January 15, 2003 Richard Talaga 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

January 15, 2003 Richard Talaga 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 @10kV– HV System: 1ch/layer 300 channels for entire detector

• 1ch for 100 RPCs

January 15, 2003 Richard Talaga 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)

January 15, 2003 Richard Talaga 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

HV Channel

Distribution box

Detector cross section

January 15, 2003 Richard Talaga 5

Parts and Costs

• HV System: CAEN SY1527 (replaces SY 127)– Module A1526: 6 HV channels @ 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 @ ~$100/box (no connectors) $120k

• 10 kV connectors to PS• 300 x $35 $10k

• Total HV M&S costs $1.28M

January 15, 2003 Richard Talaga 6

Parts and Costs: Notes

• CAEN HV modules– 10 kV are being discontinued: SY 127 model A328

• 2mA @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

January 15, 2003 Richard Talaga 7

A Possible Alternative to Conventional System

• Use Cockroft-Walton HV supplies– Used in ZEUS @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