In order to improve the Kaon identification up to 1 GeV/c the FOPI detector will be upgraded by an array of 150 Multi-strip MRPCs . This requires a time resolution σt ≤ 100 ps for single and double-hits in the counters . The counter design is finalized (cf. Fig. 1): active area 46 x 900 mm 2, 8 gaps of 220 µm, 16 separate anode strips, operation voltage 9 to 10 kV; a gas mixture Freon/i-But/SF6 (85/5/10)is used. The mass production has started, the system shall be operational by the end of 2006. the detector response is similar for the various gain settings, a higher gain leads to a shift of the curves to lower fields. At given field a higher gain provides a better resolution, likewise at given gain a certain resolution is reached at a lower field strength. For example we reach at G ∼ 77 a time resolution of σt ≤75 ps at E ≥ 120 kV/cm; at G ∼ 220 a resolution σt ≤ 50 ps is reached at E ≥ 108 kV/cm already. Similarly the detector becomes fully efficient at lower electric fields when the gain is higher
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