1. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Experimental features of strip-RPCs Motivation FOPIs Multistrip-Multigap-RPCs Results Conclusions

2. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Motivation CBM ToF wall area ~ 100 m 2 100 modules with ~ 1 m 2  t 95 % rate ~ 2 -20 kHz/cm 2 ~ 60000 channels Multi strip RPCs are one of the possibilities to fulfill the CBM-ToF requirements. The characteristical features of strip-RPCs can be determined with the FOPI Multistrip-Multigap-RPCs.

3. CBM Collaboration Meeting, GSI 10 - 13.03.2009 MMRPC design Multi-pin connector Multi-strip anode Capacitor block FOPIs MMRPC - parameters active area 90 x 4,6 cm strips16 strip / gap 1.64 / 0.9 mm glass thickness1 mm / 0.5 mm number of gaps2 x 4 gap width 220  m gas: Reclin/SF 6 /iso-But 80/15/5 Mounting table MRPC glass stack

4. CBM Collaboration Meeting, GSI 10 - 13.03.2009 FOPIs MMRPC barrel FOPI´s new ToF-barrel was used during the first Ni+Ni run in September 2007 MMRPC Barrel characteristics: - 30 SM, 5 counters each with 16 strips - 4800 time + 2400 charge channels - active area 5.12 m 2 -  t 95 %, rate ~ 0,02 kHz/cm 2 RPCPreamp.Disc. QDCTAC FEE 5 Taquila input pulser QDC ouput TAC ouput Elec. resol. FEE ~ 18 ps TAC ~ 10 ps  t ~ 15 ps  E < 25 ps 10 bit12 bit free running common stop system at 40 MHz

5. CBM Collaboration Meeting, GSI 10 - 13.03.2009 MMRPC performance  t < 94 ps v [cm/ns] p [GeV/c] p K+K+ ++ d t T.I. Kang system time resolution

6. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Cluster size Cluster size drops at the edges - pure geometrical effect mean cluster size is  4.2 for the inner strips cluster cluster = group of neighboring strips with signals generated by a single avalanche 11 mm

7. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Cluster charge vs.  minimum ionizing particles correlation between mean cluster charge and energy deposition of the particle (Bethe-Bloch) mean cluster charge

8. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Mean cluster charge - charge drops on the size strips - edge effects diminish the electrical field cathode anode strips ~5 mm strip: 1.64 mm gap: 0.6 mm

9. CBM Collaboration Meeting, GSI 10 - 13.03.2009 intrinsic time resolution intrinsic time resolution = time difference between hits in different strips for one cluster in the middle region of the rpc the intrinsic time resolution is about 30 ps  electronic time res. The degradation towards the sides can be understood by the decreasing signal-to-noise ratio caused by the dropping pulse hight.

10. CBM Collaboration Meeting, GSI 10 - 13.03.2009 cluster size dependence Same argumentation as in the slide before. more strips per cluster  more charge and pulse hight  better signal-to-noise ratio  better intr. time resolution

11. CBM Collaboration Meeting, GSI 10 - 13.03.2009 cluster size dependence charge per cluster grows linearly with the cluster size

12. CBM Collaboration Meeting, GSI 10 - 13.03.2009 Conclusions -The FOPI MMRPC is ideal to study the characteristics of narrow strip counters. - side effects are clearly identified  build larger structures. - cross talk does not seem to be a problem (so far) - multihit analysis just started pickup electrode RPC development for CBM active area 20 x 16,5 cm strips8 strip / gap 19.1 / 0.9 mm 4 strips are subdivided sub-strip / gap 1.6 / 0.9 mm glass typefloat glass thickness0.5 mm number of gaps2 x 4 gap width 220  m FOPI type read out

13. CBM Collaboration Meeting, GSI 10 - 13.03.2009 People GSI – FOPI:Uni-HD:Korea University, K.Hildenbrand M.CiobanuSeoul: T.I.Kang I.DeppnerB.Hong Y.J.Kim N.Herrmann M.Kis P-A. Loizeau P.Koczon K.Piasecki GSI-EE: Y.Leifels A.Reischl E.Badura M.Marquardt Y. ZhangR.Hardel W.ReisdorfK.Koch M.S.RyuNIPNE Bucharest:N.Kurz A.SchüttaufM.PetroviciW.Ott J.WeinertV.SimionR.Schulze X.Zhang N.Zernezki thank you