RPC Update

José RepondArgonne National Laboratory

American Working Group On Linear Collider Calorimetry24 November 2003

What’s new since September…

• New chamber construction

• New gas

• Multi-channel VME boards

• HV system

• Prototype system

• Plans for the next few months

Outline

Argonne built 3 chambers early in 2003

2-gas gap chamber

- extensive tests with single pads - extensive tests with multi-pads - geometrical tests

Now built one more

Single-gas gap chamber

- first tests: same efficiency higher charge - tests with multi-pads needed: ‘cross-talk’?

Chamber construction

In the past used mostly

Freon:Argon:Isobutane = 62:30:8

Now using new gas

Freon:Isobutane:SF6= 94.5:5:0.5

- Higher charge: <Q> ~ 1pC - Wider HV plateau without streamers

New Gas

Large avalanche signal

up to ~1.5 pC

Mild streamer signal

Setting threshold

Threshold of 400 pC possible with >95% efficiency

Expect excellent noise suppression

Multi-channel VME readout

6U x 160 VME board

VME64 compliant Contains 64 discriminators Optional amplification Records time-stamps of hits and hit patterns

Commissioning

Card can be read out! Front-end works for streamer signals (~10 pC) More work needed to provide enough amplification for avalanche mode

High Voltage SystemBeing developed at ANL

Based on ZEUS BCAL HV bases Cockcroft-Walton technology Cheaper than Bertran

Prototypes

Built and tested with RPCs For avalanche mode: need external filters Able to get σnoise to 10 fC

Prototype section: 1m3

Mechanical design

Working on layout

Electronic readout

Ready for specification of FE ASIC Initiated discussions with FNAL In discussions with CALICE concerning back end

Plans for the next few months

Application of graphite layer

Workable paint in hand Encouraging results with silk screening

Prototype section

Design larger chambers, specify ASIC

Geometrical efficiencies

Investigate effect of HV leads and spacers

Multi-channel VME readout

Develop a useable FE for avalanche mode

Measurements

Multipad: efficiencies, noise rate, cross-talk…