14 July 2003 Mark Oreglia, LCW Cornell 1 Progress on RPC Tests at the University of Chicago Outline: Prototype chamber Gas mixer Pulses and spectra Future plans

14 July 2003 Mark Oreglia, LCW Cornell 2 The Default Design ANL was kind enough to send us a chamber, which we have reworked several times Our aim is to test gas mixtures and look for surface damage, so we have a single readout pad The resistive layer is sprayed graphite Initial gas: R134a:Ar:Isobutane 62:30:8 future: HARP: R134a:Isobutane:SF6 90:5:5 All tests use CR telescope and trigger

14 July 2003 Mark Oreglia, LCW Cornell 3

14 July 2003 Mark Oreglia, LCW Cornell 4 Gas Mixer

14 July 2003 Mark Oreglia, LCW Cornell 5 Good Pulses It appears we have been seeing streamers, not avalanches (thresholds?)

14 July 2003 Mark Oreglia, LCW Cornell 6 Lots of double-pulses

14 July 2003 Mark Oreglia, LCW Cornell 7 … and much spontaneous pulsing

14 July 2003 Mark Oreglia, LCW Cornell 8 Trying to understand spectrum

14 July 2003 Mark Oreglia, LCW Cornell 9 A Better CR telescope Ed Blucher + Aren Jensen + Abby Kaboth Scintillator + DC for fine positioning Look for hotspots, etc

14 July 2003 Mark Oreglia, LCW Cornell 10 Good Position Info Now

14 July 2003 Mark Oreglia, LCW Cornell 11 What We are Investigating Origin of spontaneous discharges Effects of surface quality Surface damage Gas mixtures and their relation to the problems mentioned above Gas pressure and chamber ballooning –A real problem… –Stable operation disrupted for very slight deformation of chamber