Final Parameters Final Parameters for the for the FOPI RPCFOPI RPC upgrade upgrade

Everard Cordier(Heidelberg University, Germany)

Everard Cordier(Heidelberg University, Germany)

Outline:

• RPC-6 gaps performance (test Nov-Dec 03)• RPC-8 gaps performance (test Aug 04)• Application for CBM• Next steps• Conclusions

CBMCBM MEETING Oct 2004 MEETING Oct 2004

Full system test Nov-Dec 03 (CDC+RPC)

Intrinsic performance (start counter unfolded)

• Single hit : time resolution 75ps, efficiency>96%

• Multihit : time resolution 95ps, efficiency>90%

System: U+Au @ 900 AMeV (~ 6.105 events in total)

RPC 90*4.6 cm²/6 gaps/14strips

Particle identification : momentum and velocity

Time difference spectrumfor fast pions (single and double hits)

Gap 300μmGlass 1mm

Background studies

Status in April 04 : background (single and double hit) ~ 5%

Mass cuted (GeV/c2)

Strong cuts on CDC tracks quality

Background 0.5%

Background 2.5%

New electronics (Aug 04)(see talk K. Koch)

Time resolution 25 ps

Next step (last) : 1 round with new connectors(Samtec)

Next time resolution 20 ps ?

Darkrate

Darkrate 1Hz/cm2

New long counter

8 gaps, 14 strips glass plates : 1.1/0.5mm gap size : 250μm

• A cluster is defined by the number of strips fired for one event• The cluster size (or width) is the mean obtained for several events

What is a cluster ?

Each event can fire several strips

2mm strip1mm gap

90 cm

In multihit situation the width should be as small as possible

Cluster and charge studies

In the inefficient region of the RPC mean and RMS of the charge distribution are nearly constant.

When the counter gets fully efficient it’s a linear rise of both

Linear increase of mean and widthof clusters with the voltage

Direct P/π beam

Smaller cluster size and better charge distribution for 8 gaps than for 6 gaps

Timing and efficiency resultsTiming and efficiency results

Needed for CBM

Operating window of the 8 gap RPC

At a voltage between 11.75-12.5

Fully efficient >98 %Time resolution <65 ps

Cluster width <2 strips

Charge mean far away from threshold ()

We can optimize cluster distribution and charge

Application for CBM

(Plot from L. Slusarczyk)

Resolution at 100 Hz / cm2 : 60 psat 1 kHz / cm2 : 85 ps

Estimation (linear extrapolation) : 80 ps for a rate of 820 Hz / cm80 ps for a rate of 820 Hz / cm22

Total area of the TOF wall at 10 meters : 150 m2

Total area with rate 1 kHz/ cm2 : 50 m2

Total area with rate 800 Hz/ cm2 : 38 m2

Au+Au @ 25 AGeVInteraction rate 107

10% central collisions

Can already be covered by FOPI counters (25 % of the total area)

Could be covered by FOPI counters (33 % of the total area)

Next stepNext stepSupermodule test Supermodule test Nov 04 :Nov 04 :

Build the supermodule 0 :

5 long RPCs (8 gap 250 μm, 16 strips, 1.1/0.5 mm glass)

+ new FEE (Samtec connectors)+ new Taquila + new mechanics

Beam test : full system performance with high statistics

GSI-KPI :M.Ciobanu

K.Hildenbrand M.MarquardtA.SchüttaufA.Weinert

HD-UniversityE.Cordier

N.HerrmannA.Mangiarotti

IPNE, Bucharest M.PetroviciV.Simion

GSI-DVEEE.BaduraR.HardelK.Koch

People

Thank you !!!

Conclusion

Next step FOPI Test Supermodule 0Supermodule 0 (5 MRPCs 8 gap) in experiment with

high statistics with full FOPI system. Adopt this solution for the TOF ugrade.

Next step CBM Determine time resolution needed (simulations) Increase performance (new electronics, gas or glass

studies) Cover a large part of the TOF wall with this RPCs ?

From Peter Senger (Oct 6. 04)