Resistive plate chamber performance in the BaBar IFR system

The BaBar Collaboration has operated a system covering over 2000 m² with resistive plate chambers for nearly three years. The chambers are constructed of bakelite sheets separated by 2 mm. The inner surfaces are coated with linseed oil. This system provides muon and neutral hadron detection for BaBar. Installation and commissioning were completed in 1998, and operation began mid-1999. While initial performance of the system reached design, over time, a significant fraction of the resistive plate chambers demonstrated significant degradation, marked by increased currents and reduced efficiency. A coordinated investigative effort has identified many of the elements responsible for the degradation.