Download Front end on-chamber connections - Indico

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
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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Front end on-chamber connections (II)
CERN – 7 Oct 04
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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Grounding components
Grounding
Safety connections
HV connections
Front End On-chamber connections
Front End Off-chamber connections
LVPS connections
CERN – 7 Oct 04
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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
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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
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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
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