July 8, 2003 V.Ammosov GSI, CBM meeting 1

RPC TOF systemfor HARP experiment

(Applicability for CBM)

Vladimir Ammosov

Institute for High Energy Physics

Protvino Moscow region, Russia

July 8, 2003 V.Ammosov GSI, CBM meeting 2

Content

1. R&D results

2. RPC TOF system for HARP

3. Applicability for CBM

4. Alternative option

5. Conclusion

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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

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R&D resultsRequirements

1. t ~200 ps2. Rate ~100 Hz/cm2

3. In 2T mag field4. Thin ~10 mm5. Simple design

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R&D resultsProposed 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 multigapt ~ 1/Et ~ 1/Ngap

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R&D resultsUsual approach for t

It is needed to split each channel for TDC and QDC to apply T-Q correctionif simple discrimination in time branch is used

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R&D resultst vs pad size

HV plateau ~ 200 V t (ps) = 70+.26ps/cm2 x S for St (ps) = 71+.13ps/cm2 x S for el sum

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R&D resultsEff. vs pad size

- eff. decreases vs S - full eff. ~ 99% for small S (< 50 cm2)- eff. for 3 t is 2% less

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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.

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R&D results90 x 2.5 cm2 strips

t ~ 100 ps

Eff for 3t ~ 94%

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R&D resultsRate capability

150 cm2 pad

It seems thatt and eff. are constant

forrates 500 Hz/cm2

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R&D resultsConclusion

2x(2x0.3 mm) RPC allows for small pad readout ( 50 cm2)

to have in saturated avalanche modeusing thin window glass plates ( ~ 1013 cm)

1. t ~ 80 ps2. Full eff. ~ 99%, eff. for 3 t ~ 97%3. Rate capability 500 Hz/cm2

4. Cross talks ~ 20%5. Noise ~ 0.1 Hz/cm2 6. HV plateau ~ 200 V7. Use of CFD

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HARP RPC TOF systemFor soft momentum large angle e/, e/p separation

e/ 250 MeV/c

e/p 1 GeV/cFlight pass 0.5 – 2 m

10 m2 RPC area46 chambers368 channels in total8 ch/chamber30 RPCs – barrel16 RPCs - forward

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HARP RPC TOF system

RPC coveragein barrel

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HARP RPC TOF systemRPC design

- RPC active area 104x1920 mm2

- strip size 104x30 mm2, 64 totally in length- 8 strips are summed electronically

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HARP RPC TOF systemPicture of RPC glass stack

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HARP RPC TOF system

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Obtained eff ~ 99% OK

Obtained t ~ 140-160 psis slightly worse than

expected 130 ps

HARP RPC TOF system

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Applicability for CBM

L (target – RPC wall) ~12 m

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Assume t = 100 ps2t separation 300 ps

max p, GeV/ce/ 1.2/k 4.0

k/p 7.0

Applicability for CBM

-----------------2t

separation

L=12 m

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Applicability for CBM

N problem point value comment1 Granularity ~ 4 cm2 no problem2 Cross talk ~ 20% no problem3 Large scale ~ 100 m2 no problem4 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

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RPC applicability for CBM

1.2 mm monogap1x1 cm2 pads

Sat avalanche mode

<m> vs anode thickness

Should be as small aspossible

Knee

=0.6 mm

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RPC applicability for CBM

1.2 mm monogap1x1 cm2 pads

Eff. vs rate

Rate capabilitystreamer ~1-2 Hz/cm2

avalanche ~100 Hz/cm2 - avalanche mode, <Q> = 4 pC

- streamer mode, <Q> = 400 pC

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Applicability for CBMAlternative 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)

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Applicability for CBMAlternative 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

July 8, 2003 V.Ammosov GSI, CBM meeting 26

Applicability for CBMAlternative option – Silicon PM (MRS systems)

50 100 150 200 250 300 350 400 450 500 550 6000,1

1

10

100

ray levelexpected cosmic

Dar

k ra

te,

Hz

Threshould, channels

50 100 150 200 250 300 350 400 450 500 550 6000

50

100

150

200

250

30095%

90%MIP efficiency

Num

ber

of e

vent

s

Channel number

MEPhI+PULSAR+ITEP collaboration for TESLA tile HCAL

3M mirror

SiPM

Vladimir’s tile

<AMIP> = 23 ph.e

50x50x5 mm3

molded PS

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Conclusion

1. It is challenge for RPC TOF system to reach 105 MHz/cm2 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.