Development and Application of SONIC Divertor Simulation Code to Power Exhaust Design of Japanese DEMO Divertor
, Kazuo Hoshino 2, Yuki Homma 3, Yoshiteru Sakamoto 3 and Joint Special Design Team for Fusion DEMO †Round 1
Reviewer 1 Report
Manuscript # processes - 160376
Development and application of SONIC divertor simulation code to power exhaust design of Japanese DEMO divertor
By H. N. Asakura, K. Hoshino, Y. Homma, Y. Sakamoto, and Joint Spetcial design Team for Fusion DEMO
The manuscript presented by the authors deals with the modeling of the plasma-wall interaction in the context of tokamak plasma physics and the international ITER project, and more precisely with the JA-DEMO divertor configuration. The divertor concept was introduced in ASDEX and highlighted the mechanism of the LH transition in the so-called scrape-off-layer region at the tokamak edge. In the design of ITER and then in DEMO, the choice of a divertor was retained. The topics discussed in the paper are the design of the divertor, the associated physics of the SOL, the consideration of impurities and radiative processes, until the plasma detachment regime is obtained.
In the detachment regime, the ionization front of the neutral particles is no longer localized in the immediate vicinity of the surface of the components but is detached from the wall to finally move into the divertor region
These various works were carried out from modeling and numerical simulations carried out from several numerical codes gathered under the name SONIC: SOLDOR for the 2D multi-fluid modeling of the SOL, the transport of impurities (IMPMC?) and NEUT2D for the neutrals.
I believe the paper contains significant results and should be published after the following matters are dealt with properly. For publication the presentation needs improvement in several respects. Items to be addressed by the authors:
1)The manuscript is particularly difficult to read and, in its present form, is mainly intended for specialists. In order to make it more accessible to a wider community, a rewriting of some parts is necessary. The paper contains almost no details on the physical equations of the various codes, even if these codes are detailed elsewhere, the only fact of putting these citations in reference is not sufficient, the authors should recall in appendix at least the basic equations of the various physical models used.
2) It is difficult to estimate, from the only presentation of the results, if the objectives can be reached from this type of modeling, it would perhaps be good to recall, in a more concise form, perhaps in the form of tables, a summary of the results obtained and in which categories of problems.
3)I did not find any comparison with experimental measurements to validate the approaches used in the modeling, at least for the JT-60U tokamak, or even the advantages or disadvantages of the fluid approach chosen for the description of the turbulence in the SOL.
4)In part 4.1 entitled "improvement of kinetic model in impurity transport", the transport of impurities generally verifies a neoclassical transport whereas that of lighter ions or electrons is closer to the so-called "anomalous" regime where turbulence plays a fundamental role. How are these two types of transport taken into account in the various models?
5)In part 4.2 "development of photon transport model", could the authors indicate how photon transport is taken into account in the model used?
6)The authors refer to the so-called "backflow model" in section 2.3, line 165, could the authors clarify what they mean by this expression?
7)The authors refer to the EDGE2D-EIRENE code line 55, page 2, it seems that the latest version of the code is SOLEDGE2D- EIRENE.
8)I found no reference to the problem of the LH transition in the SOL region, which remains one of the scientific locks for ITER. Does the SONIC code version allow to confirm some experimental measurements, observed in this transition?
9) I am a bit surprised that the SONIC code finds an estimate of the thermal diffusivity coefficient of 1m2s-1because the modeling of anomalous transport generally requires the use of gyrokinetic type modeling and that purely fluid modeling is often insufficient even including Fokker-Planck type modeling. Could the authors comment on this point?
10) How the core-edge boundary surface (in figure 2) is treated in the model. It is generally accepted that the turbulent flows produced in the core region have a significant effect on the physics of the SOL. Is the opposite process observed?
Comments for author File: 
Comments.pdf
Author Response
Dear Sir,
Thank you for positive comments and suggestions. I think I revised most of your comments, which are explained in Response PDF file.
And I also attached our revised manuscript with Red marks.
If you check them and agree with my responses, should appreciate it.
Best regards
Nobuyuki Asakura
Author Response File: Author Response.pdf
Reviewer 2 Report
The article presents the progress of the Monte Carlo SONIC code which was developed to simulate the transport of the plasma, neutral and impurities in the scrape-off layer and divertor. SONIC was used to simulate the plasma detachment in JT-60U experiments, and to design the divertor of JT-60SA. The newly developed SONIC is being used to develop a DEMO divertor.
The article is devoted to an actual and interesting topic, which is currently not sufficiently researched. Studying the operation of the divertor in the detachment mode is very important to reduce the peak thermal loads on the plates of the tokamak divertor. Therefore, I recommend the article for publication in MDPI.
Author Response
Dear Sir,
Thank you for your positive comment.
I attached revision summary and our revised manuscript with Red marks.
If you check them and agree with my responses, I should appreciate it.
Best regards
Nobuyuki Asakura
Author Response File: Author Response.pdf
Reviewer 3 Report
Nobuyuki Asakura, et al. investigated the development and application of SONIC divertor simulation code to power exhaust design of Japanese DEMO divertor. Basically, this is a good study. I just recommend that the authors emphasize this study's significance and novelty in the INTRODUCTION part.
Author Response
Dear Sir,
Thank you for your positive comment and suggestion.
I think I revised both the abstract and Introduction part of each subsection (line 121-127) as Reviewer requested. I also revised Section 5: Conclusion as was explained in general revision (6).
I attached revision summary and our revised manuscript with Red marks.
If you check them and agree with my responses, I should appreciate it.
Best regards
Nobuyuki Asakura
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Manuscript # processes - 1603762
Development and application of SONIC divertor simulation code to power exhaust design of Japanese DEMO divertor
By H. N. Asakura, K. Hoshino, Y. Homma, Y. Sakamoto, and Joint Special design Team for Fusion DEMO
The manuscript presented by the authors deals with the modeling of the plasma-wall interaction in the context of tokamak plasma physics and the international ITER project, and more precisely with the JA-DEMO divertor configuration. The divertor concept was introduced in ASDEX and highlighted the mechanism of the LH transition in the so-called scrape-off-layer region at the tokamak edge. In the design of ITER and then in DEMO, the choice of a divertor was retained. The topics discussed in the paper are the design of the divertor, the associated physics of the SOL, the consideration of impurities and radiative processes, until the plasma detachment regime is obtained.
The authors have perfectly answered the questions asked and modified the manuscript accordingly. I believe the paper contains significant results and should be published in its present form.
