Spectral Intensity of Electron Cyclotron Radiation Emerging from the Plasma to the First Wall in ITER
Round 1
Reviewer 1 Report
The reviewed manuscript "Spectral intensity of electron cyclotron radiation emerging from the plasma to the first wall in ITER" presents calculations of the stray radiation energy fluxes due to the cycl
emission of electrons.
The paper consists of four major parts: introduction, methodology, results, and conclusions. I will start from the author's list:
Dr. Kukushlin is indicated as a corresponding author, however it is suggsted to use the email address of Dr. Minashin for contacts. I suggest authors to sort out who of them should the main contact.
Introduction is well-written and gives a short and pedagogical view into the principles of CYNEQ and other codes used for its benchmarking.
I have questions to the section 3 (results):
1. Authors present scenarios that are not considered any longer. The authors admit it themselves when introducing the LH scenario, I am not sure about the remaining ones. I suggest to actualize the scenarios that you are presenting. As such, those different scen
do not have any fundamental meaning and the results of your simulations should be used as a look-up table.
2. What is a point of Fig. 2 with steady-state time traces? It can be described within the text in one sentense.
3. Table 3 is wrong: current ECRH-assisted start-up scenarios imply using a vertical launcher with P=5.87 MW and the non-absorbed power is mainly directed into the microwave beam load (~95% of unabsorbed power should be absorbed in the load and not converted into stray radiation).
4. Using eq. 6 is probably OK for calculations of the stray radiation fluxes from ECE since it is a distributed source, however it is an oversimplification for such point-like sources like gyrotrons, they produce non-uniformally distributed stray radiation even in highly reflective vacuum vessels.
5. I wonder about practical applicability of Table 2: it gives values in the vacuum vessel itself. However, as you correctly stated in the introduction, propagation of stray radiation matters for the diagnostics, cryopumps, cable looms behind the first wall etc. It is not straightforward to use Table 2 in order to estimate the stray radiation propagation. What could potentially have an added value is spectral density of plasma power losses due to ECE, MW/GHz. That result could be fed into coupled-cavity models that contain actual geometry of ITER ports, divertor, etc.
Author Response
The response is given in the attached file
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The subject is of interest to the readership of Symmetry and in particular for the Special Issue. It is an original contribution, with title and abstract adequate to the content of the paper. The authors are very well known and well published in this domain. Within the assumption made, the model used, on which the CYNEQ code used in this paper is based, is well established and benchmarked against a variety of other models. The added value of this paper is related to the application of the model to five ITER scenarios by using the CYNEQ code for determining the spectral intensity of the EC radiation emerging from the plasma and eventually absorbed in the first wall. The paper is very well written.
My main point is related to the fact that the "Effective reflection coefficient" is considered as frequency independent. I understand that this probably allows a great simplification in the model, but this limitation should be discussed in detail by the authors, in particular since the spectral analysis of the EC-radiation shows that the EC radiation spectrum covers a very wide frequency range.
I would recommend the publication of the manuscript provided that the author address the main point above and the points listed below:
1. In equation (7) it should be specified if the plasma parameters ne, Te, B0 are local quantities or volume averaged quantities?
2. In equation (8) & (9) on which arguments the reference reflectivity Rw = 0.8 is chosen? Please comment.
3. The reflection coefficient used in the paper is an "effective reflection coefficient". However, depending on the type of material on which the radiation is absorbed and on the frequency of the incident EC radiation, the local reflection coefficient (and absorption) might significantly deviate from the "effective reflection coefficient". The author should comment on this point which is of particular importance since the thermomechanical limits of some internal components depend on the local reflection coefficients rather than on the "effective reflection coefficient". This point is related to the main point above.
4. In ITER are there materials other than the ones considered in Fig.11?
5. What about the effect of EC-radiation on diagnostics based on optical systems which are located in port-plugs where the EC-radiation will eventually be transmitted?
Author Response
The response is given in the attached file
Author Response File: Author Response.pdf
Reviewer 3 Report
Reviewer comments
Spectral intensity of electron cyclotron radiation emerging from the plasma to the first wall in ITER
- The introduction doesn’t motivate the topic of this work and provides very little context in terms of the previous works in this field as well as the motivation for choosing this specific topic. The authors are requested to provided more details about previous studies on electron cyclotron radiation in tokamak reactors and why their work is important and what areas does it focus on which is missing in the previous works
2. In section 2, the authors describe the CYNEQ code but don;’t provide details of other numerical studies which have simulated the phenomenon without CYNEQ code.The authors talk about a number of different codes in this section, without providing even a brief explanation about the others codes such as CYTRAN. Why did the authors choose CYNEQ code over stay other numerical techniques out there? ; it is important to understand the advantages on this over the other techniques out there
3. The author chooses five different scenarios for presenting the results.How were these choices made and these are a lot of different parameters to present in a single publication. Typically it is advisable to tackle 1-2 parameters so as to allow authors to go into greater details without loosing focus. It is advisable to choose two main modes of operation as parameters and analyses in greater details as compared to exploring fives different settings in not so much detail.
Author Response
The response is given in the attached file
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I believe that the paper has improved. I also agree with the author that using eq 6 for calculating the stray radiation from ECE makes sense, since it is a distributed source. Regarding ECE I believe the analysis is made correctly. Regarding ECRH/ECCD, after reading ref [4], I think the author makes misleading statements which may have real-life consequences, should anybody use this paper's results for designing the diagnostic. It is shown in [4] that the lower the quality factor of the resonators (lower wall reflectivity), the larger variations of stray radiation fluxes in the vessel are. Thus, using average flux as teh authors do in Table 3 can be very misleading, should anybody use this table for the actual design. The authors should clarify it in the manuscript.
Author Response
Our answer is in the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors have incorporated my corrections and I recommend this journal for publication.
Author Response
We thank the third reviewer for helpful comment and approval of the manuscript.
