High Voltage Distribution for RPCs

1
High Voltage Distribution for RPCs

• Simple Model of Detector HV
• Specifications Requirements
• Simple HV Distribution Layout
• Parts Costs
• A Possible Alternative to Conventional System

2
Simple Model of Detector HV

• Detector
• 300 repetitive layers
• 20m x 20m cross section
• 2m x 2m per RPC
• ? 100 RPCs per layer
• HV
• 1µA/m2 dark current (BELLE result)
• mostly through noryl spacers
• 400 µA per layer, at best
• Typical commercial HV channel provides 1mA _at_10kV
• HV System 1ch/layer ? 300 channels for entire
  detector
• 1ch for 100 RPCs

3
Specifications Requirements

• HV distribution per layer
• Ability to turn on/off
• Any one RPC?
• Any of one cluster of RPCs ?
• Ability to provide more than 1 value of HV per
  plane
• Ability to track down bad RPC (high current)

4
Simple HV Distribution Layout

• 100 RPC/layer
• Assume 100 RPC connections to the outside
• Four HV distribution boxes per layer (25 ch/box)
• 100 pairs of HV connectors/layer 8 pairs for
  boxes
• 240m of cables per quadrant ? 960 m/layer

Distribution box
HV Channel
Detector cross section
5
Parts and Costs

• HV System CAEN SY1527 (replaces SY 127)
• Module A1526 6 HV channels _at_ 1mA/15kV per
  channel
• 50 modules ? 300 channels (1 per layer) 250k
• Crate SY1527 fits 8 Modules A1526
• 7 crates (6 full 1 with two modules) 82k
• RG58 cable
• 960m/layer x 300 layers 288,000m 950,000 ft
• 136/1000ft spool ? 129k
• SHV connectors one pair per RPC
• RPC end is soldered
• 30,000 RPCs x 23/pair (for qty of 100) 690k
• Distribution boxes
• 1200 boxes _at_ 100/box (no connectors) 120k
• 10 kV connectors to PS
• 300 x 35 10k
• Total HV MS costs 1.28M

6
Parts and Costs Notes

• CAEN HV modules
• 10 kV are being discontinued SY 127 model A328
• 2mA _at_10kV (1,400/channel)
• 15 kV model A1526 may be built to provide 10 kV
  with increased current 1.3 mA and less potent
  HV connectors
• Note 830/channel for standard model
• Connector cost
• 10kV connectors cost 70/pair 36 for bulkhead
  34 for cable
• 8kV SHV connectors cost 23/pair 9 for
  bulkhead 14 cable
• SHV connector cost may be less because quote for
  qty 100

7
A Possible Alternative to Conventional System

• Use Cockroft-Walton HV supplies
• Used in ZEUS _at_2kV
• Each RPC has its own supply, mounted nearby (in
  absorber material ?)
• One low voltage cable replaces HV cable HV
  connectors
• Reduce the possible corona discharge in long HV
  cables
• Safer No HV outside the detector
• Cost compared to 1.3M conventional system
• Possibly 20-30 per channel
• At 40/channel x 30,000 ch 1.2M