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RPC TOF systemfor HARP experiment(Applicability for CBM): 

RPC TOF system for HARP experiment (Applicability for CBM) Vladimir Ammosov Institute for High Energy Physics Protvino Moscow region, Russia

Content: 

Content 1. R&D results 2. RPC TOF system for HARP 3. Applicability for CBM 4. Alternative option 5. Conclusion

Contributors to results: 

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

R&D results: 

R&D results Requirements t ~200 ps Rate ~100 Hz/cm2 In 2T mag field Thin ~10 mm Simple design

R&D results: 

R&D results Proposed solution 2x(2x0.3 mm) chamber thin (0.6 mm) glass plates ( ~ 1013 cm) 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

R&D results: 

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

R&D results: 

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

R&D results: 

R&D results Eff. vs pad size eff. decreases vs S  full eff. ~ 99% for small S (< 50 cm2) eff. for 3 t is 2% less

R&D results: 

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.

R&D results: 

R&D results 90 x 2.5 cm2 strips t ~ 100 ps Eff for 3t ~ 94%

R&D results: 

R&D results Rate capability 150 cm2 pad It seems that t and eff. are constant for rates  500 Hz/cm2

R&D results: 

R&D results Conclusion 2x(2x0.3 mm) RPC allows for small pad readout ( 50 cm2) to have in saturated avalanche mode using thin window glass plates ( ~ 1013 cm) t ~ 80 ps Full eff. ~ 99%, eff. for 3 t ~ 97% Rate capability  500 Hz/cm2 Cross talks ~ 20% Noise ~ 0.1 Hz/cm2 HV plateau ~ 200 V Use of CFD

HARP RPC TOF system: 

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 m2 RPC area 46 chambers 368 channels in total 8 ch/chamber 30 RPCs – barrel 16 RPCs - forward

HARP RPC TOF system: 

HARP RPC TOF system RPC coverage in barrel

HARP RPC TOF system: 

HARP RPC TOF system RPC design RPC active area 104x1920 mm2 strip size 104x30 mm2, 64 totally in length 8 strips are summed electronically

HARP RPC TOF system: 

HARP RPC TOF system Picture of RPC glass stack

HARP RPC TOF system: 

HARP RPC TOF system

HARP RPC TOF system: 

Obtained eff ~ 99% OK Obtained t ~ 140-160 ps is slightly worse than expected 130 ps HARP RPC TOF system

Applicability for CBM: 

Applicability for CBM L (target – RPC wall) ~12 m

Applicability for CBM: 

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

Applicability for CBM: 

Applicability for CBM N problem point value comment Granularity ~ 4 cm2 no problem Cross talk ~ 20% no problem Large scale ~ 100 m2 no problem Rate capability ~105 Hz/cm2 CHALLENGE ! Now ~103 Hz/cm2 Possible ways: - reduce charge in gap - reduce plate resistivity Goal of INTAS-GSI project RPC applicability

RPC applicability for CBM: 

RPC applicability for CBM 1.2 mm monogap 1x1 cm2 pads Sat avalanche mode <m> vs anode thickness Should be as small as possible Knee  =0.6 mm

RPC applicability for CBM: 

RPC applicability for CBM 1.2 mm monogap 1x1 cm2 pads Eff. vs rate Rate capability streamer ~1-2 Hz/cm2 avalanche ~100 Hz/cm2 - avalanche mode, <Q> = 4 pC - streamer mode, <Q> = 400 pC

Applicability for CBM: 

Applicability for CBM Alternative option – Silicon PM (MRS systems) P. Buzhan et al., ICFA Instrum.Bull.23:28-41,2001 SiPM size ~ 1 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 Moscow: Pulsar + MEPhI (B. Dolgoshein) CPTA (V.Golovin)

Applicability for CBM: 

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 (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

Applicability for CBM: 

Applicability for CBM Alternative option – Silicon PM (MRS systems) MEPhI+PULSAR+ITEP collaboration for TESLA tile HCAL <AMIP> = 23 ph.e 50x50x5 mm3 molded PS

Conclusion: 

Conclusion It is challenge for RPC TOF system to reach 105 MHz/cm2 rate capability. It seems the SiPM option should be tried. Both options will be investigated within the INTAS-GSI project for the CBM TOF system.