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Time alignment

Time alignment. All sub-detectors are optimising readout as compromise between robustness and cost. OK, but…….. We must consider special scenarios where more information is required ( eg more bits of BXID). For example, time alignment within each sub-detector t ime alignment of LHCb

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Time alignment

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  1. Time alignment • All sub-detectors are optimising readout as compromise between robustness and cost. OK, but…….. • We must consider special scenarios where more information is required (eg more bits of BXID). • For example, • time alignment within each sub-detector • time alignment of LHCb • (Remember we don’t have the L0 trigger !!!!) LHCb electronics, 12th December 2013

  2. BX0 BX1 BX2 BX3 BX4 BX5 BX6 BX7 BX8 BX9 BX10 BX11 BX12 BX13 BX14 BX15 BXIDRst -SODIN BXIDRstA delayA BXIDA 3562 3563 0 1 2 3 4 5 6 7 8 9 10 11 12 13 delayB BXIDRstB BXIDB 3560 3561 3562 3563 0 1 2 3 4 5 6 7 8 9 10 11 ‘Beam’ data in A and B Beams collide in only one BX (or a few well-spaced BXs) Detector A sends a packet with data and BXID = 4 Detector A sends a packet with data and BXID = 2 Difference used to align BXIDResets H3653 H0 H1 H3653 H0 H1 H2 H3 H4 H2 Data2 Data4 H5 H3 H4 H5 H6 H7 H6 H7 LHCb electronics, 12th December 2013

  3. Time alignment: useful tools Example of a SPECIAL MODE: VELO data packets (30-bits): Normal running 9-bit BXID 8-bit Super-pixel Hit Map 13-bit Super-pixel address Time alignment running 12-bit BXID 2-bit ? 3-bit SP Hit Count 13-bit Super-pixel address Another example (in FE specs!): TFC-alignment mode: Replace data with TFC command received for each BX TFC alignment 12-bit BXID = N TFC command received at BXID = N Then compare to see if offsets are correct/consistent LHCb electronics, 12th December 2013

  4. Time alignment possibilities Test pulse injection (TFC triggered & phase adjustable) But is still sensitive to cable delays Cosmics Gives absolute timing, but rare…… Laser (or similar, TFC triggered & phase adjustable) Very useful, but not all detectors are sensitive Beam Ultimate tool, but quite expensive! LHCb electronics, 12th December 2013

  5. We still have time to put helpful features in the front-end designs, so……. Next meeting in Feb 2014: sub-detector ideas for time-alignment & commissioning, and how to implement them LHCb electronics, 12th December 2013

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