Efficiency Studies of Fast Neutron Tracking Using MCNP

Round 1

Reviewer 1 Report

The paper is an interesting Monte Carlo exercise towards the definition of a fast-neutron detector with tracking capability. Clearly, it deserves publication, however it seems to be prepared in a rush. For instance:

- Abstract: [...] the fast neutron momentum can be measured. Ref. [ 1]  introduced the theoretical concept that the initial fast neutron momentum ... --> Do not use references in the Abstract. "Zang an Morris introduced..."
- Caption of Figure 1: The schematic of three consecutive recoil ion tracks. Unknown neutron momentum P0. [...] --> The schematic view of three consecutive recoil ion tracks, induced by a neutron with unknown momentum P0
- 2. Basic idea of fast neutron tracking: "In the method 2 (M2), the time-of-flight (TOP) ..." --> usually acronym is time of flight is TOF. Please adopt it
- 2. Basic idea of fast neutron tracking (46): "where p1 in Eq. 8 and Q1 in Eq. 10" --> add the verb (are defined?)
- Figure 2: Add the beam direction. Larger figure is needed to appreciate the points.
- Figure 2: Add the case of He.
- Figure 3: Readapt the caption to this journal (it is not top and bottom).
- Figure 3: Figures should be page-width.
- Caption of Figure 3: "TALYS is not allowed to calculate the neutron-4He cross section" --> What is the meaning of this sentence?
- 4. Results and Discussions: Please explain which cross section are used in the simulations.
- Figure 4: Readapt the caption to this journal (it is not top and bottom).
- Figure 5: Readapt the caption to this journal (it is not top and bottom).
- Caption of Fig. 5 is partially covered by the panels of Fig. 6

Just to mention a few.

I strongly suggest that the authors finalize the article with the required attention and resubmit a new version of the manuscript (which as I anticipated, I will recommend for the publication in this journal).

Author Response

We thank the reviewer for his/her suggestions and comments. We have updated the manuscript with the following details.

The paper is an interesting Monte Carlo exercise towards the definition of a fast-neutron detector with tracking capability. Clearly, it deserves publication, however it seems to be prepared in a rush. For instance:

- Abstract: [...] the fast neutron momentum can be measured. Ref. [ 1]  introduced the theoretical concept that the initial fast neutron momentum ... --> Do not use references in the Abstract. "Zang an Morris introduced..."

Our reply: Fixed.

- Caption of Figure 1: The schematic of three consecutive recoil ion tracks. Unknown neutron momentum P0. [...] --> The schematic view of three consecutive recoil ion tracks, induced by a neutron with unknown momentum P0

Our reply: Fixed.

- 2. Basic idea of fast neutron tracking: "In the method 2 (M2), the time-of-flight (TOP) ..." --> usually acronym is time of flight is TOF. Please adopt it

Our reply: Fixed

- 2. Basic idea of fast neutron tracking (46): "where p1 in Eq. 8 and Q1 in Eq. 10" --> add the verb (are defined?)

Our Reply: Fixed

- Figure 2: Add the beam direction. Larger figure is needed to appreciate the points.

Our Reply: Fixed

- Figure 2: Add the case of He.

Our reply: Fixed

- Figure 3: Readapt the caption to this journal (it is not top and bottom).

Our Reply: Fixed

- Figure 3: Figures should be page-width.

Our Reply: Fixed

- Caption of Figure 3: "TALYS is not allowed to calculate the neutron-4He cross section" --> What is the meaning of this sentence?

Our Reply:

We did not use TALYS to calculate neutron-4He cross section. In the TALYS manual, it says “Either the nuclear symbol or the charge number Z of the target nucleus can be given. Possible values for element range from Li (3) to C4 (124). To accommodate target nuclides with Z > 110 the element names are defined as follows: Rg(111), Cn(112), Nh(113), Fl(114), Mc(115), Lv(116), Ts(117), Og(118), B9(119), C0-4(120-124). Obviously, the symbols for Z above 118 will be changed when official names are assigned to them.”

Change to “TALYS does not calculate the neutron-4He cross section.”

- 4. Results and Discussions: Please explain which cross section are used in the simulations.

Our reply: Add “The MCNP cross section is used in the MCNP simulation while the TALYS cross section is just for the comparison.”

- Figure 4: Readapt the caption to this journal (it is not top and bottom).

Our reply: Fixed

- Figure 5: Readapt the caption to this journal (it is not top and bottom).

Our reply: Fixed

- Caption of Fig. 5 is partially covered by the panels of Fig. 6

Our reply: Fixed

Just to mention a few.

I strongly suggest that the authors finalize the article with the required attention and resubmit a new version of the manuscript (which as I anticipated, I will recommend for the publication in this journal).

Our Reply: See above and Thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

please look at my comments addressed in the attached file.

The paper is surely interesting but it requires a Major Revision (see my comments for the motivations)

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for his/her suggestions and comments. We have updated the manuscript accordingly with the following details.

GENERAL COMMENT

The paper discusses the verification, by mean of Monte Carlo (MC) simulation, of already proposed methods (two) to track fast neutrons moving in a medium. The methods allows to reconstruct the neutron track starting from collisional data available from scattering theory and available in the used MC code. A third method, based on information from recoils deposited energy is proposed too.

The paper is clearly written and also interesting, however not novelties can be found since all the used equations and the proposed methods rely on the well-known (fast) neutron-scattering theory. It is appreciable that relativistic equations are used, this renders the method useful to high energy neutrons.

The used calculation method is based upon the capability of the MCNP Monte Carlo code used for the calculation to record all the needed information in a dedicated file (PTRACK). Indeed, the capability to calculate and record all the tracking information is the basis of any MC.

The authors claim (Sect.1, `, lines 27-28) : “In this paper, we validate these three methods for fast neutron tracking using…etc.” This reviewer thinks that this is not a “validation” but rather a “verification” of the three methods. Validation, usually, is against experimental data.

Our Reply: Fixed. We change “validate” to “verify”.

To this end since the MCNP calculation is performed for two different materials it not clear whether this paper is intended to design these detectors or it is just a calculation exercise. I think this is an important point to be addressed already in the Introduction section (which is perhaps too short).

Our Reply: We added a sentence to address the usefulness of this study in the introduction. We also added a paragraph to summarize each section in the introduction.

The doubt arises because at Page 5, lines 99-100 it is stated that a pixel detector made of Silicon can be constructed. I think this is an important point for the paper otherwise it is just a pure simulation without any practical use.

Our reply: We concur with the suggestion and have now addressed this point in the updated Introduction and Conclusion.

Another point to mention is with the fact that often trivial conclusions from the calculation are drown concerning the behavior of scattered particles (please see the attached file with highlighted in yellow some of these sentences and the other comments).

Last, but not least :

1_All the figures have wrong captions. In all the figures the authors refer to TOP and BOTTOM figure. It seems to me they are RIGHT and LEFT. Please modify all.

Our reply: Fixed.

2_I would expect more references so to know e.g. which cross section file was used for MCNP, which version of TALYS etc.

Our Reply: Fixed. It is MCNP-6.2 and TALYS-1.95. We already added the corresponding references for TALYS.

3_The quality of the figures must be improved, e.g. Fig. 5 (left and right) the error bars are overlapping and only in a coloured printing can be possible to distinguish in between the different data. The same applies to Fig. 6.

Our Reply: Fixed. Use different marker styles and line styles.

4_To note that Figure 8 is never mentioned in the text.

Our reply: We modified the text to “Figure 8 shows the distribution of the ion energy with the momentum Q1 and Q2”.

5_I have also some comments about the reported needs of the tracking detector. Resolution time of 0.1 ns is at the limit of the present technology, but 1-micron spatial resolution is not so bad for even for ions. It depends upon the application of the detector

Our reply: We agree with the reviewer’s suggestion. We change to “they may be proper for ion tracking with high-energy neutrons, depending on the application of the detector.”

6_In the Conclusions section, I suggest to add a few words about the spatial resolution.

Concluding my review I am proposing MAJOR CORRECTIONS.

>you are not validating the theoretical method 8no experiments), just using it with MCNP (strictly speaking you can use this method just because MC calculation do exactly it!!!

Our reply: We changed “validate” to “verify”.

> This comment is quite obvious; this is intrinsic in the scattering theory. It also depends on the mass of the nucleus.

Our reply: We added the following “This is intrinsic in the scattering theory, depending on the mass of the nucleus.”

> Which cross section file was used ?? ENDF/B-???? PLEASE SPECIFY and add references.

Our reply: We clarify the MCNP-6.2 version (use ENDF/B-VII.1) and TALYS-1.95 version. TALYS is pure computation.

> Which version of TALYS?? Please specify and add references

Our reply: TALYS-1.95

> No fission with Si and He !! but rather (n,x) reactions!!! where x could be p, d, T, alpha etc.

Our reply: We removed “fission”.

> ???? what does it mean??

Our reply: Here we mean the angular distribution is more uniform and isotropic for low-energy neutrons, as shown in Fig.2.

> This is not true; it is depending upon the scope of the detector and its application. There are several trackers with spatial resolutions of the order of microns

Our reply: Thanks for the comments. We updated the manuscript accordingly.

>Hence?? Method M3 is OK? Please conclude this discussion with a clear statement on this point which is very important for the usefulness of this work. One point missing in the paper is a discussion about its scope? are you designing a tracking detector based on this method?

Our reply: Here we updated the conclusion that the silicon pixel detectors can be used to measure neutrons with M3. One of the contributions of this study is therefore to provide simulation basis to design a track detector with silicon. We also added more discussion in the end of the Sec. 5.

> The spatial resolution has to be mentioned too in the Conclusions!!!

Our reply: We added the discussion of the spatial resolution in the conclusion.

Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addresseed my comments and therefore this version of the manuscript can be considered for publication.

Reviewer 2 Report

Dear Authors,

thank you for your revision and for considering my comments.

I think the paper is now suitable for pubblication and it is ACCEPTED.