DESY Institutional Review -------------------- Dear authors, congratulations to putting together such an impressively long document, which was due to its pure size very difficult for us to review within two weeks. Please find below our comments, split into general comments and into comments per chapter. General: ------ It is well visible that the whole document was hastily stitched together because of time issues, and especially the appendix would have profited from one final read of a LE (and a spell checker) before putting it into CWR. Many figures have legends that are, if at all readable, not informative, since the strange abbreviations do not make much sense without a better description in the figure caption. We suggest that the authors look at each of the figures and improve them, but will give examples later on. Some figures have really bad resolution, so that also when zooming in it is impossible to read some of the numbers. Please check all figures and update the ones that are too bad quality. Tables should always have the caption on top, please check all tables and correct where it is necessary. Check consistent capitalization in chapter and section captions (follow CMS rules!) Acronyms are very inconsistently used (not introduced, introduced twice, ...). While you have a nice glossary of all abbreviations, we do think it is necessary to define them whereever they appear for the first time. This is of course difficult if the different chapters are done by different people, but even within the first chapter many abbreviations appear w/o definition, or get defined later. We will point to some cases, but think that the authors need to go through the whole document and try to improve it. You use quite often the symbol \approx for approximate, which we think does not read well (sometimes used in a context even with the terms "order of" or "approximately", sometimes not). In most cases we think it is nicer if you write 'about' and the number without another symbol in front of it. Please grep for it in each case and check how to improve, we will give some examples in our detailed comments later on. Check for punctuation in Figure captions, final full stop is often missing Check for articles. This might be cumbersome, but there are loads of articles missing, sometimes it's wrong, sometimes just hard to read. Some are noted in the following, but not all of them. Inconsistency in spelling for the following terms (found in Ch3, but found to be inconsistent throughout the TDR): * radiation hard / radiation-hard * time over threshold / time-over-threshold * time walk / timewalk / time-walk * preamplifier / pre-amplifier * hit buffer (capitalization) * wire bonding / wire-bonding * bump bonding / bump-bonding * Level-1 accept (often lower case "accept"), also the acronym is introduced but not consistently used * x-bit / x bit (e.g. 8-bit / 8 bit) * readout / read-out * coordinate axis naming ("x-y coordinates" in line 2866, somewhere I found "XY"...) Chapter 1: -------- B type: 195 the ≈200 nearly-simultaneous -> the up to 200 nearly-simultaneous 192 MIP is not written out, should be 'minimal ionising particle (MIP)' 207 smaller beams -> can you be more precise in what is smaller in the new beams? Maybe better write 'more collimated' 210 much higher collision rates -> can be anything, suggest to write: five times higher collision rates 263 when PUPPI is given as name, it would be helpful to have one (or two) sentences explaining it... 282ff: First sentence: Saying that we are back to old performance and have no problem if we have the MIP-TD + ECAL timing, but the last sentence in this says ' this approach requires a dedicated detector for precision timing of MIPs,' - this is clear from the first sentence already, better remove the last part of the paragraph from l. 290ff (from 'At the reconstruction level'). Better continue here already with the next paragraph. 319ff: Should all go into the next section (in line 357) from 'The removal of...' onwards, since this describes the impact of the MTD on physics, so it should be found in this section rather than in the introduction 336ff: Why are the studies done with 30-40 ps if this is not achievable? Does this make sense? Isn't it better if the studies are done with a realistic scenario, i.e. 40-50 ps? 406: Use CMS penname for neutralino, so that it gets a 'widetilde' on top of it. 418: Move definition of mid-rapidity from l. 426 here Table 1.2: Add unit to the last column 452: CE is not defined 466: TST is not defined 543 "Dark Current Rate" -? 625 will be ≈331 776 -> Is it really approximately 331 776? The number you give is quite precise, so we suggest to remove the 'approximately' here Fig. 1.7 (left) is not really referred to in the text, only 1.7 (right). The left part should be made a separate figure and moved to Chapter 2, where it is also referred to. 636-638 (0.540%) do you really has such good precision on momentum resolution? - In any case, CMS rule requires to reduce to 0.54 etc. (please round the rest of the numbers and check also the rest of the document) 664-671: We think that this is very detailed for an introduction, and could well go into the following chapters. If you want to keep it, move it behind L682. If you don't want to do this, move at least 672-675 somewhere else, since here it is completely out of context. If you move 664ff behind 682, it would work. A type: In several places you have unnecessarily long sentences ( for example L342-346, L518-521, L584-588) 203 "BSM" is just Beyond the Standard Model (remove 'of particle interactions') 446 motivate -> motivates 465 has now been defined to -> is defined to 493 collision hall -> experimental cavern 521 and small the dead area between sensors -> as small dead area between the sensors as possible 535 must conform -> must be conform 584ff: Not understandable, suggest to rewrite as follows: For the BTL, the best available technology are crystal scintillators that are read out with silicon photomultipliers (SiPMs) [22–24], which are pixelated avalanche photodiodes operating in Geiger breakdown mode. For the ETL the best performance comes from Low Gain Avalanche Detectors (LGADs) [25–27], which are silicon sensors with internal gain of about 10–30. 642 "is that, because" not nice English 645 remove the approx. before -30 degrees, since you already say 'typically' 650 change the approx. before 10^5 to the order of 10^5 688: annular -> angular Chapter 2: -------- B-type: 827: While before we discuss the time resolution of 30-40 ps, or 40-50 ps, here we refer to 45 ps. Maybe nicer to write it consistently, i.e. also write 40-50 ps. 842: Move Fig. 1.7 (left) here, where it is referred to. A-type: 831: Can you refer to the material consistently: here it is L(Y)SO:Ce and later LYSO:Ce (also in L1084 L(Y)SO:Ce and four lines later again LYSO:Ce). And the full definition just comes in Section 2.2.(L1028), we think it should be defined at the first appearance. 849: The BTL geometry and modularity was previously and is summarized in Table 2.1. -> The BTL geometry and modularity is summarized in Table 2.1. 1111: Remove the two 'also' in this sentence, as they make no sense here (maybe the 2nd one can be argued, but not the first). Chapter 3: -------- General remarks: * The term "sth is needed ..." or similar is used very often. Replace some occurences by "required" * Sensor size is inconsistent throughout the chapter * The image quality is often poor, consider enhancing or using different figures * Consistency in in-line enumeration styles, sometimes (i), ... but also other styles used. Remarks in Ch. 3 line by line: 2663: eta=2.9 contradicts L.689 Fig 3.1: Poor quality 2678: "90deg structures" -> "quarters" ? Fig 3.1 caption: state what color depicts what Fig 3.4 caption: "three times" -> "points in time" ? Fig 3.4 caption: "fluence reached" -> "fluence experienced" ? Fig 3.4 right: Axis label incomplete, "% of ETL area" 2719: Subscript exceeds line 2720: either "using a correction" or "using corrections" 2726-2728: Not a sentence, or not an understandable one 2728: "is reaches" -> "reaches" 2729: "... due to the non-uniform ..." 2729: "... and the non-saturated ..." 2731: Remove quotation marks, since this term is widely known? 2734: "to the non-saturated" 2735: "the charge carriers'" is more clear 2739: Switch "precision" and "hermetic"? 2748: Remove "that locally generates very high fields when depleted", this is unnecessary 2749: "strong function" sounds odd. "strongly dependent" or just "a function of" ? 2760: "are" -> "is" 2763: Inconsistent sensor size. Later, 21.6mm is used, which would round to 22 mm Fig 3.5 right: "Ultra-Fast Silicon Detector" (as in the text above) 2774: "towards the ultimate" 2795: no parantheses 2796: State name or description of g_eff, also "eff" could be \textnormal 2800f: Sentence out of context. Suggestion: move to the end of the paragraph 2812ff: The enumeration does not list "irradiation facilities", to be precise. It enumerates irradiation particles and energies. 2820: rephrase "strong function" 2822: NIEL doesn't "convert" fluences, it scales or calculates equivalents, rephrase 2825: remove "two" and "most likely" 2826: remove "ETL" 2826: "energy points" sounds odd. Replace by "proton energies"? 2827: It's not the job of a TDR to test the NIEL hypothesis, and it's known to not be fully adequate for all observed irradiation effects. Minimal invasive change: phrase "to test the compliance with the NIEL hypothesis". More elaborate change: Remove the testing of NIEL (also in the whole section) and state that it is known not to describe all effects. The latter would be nicer, since it's really not the job of a TDR to test NIEL and you can just state what the observed effects on your sensors are. 2830: remove parantheses, make "where A ..." a subordinate clause Fig 3.8: Hard to distinguish orange from red. What do the labels mean (e.g. UFSD W7 C_B)? Can you use different markers/colors that actually have a meaning (e.g. different colors for different carbon doses and different markers for different vendors)? That would make things much easier. 2836: "understimates" 2839: "for the ETL" Tab 3.1: Caption above table! Tab 3.1: Right half of the table shows different values than the left half. Confusing. Make it two tables? 2849: Second occurence of "HPK" and "CNM" sloppy. Try "sensors from HPK and CNM" as before. 2851: "bias voltage". Remove "as a function of fluence", this is out of context. 2852 / Fig. 3.9 / 2860 / 2875: Is the gain below 10 or not? In 2860 it's stated to be >10 in any case, Fig. 3.9 (e.g. the violet curve at 3e15 neq/cm2) doesn't reach 10, and the text in 2860/2875 says that the full gain can't be reached. Fig 3.10: I get that these fits are required for Fig. 3.11, but still they seem very arbitrary, especially the blue one. Fig 3.11 right: Why does this saturate? Is gain=10 really reached at 700 volts at the end of lifetime? If not, just end the lines, otherwise it's wrong. 2866 f: sensor size, give mm values consistently 2868: "bias value" sloppy -> "bias voltage" 2875: No comma after "layer" 2878: "contribute to an increase of the sensor..." Fig 3.13 caption: "Power consumption" 2886: "crossing the ETL" 2889: Colon at the end 2893: "the production" 2898: "sensor, so all" 2899: "an excellent" 2899: "is" -> "can only", since this is not the only requirement 2901: "the stability" 2923ff: "as a function of the laser spot position" 2924: "The distance between the 50%" Fig 3.14: LGAD <-> UFSD. It's the same, but still, write the same to make it easier Fig 3.14 caption: "the drift lines" -> "the charge carrier drift lines" Fig 3.15 caption: "gain-to-gain separation" and "no-gain distance" are the same right? If yes, write the same or explain these terms 2936: This sentence does not make sense. The sum of an area and an edge doesn't give a fill factor. Rephrase 2937: Are failure modes really mentioned in this section? I didn't find them. 2938: Sensor size consistency 2941: Stated sensor size (1.6x2.6 contradicts label in Fig. 3.16) 2941: Forgot the (ii) enumeration, probably after "pads" 2943: remove "for the first time", not of interest Tab 3.3 caption: "for sensors from CNM..." Fig 3.16: sensor size labels contradict text Tab 3.4: "# Sensors tested" (forgot an "s") 2947: "IV set-up" sloppy, rephrase 2948: remove "it" 2949: remove "that" 2952f: The "mean current" is influenced by these pads, isn't this measurement somewhat biased then? Shouldn't there be a hard limit? Fig 3.17: What is a "Bad pad"? Not explained. Is it "hot"? 2962: "measured" -> "observed"/"detected"? 2964: "Tor" typo 2966: "will be part of the ...". Aspects are not part of the requirements. "will influence the..."? 2971: "of the CNM" 2975: What is this metal? Why is it there? Is it just the metalization layer? Why are there regions without then? Explain. Fig 3.18: z-axis label missing Fig 3.18 caption: "sensor" (singular). Maybe "16 pad" -> "16-pad" 2978: "The uniformity" has not been measured in this plot - the efficiency has been measured. Suggestion: replace "The uniformity" by "The efficiency", and switch "finding very good uniformity" with "almost 100% efficiency throighout the full sensor" (which actually already states uniformity) 2986: "bias conditions" sloppy. "bias voltages" or "operating conditions"? 2994: "loss of gain layer" -> "loss of gain". 3002f: Isn't it always good to run your sensor below breakdown? This is a small aspect, but there are much more important aspects that suggest running belor breakdown. Rephrase 3004f: "when" used twice, bad style 3013: "of" -> "or" 3016: At -20C or -30C there is no annealing. So, why do you test this? Explain. 3025: "for UFSD use in CMS" sloppy -> "for the use of UFSDs in CMS"? Fig 3.19 caption: The formula belongs to the text, not the caption 3059ff: "when new" sloppy. How about "initial"? 3083: "informed" not used correctly, find another verb Fig 3.20: Do these plots exist as vector graphic? This looks pixelated 3086f: no comma after "test beams" and "phases" 3094: double "that" 3094f: This is not a good sentence. What is the "and that sensors being used in module assembly" do here? 3120: "each of the two" -> "both"? 3122ff: This is pretty much a copy of the enumeration in ll. 2707ff Fig 3.21 caption: Punctuation Fig 3.21: "CAL" not explained Fig 3.21: Put an oval/rectangle around the blocks of the periphery to group them 3135: colon wrong 3139: Itemization style (previously used (i)...) 3140: "an oscilloscope" Tab 3.5: Font in top center box Tab 3.5: The comments for "Timing resolution" are in the text, too detailed here Tab 3.5: The sensor does not require a TID of 100 MRad. "TID resistance"? 3168: Join sentence with previous paragraph 3170f: LE and TOT are introduced, why again? 3177: "Figure 3.23 left shows" 3179ff: And again introducing LE and TOT 3181: "two times need to be" -> "two values need to be"? It's hard to measure "time" itself 3185: CFD already used in this chapter. Consistency. 3189: remove space before comma Fig 3.23 caption: Very long caption. Move some of it to the text Tab 3.6: "sensor irradiation" - isn't it more the radiation to the readout chip? Or is it the sensor contribution here? How is it decoupled? Usually you can only measure both. Also it's not an impact on the "LE+TOT" method, but on the resolutions obtained with this method. Tab 3.6: Remove hyphen in "sensor-irradiation" Fig 3.25 caption: "additional error" - it sais resolution (absolute), not "additional". If "additional", then additional to what? 3205: Not a good style (the pluses) 3206: Why is this expected? Explain 3228: "using an LGAD" Fig 3.27 caption: "in 65 nm" slang. Add "technology"/"process" 3256: What is the number of bits of this digitizer? Fig 3.30 caption: What is IBSelB? It's not explained in the text Fig 3.31: PreAmp <-> preamps, consistency Fig 3.31/3.32 caption: Punctuation 3268: "An LGAD simulation" 3268: "evaluate the overall" 3269: Colon before enumeration? Suggest: "at different irradiation levels are used: pre-irradiation, .." 3274: "the time resolution" 3274: "reduced charge." Reduced charge what? Charge collection? Gain? 3277: "high radiation" slang, say "fluence" or similar 3277: "the dependence" does not become larger. "the slope"? 3278: "in an overall" 3272: "higher power consumption" 3276: "high radiation case" -> "high radiation fluence" 3292: space before "To" 3293: New paragraph before "The first", does not belong together I think Fig 3.42 caption: repetition "preliminary" 3376: "in 65 nm technology"? 3377: Introduce "ELT" 3377: remove comma 3432: "DLL's" -> "DLLs" 3441: typos "window" and "feature" and "allows us" 3443: "for the heavy", "flavor", "for the heavy" 3447: "in a significant" 3486f: Referencing 3.51 before 3.50 Fig 3.51: x-axis units? Axis labels? 3506: "relatively low" 3507/3518: What is "valid"? Explain? 3510ff: Level-1 Accept, spelling consistency or use acronym 3514: "ties into" slang, rephrase Fig 3.53 is never referenced in the text 3530: "checks"? 3531: "EMPTY" flag is not introduced 3547: check grammar. "reading out", but "writes" - does not match 3550: "received until output start of frame" rephrase, not understandable 3567: Why is this SOF pattern used then? Why not creating sth that is unique, like 00000000 or 11111111? 3592-3601: Style, rewrite? 3584: "A decoder decodes", rephrase 3616: Squeeze ">10" into one line 3632: "E-link s" typo 3653f: "width" and "length" of what? Specify Fig 3.56: Reduce figure size? 3662: "TDC delay cell time spread" rephrase, hard to understand 3663: "of the TDC" 3669: Introcuce Vt and W 3677: "Radiation hardness" 3678: "are larger" 3689f: Why are the replicas separated in time? This is not intuitive. Explain Fig 3.57 is never referenced 3747: "clocking" is slang, rephrase 3761: "The ETROC2" 3765: "The ETROC3" 3783: "makes the modules into" rephrase 3871: unclear sentence. It would probably help to introduce a subordinate clause, e.g. by a comma before "should" 3876ff: spelling consistency "-bonded" with hyphen or not? Fig 3.59 caption: spelling consistency "-bonded" with hyphen or not? Fig 3.59 caption: "time of writing this text" odd. Rather state the time (e.g. March 2019) Fig 3.59 caption: comma before "including"? Fig 3.59 caption: "including the investigation" 3902: "See Fig. 3.60(left)" is not a sentence. 3908: "At a collaborating institute" - at one? At all institutes? Clear statement. 3909: "The performance" 3910: Remove "existing" 3928: "will be connected to" Fig 3.62: Indicate a single module for a better overview, it is quite hard to see what is shown 3948: Consistency "radiation-hard" Chapter 4: -------- 4329ff: Therefore, all links communicating with the MTD on-detector electronics will be bidirectional. -> This is ok to write in principle, but with the DAQ system that you have chosen the connection is anyhow bidirectional by definition of the hardware. 4453ff: You do not define what a simplified distribution tree is, nor what the more realistic clock distribution is like, so this information is not helpful at all. 4564: Upon receipt of an L1-A the full detector is then read out and processing in the high level trigger (HLT) proceeds. -> Upon receipt of an L1-A the full detector is then read out and handed over to the high level trigger (HLT). Chapter 5: -------- Not read since we were told that this will undergo another small CWR after being updated. Chapter 6: -------- General: The org chart is reasonable. In the schedule one year is missing, at least in my conservative approach where you should have at least a single channel prototyped before starting the mass production. The TOFHiR1 is a derivative of the TOFPET chip and not yet in rad-hard technology, while the rad-hard TOFHIR2-V1 -still one version before final - will not be validated before end 2020, early 21. Only with this chip the DCR noice cancellation, critical for operation at HL-LHC, will be implemented. It is true that with the TOFHIR1 the system integration can be validated - but not the system performance. Likewise, V2 ist to be submitted in Nov 20 while V1 is validated only in Mar 21. So there is no time to feed back potential problems appearing only at module level back to ASIC designers. Here another 6 months are missing. The matrix of interested institutes has no entry for CERN. Is this really true? 5697 The SC includes the deputy PM, the IB chair, the resource and technical managers, and members -> The SC is chaired by the PM and includes the deputy PM, … 5698 of the Project Office and of the Finance Board. The SC meets regularly and discusses ->The SC meets regularly (how often ?) 5702 the progress and planning of the MTD project during the construction period. There will be a yearly review of the project held by CMS Upgrade Coordination. -> The SC will assist in the yearly reviews of the project held by…. 5707 for the barrel and one for the endcap. The coordination will comprise one BTL and one ETL -> for the barrel (BTL) and one for the endcap (ETL)…. 5708 technical manager (TM). They will be responsible for the planning, the safety, the quality as -> How will the TMs be appointed/elected/approved? 5714 and the Operation and Online System manager (OOM), the DAQ and clock coordinator, and -> What about the others (L1, Power, Safety?) 5715 the MTD link-person to the CMS technical coordination group (TCG). The Project Office shall meet regularly to verify the progress of the project. The link-person to the TCG will liaise with the ETL and BTL technical managers and shall keep the TCG informed of MTD technical progress and the MTD of changes that are requested by the CMS TCG. -> Where is the link-person in the org-chart (Fig.6.1) located? -> There may be a conflict in responsibilities with the TMs who should also meet regularly with CMS TCG. (see line 5726) 5756 The MTD Finance Board (FB), through the resource manager (RM) as chairperson, consists of -> …(FB), led by the resource manager (RM)… Or should the phrase ‘through the RM’ suggest that something is done by the FB which is missing in the sentence ? Probably this is what comes later as table ? How is the RM appointed/approved? 5771 the autumn; the sub-detector resource manager shall present the report to the FB, -> What is the sub-detector resource manager ? Are there one for BLT and ELT or is it the RM 5811 In BTL, the design prototyping phase with validation of the components as well as of systems -> …, the design and prototyping phase … Table 6.3 Line 1.3.4 Colock and links -> Clock and links Appendices: ---------- General remarks: * Is the naming of the appendix sections correct like this, e.g. having subsection A in appendix B.1 (see l. 6044), this looks odd to me * In Appendix A, a bit more technical information on the test beams would be nice to have for clarification, since the results depend on this, but probably not mandatory in a TDR. Line-by-line: 5917: Capitalize "Barrel Timing Layer"? 5922: "test beam campaign" 5929: "time stamps" 5936: "test beam facilities" 5940: "and a measurement" Tab A.1: Move caption above table Tab A.1: "Test of different SiPM manufacturers" might not be a good statement. How about "Test of sensors from different manufacturers"? Fig A.1 caption: "test beam campaign" 5954: "with a surface" (article), or rather "with an area of..." 5964: "of which there are many from pileup" rephrase, e.g. "of which there are many due to pileup" 5965: move "in quadrature" to the end of the sentence for better readability Fig A.2 caption: Rephrase caption, especially "in bins of x averaged over y-position" and the similar following sentence, this is not nicely readable Fig A.2 caption: "m^2" -> "mm^2" Fig A.3 caption: "XY bin" rephrase for consistency, different styles used within the document (e.g. "x-y position in the caption of Fig A.2) 5978: "the better the light collection efficiency" 5983: remove "of tile sensor" or insert an article 5984: Reference to Fig A.5 missing in this paragraph, please add Fig A.5: Ambiguity for the FNALs: In the caption FNAL is the readout chip, in the legend FNAL is the test beam location, if I get it right. Please clarify 5986: "43 ps" contradicts ll. 5920 and 5973 5991: remove parantheses underneath the square root 6002: "a longer path" 6006: remove "unwanted", it's obvious 6016: Insert space between sentences 6022: There's no verb in this sentence, please check Fig A.7 caption: "test beam studies" or "a/the test beam study" Fig A.9 is not referenced in the text 6023: "test beam studies" 6051f: Change line break "time-stamp" 6051: "furthest downstream" please clarify whether before or after the DUT 6052: "better than 7 ps", precision can't be less, resolution can. Fig B.1: "and the cold box" 6056: add number of bits of the ADC, since you already mention everything else 6060: Reference to the Monicelli software package? 6061: "test beam" without hyphen 6063: "Both DAQ systems" 6064: typo in "measurements" 6073: How many particles are in that spill? 6083: "wire bonding", or otherwise, consistent with the test (e.g. in chapter 3) 6087: "to jumper" is slang, please rephrase 6089: "16 channels", no hyphen 6091: "in the Dec 2018 test beam campaign" 6104: "10x gain" style, maybe "with a gain of 10" 6111/6120: LSBs/least significant bits, consistent use of acronyms 6120: space after "Fig." Fig B.3 caption: remove "which has been developed" or add something to this sentence. If it would not have been developed, it weren't there, so what is the point here? 6130: What is this: "[Ref-x: check]? 6137: "6 bit" consistent use (sometimes I've seen x-bit with hyphen) 6149: "as shown in Fig. B.5" This 65 nm processing is actually not shown in the Figure, please rephrase 6152: Rephrase to get rid of the "+" Figs B.4, B.5, B.6, B.7, B.8: Image quality is bad Fig B.4 caption: remove "which has been developed" or add something to this sentence. If it would not have been developed, it weren't there, so what is the point here? Fig B.5 caption: What do I see at the top left image? Not really stated in the caption 6155: "300 x 50 um^2" would look better 6163: "two-stage" instead of "2-stage" Fig B.7 caption: Rephrase "screenshot" 6165: "a 320 MHz clock" 6167f: "estimated" and "approximately" is too much, either one or the other 6176f: "be synchronized" and "be spatially" -> "are" and "is" 6181: What is a "time propagation"? Explain or rephrase 6184: "to a hit" 6186: "depending on" 6191f: I don't understand. Why do you compare the precision of the alignment to the spatial resolution, this does not seem useful to me 6195: "exploit timing information in ..." 6197/6198: "timing information" 6209: "C.1-left" style, consistent referencing of subfigures please 6210: "0.65, 0.65" looks odd, please rephrase 6219: "effects do not", singular Fig C.1: y-axis label is on top of numbers Fig C.1 caption: Here's the word "simulation". Is this a measurement or a simulation? Please clarify