1. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 1 IHEP possible participation in CBM TOF system Vladimir Ammosov Institute for High Energy Physics Protvino Moscow region, Russia

2. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 2 CBM challenge for TOF Item value comment Time resolution ~50 ps for R&D ~80 ps for system Rate capability ~10 5 Hz/cm 2 High granularity  4 cm 2 and large scale ~ 100 m 2 It is intended to use RPCs in the CBM TOF system. Currently there are no real TOF RPC systems with such time resolution and rate capability. IHEP group is interested to participate in R&D challenge and TOF system construction

3. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 3 IHEP TOF group We were/are busy with RPCs since 1993 -ATLAS muon system -HARP TOF system -R&D for hadron calorimer for LC Group comprises 4 hardware physicists 1 software phys. 2 engineers 2 technicians

4. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 4 Possible solution – multigap RPC - 2x(2x0.3 mm) chamber - thin (0.6 mm) glass plates - 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 HARP example

5. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 5 HARP 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

6. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 6 Obtained eff ~ 98-99% OK Obtained  t ~ 160-180 ps is worse than R&D 130 ps (~sqrt (2) ) HARP RPC TOF system

7. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 7 Our current R&D vision 1 RPC TOF option Intend to continue searching for plastics, glass, enamels with proper resistivity to reach rate capability up to ~10 5 Hz/cm 2 with required signal, efficiency and noise levels Joint work with INR, ITEP and Western groups within the INTAS-GSI project for CBM TOF system 2 Si PM as back up TOF forward option Intend to study possibility to reach 50 ps time resolution with scintillator+SiPM

8. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 8 Possible participation in TOF construction Up to now IHEP still has some infrastructure to - construct RPC detectors - test RPC detectors We are interested to contribute to these items sizeably Furthermore participation in design and construction of front-end electronics can be considered

9. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 9 RPC R&D Pestov glass Cathode – SS Anode - window glass (WG)  ~8·10 12  ·cm or - Pestov glass (BG)  ~4·10 10  ·cm Sat. avalanche mode TFE/IB/SF6 = 90/5/5 Gap = 1.2 mm Was tested in 5 Gev h+ beam at IHEP, Protvino

10. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 10 RPC R&D Pestov glass Comparison of efficiency Thr. 0.6 mV Rate 50 Hz/cm2 Level of eff. ~ 90% Some drop of eff. for WG Pestov glass WG

11. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 11 RPC R&D Pestov glass Comparison of average charge Thr. 0.6 mV Rate 50 Hz/cm2 Same level of charges Drop of charge for WG at high HV Pestov glass WG

12. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 12 RPC R&D Pestov glass Comparison of noise Usual WG RPC with c&a = WG, gap=1.2 mm Higher level of noise with SS cathode Higher noise of Pestov glass in working region Pestov glass WG usual WG RPC

13. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 13 RPC R&D Pestov glass Comparison of rate Thr. 0.6 mV Pestov glass rate capability ~ 5 kHz/cm2 practical maximum which is available with beam Pestov glass usual WG RPC WG

14. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 14 RPC R&D Pestov glass Comparison of resistivity behavior vs HV Resistivity is not constant for bakelite and Pestov glass Window glass Bakelite Pestov glass

15. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 15 RPC R&D Epoxy enamel Cathode and anode are epoxy enamel ETAL-47 with  ~10 10  ·cm 0.4 mm thick Sat. avalanche mode TFE/IB/SF6 = 90/5/5 Gap = 0.55 mm Was tested in 5 Gev h+ beam at IHEP, Protvino

16. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 16 RPC R&D Epoxy enamel Efficiency vs HV Thr. 1.25 mV Eff. is ~90% which is reasonable for 0.55 mm gap

17. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 17 RPC R&D Epoxy enamel Comparison of noise Noise for enamel is rather larger at working HV point 4.9 kV noise for enamel ~ 200 Hz/cm2

18. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 18 RPC R&D Epoxy enamel Comparison of rate capability for enamel up to 10 kHz/cm2 – maximal beam intensity which was available for usual glass RPC ~100 Hz/cm2 enamel Usual 1.2mm gap WG RPC

19. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 19 Conclusion 1 RPC TOF option Intend to continue searching for plastics, glass, enamels with proper resistivity to reach rate capability up to ~10 6 Hz/cm 2 with required signal, efficiency and noise levels 2 Si PM back up TOF option for small  Intend to study possibility to reach 50 ps time resolution with scintillator+SiPM

20. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 20 Si PM option for TOF P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001 SiPM size ~ 1, 9 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 Russia: Pulsar + MEPhI (B. Dolgoshein) CPTA (V.Golovin) Dubna (Z.Sadygov)

21. November 5, 2004V.Ammosov ITEP-Moscow, Russian CBM meeting 21 Si PM option for TOF 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