CMS ME CSC HV system

1
CMS ME CSC HV system

• Alex Madorsky
• University of Florida

2
Cathode Strip Chambers

• Main purpose of the CMS EMU CSC HV system
• Provide High Voltage for CMS Endcap Muon Cathode
  Strip Chambers (CSC)
• CSC features that affect HV system design
• Small HV segments high tolerance to HV failures
• Same working voltage with small variations from
  segment to segment
• Problematic segment can be fixed by
• Reducing voltage
• Disconnecting from HV
• Needs precise consumption current measurement for
  each segment

One HV segment
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Voltage and current parameters

• Voltage
• The operational point 3.6 kV (full efficiency)
• The end of plateau is at 3.9 kV
• Current
• Current per channel averaged over the full Encap
  Muon System 0.7 uA/segment
• Maximum expected current per segment 2uA
• Needs to be monitored on each segment with good
  precision, to detect possible troubles.

4
UF/PNPI design

• UF/PNPI HV system design
• 3.5 years of development
• 3 prototypes pre-production prototype produced
• Prototypes passed all tests

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Target specifications (1)
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Target specifications (2)
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Target specifications (3)
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Target specifications (4)

• System structure defined by us
• Master HV sources and control computers in
  Control Room
• Voltage regulation and monitoring, current
  measurement by Distribution boards near disks

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Target specifications (5)

• Two types of distribution boards
• 36 channels (two small chambers)
• 30 channels (one large chamber)
• Output connector defined by us.

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UF/PNPI HV system architecture
Multiwire HV cables, 100 m, one per 18
distribution boards

• Primary HV power supplies off the shelf
• Master board One output per distribution board.
  Regulates voltage 0-4KV (VMAX), measures current
  on each output.
• Remote Distribution board powers one large or
  two small chambers (36 outputs max). Regulates
  voltage 1KV down from VMAX, measures current on
  each output. Each output can be disconnected from
  HV if necessary.

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Control interface
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US CMS Review

• Conducted on June 24th 2003 in UF
• UF/PNPI system selected over CAEN
• Reasons
• Price
• Design features
• Simple and robust design
• No programmable logic in radiation no SEU

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UF/ PNPI CMS EMU CSC HV System Main Design
Features

• Main technical approaches are shown
• HV regulator
• Current sensor
• Fuse control
• Digital control interface
• Mechanical design

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HV regulator (distribution board)

• Output voltage controlled by linear regulator
  (Q1)
• Regulates down to 1000V from input voltage
• Voltage measured by divider R1-R2 and U1A opamp.
• Regulator feedback via U2A
• Q2 and C1 provide HV decoupling

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Current sensor
I
UIRs
R2
R3
Rs
CvKU
D1
C1
C2
Ug
CHARGE SENSITIVE AMP.
U3A
R4
QUgCv
Uout

-
R5
Cf
UoutQCfUgCvKuIRsCfKI

• Current measured across Rs
• Varicap D1 is used as voltage-sensitive element
• Input pulse is applied via C1
• U3A is a charge-sensitive amplifier

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Fuse control

• Situation requiring permanent disconnect is
  extremely rare (never happened on FAST sites)
• Fuse is used to disconnect channel from HV
  permanently
• To blow fuse
• Low negative voltage applied to channel input
• Switch Q3 shorted
• Fuse can be quickly replaced during short access

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Control interface

• Differential signal transmission (RS-485)
• Optically insulated
• Built completely on discrete logic

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Control software

• Based on PVSS and DIM server
• Initial version of DIM server and PVSS shell
  works
• Written with excellent assistance of Valery
  Sytnik (UC Riverside)
• Targeted for full DCS compatibility
• Work in progress

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Mechanical construction

• Final mechanical construction
• Simple and rugged design
• PCB is optimized for automatic assembly

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Distribution Rack
Fan unit heat exchanger

• Need from CMS
• Racks
• Fan units heat exchangers
• Strain reliefs
• Space in front and behind the racks
• Low Voltage power for distribution boards

Distribution crate
Distribution boards
HV and control cables patch panel
Output HV cables to chambers
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Distribution Racks
Disk 1(Station 1) Disk 2 (Stations 2 and 3) Disk 2 (Stations 2 and 3) Disk 3 (Station 4)
Position in Rack Rack 1 Rack 1 (right half of the disk) Rack 2 (left half of the disk) Rack 1
TOP Crate 1 9?36 Crate 1 9?30 Crate 1 9?30
Crate 2 9?36 Crate 2 9?30 Crate 2 9?30
Crate 3 9?36 Crate 3 9?30 Crate 3 9?30
Crate 4 9?36 Crate 4 9?30 Crate 4 9?30 Crate 1 9?36
BOTTOM Crate 5 9?36 Crate 5 9?36

• In the table above
• 9x30 means 9 boards of 30 channels. One board of
  30 channels powers one ME23/2 chamber
• 9x36 means 9 boards of 36 channels. One board of
  36 channels powers two ME23/1 (or similar)
  chambers
• This table shows the HV distribution boards
  necessary for one Endcap ( or -).

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Rack position for YE1 and YE2
YE1 has only one rack
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Low Voltage Requirements for Remote Distribution
Cards
Parameter Min Max
Positive voltage 7 V 8 V
Negative voltage -8 V -7 V
Current on both channels 300 mA
Power per distribution board 4.2 W 4.8 W
Ripple/noise 100 mV

• Low voltage power will be provided by CMS AC/DC
  LV system

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Cooling

• Only remote distribution racks are discussed.
• Dissipated heat
• 4.8 W maximum per distribution board (about 3-4
  of one chamber LV power)
• 216 W per rack maximum (45 boards)
• 1335 W for all distribution boards
• Cooling of distribution boards
• No enforced cooling is currently planned
• Racks must be open on top and bottom for
  convection
• Need heat exchangers to remove generated heat
• May need fans (unlikely, will decide later)

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Safety

• HV Cables
• KERPEN halogen-free cables
• Passed CERN flammability test
• HV Connectors
• LEMO/REDEL, bought from CERN stock
• PCB material
• FR-4, flammability rating 94-V0
• Other components
• Will be checked for CERN safety compliance

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Design status

• Boards design complete (electrical and
  mechanical)
• Pre-production prototype constructed in UF, under
  tests now
• Tests of the pre-production prototype
• Full bench test OK
• Chamber test on FAST site OK
• Radiation test OK
• Magnetic field test November 03
• Production boards - exact copy of the
  pre-production prototype

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UF-PNPI collaboration

• MOU between UF and PNPI is signed
• Arrangement is very similar to chamber production
• UF responsibility
• Development and production management
• Pre-production prototype construction and testing
• Test stands construction
• Test procedures verification, instructions
• Off-the-shelf components procurement
• Bare PCBs manufacturing
• Automated SMT assembly
• US labor and components contingency

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UF-PNPI collaboration

• PNPI responsibility
• Simple mechanical components manufactured
• Pre-production and production manual assembly
• Pre-production and production testing
• PNPI labor and space contingency

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Schedule

• ESR November 03
• Board production and SMT assembly start in US
  end of November 03
• Start of pre-production run in PNPI end of
  January 04
• Pre-production system test in UF May 04
• PNPI production readiness review, production
  start July 04
• Production finish June 05

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Installation and commissioning

• Installation
• To be done by CERN crew UF/PNPI visitors
• Will start as soon as the first shipment arrives
  to CERN (Oct 04)
• Very uncomplicated
• 278 distribution boards, 30 crates
• HV cables already installed by that time
• Commissioning
• LV power supplies are necessary at least
  prototype
• Would like to start as early as possible (Oct 04)

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Conclusions

• Design solutions are proved to be working
• Pre-production prototype built
• Pre-production prototype passed tests
• Satisfies CMS EMU CSC HV system specs
• Production documentation is being prepared

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Radiation environment

• Expected
• Neutron Fluence (1 - 4) x 1010/sq cm
• Total Ionizing Dose ( 0.07 0. 7) kRad