1. July 8, 2003V.Ammosov GSI, CBM meeting1 RPC TOF system for HARP experiment (Applicability for CBM) Vladimir Ammosov Institute for High Energy Physics Protvino Moscow region, Russia

2. July 8, 2003V.Ammosov GSI, CBM meeting2 Content 1. R&D results 2. RPC TOF system for HARP 3. Applicability for CBM 4. Alternative option 5. Conclusion

3. July 8, 2003V.Ammosov GSI, CBM meeting3 Contributors to results R&D IHEP V.Ammosov, V.Gapienko, A.Semak, Yu.Sviridov, E.Usenko, V.Zaets CERN F.Dydak HARP IHEP V.Gapienko, A.Semak, Yu.Sviridov, E.Usenko, V.Zaets CERN M.Bogomilov, F.Dydak, R.Dumps, J.Wotschak JINR D.Dedovich

4. July 8, 2003V.Ammosov GSI, CBM meeting4 R&D results Requirements 1.  t ~200 ps 2.Rate ~100 Hz/cm 2 3.In 2T mag field 4.Thin ~10 mm 5.Simple design

5. July 8, 2003V.Ammosov GSI, CBM meeting5 R&D results Proposed solution - 2x(2x0.3 mm) chamber - thin (0.6 mm) glass plates (  ~ 10 13  cm) - read out in the middle - gas mixture TFE=C 2 H 2 F 4 /IB/SF 6 =80/5/5 8 ion.cl./mm -saturated avalanche mode IB – quencher SF 6 – streamer suppressor ~1 pC Reason for multigap  t ~ 1/E  t ~ 1/  N gap

6. July 8, 2003V.Ammosov GSI, CBM meeting6 R&D results Usual approach for  t It is needed to split each channel for TDC and QDC to apply T-Q correction if simple discrimination in time branch is used

7. July 8, 2003V.Ammosov GSI, CBM meeting7 R&D results  t vs pad size HV plateau ~ 200 V  t (ps) = 70+.26ps/cm 2 x S for S  t (ps) = 71+.13ps/cm 2 x S for el sum

8. July 8, 2003V.Ammosov GSI, CBM meeting8 R&D results Eff. vs pad size - eff. decreases vs S  - full eff. ~ 99% for small S (< 50 cm 2 ) - eff. for 3  t is 2% less

9. July 8, 2003V.Ammosov GSI, CBM meeting9 R&D results  t for CFD It seems that it is not needed to have T-Q correction for FEE with CFD. One TDC branch is enough.  t is compatible with usual.

10. July 8, 2003V.Ammosov GSI, CBM meeting10 R&D results 90 x 2.5 cm 2 strips  t ~ 100 ps Eff for 3  t ~ 94%

11. July 8, 2003V.Ammosov GSI, CBM meeting11 R&D results Rate capability 150 cm 2 pad It seems that  t and eff. are constant for rates  500 Hz/cm 2

12. July 8, 2003V.Ammosov GSI, CBM meeting12 R&D results Conclusion 2x(2x0.3 mm) RPC allows for small pad readout (  50 cm 2 ) to have in saturated avalanche mode using thin window glass plates (  ~ 10 13  cm) 1.  t ~ 80 ps 2.Full eff. ~ 99%, eff. for 3  t ~ 97% 3.Rate capability  500 Hz/cm 2 4.Cross talks ~ 20% 5.Noise ~ 0.1 Hz/cm 2 6.HV plateau ~ 200 V 7.Use of CFD

13. July 8, 2003V.Ammosov GSI, CBM meeting13 HARP RPC TOF system For soft momentum large angle e/ , e/p separation e/   250 MeV/c e/p  1 GeV/c Flight pass 0.5 – 2 m 10 m 2 RPC area 46 chambers 368 channels in total 8 ch/chamber 30 RPCs – barrel 16 RPCs - forward

14. July 8, 2003V.Ammosov GSI, CBM meeting14 HARP RPC TOF system RPC coverage in barrel

15. July 8, 2003V.Ammosov GSI, CBM meeting15 HARP RPC TOF system RPC design - RPC active area 104x1920 mm 2 - strip size 104x30 mm 2, 64 totally in length - 8 strips are summed electronically

16. July 8, 2003V.Ammosov GSI, CBM meeting16 HARP RPC TOF system Picture of RPC glass stack

17. July 8, 2003V.Ammosov GSI, CBM meeting17 HARP RPC TOF system

18. July 8, 2003V.Ammosov GSI, CBM meeting18 Obtained eff ~ 99% OK Obtained  t ~ 140-160 ps is slightly worse than expected 130 ps HARP RPC TOF system

19. July 8, 2003V.Ammosov GSI, CBM meeting19 Applicability for CBM L (target – RPC wall) ~12 m

20. July 8, 2003V.Ammosov GSI, CBM meeting20 Assume  t = 100 ps 2  t separation  300 ps max p, GeV/c e/  1.2  /k 4.0 k/p 7.0 Applicability for CBM -----------------  2  t separation L=12 m

21. July 8, 2003V.Ammosov GSI, CBM meeting21 Applicability for CBM N problem point value comment 1Granularity ~ 4 cm 2 no problem 2Cross talk ~ 20% no problem 3Large scale ~ 100 m 2 no problem 4Rate capability ~10 5 Hz/cm 2 CHALLENGE ! Now ~10 3 Hz/cm 2 Possible ways: - reduce charge in gap - reduce plate resistivity Goal of INTAS-GSI project RPC applicability

22. July 8, 2003V.Ammosov GSI, CBM meeting22 RPC applicability for CBM 1.2 mm monogap 1x1 cm 2 pads Sat avalanche mode vs anode thickness Should be as small as possible Knee  =0.6 mm

23. July 8, 2003V.Ammosov GSI, CBM meeting23 RPC applicability for CBM 1.2 mm monogap 1x1 cm 2 pads Eff. vs rate Rate capability streamer ~1-2 Hz/cm 2 avalanche ~100 Hz/cm 2 - avalanche mode, = 4 pC - streamer mode, = 400 pC

24. July 8, 2003V.Ammosov GSI, CBM meeting24 Applicability for CBM Alternative option – Silicon PM (MRS systems) P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001 SiPM size ~ 1 mm 2, ~ 1000 cells of 30x30  2 Max light sensitivity at 570 nm, overall  ~14% Each cell works in Geiger mode independently, gain ~10 6 Developers in Moscow: Pulsar + MEPhI (B. Dolgoshein) CPTA (V.Golovin)

25. July 8, 2003V.Ammosov GSI, CBM meeting25 Applicability for CBM Alternative option – Silicon PM (MRS systems) For cell intrinsic  A /A ~0.1  1,2,3,4 ph. electrons are seen recovery time <100 ns  >10 MHz rate capability intrinsic  t = 100 ps/sqrt (N cell ) Noise for 1 cell (ph.e.) ~1 MHz, decrease with N cell increase  t,ps N cell P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001

26. July 8, 2003V.Ammosov GSI, CBM meeting26 Applicability for CBM Alternative option – Silicon PM (MRS systems) MEPhI+PULSAR+ITEP collaboration for TESLA tile HCAL 3M mirror SiPM Vladimir’s tile = 23 ph.e 50x50x5 mm 3 molded PS

27. July 8, 2003V.Ammosov GSI, CBM meeting27 Conclusion 1.It is challenge for RPC TOF system to reach 10 5 MHz/cm 2 rate capability. 2.It seems the SiPM option should be tried. 3.Both options will be investigated within the INTAS-GSI project for the CBM TOF system.