Over-Size Pill-Box Window for Sub-Terahertz Vacuum Electronic Devices

Round 1

Reviewer 1 Report

Well written manuscript which broadens the authors previous work to higher frequencies.

Small things to improve:

• add space between values units (especially chapter 2 rows 129, 133, 135, etc)
• please present the simulation software that was used in chapter 2
• Figure 6; The first testing is done without sapphire disc? (box 3). Is the sapphire part of the pill-box window or not? The figure 6 does not open up the test process, but confuses it.
• On lines 225-226 is written "According to the structural parameters optimized by the simulation, the components of the over-size pill-box window are processed, as shown in Figure 7." This figures does not show the processing but the components. There are two windows in figure. Are they different or similar? Only one was presented in simulations.
• Figure 8 is poor quality in the pdf version. Also add boxes to the text that the text embedded in figure would be readable.
• Figure 9 is poor quality in the pdf version.
• The measurement results in figure 9 should be compared to the simulation results. 
• Also the effect of the brazing and sapphire metallization could be presented and compared to the final window measurements.

Overall the manuscript is well written but chapter 3 Experimental Results needs more work. Rows 198-237 should be rewritten and re-srtuctured. Also more information of the measurements are required.

Author Response

My detailed response is in the attachment,

Author Response File: Author Response.pdf

Reviewer 2 Report

Some references do not appear in the text ([1,2,3,4,5,9,14,15]). Moreover, first reference should be [1], and not [11]. Please, keep the order of references in the text and write properly the list of references.

Due to the similar structure, figures, results and analyses with reference [1], the differences between it and the current paper must be indicated in the introduction. The novelty regarding [10] must be pointed out. Moreover, since section 2 in both papers are practically the same, all it could be referenced here and not written again.

Sentence in line 45-46 needs a reference.

Line 83: Please indicate the loss factor too, and for which frequency are these data valid.

Eq. (2):

- It´s not complete (right-edge does not appear).

- Explain why M4=I (unit matrix).

- Which is the meaning of * in M2 and M3?

I cannot see how eq. (3) is obtained from [15].  Please explain it in more detail.

Line 133-134: please explain why the length of the circular waveguide must be between the length of the dielectric sheet and a waveguide wavelength.

Line 144-145: please explain (or cite a reference) why the error capacity of the circular waveguide length is the biggest factor affecting the pill-box window test results.

Line 158: Please, check the English grammar in “Perform…”.

Fig. 3: It is not clear for me whether these results are from the theoretical calculations or from EM simulation. Please, clarify it. Moreover, explain what “tridition window” means. I assume you mean “traditional”.

Line 176: there is an “is” missed between “sapphire” and “finally”.

Please, indicate the numerical method and the EM simulation software employed. Moreover, indicate the applied boundary conditions, I mean, is the sapphire outside of the waveguide (open boundary conditions), or is it surrounded by a PEC?

Caption in fig. 5 is wrong. It is not “the simulation structure…”, but the electric field distribution (magnitude) on the XZ plane of the structure. The same for text in line 178-179. In fact, the current figure doesn’t provide information that is used in the text. I propose to change this figure for a more illustrative 3D figure of the simulated structure. In this regard, fig. 7 is too small to understand where are the different parts of the structure and how is the sapphire welded. Please identify on it the different parts / components.

I don´t completely understand paragraph in lines 187-194. Does the large tolerance of L1 and R0 mean that the reflection coefficient is not sensible to small changes on them? I don´t see it in the figure. More data (graphs) should be included justifying the sentence in lines 192-194. Please, clarify this paragraph.

In lines 211 – 215, information is repeated. Please, simplify the text.

In line 220, imperative form is used. Please correct the grammar.

Section 4 should be a “Conclusion”, instead of a “Summary”. Please, change title and text, focusing in the main results and their consequences on pill-box window design and manufacturing.

Author Response

Some references do not appear in the text ([1,2,3,4,5,9,14,15]). Moreover, first reference should be [1], and not [11]. Please, keep the order of references in the text and write properly the list of references.

Re:

Errors in references have been corrected.

Due to the similar structure, figures, results and analyses with reference [1], the differences between it and the current paper must be indicated in the introduction. The novelty regarding [10] must be pointed out. Moreover, since section 2 in both papers are practically the same, all it could be referenced here and not written again.

Re:

" In the W-band, an asymmetric structure is used, and the influence of processing errors on the test results of the box window can be reduced through multiple transmission tests [6]. However, in the G-band, the asymmetric structure cannot solve the problem of too small welding surface, and the air tightness of the pill-box window cannot be guaranteed." Lines 61-65 in the manuscript explain the difference from reference [10], and simplify the formula derivation of the section 2, only the necessary structural parameter equations and equivalent model diagrams are written.

Sentence in line 45-46 needs a reference.

Re:

References have been added.

Line 83: Please indicate the loss factor too, and for which frequency are these data valid.

Re:

In the theoretical calculation, the loss angle is not taken into consideration. "In the simulation, the dielectric constant of sapphire is 9.4, and the dielectric loss tangent is 0.006." added in Lines 146-147 in the manuscript. The loss factors are the HFSS default values.

Eq. (2):

- It´s not complete (right-edge does not appear).

- Explain why M4=I (unit matrix).

- Which is the meaning of * in M2 and M3?

I cannot see how eq. (3) is obtained from [15].  Please explain it in more detail.

Re:

Formula 2 has been deleted, and the * in the matrix of M2 and M3 are mislabeled. Now the matrices M4 and M*4 in the equivalent circuit can be written as:

Where P is the ratio of the radius of the circular waveguide to the radius of the dielectric circular waveguide.

Formula 3 is quoted from the formula 4 in Section 2 of reference [7] "Theoretical and Experimental Study of the Modified Pill-Box Window for the 220-GHz Folded Waveguide BWO." The specific derivation process can be derived from the literature "An Analysis of a Vacuum Window for Lower Hybrid Heating" found.

Line 133-134: please explain why the length of the circular waveguide must be between the length of the dielectric sheet and a waveguide wavelength.

Re:

Added clarification in lines 134-137 in the manuscript.

Line 144-145: please explain (or cite a reference) why the error capacity of the circular waveguide length is the biggest factor affecting the pill-box window test results.

Re:

Added references to the text.

Line 158: Please, check the English grammar in “Perform…”.

Re:

It has been modified in the manuscript.

Fig. 3: It is not clear for me whether these results are from the theoretical calculations or from EM simulation. Please, clarify it. Moreover, explain what “tridition window” means. I assume you mean “traditional”.

Re:

The result in Figure 3 is the simulation result, with a description added in the title. The "tridition" in the Fig 3 is a spelling error and has been corrected

Line 176: there is an “is” missed between “sapphire” and “finally”.

Re:

It has been modified in the manuscript.

Please, indicate the numerical method and the EM simulation software employed. Moreover, indicate the applied boundary conditions, I mean, is the sapphire outside of the waveguide (open boundary conditions), or is it surrounded by a PEC?

Re:

Added clarification in lines 181-185 in the manuscript.

Caption in fig. 5 is wrong. It is not “the simulation structure…”, but the electric field distribution (magnitude) on the XZ plane of the structure. The same for text in line 178-179. In fact, the current figure doesn’t provide information that is used in the text. I propose to change this figure for a more illustrative 3D figure of the simulated structure. In this regard, fig. 7 is too small to understand where are the different parts of the structure and how is the sapphire welded. Please identify on it the different parts / components.

Re:

The fig.5 has been replaced with D figure of the simulated structure. Figure 7 has been changed to Figure 9, and a brazing model diagram has been added to illustrate the welding scheme

I don´t completely understand paragraph in lines 187-194. Does the large tolerance of L1 and R0 mean that the reflection coefficient is not sensible to small changes on them? I don´t see it in the figure. More data (graphs) should be included justifying the sentence in lines 192-194. Please, clarify this paragraph.

Re:

The error analysis results and explanations of L1 and R0 are added to the manuscript (Lines 201-210, Figure 6 and Figure 7).

In lines 211 – 215, information is repeated. Please, simplify the text.

Re:

It has been modified in the manuscript.

In line 220, imperative form is used. Please correct the grammar.

Re:

It has been modified in the manuscript.

Section 4 should be a “Conclusion”, instead of a “Summary”. Please, change title and text, focusing in the main results and their consequences on pill-box window design and manufacturing.

Re:

Section 4 has been revised.

Thank you very much for your review and suggestions!

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

None.