Dear authors, Congratulations on a well written paper and clear paper with very nice results. Below you will find my institutional comments base on v5 of the paper draft. They are divided into "General", "line-by-line" (minor text/clarifying), and "Figure" comments. best, Eva Halkiadakis ============================== Institutional comments on v5 https://twiki.cern.ch/twiki/pub/Sandbox/CROCAnalogFEPaper/12240_RD53A_AFE_evaluation_article_v5.pdf ============================ General: --------- - As stated in lines 150-150, is not the first evaluation of the AFEs, but the first rigorous application of CMS criteria to the measurements. To make this point better, perhaps this should be stated in the introduction instead of the end of section 2. - The "chosen" AFE is none of the three - it's modified LIN, and it only has been simulated, not tested in hardware. This probably also should be emphasized. It is definitely confusing that Figure 7 shows the modified, not tested AFE. - The tests were done at -10C. What is the reason for the choice? Does it matter that it's warmer than the expected CMS environment? - In the title and elsewhere in the text: replace "Phase-2" with "High Luminosity LHC" or "HL-LHC" as appropriate - Some clarification is required on the following: Line 60 states two pitches are considered: 100 x 25 and 50 x 50 but line 93: states 50 um pitch in the demonstrator. So has the choice been made already? This needs some clarity. Perhaps the 50x50 is a tighter constraint on the pixel unit cell from an electronic layout point of view? - Should CMS requirements (Section 3) be discussed before the discussion about the proposed design? Please considier moving that section up. - Section 5,6: Are these "after irradiation"? Should be consistent with Section 4? line-by-line: --------------- - line 13: the NEW Inner Tracker - line 15: processes --> digitizes - line 21: "Moreover a saturation" --> "Moreover, a saturation" (add comma) - lines 22-23: "The Synchronous front-end showed a very good timing performance, but also a higher noise." --> "The Synchronous front-end showed very good timing performance, but also higher noise." - lines 23-24: "The Linear front-end had the slowest time response:" --> I think the ":" should be replaced by a ";" - line 44: inner tracker does not record TRAJECTORIES. It records hits used to reconstruct trajectories. - line 45: remove the sentence "it will be entirely replaced..." Clear form the context, and does not provide the actual information (e.g. what radiation dose current IT would die in, what is its granularity and how it affects reconstruction, etc) - line 53: latest? Is it not final? Change it to "proposed" if it's not final? - line 54: barrel part --> barrel component - line 62: billions --> billion - line 62: "The mass of the detector has to be as low as possible" --> "The detector design strives for a minimal mass of the detector" - line 71: "passive components and connectors, called high density interconnect" --> "passive components and connectors, called the high density interconnect" - line 73: The signal PRODUCED in the sensor is TRANSMITTED to ... - line 75: Here and in few other places where comparisons of the old and new detector: condiser moving them all up to the beginning of section 2? (latency, trigger rate, pixel size, radiation dose) - line 75: "Only after receipt of a Level-1 trigger signal the hit information" --> "Only after receipt of a Level-1 trigger signal is the hit information" - line 87: Is "intellectual property" spelled out not to define IP-blocks? May be just drop "intellectual property"? - line 92: drop ", as it was sharing reticle..." -> what's the point of spelling it out? It's a test chip anyway, no reason for it to be the same size. - line 96-97: long sentence. Break it up as follows: "The analogue-to-digital conversion is performed by the analogue front-end (AFE), whose basic structure (shown in Figure 3) consists of" --> "The analogue-to-digital conversion is performed by the analogue front-end (AFE), whose basic structure is shown in Figure 3. It consists of" - Section 3 title: perhaps consider instead "AFE evaluation criteria" or something similar. "CMS requirements" sounds too general. - line 114: 8x8 pixel cores: are those 2x2 assemblies of the analog islands? If so, please say it explicitly. - line 172: how much fluence did the 150 um sensor get? Its in the Figure, but should be here as well. - line 187: The CMS --> The CMS collaboration - line 189: what does "higher radiation tolerance is privileged" mean? It is never actually spelled out WHAT the spec for radiation dose? It would be good to do that. It seems that there are 4 different numbers: total dose in layer 2, total dose in layer 1, and dose in layer 1 for two different scenarios for layer 1 replacement. Would be good to have them all shown in one place (e.g. in a table?) - line 195: what is the exact justification for setting the noise threshold 100 times below the occupancy? The tracking studies referred to later do not mention it. - line 220: "The impact of the charge resolution on the tracking performance" --> "The impact of charge resolution on tracking performance" - line 221: "The simulation of the tracking performance for the reconstruction of single muons" --> "Simulation of tracking performance for the reconstruction of single muons" - line 392: Isn't CMSSW used already in some of the previous MC simulation studies? If so, then this description should be mentioned earlier (e.g. section 3). Also, CMSSW isn't as important as saying that it's a Geant based simulation etc. - line 395: what kind of hits are used for this? Are they from particles that we have a chance of reconstructing? (i.e. should not include loopers, low pT secondaries, etc) - line 399: what kind of events were generated? And what constitutes a hit here? Is hit = pixel with charge? Since charge sharing is important, this should be very clearly specified. It may not be terrible if the time walk makes second pixel in a cluster detected in a different crossing - while there would be effect on spatial resolution, the other hit could clearly still be used for pattern recognition. - line 406: plot --> replace with figure or graph - line 426: " ...variations in the length of the electrical links, the jitter and" --> "...variations in the length of the electrical links, jitter and" - line 489: " However, given the radiation levels expected in CMS, such operation range" --> "However, given the radiation levels expected in CMS, such an operation range" - Section 8: Conclusion --> Conclusions Figures: --------- - Figure 1: * Move description of the brown TEPX ring to figure caption instead of the footnote. * Also the gray line should be explained or removed. Beampipe envelope? - Figure 7: Please make two versions of it, as tested and as proposed after fixes. - Figure 9: * Add on each figure themselves somewhere that one is before and the other is after the irriadiation. (not just in caption) * Also, is this figure relevant? It's not the Phase 2 pixel area, and not the expected irradiation dose, right? - Figure 11: * add "blue" and "green" in figure caption where appropriate. Also explicitly mention the meaning red line in caption. - Figure 12: - add to figures that this is from simulation. - caption should mention that the simulation is single muons. - why not also mention the colors in the caption? - Figure 15: * what is "out of scale: 5.8%"? Why not "Overflows"? - Figure 14: * minor comment, but it may be nice to have these three figures show (a), (b), (c), to have a consistent figure naming scheme as in Figure 13 and others. - Figure 22: * similar comment as for Figure 14 * Also, should there be a horizontal red line corresponding to the expected operational threshold? May be would be good to have it shown in Fig 21 as well. - Figure 24: * It would be easier to guide the eye if it says: denoted "e" etc... Or put in italics? * The simulated modified LIN should be presented in this plot, too. - Figure 26: * similar comment as for Figure 24 ==============================