The HARP RPC time-of-flight system

The time-of-flight system based on thin-gap glass resistive plate chambers (RPCs) for the HARP detector at CERN is described and first experience with the chamber operation and performance is reported. The system consists of 46 chambers, covers an area of 10 m**2 and has 368 readout channels. The chambers are 2 m long, 150 mm wide, and 10 mm thick and have four gas gaps of 0.3 mm each, the glass plates are 0.7 mm thick. The RPCs are operated in avalanche mode with a mixture of 90% C//2F//4H//2, 5% SF//6, and 5% C//4H//1//0.