Module Tester for Positron Emission Tomography and Particle Physics

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript introduced a setup to test the LYSO + SiPM modules that are already bonded but without boxing. 

The authors give a detailed explanation of the experimental and data analysis setup. However, the goal of the setup, which is to measure small deviations of the bonding, is lacking in detail. If Fig.17 and 18 are the final result, more explanation is needed (e.g. what does the red line in Fig.17 stand for, what can we learn from these two plots). 

My other comments about the format/language of the manuscript:

1. Page.6, `opposite` is spelled `opposit`, `by` is spelled `my`.

2.  On page 8, some words are crossed. On page 9, some words are bolded. 

3. The font size in various plots needs to be bigger.

4. There are some abbreviations that I feel are unnecessary. For example, HV (stands for high voltage).

Author Response

Comment 1: Page 6, 'opposite' is spelled 'opposit', 'by' is spelled 'my'.

Response: Thank you for pointing this out. We have corrected these typos. 'Opposite' can be found corrected in line 186 and 'by' in line 189, both on page 6.

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Comment 2: On page 8, some words are crossed. On page 9, some words are bolded.

Response: We appreciate your observation. The crossed-out words have been removed, and we have adjusted the bold formatting as well.

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Comment 3. The font size in various plots needs to be bigger.

Response: Changed it.

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Comment 4: There are some abbreviations that I feel are unnecessary. For example, HV (stands for high voltage). 
Response: Thank you for your comment. We acknowledge your point regarding the unnecessary abbreviations. We have revised the manuscript to remove the abbreviations for Bq, eV, HV, and RAM, which are commonly understood.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

I have reviewed your manuscript titled "Module Tester for PET and Particle Physics" for the journal Electronics. I recognize the significant effort you have put into developing instruments for positron emission tomography and particle physics applications. The topic is highly relevant, and your study provides valuable insights into the design of the module tester and the use of Monte Carlo simulations to analyze the module tester's response to a Cs-137 radioactive source.

However, after a thorough analysis, I believe that the manuscript would benefit greatly from a major revision. While the foundation of your study is strong, there are areas that need further refinement to improve the overall impact and clarity of your findings.

I will be providing detailed general and specific comments separately. These comments are meant to help you strengthen your arguments, clarify your results, and ensure that your research is presented as effectively as possible.

I strongly encourage you to carefully consider these revisions, as they are aimed at enhancing the quality and rigor of your manuscript. Your research has the potential to make a significant contribution to the field, and I am confident that with these adjustments, your work will be well-received by the medical and high energy physics community.

Thank you for allowing me to review your work. I am looking forward to seeing the revised version of your manuscript.

Best regards,

Reviewer.

 

General comments.

An abstract helps readers quickly understand the main goals and key findings of your study without needing to read the whole paper. While it is acceptable to use abbreviations in an abstract, it is important to define them the first time they appear to ensure that all readers can comprehend the content. Be sure to define any abbreviations used within the abstract itself.

In the "Introduction" section, provide a summary of key findings from earlier studies that are related to your current work. This will show the reader the groundwork upon which your new study is based. Make sure to include proper citations to acknowledge the work of others in the field.

Please ensure that the notation for numbers is consistent throughout the manuscript. For example, in line 97, it is written as "1 MHz," whereas in line 101, it is written as "1MHz." Sometimes there is a space between the unit value and its dimensions, and sometimes there is not. Consistency in notation will help maintain clarity throughout the document.

Please update the abbreviation list at the end of the manuscript to ensure it includes all the abbreviations mentioned in the text. Also, make sure to define each abbreviation the first time it appears within the main text, even if you have already defined them in the abstract. Since the abstract is often read separately from the main text, the definitions provided there might not be recalled by the reader when they read the rest of the paper.

The conclusion section is not included in the manuscript.

 

Specific comments.

Section 2.1. SiPM sensors.

Providing a reference to the manufacturer's website for the Silicon Photomultiplier (SiPM) sensors used in your work can be very helpful for readers. This allows them to obtain detailed specifications and any other relevant information directly from the source.

Section 2.2. CMS BTL Tester.

It would be useful for readers if the authors provided a link to the manufacturer's website for the electronic components mentioned in this study.

Lines 115 to 122.

It is not clear what the advantage is of using two parallel DAQ systems to measure radioactive sources. Please explain why a single system is insufficient and what the advantages or disadvantages are of having single versus dual DAQ system configurations.

Sections 2.3 and 2.4.

If it possible for authors, it would be useful to readers to have access to the methods of readout software and shared library to be part of supplementary materials. The Open Science Framework (OSF) platform (https://osf.io) that enables researchers to transparently share their work throughout the entire research life cycle, can help with this idea.

Line 149.

It is unclear which radioactive strengths of Cs-137 were utilized. The provided range of 100 kBq to 1 MBq doesn't logically apply to a single source.

Figure 7.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows.

Figure 8.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows.

Lines 156, 157.

There is no dominant 667 keV gamma radiation emitted during the decay of Cs-137 (https://www.nndc.bnl.gov/nudat3/decaysearchdirect.jsp?nuc=137Cs&unc=NDS).

Lines 162 to 167.

The explanation given in this section is confusing. If the focus is on explaining the decay mechanism of Cs-137 and how the 667 keV gamma rays (see previous comment) interact with scintillation materials, it is unclear why the typical range of 100 keV to 2 MeV gammas for nuclear reactions is mentioned here. 

Lines 164 to 165.

Please provide a citation for the information stating that "Since the light yield of the LYSO crystal is about 32,000 photons per 1000 keV."

Line 184.

It is not clear what "PDE" stands for.

Line 187.

The meaning of "my optical methods" is not clear.

Figure 9.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows. 

Figure 9 (b).

The graph is unclear. The text mentions "Plotting the mean and its standard deviation of the Gaussian fit of the 16 photopeaks," but the graph displays three lines labeled: "photopeak," "trig by negative," and "trig by positive." Extra explanations are needed to clarify where the standard deviation is illustrated in the Figure 9 (b) graph.

Figure 10.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows. 

Line 210.

The meaning of "ptical tests" is not clear.

Lines 203 to 208.

This section's explanation is unclear. Why are the waveforms offset, and why is this important for cross-talk measurement?

Section 4.

If the authors can, it would be beneficial for readers if the source code used for Geant4 Monte Carlo simulations is included in the supplementary materials. The Open Science Framework (OSF) platform (https://osf.io) that enables researchers to transparently share their work throughout the entire research life cycle, can help with this idea.

Line 217.

Please also include a reference to the GEANT4 website.

Line 241.

Can you please provide evidence to demonstrate that using only 1% of the light yield will produce the same results as using 100% of the light yield?

Line 242.

Refer to the source where "the actual light yield of LYSO, which is approximately 32000 photons per MeV" has been measured.

Lines 248, 249.

Geant4 includes a feature known as the radioactive decay module, which is capable of simulating all the particles emitted during the decay of Cs-137. Did you use this option, or did you simply simulate a single gamma source with an energy of 667 keV (please see comment for lines 156, 157)? Please provide more details.

Lines 253, 254.

The photo in Figure 7 (a) illustrates that the Cs-137 radioactive source is encased in transparent plastic. Were the geometry and materials of the Cs-137 source simulated, or was the source approximated as a point-like object? Please provide more details, as this information might affect the simulation outcomes.

Lines 277 to 279.

To simulate the waveform of a single optical photon, the authors suggested using a model described in lines 259 and 261, involving a linear fit for the rising edge and an exponential fit for the falling edges. The caption in Figure 13 mentions: "Slopes from linear fitting of the left and right waveform." However, the authors also state that "we randomly select values from the distributions of the rising edge (Figure 13) and the falling edge (Figure 13) of the left and right SiPMs." How was the selection for the falling edges organized?

Lines 281, 282.

The number of photons detected by each SiPM was determined using Geant4 simulations. Have you adjusted the simulation results to account for the 1% light yield that was used to expedite the simulations? If so, please explain how this adjustment was implemented.

Author Response

Comment: In the "Introduction" section, provide a summary of key findings from earlier studies that are related to your current work. This will show the reader the groundwork upon which your new study is based. Make sure to include proper citations to acknowledge the work of others in the field.

Response: The introduction has been expanded

Comment: Please ensure that the notation for numbers is consistent throughout the manuscript. For example, in line 97, it is written as "1 MHz," whereas in line 101, it is written as "1MHz." Sometimes there is a space between the unit value and its dimensions, and sometimes there is not. Consistency in notation will help maintain clarity throughout the document.

Specific comments.

Section 2.1. SiPM sensors.

Providing a reference to the manufacturer's website for the Silicon Photomultiplier (SiPM) sensors used in your work can be very helpful for readers. This allows them to obtain detailed specifications and any other relevant information directly from the source.

Response: For CMS BTL the sensors are prototype, the most similar sensors were listed

Section 2.2. CMS BTL Tester.

It would be useful for readers if the authors provided a link to the manufacturer's website for the electronic components mentioned in this study.

Response: Added as footnote

Lines 115 to 122.

It is not clear what the advantage is of using two parallel DAQ systems to measure radioactive sources. Please explain why a single system is insufficient and what the advantages or disadvantages are of having single versus dual DAQ system configurations.

Response: Addded in the text, the smaller one if for optimisation, the second is for mass testing

Sections 2.3 and 2.4.

If it possible for authors, it would be useful to readers to have access to the methods of readout software and shared library to be part of supplementary materials. The Open Science Framework (OSF) platform (https://osf.io) that enables researchers to transparently share their work throughout the entire research life cycle, can help with this idea.

Response: Git repository added as footnotes

Line 149.

It is unclear which radioactive strengths of Cs-137 were utilized. The provided range of 100 kBq to 1 MBq doesn't logically apply to a single source.

Response: you are right, we used several sources during the test, corrected in the text.

Figure 7.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows.

Response: Added the summary

Figure 8.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows.

Response: Added the summary

Lines 156, 157.

There is no dominant 667 keV gamma radiation emitted during the decay of Cs-137 (https://www.nndc.bnl.gov/nudat3/decaysearchdirect.jsp?nuc=137Cs&unc=NDS).

Response: Thanks, typo, it is 661.657 keV (I will use 662, since this is not a precise calorimeter, this module will be use for timing) with 85%

Lines 162 to 167.

The explanation given in this section is confusing. If the focus is on explaining the decay mechanism of Cs-137 and how the 667 keV gamma rays (see previous comment) interact with scintillation materials, it is unclear why the typical range of 100 keV to 2 MeV gammas for nuclear reactions is mentioned here. 

Response: Removed the confusing sentence.

Lines 164 to 165.

Please provide a citation for the information stating that "Since the light yield of the LYSO crystal is about 32,000 photons per 1000 keV."

Response: Added

Line 184.

It is not clear what "PDE" stands for.

Response: Added to the "Abbreviations", it is the photon detection efficiency, the probability that a photon causes a hit in a pixel of the SiPM

Line 187.

The meaning of "my optical methods" is not clear.

Response:  Changed the text to be clear, it's a geometrical test done by an another group, I found a poster about it, it's in the footnote now

Figure 9.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows. 

Response:  Added more detailes in the text

Figure 9 (b).

The graph is unclear. The text mentions "Plotting the mean and its standard deviation of the Gaussian fit of the 16 photopeaks," but the graph displays three lines labeled: "photopeak," "trig by negative," and "trig by positive." Extra explanations are needed to clarify where the standard deviation is illustrated in the Figure 9 (b) graph.

Response: Explained in the text

Figure 10.

The caption for the figure isn't very helpful and doesn't give much detail. Please summarize what the figure shows. 

Response:  Add short explanation

Line 210.

The meaning of "ptical tests" is not clear.

Response:  corrected

Lines 203 to 208.

This section's explanation is unclear. Why are the waveforms offset, and why is this important for cross-talk measurement?

Response:  Removed the 'waveform offset...' sentence, and explained in earlier, in the Measurement section. 

Section 4.

If the authors can, it would be beneficial for readers if the source code used for Geant4 Monte Carlo simulations is included in the supplementary materials. The Open Science Framework (OSF) platform (https://osf.io) that enables researchers to transparently share their work throughout the entire research life cycle, can help with this idea.

Response: added the git link

Line 217.

Please also include a reference to the GEANT4 website.

Response: Thank you for the suggestion. We have included a reference to the GEANT4 website (ref. 8) as requested.

Line 241.

Can you please provide evidence to demonstrate that using only 1% of the light yield will produce the same results as using 100% of the light yield?

Response: we repeated the simulations with 33k optical photon / 1 MeV to have the correct estimation.

Line 242.

Refer to the source where "the actual light yield of LYSO, which is approximately 32000 photons per MeV" has been measured.

Response: We have added the reference for this

Lines 248, 249.

Geant4 includes a feature known as the radioactive decay module, which is capable of simulating all the particles emitted during the decay of Cs-137. Did you use this option, or did you simply simulate a single gamma source with an energy of 667 keV (please see comment for lines 156, 157)? Please provide more details.

Response: We simply used a 662 keV gamma source and did not utilize the radioactive decay module in Geant4. The other dacey channels would increas only the backgrounds and not the photopeaks we used for this analysis.

Lines 253, 254.

The photo in Figure 7 (a) illustrates that the Cs-137 radioactive source is encased in transparent plastic. Were the geometry and materials of the Cs-137 source simulated, or was the source approximated as a point-like object? Please provide more details, as this information might affect the simulation outcomes.

Response: It's a pointélike object in the simulation, any interaction (Compton scattering) with the plastic give hits in the background.

Lines 277 to 279.

To simulate the waveform of a single optical photon, the authors suggested using a model described in lines 259 and 261, involving a linear fit for the rising edge and an exponential fit for the falling edges. The caption in Figure 13 mentions: "Slopes from linear fitting of the left and right waveform." However, the authors also state that "we randomly select values from the distributions of the rising edge (Figure 13) and the falling edge (Figure 13) of the left and right SiPMs." How was the selection for the falling edges organized?

Response: We have corrected the figure reference from "Figure 13" to "Figure 14" for the falling edge in the revised version.

Lines 281, 282.

The number of photons detected by each SiPM was determined using Geant4 simulations. Have you adjusted the simulation results to account for the 1% light yield that was used to expedite the simulations? If so, please explain how this adjustment was implemented.

Response: we repeated the simulations with 33k optical photon / 1 MeV to have the correct estimation. 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all of my comments.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for addressing my comments and suggestions. The revised version of the manuscript titled "Module Tester for PET and Particle Physics" has significantly improved, and I would recommend it for publication in the journal Electronics.

I appreciate that the text changes were highlighted, making the review process much easier. Additionally, thank you for providing the links to the manufacturers' websites and the electronic components used in this research. It is also beneficial for readers to have access to the analysis code/program used in this study.

Reviewer.