Cosmic-Ray Tomography for Border Security

Round 1

Reviewer 1 Report

This review is well written and covers a very extensive literature with fairness and enough detail to allow the reader to have a good understanding of the current status of CRT applied to border security.

Author Response

Dear Reviewer,

Thank you for giving us the opportunity to submit  the manuscript Cosmic-Ray Tomography for Border Security" for publication in the Journal of Instruments-MDPI. We appreciate the time and effort you dedicated to providing feedback on our manuscript and are grateful for the insightful comments to our paper.

Reviewer 2 Report

Dear Authors,
thanks for this review of available detector techniques for cosmic-ray tomography.
Although it is remaining qualitative in many aspects, as probably unavoidable for a review of so many detectors and methods, it is providing a good overview of the methods currently studied and applied.
Please find below some detailed comments:

- line 462: the sentence might be rephrased in a bit more clear way, for example clarifying why two vertical surfaces are expected to be covered ?

- line 478: tools -> tool

- line 495: the position sensitivity needed to obtain 10 mrad angular resolution depends on the detector setup ( number of planes and most of all the distances among them). So it would be better not to mention here 500 microns as reference. In fact in the following you report detectors with
position resolutions very different from that but still angular resolutions in the ~10 mrad range

- line 540: theta and phi have not been defined. If they are mentioned they should be described in relation to the detector setup and geometry

- line 547: it would be useful to indicate to which points in Fig 11 right the two materials correspond

- line 548: in this section ( but also in all other sections describing drift detectors ) it would be useful to add more details on e.g. the gas mixture used.

- line 558: why is in this case the scanning time needed larger than in other cases ? ( given that the resolution is in the range of 500 microns that was stated before to be the needed resolution ). Maybe an additional explanation could be given.

- lines 577-579: here accuracies are quoted ( without errors ) but immediately after it is said that the results taken at different times differ significantly from each other because of the low efficiency. But does this mean that the stat errors are large ? ( it doesn't seem to be the case based on the previous sentence ). Or that the results are not reproducible ? ( i.e. the systematic component is large ). And why is the detection efficiency low ?

- line 642: why now the resolution for protons is mentioned ? ( they should not be relevant for cosmic-rays tomography ).

- line 646: in this case a 3.5 mm resolution corresponds to a 7 mrad resolution. Does it depend on the detector layout ?

- line 682: the efficiency expression is not clear, probably 0.9^16 is meant, i.e. the efficiency of the single layer is 90% ? Maybe this can be explained better ? Are all 16 layers needed for track reconstruction ? Decreasing the majority the efficiency could otherwise be increased a lot.

- line 696: here probably 120 micron per layer is meant ?

- line 712: is a reference for "Anger logic" available ?

- Figure 15: the names of the algs are not visible when printing in black and white

- line 617-619: this has already been said before in the document

- line 830: the acronyms of the various models (e.g. PoCA) have already been defined before.

- line 865: is it -> is that it is

- line 878: (see ... the extended ) -> ( see ... for an extended )

- line 966: has SVM been defined ?

- line 981: the sentence seems somehow truncated

- line 992: segregated -> separated

- line 1109: categorized -> categorize

- line 1122: that their combination -> so that their combination

Author Response

Dear Reviewer, 

Thank you for giving us the opportunity to submit a revised draft of the manuscript "Cosmic-Ray Tomography for Border Security" for publication in the Journal of Instruments-MDPI. We appreciate the time and effort you dedicated to providing feedback on our manuscript and are grateful for the insightful comments and valuable improvements to our paper. 

We have incorporated the suggestions. Please see the attachment, we provide the changes in green for a point-by-point response to the reviewers’ comments. The line numbers refer to the revised manuscript file. I hope that these changes have addressed your concerns and improved the clarity and quality of the paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear Authors,

thanks for the new document, I am happy with the modifications implemented and with the answers provided.