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LHCb Muon Grounding Alessandro Balla, Paolo Ciambrone, Maurizio Carletti, Giovanni Corradi, Giulietto Felici, Rosario Lenci INFN - Laboratori Nazionali di Frascati Maurizio Gatta INFN - RomaII Anatoli Katchouk CERN CERN – 7 Oct 04 1 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 2 How many grounds ? • Grounding, shielding and power distribution must be handled together to avoid EMI pickup and preserve signal integrity Signal ground Reference ground Safety ground • Signal ground : on-detector electronics ground reference • Reference ground : off-detector electronics ground reference • Safety ground : connection to earth CERN – 7 Oct 04 3 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 4 Safety connections • Detector must be connected to earth for safety reasons Chamb 1 Chamb 2 Chamb 3 Chamb … Copper braid Z1 Z2 Copper braid CERN – 7 Oct 04 Z3 (sitting on the edge of the wall) Z4 Zstrip 5 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 6 HV connections • HV supply voltage is distributed using shielded cables • Shield can not be connected to ground to both sides to avoid ground loops • A resistor (~ 1-10 k) is used on the detector side to break the loop • Some current will flow through the low resistance safety earth network (unavoidable) Load HV PS 1-10 k CERN – 7 Oct 04 7 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 8 Front end on-chamber connections (I) • Safety ground must be connected to FC through a low impedance path (copper braid) • Faraday cage is the chamber signal ground LVPS regulator board LVPS connector CERN – 7 Oct 04 Faraday cage Ground connection OPB SPB CARDIAC CARDIAC connector 9 Front end on-chamber connections (II) CERN – 7 Oct 04 10 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 11 Front End Off-chamber connections • Data transmission between front end electronics and DAQ system is implemented via differential electrical connections (LVDS) good immunity to common mode noise • As we will use shielded cables one end is connected directly to ground while the other end could be connected to ground through a capacitor to avoid low frequency loops Shielded Twisted cable A B Exceeding the common mode range can damage LVDS driver/receiver circuits |VA-VB| must be less than the LVDS common mode range CERN – 7 Oct 04 12 Grounding components Grounding Safety connections HV connections Front End On-chamber connections Front End Off-chamber connections LVPS connections CERN – 7 Oct 04 13 LVPS connections (I) Front end current requirements (LHCb 2004-006 internal note) CARIOCA 135 mA @ 2.5 V DIALOG 160 mA @ 2.5 V Number of Chambers FEE boards x Chamber Icc x Chamber (A) Icc (A) x Station R4 192 3 1,38 264,96 R3 48 12 5,52 264,96 R2 24 24 11,04 264,96 R1 12 24 11,04 132,48 R4 192 3 1,38 264,96 R3 48 12 5,52 264,96 R2 24 22 10,12 242,88 R1 12 14 6,44 77,28 R4 192 3 1,38 264,96 R3 48 6 2,76 132,48 R2 24 6 2,76 66,24 R1 12 12 5,52 66,24 M1 927,36 M2/M3 850,08 529,92 M4/M5 Total CERN – 7 Oct 04 Total (A) Current 4217,28 14 LVPS connections (II) 40 A Module N 8 Chambers @ 4.8 A M1R3 M2/M3-R3 M4/M5-R1 N 16 Chambers @ 2.4 A M4/M5-R3 Patch panel & fuses LVPS N 32 Chambers @ 1.2 A M1R4 M2/M3-R4 M4/M5-R4 Chamber 1 Chamber 2 Chamber n CERN – 7 Oct 04 15 Conclusions • The on-chamber shielding and grounding scheme has been studied and successfully tested in several TB • The proposed grounding scheme requires : • FC as detector signal ground reference • Floating low voltage power supply • Chamber connected only to the safety ground • High voltage ground broken by resistor The maximum ground voltage difference between ondetector and off-detector electronics must be less than LVDS allowed common voltage CERN – 7 Oct 04 16