Neutral Beam Coupling with Plasma in a Compact Fusion Neutron Source

Round 1

Reviewer 1 Report

Reviewers comments on ‘Neutral beam coupling with plasma in a compact fusion neutron source’ by Dlougach et al. 

The authors present a detailed design study of the efficacy of using neutral beam injection into a spherical tokamak in order to enable the driving of a plasma current and steady-state production of neutrons.  Specialist software is used to model the beam interaction and neutron production including neutral beam shine-through the plasma, the trapping of ions (which does not drive current) and other issues.  The paper shows capability in the modelling, but the paper would be improved if the authors could demonstrate more clearly optimum parameters in, for example, the abstract and conclusion.  In addition, the presentation and language make the paper difficult to follow.  I suggest the following:

1.      It is not clear if the results quoted in the abstract and introduction have been determined by the present study.  For example, are the neutron yield of 10^18 n/s and 99% production of neutrons from the injected beam verified by the work of the paper, a design criterion or just some desired result not yet achieved?

2.      Figures 3 - 7 have important details of e.g. position and power listed on them in small type which may become unreadable when the figures are reduced.   The values should be given in the figure captions. 

3.      The authors should clearly define what is meant by the ‘phase’ of the neutral beam (Figures 6 and 7).

4.      The y, z axes of figure 4 and 5 should be defined in text.

5.      The color coding for power density of figure 3 should be given. 

6.      The language makes it difficult to discern what has been achieved in the paper.  For example, line 86 states ‘The paper is intended to introduce …’ . This language suggest that the authors have NOT achieved their aim.  Better to say: ‘The paper introduces ….’ . 

Author Response

1: Indeed, the design criteria and the optimization targets (NBCD and neutron production) are close, so we don’t actually separate them in our study. However, we’ll give more clear definitions to the research targets. Thank you for this comment. 

2: This will be corrected accordingly.

3-4: This will be certainly done.

5: The current version of BTR code (BTR-5) is supplied with a minimum set of built-in visualization tools written manually, without any graphical libraries imported. The images shown in figs 2-5 correspond to BTR User Interface embedded graphics: the color coding is not included to the default toolset, as BTR offers the user many other ways to inspect the results interactively. We note, that some users at present prefer to export the maps from BTR and to process them with dedicated visialization packages (like Paraview) – this is why BTR code  is not focused on graphics very much. Therefore, we’ll fix the color coding issue -  either by adding the labels onto the maps, or by direct explanation in the figs captions.

6: Thank you very much for your attention to the language! The authors recognise the issue very well; they will state their intentions and achievements more clearly. In particular, the abstract, introduction and conclusion parts will be corrected to make the paper easier to follow.   

             With gratefulness, the authors.   

Reviewer 2 Report

In this manuscript, the authors offer an interesting investigation of the impact of toroidal field configuration and 585 neutral beam shaping on the beam driven effects, by making use of a specialized software BTR-BTOR. In my opinion, the results may be found meaningful and interesting for the journal readership. The paper is clearly written and interesting to read. Overall, I recommend publication.

Minor suggestions: The authors may improve the bibliography with recent similar analysis and/or review papers. Also, please standardize the references according to the journal guidelines. 

Author Response

Thank you very much for your positive feedback!

Our future target will be NB shaping upgrade from 585 to 999, probably with the beam-plasma feedback consideration.

We’ll add more references to the bibliography. Although this is not too easy today, from our location.  

Sincerely yours, 

authors