Beam test of pad tRPCs with ultra-thin glass Status of IHEP+INR activity for high rate RPCs

1. Beam test of pad tRPCs with ultra-thin glassStatus of IHEP+INR activity for high rate RPCs V. Ammosov 13th CBM meeting,GSI,March 10

2. Goal is rate capability ~ 1/glass thickness ? • Previously RPCs with semiconductive glasses were tested. Rate capability ~ 20 kHz/cm2 was found - but this way is expensive, no long term stability too • Comparison of rate capability of pad RPCs for 0.17 mm thick microscope slips (China) and 0.85 mm Glaverbel glass was done • Bulk resistivity of both glasses ~ 1012 Ohmcm (with factor of 2) • Three chambers were tested at IHEP accelerator in Dec08 1) 1x0.3 mm RPC with 0.17 mm glass plates 2) 1x0.3 mm RPC with 0.85 mm glass plates 3) 6x0.3 mm RPC with 0.17 mm glass plates 24x24 mm2 – glass plates, 18x18 mm2 – pads • High rate irradiation via 90Sr source V. Ammosov 13th CBM meeting,GSI,March 10

3. PMMA RPC designs d scotch s.c. enamel 1M/ Cu tape 0.05 Glass 0.17 Fishing line 0.3 V. Ammosov 13th CBM meeting,GSI,March 10

4. Layout in test area S1,S2 are beam counters with 1x1x1 cm3 scintillator each. T1,T2,T3,T4 are timing counters: pair of PMTs, “FEU87”, reads one scintillator Beam intensity ~30 Hz/cm2 a few GeV positive beam, mostly hadrons at IHEP accelerator V. Ammosov 13th CBM meeting,GSI,March 10

5. Read-out system • Signals from T1,T2,T3,T4 counters were fed to constant fraction discriminators (CFDs). Output of CFD was connected with LeCroy 2228A TDC having 47ps count. • RPC anode pad was connected with the FOPI 4 channel amplifier-discriminator After amplification a signal was split into two ones: one of which after discrimination with threshold of ~20fC was sent to TDC , another one to QDC. • Slewing time – charge correction was applied. • Start/gate for TDC/QDC was generated if a coincidence of six signals occurred: S1*S2*T1*T2*T3*T4. (This selected beam spot of 1x1 cm2 )‏ V. Ammosov 13th CBM meeting,GSI,March 10

6. T0 time was taken as T0=(T1+T2+T3+T4)/4 From difference between two sets of counters T12-T34 =(T1+T2)/2-(T3+T4)/2 it was found that accuracy in time determined via four counters isσref~52 ps V. Ammosov 13th CBM meeting,GSI,March 10

7. Slewing correction ? V. Ammosov 13th CBM meeting,GSI,March 10

8. Time distributions V. Ammosov 13th CBM meeting,GSI,March 10

9. Charge distributions for different rates V. Ammosov 13th CBM meeting,GSI,March 10

10. No 90Sr irradiation Counting rate in beam ~ 30 Hz/cm2 V. Ammosov 13th CBM meeting,GSI,March 10

11. No 90Sr irradiation Counting rate in beam ~ 30 Hz/cm2 Dark counting rate a few Hz/cm2 Dark current < 1 microamp V. Ammosov 13th CBM meeting,GSI,March 10

12. No 90Sr irradiation Counting rate in beam ~ 30 Hz/cm2 Tails = (all hist- gaus)/all hist V. Ammosov 13th CBM meeting,GSI,March 10

13. N.B. Total counting rate for 6 gap RPC is six times higher V. Ammosov 13th CBM meeting,GSI,March 10

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16. At maximal 90Sr irradiation V. Ammosov 13th CBM meeting,GSI,March 10

17. Conclusion • It seems reasonable to play with ultra-thin glasses for high rates, indeed h.r. capability ~ 1/d • Is it possible to reach 20 kHz/cm2 with it ? actionfactor 170 m 50 m ~ 3 slips are not available cathode = metal ~ 2 thinner gap(Q) ~2-3 totally >10 May be possible Intend to study these factors during April09 IHEP run • and also 6 indep. gaps v.s. 6 floating gaps will be tested V. Ammosov 13th CBM meeting,GSI,March 10

18. Intend to construct and test in Nov09 IHEP run a 96 channel prototype: • basic element – single cell (pad) RPC • final RPC features will be defined in April09 IHEP run • willing to have independent gaps in a cell RPC Plans with a 96 ch. prototype V. Ammosov 13th CBM meeting,GSI,March 10

19. It is planned to have 8x12 overlapped cells Why 96 channels = 4x24ch It is fitted with NINO 24 ch cards as back up solution (+HPTDC) Is it feasible to test new CBM chain FEE+TDC for 96 channels in Nov09 IHEP run? Is it needed for design to be fitted into some super prototype ? Plans with a 96 ch. prototype V. Ammosov 13th CBM meeting,GSI,March 10