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DT Upgrade: Phase 2 RO

DT Upgrade: Phase 2 RO. C. F. Bedoya. December 11th , 2012. C. F. Bedoya December 11th , 2012. 2. CMS Phase 2. TSWG (Trigger Strategy Working Group) CMS is discussing the possibility of operating in Phase 2 with: - 1 MHz L1A rate (instead of 100 kHz)

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DT Upgrade: Phase 2 RO

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  1. DT Upgrade: Phase 2 RO C. F. Bedoya December 11th, 2012

  2. C. F. BedoyaDecember 11th, 2012 2 CMS Phase 2 • TSWG (Trigger Strategy Working Group) • CMS is discussing the possibility of operating in Phase 2 with: • - 1 MHz L1A rate (instead of 100 kHz) • - 20 us latency (instead of 6 us as previously assumed. Now 3.2 us) • We are asked to provide statements about the implications in our subsystem. • Two meetings already took place: • - https://indico.cern.ch/conferenceDisplay.py?confId=195153 • - https://indico.cern.ch/conferenceDisplay.py?confId=200590 • It appeared unlikely because it meant replace all ECAL electronics, but now this is not considered so difficult. • (Wouldthis mean that tracking triggerisnot so mandatoryifwe can increasethetriggerrateto 1 Mhz? notclear)

  3. C. F. Bedoya December 11th, 2012 3 CMS DT Phase 2 * L1A rate and latency will impact only readout chain * ROS will be redesigned between LS1 and LS2. * Will try to incorporate DDU functionality to remove further bottlenecks * i.e. impact is on the ROB • Higher LHC luminosity will imply larger occupancies in the DT chambers, which will turn into a higher hit frequency. The consequences of this higher occupancy are the following: • -increase buffers occupancy at the different levels • -slow down the time to process an event (reduce processing speed) • -increase the required bandwidth for the output link • Increase of trigger rate and/or trigger latency only makes this scenario even harder.

  4. C. F. BedoyaDecember 11th, 2012 4 Background estimations Rate outside the trains, no muons included (basically neutrons) Big difference between chambers,: - YB-2 S4 MB4 27 kHz/TDC channel - YB-/+2 MB1s 12 kHz/TDC channel Accounting inside trains may increase 3.6 kHz in MB1 and 0.3 kHz in MB4 (¿?) 1035 From Gianni CMS week June 1035

  5. C. F. BedoyaDecember 11th, 2012 5 Background estimations Gianni CMS week June * Upper sectors MB4 * Leaks between barrel and endcap in MB1s

  6. C. F. BedoyaDecember 11th, 2012 6 Muon rate estimations Phi rates • YB-/+2 MB1s at 1035 : • 350 kHz “muon” rate (per chamber) • 114 kHz “muon” rate per ROB • 29 kHz “muon” rate per TDC This are chamber rates (DTTF input counters) From I. Redondo

  7. C. F. BedoyaDecember 11th, 2012 7 Muon rate estimations eta From I. Redondo

  8. C. F. BedoyaDecember 11th, 2012 8 Impact on the ROB • Hit rate 27 kHz => 37 us between hits. Since there are: • 128 channels/ROB, => one hit per ROB each 0.29 us(3.5 hits/ROB/event) • 32 channels/TDC, => one hit per TDC each 1.2 us. • Including muons, adds 8 hits per L1buffer FIFO(or more): • Worst muon rate 350 kHz => 29kHz/TDC => 1 muon every 35 us/TDC Hits stored in L1buffer until the L1A arrives. So if the L1A latency was 20 us, this means we will have to store max 1 hit/channel, i.e. 32 hits/TDC until the L1A arrive+ 8 hits/TDC from muons until the L1A arrive This represents 12 hits per L1buffer FIFO/event, while they are 256 positions in the FIFO. It seems it should be possible to work with 20 us latency in phase 2 LATENCY impact => L1 buffers (slower matching?)

  9. C. F. BedoyaDecember 11th, 2012 9 Impact on the ROB L1A rate impact -Readout FIFO -Event processing speed -Output link bandwidth byte-wise mode at 20 MHz Header,trailer, hits = 32 bit words It takes 8 BXs to send each hit (minimum) + 16 BXs header+ trailer+ 8 BXs token sharing + seems there is more... (next slide) Time window is approximately 1 us, and we will have 1 hit/TDC each 1.2 us, that is the number of hits per event that are expected to be stored in the Readout FIFO But the limiting factor is the speed at which you output the data

  10. C. F. BedoyaDecember 11th, 2012 10 ROB Trigger rate test Test perform on a ROB at lab with fixed trigger rate: No muons <- 3.5 hits/ROB Max 500 kHz... probably optimistic If one includes the worst case muon rate (350 kHz/chamber => 1 muon/ROB every 9 us) => MAX 300 kHz (one could reduce the time window, increase the threshold or start being inefficient...)

  11. C. F. BedoyaDecember 11th, 2012 11 Options without replacing ROB? • trigger matching: reduces the payload. (100 kHz L1A rate => one L1A each 10 us with a sampling window of 1 us => we read 10% of the time) • At 1 MHz L1A rate => we will be reading 100% of the data, thus trigger matching is an overhead of processing time and bandwidth (headers and trailers) • In principle, it is possible to run the HPTDCs in continuous mode: • - hits sent as arrive from chambers, • - time measurement referred to BC0 • Latency and L1A rate becomes irrelevant for the ROB • Trigger matching in the new ROS may be possible (needs study and will imply detailed calibration of the different absolute BXs ID between the ROBs and the ROS). • It may open possibility to use TDC data in the trigger (?)... (output delay not deterministic and long...) • Limiting factor in this mode of operation is the bandwidth of the readout link: • 27 kHz * 128 ch * 32 bits/hit = 110 Mbps • With muons (350 kHz/chamber => 114 kHz/ROB of 8 hits muons => 114 Mbps • Max bandwidth is 160 Mbps => hit rate 39 Hz/cm2 (to be checked) MB4s are close... • This may work depending on the uncertainty of the background. If it is large, then we start o be inefficient

  12. C. F. BedoyaDecember 11th, 2012 12 CONCLUSIONS • We don´t expect any problem for running present ROBs design with Phase 2 occupancies and 100 kHz L1A rate and 6 us L1A latency • With the background rates expected in Phase 2, it is unlikely that we could run at a trigger rate higher than 500 kHz. • Latencies of 20 us could likely be achieved, although proper testing should be done. • HPTDCs could be operated in continuous mode, which should allow operation with 20 us latency and 1 MHz trigger rate. However, this means no background reduction is possible playing with the time window (no filtering is done, all hits are sent). Therefore, we could start to loose efficiency for background rates larger than 39 Hz/cm2. (This number should also be checked). MB4 rates are too close to this number (27 Hz/cm2for YB-2 S4 MB4). • Any action to place a shielding in the MB4s of the upper sectors or in the MB1s of the external wheels will reduce any possible efficiency drop. • Considering the large uncertainties (energy, extrapolation, target luminosity, etc), even if the MB4s can be shielded, replacing the ROBs of the MB1s external wheels with a higher performance board, should also not be discarded • In order to operate in continuous mode, a DC balancing is mandatory at CUOF level.

  13. BACK-UP

  14. C. F. BedoyaDecember 11th, 2012 14 Background estimations

  15. C. F. BedoyaDecember 11th, 2012 15 Background estimations

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