G-Band Broad Bandwidth Extended Interaction Klystron with Traveling-Wave Output Structure
and Yang Yan 1
Round 1
Reviewer 1 Report
Review on G-band Board Bandwidth Extended Interaction Klystron with Traveling Wave Output Structure
I have completed my review on manuscript Electronics-1914481, entitled, “G-band Board Bandwidth Extended Interaction Klystron with Traveling Wave Output Structure.” To create the broad bandwidth EIK, a large-sized beam tunnel, G-band extended-interaction klystron (EIK) with traveling wave output structure is researched. To estimate the bandwidth characteristics of cluster cavities, the high-quality factor F is introduced, and the coupling hole parameters are tuned to enhance the coupling impedance and dispersion. The device's simulation mode is created using commercial 3-D particle in cell (PIC) simulation software. In terms of output power and gain, the EIK with traveling wave output structure outperforms the traveling wave tube and has a shorter longitudinal length. Meanwhile, the device has significant potential for improving EIK bandwidth and creates critical groundwork for the design and development of a new generation of terahertz radiation sources.
Overall merit of the manuscript
I found the paper was worthy of publishing in Electronics. I have some comments and concerns on the present form of manuscript which need to be addressed first before publication.
Comments for authors on the present form of manuscript
Comment 1. In my opinion the abstract need significant modifications. What is the novelty of this work? This information is not conveyed clearly in the abstract section. Furthermore, include some concluding remarks of the findings at the end of abstract.
Comment 2. Vacuum electronics is an emerging topic of research for future applications such as radar, satellite communications, military, and medical domains. Only TWT and Klystron were mentioned in the background information. I urge that authors include information about vircators, which are also recognized as the best class of oscillators in vacuum electronics. The following recommendations are for authors who achieve record efficiency in vircators. I advise using it to strengthen your background knowledge for vacuum electronic research.
-Output-power enhancement of vircator based on second virtual cathode formed by wall charge on a dielectric reflector. IEEE Trans Electron Devices 2022. [https://doi.org/10.1109/TED.2022.3149455].
-An efficient vircator with high output power and less drifting electron loss by forming multi virtual cathodes. IEEE Electron Device Lett 2022: 1. [https://doi.org/10.1109/LED.2022.3200395].
-Multivircator as a New Highly Effective Microwave Generator With Multiple Virtual Cathodes: Concept and PIC-Simulation. IEEE Trans Plasma Sci 2020; 48: 141–5. [https://doi.org/10.1109/TPS.2019.2956833].
These publications should be included in the introductory section of this manuscript.
Comment 3. In line 29, “further increase of operating frequency” need to revised as “further increase in operating frequency.”
Comment 4. In line 31, “which is resulted from a longer slow wave structure” should be replaced with “which resulted from a long slow wave structure.”
Comment 5. In lines 48 – 49, “…bunching bandwidth can be expanded by increases the number…” consider replacing it with “…bunching bandwidth can be expanded by increasing the number…”.
Comment 6. In lines 58 – 59, The sentence “The high frequency structure of the device is in the form of five cavities, whose frequency are stagger distribution around the center frequency.” Reading this statement seems a little strange. I suggest that authors improve this sentence and remove the grammatical errors.
Comment 7. In line 67, “…periodically distribute in the outer…” consider replacing it with “…periodically distribute on the outer…”
Comment 8. In lines 83, 209, The singular noun “characteristic” follows a number other than one. Consider changing the noun to the plural form.
Comment 9. The caption for all Figures is too brief to communicate the point. I urge that authors enhance and provide more information to the legend in Figures.
Comment 10. In line 120, it seems that Figure may not agree in number with other words in this phrase. Consider replacing it with “Figures.”
Comment 11. In line 134, “consist” consider replacing it with “consists.”
Comment 12. In line 138, “different angle and height” consider replacing it with “different angles and heights.”
Comment 13: There are typos and inaccuracies in the paper, with many grammatical errors that make it difficult to comprehend the precise meaning of statements. It is difficult for me to list everything; therefore, I suggest that authors carefully read the article and address all grammatical errors.
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The article presents an interesting design and simulation study of the G-band EIK with a traveling-wave output structure. The obtained bandwidth of 1.25 GHz is really high. The article would be interesting for the vacuum electronics community. However, I found lack of some important details, which should be added to improve the clarity of presentation. The main critical points are as follows:
1. It would be great if the authors compare performance of the device with other designs of G-band EIKs. For example: F. Zhang et al., doi: 10.1109/TED.2022.3184919; R. Li et al., doi: 10.1109/TED.2018.2846580; maybe there are other works. What is the main advantage of the proposed design? Is it the traveling-wave output structure or the three-coupling hole structure or something else?
2. In the Introduction, it is mentioned that the large-sized beam tunnel is advantageous to achieve high power. Please provide the tunnel diameter and the beam filling factor.
3. In the Conclusion, it is mentioned that “we have tuned each cavity frequency and distributed it stagger around the center frequency”. Could you provide more information on design methodology? How did you optimize frequencies and Q-factors?
4. In the Conclusion, it says that the EIK is shorter and provide higher power than TWT. Could you add any information on performance of G-band TWTs?
5. I suggest rename Sec. 2 and 3 because actually Sec. 2 describes the results of design and simulation of cold-test parameters of the interaction structure and Sec. 3 describes simulation of beam-wave interaction.
6. In Sec 2.2, it says that π/10 and 2π/10 modes are set as operation modes of the output structure. However, from Fig. 5(a) it follows that they are actually 2π-π/10 and 2π-2π/10 modes.
7. Caption to Fig. 4 might be clarified. I guess that Figures (a) and (c) calculated at h=0.2 mm and various θ, while Figures (b) and (d) at θ=50o and various h.
8. English needs a substantial editing. There are many typos, grammar and punctuation mistakes, and poorly worded sentences. For example:
a) lines 75-76: “impedance and coupling coefficient, respectively. Which are expressed as …” à “impedance and coupling coefficient, respectively, which are expressed as …”
b) line 79: “Where Ez is …” à “where Ez is …” or “Here Ez is …”
c) line 80: “TM01-2π mode set as the operating mode” à “TM01-2π mode is set as the operating mode”
d) lines 110-111: “Using the eigenmode simulation of the CST, and combine with numerical calculation. Based on the above analysis, and fine-tune parameter d to optimize the frequency distribution of each cavity”. Please reformulate.
e) line 124: “As shown in the Figure 4. The coupling impedance increases …” à “As shown in the Figure 4, the coupling impedance increases …”
f) line 146: “Teala” à “Tesla”
g) line 152: “and then gradually further modulated” à “and then is gradually further modulated”
h) line 157: “Which indicate that the system is stable and self-oscillations has not occurred” à “This indicates that the system is stable and self-oscillations have not occurred.”
And so on. Definitely, the manuscript needs careful editing before publication.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I have completed my review on the changes made by the authors in the revised version of this manuscript. In the revised version, the authors addressed all of my remarks and concerns. The manuscript is now suitable for publication in Electronics. I suggest that this work be published in its current form.
Author Response
We thank the reviewer for their time and effort in reviewing our manuscript.
Reviewer 2 Report
The authors revised the manuscript according the reviewer's comments/suggestions. They provide reasonable answers to the questions. The clarity of presentation has been improved. However, I have some doubt in provided value of beam radius (0.12 mm) while the beam tunnel radius is 0.13 mm. Is such a high filling factor really feasible? It seems that a very small misalignment may cause quite strong beam interseption. Please comment.
Author Response
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Author Response File: Author Response.pdf
