G. Carboni – Muon Meeting – RPC situation: RPC production in GeneralTecnica (GT) has suffered large delays, due to gluing problems (spacers) detected on the latest bakelite plates (130 sheets). problem “NOT UNDERSTOOD” (U. Dosselli at last LHCC) but a solution found by cleaning plates with IMB-ketone (and “brushing”). Tests on 11 gap sample is OK. production now restarted 5 gaps for LHCb produced, but not yet delivered (?) ready to start aging test, but small hope for 10 LHCb-y dose within 2002, even in R4 RPC Coordination Committee (INFN) Meeting held in Rome on June 14 Our results on increasing resistance were presented Discovered that ATLAS aging test (to 0.35 C/cm2) gave a 30-fold resistance increase. Nevertheless, ATLAS (Aielli et al.) dubbed that “a modest increase” effect similar to ours (quantitatively and qualitatively)

G. Carboni – Muon Meeting – Aielli’s talk in DESY 2001 (see also NIM A478 (2002) 271) 32 is “moderate”

G. Carboni – Muon Meeting – ATLAS vs LHCb test ATLAS RPC: S=1.42 m 2,  in =  cm à Test: 15 months, Q=0.35 C/cm2 (12 ATLAS-years)   fin (from R=16.7 M  ) ~  cm - For us, at end of 2001 (Q=0.42 C/cm2),  fin ~  cm. So match not bad. • ATLAS now blames “large flow of dry gas” in our case (!) For ATLAS this value of resistivity limits the rate to Hz/cm2 (OK for them, if resistivity does not increase further) ATLAS believes that resistivity will stop increasing, but they don’t offer any proof  We find that  kept increasing. Now around (GP talk) From our tests, maximum tolerable is probably  fin ~  cm in Region 4 (250 Hz/cm2) à Region 3 totally ruled out

G. Carboni – Muon Meeting – Final remarks on RPCs Despite decades of R&D, the RPC (including bakelite, oil) is still far from being understood The resistivity increase seems now established as the most crucial effect for aging From our data, the safe conclusion is to rule out the RPC in LHCb little hope that the forthcoming (?) aging test will reverse the situation RPCs vs MWPCs The construction simplicity of the RPCs is mainly apparent. After the oiling and gluing problems appeared, INFN institutes have been forced to deploy an increasing number of physicists at the factory for quality control. This makes the new RPCs more manpower-intensive than the old ones. Recent changes in the production have increased the prices (washing, brushing, pipe fittings, etc) The production escapes our control (too many unknowns and too many end users; one unique supplier). That was not expected 2 years ago.