DOC 2004 Nov 40 1

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IHEP possible participation in CBM TOF system: 

IHEP possible participation in CBM TOF system Vladimir Ammosov Institute for High Energy Physics Protvino Moscow region, Russia

CBM challenge for TOF: 

CBM challenge for TOF Item value comment Time resolution ~50 ps for R&D ~80 ps for system Rate capability ~105 Hz/cm2 High granularity  4 cm2 and large scale ~ 100 m2 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

IHEP TOF group: 

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

Possible solution – multigap RPC: 

Possible solution – multigap RPC - 2x(2x0.3 mm) chamber - thin (0.6 mm) glass plates - read out in the middle gas mixture TFE=C2H2F4/IB/SF6=80/5/5 8 ion.cl./mm saturated avalanche mode IB – quencher SF6 – streamer suppressor <Q> ~1 pC Reason for multigap t ~ 1/E t ~ 1/Ngap HARP example

HARP R&D results: 

HARP R&D results t vs pad size HV plateau ~ 200 V t (ps) = 70+.26ps/cm2 x S for S t (ps) = 71+.13ps/cm2 x S for el sum

HARP RPC TOF system: 

Obtained eff ~ 98-99% OK Obtained t ~ 160-180 ps is worse than R&D 130 ps (~sqrt (2) ) HARP RPC TOF system

Our current R&D vision: 

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 ~105 Hz/cm2 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

Possible participation in TOF construction: 

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

RPC R&D: 

RPC R&D Pestov glass Cathode – SS Anode - window glass (WG)  ~8·1012  ·cm or - Pestov glass (BG)  ~4·1010  ·cm Sat. avalanche mode TFE/IB/SF6 = 90/5/5 Gap = 1.2 mm Was tested in 5 Gev h+ beam at IHEP, Protvino

RPC R&D: 

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

RPC R&D: 

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

RPC R&D: 

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

RPC R&D: 

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

RPC R&D: 

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

RPC R&D: 

RPC R&D Epoxy enamel Cathode and anode are epoxy enamel ETAL-47 with  ~1010  ·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

RPC R&D: 

RPC R&D Epoxy enamel Efficiency vs HV Thr. 1.25 mV Eff. is ~90% which is reasonable for 0.55 mm gap

RPC R&D: 

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

RPC R&D: 

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

Conclusion: 

Conclusion 1 RPC TOF option Intend to continue searching for plastics, glass, enamels with proper resistivity to reach rate capability up to ~106 Hz/cm2 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

Si PM option for TOF: 

Si PM option for TOF P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001 SiPM size ~ 1, 9 mm2, ~ 1000 cells of 30x30 2 Max light sensitivity at 570 nm, overall  ~14% Each cell works in Geiger mode independently, gain ~106 Developers in Russia: Pulsar + MEPhI (B. Dolgoshein) CPTA (V.Golovin) Dubna (Z.Sadygov)

Si PM option for TOF: 

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 (Ncell) Noise for 1 cell (ph.e.) ~1 MHz, decrease with Ncell increase t,ps Ncell P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001

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