Beam test results of CMS RPCs at high eta region under high-radiation environment

The Compact Muon Solenoid (CMS) forward resistivity plate chambers (RPCs) at the high eta region must be operated in presence of a radiation-induced rate as high as 1 kHz/cm(2). It is still unknown if the RPCs coated with linseed oil can be operated under such a high-radiation environment over the lifetime of CMS. Non-oiled RPCs may be one of the options since phenolic or melamine-coated bakelite is chemically stabler than linseed oil. We have constructed oiled and non-oiled RPCs at the high eta region of CMS using phenolic bakelite and tested them in the Gamma Irradiation Facility at CERN. While both RPCs show the same characteristics in the efficiency and the strip multiplicity, the non-oiled RPC generates an intrinsic noise rate of 50 Hz/cm(2), compared to only 5 Hz/cm(2) for the oiled RPC, both at 10.0 kV which is about 100 V above the 95% knee of the efficiency curve. (C) 2004 Elsevier B.V. All rights reserved.