Longitudinal Tension and Mechanical Stability of a Pressurized Straw Tube

Round  1

Reviewer 1 Report

The paper is a technical paper. It focuses on determining the ratio of inner pressure to longitudinal tension to avoid buckling of the tube. They have build a bench bank to measure the minimal tension needed and they describe clearly their procedure.   The problem is treated from the mechanical engineering point of view. and  is described in a pedagogical way to be understood by physicist.

The paper is well written but lacks  in the introduction of a description of related work in the field of straw tubes working in vacuum done for different collaborations. It does not report on current or past work on the use of straw tubes in instrumentations, and how the tension needed was determined, outside of NA62. Other current  collaborations as PANDA and Mu2e have a straw tube tracker working in vacuum and they have been used often in the past. Maybe,  this aspect should have been treated to reinforce  the interest of the paper.

Author Response

Response to Reviewer 1 Comments

Point 1: The paper is well written but lacks  in the introduction of a description of related work in the field of straw tubes working in vacuum done for different collaborations. It does not report on current or past work on the use of straw tubes in instrumentations, and how the tension needed was determined, outside of NA62. Other current  collaborations as PANDA and Mu2e have a straw tube tracker working in vacuum and they have been used often in the past. Maybe,  this aspect should have been treated to reinforce  the interest of the paper.

Answer 1: Unfortunately, in the found published technical documents people don't explain how they determine the required tension. May be they use values tested empirically, or just make their calculations using the published very approximate Poisson's ratio and apply a large safety margin. But we agree that the list of related experiments should be increased. So now the following new paragraphs are added to the Introduction:

"Another example of a physical problem that requires very accurate tracking of charged
particles is Mu2e experiment, which will measure the conversion of a negative muon into
an electron in the field of a nucleus \cite{Bartoszek:2014mya}."

"If pressurized straw tubes are close-packed and glued together to planar multi-layers, they form a stable structure. This approach is implemented, for example, for PANDA trackers \cite{Costanza:2010zz,Gianotti:2013ipa}. But a very small material budget can lead to a detector design with separate straws \cite{NA62:2017rwk,Buonaura:2016gho,Bartoszek:2014mya}. In this case, the problem of lateral stability of straws is important, and the minimum required tension applied to the straw should be evaluated. In particular, straws in the NA62 spectrometer are separated in space and strained \cite{NA62:2017rwk}. They are fixed in one lateral direction by means of thin wires and light spacers."

Reviewer 2 Report

Section-1

[Line-10]: Ref[1,2] is technical design document, but should be more general article reviewing the kaon rare decay experiments.

[Line-20] “R” should be explained later, since it is not contained in Eq-(1)., eg. should be explained in Line-21 or 22.

Section-2.4

[Line-125]: “is small.” -> “is small enough.“

Section-3.1

[Table.1] What are numbers in each bracket ?

Section-3.2

[Line-173]: The info about glue should be provided.

General Comments:

The main measurement and its consideration looks reasonable and interesting. As described in the article, this work is very useful especially for the researcher who is using/constructing the straw tracker operating in vacuum. The description in Section 3-5 is acceptable without major revise. However, Section 2 is too diffuse. The description in Section 2 is useful, but it is not a new knowledge. Knew knowledge in this article, and main subject, is Section 3-5, of course. Thus I would suggest following revision;

(Suggestion-1) Shorten Section 2 to make your article more comfortable to read.

or

(Suggestion-2) Move Section 2 to Appendix and put a short version of Section 2 to provide some essential equations to be referred in the following sections.

Author Response

Response to Reviewer 2 Comments

Point 1: [Line-10]: Ref[1,2] is technical design document, but should be more general article reviewing the kaon rare decay experiments.

Answer 1: Now we put here a reference to the published paper on the NA62 beam and detector.
Available more general reviews of the kaon experiments do not include the technical issues related to the present paper. But now the introduction includes the mention of two more experiments (requested by another Reviewer).

Point 2: [Line-20] “R” should be explained later, since it is not contained in Eq-(1)., eg. should be explained in Line-21 or 22.

Answer 2: Thank you, now it is corrected.

Point 3: [Line-125]: “is small.” -> “is small enough.“

Answer 3: Done.

Point 4: [Table.1] What are numbers in each bracket ?

Answer 4: They represent uncertainties in terms of the last significant digits.
It may be an old-fashioned notation, so we have edited the table to use more common one.


Point 5: [Line-173]: The info about glue should be provided.

Answer 5: Now we add "...using glue TRA-BOND 2115 \cite{...".


Point 6: The main measurement and its consideration looks reasonable and interesting. As described in the article, this work is very useful especially for the researcher who is using/constructing the straw tracker operating in vacuum. The description in Section 3-5 is acceptable without major revise. However, Section 2 is too diffuse. The description in Section 2 is useful, but it is not a new
knowledge. Knew knowledge in this article, and main subject, is Section 3-5, of course. Thus I would suggest following revision;
(Suggestion-1) Shorten Section 2 to make your article more comfortable to read. or
(Suggestion-2) Move Section 2 to Appendix and put a short version of Section 2 to provide some essential equations to be referred in the following sections.

Answer 6: Thank you, we mainly accept your Suggestion-2. We move the Section 2 to Appendix, and all the needed equations are now referred directly from there.
We just add the following sentence to the end of Introduction:
"The equations used, which determine the behavior of straw under internal pressure, are given in Appendix."

Reviewer 3 Report

General remarks:

The content and results of the paper are interesting for straw detector developments based on thin wall tubes for minimal material budget. The paper describes in detail the formulas, measurements and obtained results for straw specifications in the NA62 experiment. The results therefore have high significance for this experiment, but the paper is also interesting for straw detector developers in general as a collection of the principles and formulas describing the film tube properties of pressurized straws.

The effect of the longitudinal welding (seam?) on the Poisson's ratio measurements and formulas are not discussed. For instance, measurements of the straw buckling (Fig. 2) could be done with the welding located at the bottom side and next at the top side of the tensioned tube.

The general the straw configuration in the NA62 tracker is not described. For instance, the buckling behaviour might be different if straw tubes are glued or packed together.

The paper shows a very good command of the english language and is easy to read.

Detailed comments:

Fig. 3 and 4: pressure unit (atm) instead of (at)

Table 2: Explanation is missing, why k values are different in sign for the two specimen. This gives an opposite contribution of the tension dependent tension in eq. (14). The values of radius correction, radius value, T, and P scale are not clearly described in the text. 

line 211, 212: Remark is unclear and not explained from the table.

line 226: A value of 0.34 for mu_perp for specimen 1 is not consistent with 0.37-0.44. Please rephrase, use a weaker statement.

Author Response

Response to Reviewer 3 Comments


Point 1: The effect of the longitudinal welding (seam?) on the Poisson's ratio measurements and formulas are not discussed. For instance, measurements of the straw buckling (Fig. 2) could be done with the welding located at the bottom side and next at the top side of the tensioned tube.

Answer 1: We add the following sentence at the line 173 (the paper first version numbering):
" A longitudinal straw seam is located on a side to reproduce the conditions of the NA62 spectrometer for horizontal straws. The seam can change the measured values, but the violation of axial symmetry is considered insignificant when long straw is strained."

Point 2: The general the straw configuration in the NA62 tracker is not described. For instance, the buckling behaviour might be different if straw tubes are glued or packed together.

Answer 2: Now we add the relevant information to the Introduction:
"If pressurized straw tubes are close-packed and glued together to planar multi-layers, they form a stable structure. This approach is implemented, for example, for PANDA trackers \cite{Costanza:2010zz,Gianotti:2013ipa}. But a very small material budget can lead to a detector design with separate straws \cite{NA62:2017rwk,Buonaura:2016gho,Bartoszek:2014mya}. In this case, the problem of lateral stability of straws is important, and the minimum required tension applied to the straw should be evaluated. In particular, straws in the NA62 spectrometer are separated in space and strained \cite{NA62:2017rwk}. They are fixed in one lateral direction by means of thin wires and light spacers."

Also we make the following replacement:
"Therefore, estimation of the minimum pre-tension of the straw is necessary for any design of a straw tracker operating in vacuum." ->
"Therefore, estimation of the minimum pre-tension of the straw is necessary for any design of a straw tracker based on separated straws operating in vacuum."

Point 3: Fig. 3 and 4: pressure unit (atm) instead of (at)

Answer 3: Now we add the following sentence: "The units of technical atmosphere at are used for the overpressure values P." (Pressure unit "atm" means "standard atmosphere" = 1.033227452799886 technical atmospheres).


Point 4: Table 2: Explanation is missing, why k values are different in sign for the two specimen. This gives an opposite contribution of the tension dependent tension in eq. (14).

Answer 4: Now we will mention in the text (see the Answer 6) that the value of k for the second specimen has a large measurement uncertainty, which covers the entire difference between the specimens.


Point 5: The values of radius correction, radius value, T, and P scale are not clearly described in the text.

Answer 5: The following changes have been made to make the description more clear (the paper first version numbering is used here):
line 213: "...The radius correction effect is considered, but it is also..."  ->

             "...The radius correction (13) is taken into account, but its effect is also..."
line 217: "...diameter systematic uncertainty of 0.1 mm for the tested specimens..."  -> 

             "...radius systematic uncertainty of 0.05 mm for the tested specimens..."
line 218: "...the effects of systematic scale shift of 5% on both the measured effective tension and measured pressure..." ->
          "...the effects of scale change by the factor of 1.05 for both the measured effective tension $T_P$ and measured overpressure $P$ ..."


Point 6: line 211, 212: Remark is unclear and not explained from the table.

Answer 6: You are right, the correlation coefficients are not informative here, so we remove them. The sentence is now rephrased as follows:
"For the second specimen, the uncertainty of the nonlinearity coefficient k is so large that its measured value is consistent with both zero and the result for the first sample."


Point 7: line 226: A value of 0.34 for mu_perp for specimen 1 is not consistent with 0.37-0.44. Please rephrase, use a weaker statement.

Answer 7: The error of measurement given in the Table for this case is 0.035. So we rephrase the statement as follows:
"...the obtained mu_perp values are consistent with them, given the uncertainties of our measurements."

Reviewer 4 Report

The article has been carefully prepared and its content is of interest for people building straw tube detectors. Therefore, I suggest to accept it for publication.

Author Response

Response to Reviewer 4 Comments


Point 1: The article has been carefully prepared and its content is of interest for people building straw tube detectors. Therefore, I suggest to accept it for publication.

Answer 1: Thank you, we hope that the improvements motivated by other reviewers will also be satisfactory for you.