be seen from different perspectives. 1) In the context of this paper, it mainly attempts to provide an overview of the particle balance in the divertor by providing estimates of ion sources/sinks integrated throughout the entire viewing cone and compare this against the ion target current using an analysis which is supposed to provide line-integrated ion source/sink estimates. This argument is not very sensitive to where the various ion sources/sinks are along the lines of sight – as long as they are being caught by the analysis (and contribute to the outer target ion target current). The exception to this, however, is that when we compare the integrated ion sources/sinks to the ion target current we find a mismatch during the detached phase, indicative of a net ion flow to the target (as ion sources – ion sinks < ion target current). We do not know where this net ion flow would come from spatially and with a spatially resolved analysis one could estimate this. A comment on this has been added. 2) I think the main complication with line-integrated effects probably is that the analysis technique oversimplifies the various emission regions. A paragraph on this has been added referring to the analysis paper as well as a previous paper which discusses this. The main argument is that although the technique oversimplifies the various emission regions, it is fairly robust against chordal integral effects (e.g. despite the simplification of the emission profiles in the analysis it can still provide sensible estimates for the integrated ion source/sinks) – which is also indicated by testing the analysis against SOLPS synthetically in the analysis paper. There, the emission profiles along the line of sight are quite different for the different processes in the SOLPS simulations (especially for the MAST-U case). This will be expanded upon further in the analysis paper compared to the current version of that paper (as the question about line-integration effects has been raised more often by others). 3) Regarding the Fulcher band emission, this is actually one of the exceptions where we do know that the emission should be fairly localised, because one needs a relative high temperature for Fulcher band emission (Te > 4 eV); so this should be localised quite closely to the separatrix given the expected TCV temperatures in that regime (which can be seen from the camera result when observing the excitation emission). https://www.dropbox.com/s/uqlcuh3ni1deg5h/KVH_PSI_27072020_v2_annotated.pdf?dl=0

Collection:
Conference
Journal:
Publisher:
Conference:
24th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI), South Korea, 24 - 29 January 2021
Published date:
14/04/2021