bKLM RPC Signal & Ground SchematicGerard Visser, Indiana University

(for the barrel KLM team)

10th B2GM, 11/2011

magnet structure GND

7mm FOAM

7mm FOAM

3mm GLASS AT +HV

3mm GLASS AT +HV

3mm GLASS AT -HV

3mm GLASS AT -HV

2mm GAS GAP

2mm GAS GAP

Signal induction strips (parallel microstrip over a solid ground plane)

Strips and planes are (DC) isolated from module case and from glass/HV

DC ground potential reference through readout crate (a legacy of old system, will not be changed)

Twisted pair 113Ω (24 pairs per cable), length ≈6m

RPC module aluminum case

strips

plane

plane

strips

Signal current flow

AS B

ELO

W

analog test pulse

to TDC FPGA

• Signals are handled — insofar as practical — in a balanced, differential manner.

• No ground loops.

FEE crate GND

FEE crate GND

bKLM RPC HV schematic

• as far as any signals (intentional or EMI) are concerned, HV circuit is all high impedance and no ground loops introduced

• positive HV has 8 units fed from one HV channel

• negative HV has individual RPC per HV channel

• leakage currents drawn from HV (through RPC glass & spacers) is of order 10 μA

magnet structure GND

7mm FOAM

7mm FOAM

3mm GLASS AT +HV

3mm GLASS AT +HV

3mm GLASS AT -HV

3mm GLASS AT -HV

2mm GAS GAP

2mm GAS GAP

RPC module aluminum case

HV input cable grounds are NO CONNECT at RPC module

HVPS

HVPS

HVPS

electronics hut safety GND

6 more

bKLM RPC FEE crate/rack locations

• No changes from Belle system• 8 readout crates (6U “VME”) on each end of detector, in the indicated racks.

bKLM RPC FEE cable route• Note that although all signals are carried on unshielded twist-n-flat, at least up to exit of magnet everything is obviously very effectively shielded and segregated from other subsystems by the magnet steel.• Reminder the signals are received balanced/differentially, although of course the source impedance is unbalanced.

No changes from Belle system

bKLM RPC FEE crate / power• Not (yet) so much to say here on this topic, although it is recognized important.• The goal is to re-use the crates (6U “VME” from ELMA) from Belle system, at most to replace the backplane and/or power supplies.• Backplane is good but 21 slot is more than needed, may limit performance (latency to deliver hit data to trigger system). If so, we’ll replace it, e.g. with a 14-slot backplane.

• Supply voltages and currents probably quite different for new design, TBD at present. It may lead to replacing the supplies.• Old system used linear supplies, but if replaced would (likely) use some switching PS. Will evaluate noise carefully, of course...

Conclusions• bKLM RPC should be reasonably immune to EMI from differential signal path design• for the same reason, and due to small (normal) signal size, bKLM RPC should generate no EMI to other subsystems• we are taking this all into account in design and look forward to further discussion and review

THANK YOU