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

V. Ammosov 13th CBM meeting,GSI,March 102 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 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 Comparison of rate capability of pad RPCs for 0.17 mm thick microscope slips (China) and 0.17 mm thick microscope slips (China) and 0.85 mm Glaverbel glass was done 0.85 mm Glaverbel glass was done Bulk resistivity of both glasses ~ Ohm  cm (with factor of 2) Bulk resistivity of both glasses ~ Ohm  cm (with factor of 2) Three chambers were tested at IHEP accelerator in Dec08 Three chambers were tested at IHEP accelerator in Dec08 1) 1x0.3 mm RPC with 0.17 mm glass plates 1) 1x0.3 mm RPC with 0.17 mm glass plates 2) 1x0.3 mm RPC with 0.85 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 3) 6x0.3 mm RPC with 0.17 mm glass plates 24x24 mm 2 – glass plates, 18x18 mm 2 – pads 24x24 mm 2 – glass plates, 18x18 mm 2 – pads High rate irradiation via 90 Sr source High rate irradiation via 90 Sr source

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

V. Ammosov 13th CBM meeting,GSI,March 104 Layout in test area S1,S2 are beam counters with 1x1x1 cm 3 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 105 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 cm 2 )‏

V. Ammosov 13th CBM meeting,GSI,March 106 T 0 time was taken as T 0 =(T1+T2+T3+T4)/4 From difference between two sets of counters T 12 -T 34 =(T1+T2)/2-(T3+T4)/2 it was found that accuracy in time determined via four counters is σ ref ~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 1010 No 90 Sr irradiation Counting rate in beam ~ 30 Hz/cm2

V. Ammosov 13th CBM meeting,GSI,March 1011 No 90 Sr irradiation Counting rate in beam ~ 30 Hz/cm 2 Dark counting rate a few Hz/cm 2 Dark current < 1 microamp

V. Ammosov 13th CBM meeting,GSI,March 1012 No 90 Sr irradiation Counting rate in beam ~ 30 Hz/cm2 Tails = (all hist- gaus)/all hist

V. Ammosov 13th CBM meeting,GSI,March 1013 N.B. Total counting rate for 6 gap RPC is six times higher

V. Ammosov 13th CBM meeting,GSI,March 1014

V. Ammosov 13th CBM meeting,GSI,March 1015

V. Ammosov 13th CBM meeting,GSI,March 1016 At maximal 90 Sr irradiation

V. Ammosov 13th CBM meeting,GSI,March 1017 Conclusion It seems reasonable to play with ultra-thin glasses for high rates, indeed h.r. capability ~ 1/d 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/cm 2 with it ? Is it possible to reach 20 kHz/cm 2 with it ? action factor action factor 170  m  50  m ~ 3 slips are not available cathode = metal ~ 2 cathode = metal ~ 2 thinner gap(Q  ) ~2-3 thinner gap(Q  ) ~2-3 totally >10 May be possible totally >10 May be possible Intend to study these factors during April09 IHEP run and also 6 indep. gaps v.s. 6 floating gaps and also 6 indep. gaps v.s. 6 floating gaps will be tested will be tested

V. Ammosov 13th CBM meeting,GSI,March Plans with a 96 ch. prototype 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

V. Ammosov 13th CBM meeting,GSI,March Plans with a 96 ch. prototype 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 ?