1. RPC Update José Repond Argonne National Laboratory American Working Group On Linear Collider Calorimetry 24 November 2003 What’s new since September…

2. New chamber construction New gas Multi-channel VME boards HV system Prototype system Plans for the next few months Outline

3. 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

4. In the past used mostly Freon:Argon:Isobutane = 62:30:8 Now using new gas Freon:Isobutane:SF 6 = 94.5:5:0.5 - Higher charge: ~ 1pC - Wider HV plateau without streamers New Gas

5. Large avalanche signal up to ~1.5 pC Mild streamer signal

6. Setting threshold Threshold of 400 pC possible with >95% efficiency Expect excellent noise suppression

7. 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

8. High Voltage System Being 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 σ noise to 10 fC

9. Prototype section: 1m 3 Mechanical design Working on layout Electronic readout Ready for specification of FE ASIC Initiated discussions with FNAL In discussions with CALICE concerning back end

10. 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…