Nb₃Sn Cavities Coated by Tin Vapor Diffusion Method at Peking University

Round 1

Reviewer 1 Report

The manuscript presents efforts by a team of researchers at PKU towards Nb3Sn superconducting RF cavities. Nb3Sn is a relatively new material for SRF cavities, and this research group is one of only a half dozen or so around the world (they cite Cornell, JLab, Fermilab, and KEK as others) to successfully make Nb3Sn SRF cavities by the vapor diffusion technique.

They show that it took some time to achieve strong results, but eventually they were able to reach reasonable accelerating gradients with high Q. Most cavities were limited at ~10 MV/m, but one reached 17 MV/m, which is quite good. The authors should be commended for showing that this took significant efforts, in that this was their 23^rd coating.

It’s a nice study and good reproduction of previous results but not really much novelty. It does have a nice assembly of relevant information, though again each of these analyses have been done by previous authors, and none of the results stand out as substantially novel compared to them. It’s probably okay for an Applied Science journal.

The authors could have done a better job at citing the literature. They should add references to the pioneering work in the field by Siemens (Hillenbrand et al) and Wuppertal (Peiniger et al.) from the 1970s. Cornell, JLab, etc. learned from them and it is inappropriate to omit the previous efforts from citations. Wuppertal should be cited for suggesting the annealing step (e.g. G. Muller et al EPAC1996). Citations should also be added for Equations 1 and 2 (e.g. direct readers to the Langmuir formula). For section 3.1 it would be worthwhile to cite previous work, e.g. https://indico.fnal.gov/event/14933/contributions/28540/attachments/17987/22615/Simulating_Nb3Sn_Coating_Process_Inside_SRF_Cavities_-_Robert_Ridgway.pdf . Reference 3 is the same as reference 24.

 

For the COMSOL simulations, it is important to explain what was assumed for how tin interacts with the walls. Does the tin stick to the walls and get absorbed? Bounce off? These boundary conditions will have a large impact on the pressure results from the simulations.

Please fix the units on plots. It’s inconsistent across the paper. Some plots use / for units, others (), others should have units added (Fig 17 needs hh:mm for example), others should have units separated from the variable (Figs 18 and 19 the unit MV/m is blended into Eacc). It would also be good to fix up the variables including putting subscripts for Eacc and Q0.

Another small item is that there is an abbreviation in the title of the paper which should be expanded.

There are language errors throughout the text. A language editing service is recommended prior to resubmission.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

There are 14 out of 25 are recent references (56%), and at least 90% are relevant to the paper. Follow the standard reference format; Some references do not have a year, the sequence between year and page is reverse, etc. Find another reference to change the thesis.

Figure must be self-explanatory. Add more detail in the caption for most of the figure.

Improve the SEM and TEM figure quality. Some of the additional text are block the image.

Standardize the graph: compare figure 3, 4, 9, 10, 12, 14 etc.

"It can be found that the samples hung at the bottom of the cavity are invaginated, and the grain of the sample upside is smaller than downside."

Find another word to replace "invaginated"

Author Response

Please see the attachment, thank you.

Author Response File: Author Response.docx

Reviewer 3 Report

 

Journal: Applied Sciences

Manuscript Number:   applsci-2507845

Title: R&D of Nb3Sn Cavities Coated by Three-tin-source Tin Vapor 2
Diffusion Method at PKU  

 

The paper is interesting and can be published in Applied Sciences after undergoing the following corrections.

 

My comments:

1-      I do not prefer to see any abbreviations in the title.

2-      I found some typos. I give here some examples:    “material science, radioactive medicine, environmental science.” should be “material science, radioactive medicine and environmental science.”;             “on samples and single cell cavities were conducted” should be “on samples and single-cell cavities were conducted”;         “University (PKU) to understand Nb3Sn growth process in vapor diffusion method” should be “University (PKU) to understand Nb3Sn growth process in the vapor diffusion method”;         “distributed along cavity axis to obtain a uniform” should be “distributed along the cavity axis to obtain a uniform”;         “Tin segregation effect was found in long time coatings” should be “Tin segregation effect was found in long-time coatings”;         “Nb3Sn cavity with 750 nm grain size were produced by 1200℃” should be “Nb3Sn cavity with 750 nm grain size was produced by 1200℃”;         “The acceleration gradient reached 17.3 MV/m without quench” should be “The acceleration gradient reached 17.3 MV/m without quenching”;         “to accelerate particles by establishing electromagnetic field inside” should be “to accelerate particles by establishing an electromagnetic field inside”;         “The Nb3Sn coated cavity can contribute to build compact accelerating systems” should be “The Nb3Sn-coated cavity can contribute to building compact accelerating systems”;             “Surface roughness are also demonstrated to influence the cavity accelerate” should be “Surface roughness is also demonstrated to influence the cavity accelerate”;           “Samples are produced to separately study the two main process” should be “Samples are produced to separately study the two main processes”;           “the cavity and tin vapor rises to the inside of cavity [3, 7-9, 12-14]” should be “the cavity and tin vapor rises to the inside of the cavity [3, 7-9, 12-14]”;           “cavity as witness sample in every coating experiment” should be “cavity as a witness sample in every coating experiment”;      And there are other typos. Please correct the whole manuscript.

3-        Cite references to the equations of section 3.

4-      Ellipsometry is an advanced technique for thin film characterization. Please mention it and use these references. Microwave and Optical Technology Letters, Vol. 56, No. 12, 2822–2826 (2014). https://doi.org/10.1002/mop.28704                 

I have provided above

Author Response

Please see the attachment, thank you!

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

In my opinion, it can be accepted in the present form.