Piecewise Linear Approximation of Elliptical Neutron Guides—A Case Study for BIFROST at ESS

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors in this paper investigates the feasibility of approximating elliptical neutron guides using piecewise linear segments for the BIFROST instrument at ESS. Through simulations using McStas, the authors examine the impact of segment lengths on neutron transport efficiency and phase space homogeneity. The work systematically compares simple elliptical guides, ballistic geometries, and the specific design of the BIFROST guide.

The overall idea presented in the paper is intriguing and has potential. However, I recommend considering the following major revisions to strengthen the work and ensure its acceptance:

1.  In abstract, the authors should effectively summarize the findings but could briefly mention the significance of the results in the broader context of neutron instrumentation.

2.  In Introduction, the author should add a brief overview of neutron guide applications in other major facilities (e.g., SNS or ILL) would contextualize the importance of the study.

3.  In introduction, the paper could benefit from a more detailed discussion of practical implementation challenges, such as alignment tolerances and manufacturing constraints.

4.  The figures are informative but occasionally dense. Simplified diagrams or additional annotations could make them more accessible.

5.  A table summarizing key findings for different segment lengths (e.g., 0.5 m, 3 m, 10 m) and their respective performance metrics would improve clarity.

6.  The authors should add a critical comparison with previous studies (e.g., those focusing on parabolic guides) could strengthen the conclusions.

7. The conclusions are well-stated, emphasizing specific recommendations for future guide designs would make the practical implications clearer.

8.  There are a few typos and grammatical errors. It is strongly recommended that you proofread thoroughly.

9. The introduction needs to be improved by the recent developments in the relevant field. For this purpose, the authors can add the following references to enrich the introductory section:

https://doi.org/10.1016/j.cnsns.2017.01.018

 

https://doi.org/10.1080/17455030.2020.1802085

Author Response

The authors in this paper investigates the feasibility of approximating ellipti-

cal neutron guides using piecewise linear segments for the BIFROST instrument

at ESS. Through simulations using McStas, the authors examine the impact of

segment lengths on neutron transport efficiency and phase space homogeneity.

The work systematically compares simple elliptical guides, ballistic geometries,

and the specific design of the BIFROST guide.

 

The overall idea presented in the paper is intriguing and has potential. How-

ever, I recommend considering the following major revisions to strengthen the

work and ensure its acceptance:

 

1. In abstract, the authors should effectively summarize the findings but

could briefly mention the significance of the results in the broader context of

neutron instrumentation.

We have added one sentence to the abstract to elucidate this aspect.

 

2. In Introduction, the author should add a brief overview of neutron guide

applications in other major facilities (e.g., SNS or ILL) would contextualize the

importance of the study.

We have added one sentence on this topic to the first paragraph of the introduction.

 

3. In introduction, the paper could benefit from a more detailed discus-

sion of practical implementation challenges, such as alignment tolerances and

manufacturing constraints.

We have added a sentence to the introduction concerning these practical implementation challenges.

 

4. The figures are informative but occasionally dense. Simplified diagrams or additional annotations could make them more accessible.

We are somewhat uncertain as to, what the referee refers to here. We have revisited the figures, and do not find them dense, nor inaccessible. We have added units to the colorbars in the figures that used these.

 

5. A table summarizing key findings for different segment lengths (e.g., 0.5

m, 3 m, 10 m) and their respective performance metrics would improve clarity.

We have added the suggested table.

 

6. The authors should add a critical comparison with previous studies (e.g.,

those focusing on parabolic guides) could strengthen the conclusions.

We have added a sentence on this in the introduction.

 

7. The conclusions are well-stated, emphasizing specific recommendations

for future guide designs would make the practical implications clearer.

We feel that the final paragraph of the conclusion serves this purpose. Hence this comment has not led to any changes.

 

8. There are a few typos and grammatical errors. It is strongly recommended

that you proofread thoroughly.

We have proofread and corrected grammatical errors.

 

9. The introduction needs to be improved by the recent developments in the

relevant field. For this purpose, the authors can add the following references to

enrich the introductory section:

https://doi.org/10.1016/j.cnsns.2017.01.018

https://doi.org/10.1080/17455030.2020.1802085

 

We fail to see the relation between neutron guides and the given DOI’s so we assume that the reference must be a mistake.

 

Reviewer 2 Report

Comments and Suggestions for Authors

This work aims to perform a systematic study on optimizing long neutron guides. Especially, study the effect of piecewise linearly tapering approximation of elliptical guides. The research using ray tracing method and find that a piecewise linear guide with a surprisingly long piece length, up to 10 m, perform almost as good as a fully elliptical guide for neutron between 2 and 5 Å, and guides with piece lengths of 3 m and below have performances equal to that of fully elliptical guides at all wavelengths. This is a major achievement for the design of new beamlines of spallation neutron sources. The mirror engineering can be facilitated this new design easier. The manuscript is well written and should be published. However, still errors can be found as follows:

 

Typo in the Figure caption of Fig. 5: Simulated at “0.8 AA” neutron wavelength.

In the figure caption of 5: It seems the neutron wavelength used is 8 A, while in the main text (line 139) , it stated that the neutron wavelength is 9 A. Which one is correct? In order to compare the unexpected result in Fig. 4, the neutron wavelength of 0.8 A should be better.

Line 154: “because the angle of incidence is too high for this m-value a such a short wavelength.”  It seems typo in this part of sentence/

Traditionally, the table caption should be placed on the top of table. However, in the table A1-A3,  the table captions were placed below the table. It is better to correct them.

Author Response

This work aims to perform a systematic study on optimizing long neutron guides. Especially, study the effect of piecewise linearly tapering approximation of elliptical guides. The research using ray tracing method and find that a piecewise linear guide with a surprisingly long piece length, up to 10 m, perform almost as good as a fully elliptical guide for neutron between 2 and 5 ˚A, and guides with piece lengths of 3 m and below have performances equal to that of fully elliptical guides at all wavelengths. This is a major achievement for the design of new beamlines of spallation neutron sources. The mirror engineering can be facilitated this new design easier. The manuscript is well written and should be published. However, still errors can be found as follows:

Typo in the Figure caption of Fig. 5: Simulated at “0.8 AA” neutron wavelength.

We have changed AA to Å.

 

In the figure caption of 5: It seems the neutron wavelength used is 8 A, while in the main text (line 139) , it stated that the neutron wavelength is 9 A. Which one is correct? In order to compare the unexpected result in Fig. 4, the neutron wavelength of 0.8 A should be better.

We have corrected the mistake in the text, as the used neutron wavelength was 0.8 A.

 

Line 154: “because the angle of incidence is too high for this m-value a such a short wavelength.” It seems typo in this part of sentence.

We have corrected the typo.

 

Traditionally, the table caption should be placed on the top of table. However, in the table A1-A3, the table captions were placed below the table. It is better to correct them.

We appreciate your comment. This is, however a layout decision, so we leave this decision to the journal. We have therefore not changed the positions of our table captions.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have revised the paper in response to the comments, and I therefore recommend it for publication in this esteemed journal

Comments on the Quality of English Language

Now ok