Performance of multigap resistive plate chambers with pure Freon 134a

The performance of Multigap Resistive Plate Chambers (MRPCs) with pure Freon 134a was investigated. Two types of MRPCs with different number of gaps and different gap width have been studied; one with 10 gaps of 250 μ m and the other with 24 gaps of 160 μ m . From the beam tests performed at CERN, the time resolution of the MRPCs flushed with pure Freon has been found to be the same as when SF6 was added to Freon. The 10 gap MRPC has a time resolution better than 50 ps and the 24 gap MRPC has a resolution of 21 ps, at full efficiency and with no streamers. With pure Freon, the streamers start to develop at a lower electric field.