The BaBar muon system upgrade

Resistive plate chambers (RPCs) were used for the instrumentation of the iron flux return of the BaBar detector as a muon system. Unfortunately the efficiency of the original RPCs degraded rapidly with time. Limited streamer tubes (LSTs) were chosen for an upgrade of the barrel portion of the detector. The phased installation started in summer 2004 with replacing two sextants of the BaBar barrel muon system with LSTs. The modules for the remaining four sextants are under long-term test at SLAC and ready for installation, expected in 2006. The modules become inaccessible once installed in BaBar, so it is critical to select only perfectly working tubes. To accomplish this a strong QC system was established during the prototype phase, and fully implemented throughout pre-production and construction. To spot any damage during transport, the final modules are subjected to comprehensive tests at SLAC immediately after arrival and kept under long-term test till installation into BaBar. Details of these tests and results from long-term testing will be discussed. Since spring 2005 the PEP-II accelerator is running and BaBar is collecting data. First experience from data taking with the LSTs will be presented and the performance of the detector discussed.