Effects of SF ₆ on the avalanche mode operation of a real-sized double-gap resistive plate chamber for the compact muon solenoid experiment

We present the design and the test results for a real-sized prototype resistive plate chamber by using cosmic-ray muons for the forward region of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). In particular, we investigate the effects of adding SF ₆ to the gas mixture for the avalanche mode operation of a resistive plate chamber. A small fraction of SF ₆ is very effective in suppressing streamer signals in a resistive plate chamber. The shapes of the muon detection efficiency and the muon cluster size remain similar, but are shifted to higher operating voltage by SF ₆. The noise cluster rate and size are not influenced by SF ₆.