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

V. Ammosov 13V. Ammosov 13th CBM meeting,GSI,March 10th CBM meeting,GSI,March 10

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Beam test of pad tRPCs with ultra-thin Beam test of pad tRPCs with ultra-thin glassglass

Status of IHEP+INR activity Status of IHEP+INR activity for high rate RPCsfor high rate RPCs


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GoalGoal is rate capability ~ 1/glass thickness ? is rate capability ~ 1/glass thickness ?

Previously RPCs with semiconductive glasses were tested. Previously RPCs with semiconductive glasses were tested. Rate capability ~ 20 kHz/cm2 was found - but this way is Rate capability ~ 20 kHz/cm2 was found - but this way is expensive, no long term stability tooexpensive, 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 slips0.17 mm thick microscope slips (China) and (China) and 0.85 mm Glaverbel glass0.85 mm Glaverbel glass was done was done Bulk resistivity of both glasses ~ 10Bulk resistivity of both glasses ~ 101212 Ohm Ohmcm (with factor cm (with factor

of 2)of 2) Three chambers were tested at IHEP accelerator in Dec08Three chambers were tested at IHEP accelerator in Dec08

1) 1x0.3 mm RPC with 0.17 mm glass plates1) 1x0.3 mm RPC with 0.17 mm glass plates

2) 1x0.3 mm RPC with 0.85 mm glass plates2) 1x0.3 mm RPC with 0.85 mm glass plates 3) 6x0.3 mm RPC with 0.17 mm glass plates3) 6x0.3 mm RPC with 0.17 mm glass plates 24x24 mm24x24 mm22 – glass plates, 18x18 mm – glass plates, 18x18 mm22 – pads – pads High rate irradiation via High rate irradiation via 9090Sr sourceSr source


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RPC designsRPC designs

PMMA

d scotch

Fishing line0.3

Glass 0.17

Cu tape 0.05 s.c. enamel1M/


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Layout in test areaLayout in test area

S1,S2 are beam counterswith 1x1x1 cm3 scintillatoreach. 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


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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 )


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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 is

σref~52 ps


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Slewing correctionSlewing correction

?


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Time distributionsTime distributions


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Charge distributions for different Charge distributions for different ratesrates


1010

No 90Sr irradiationCounting rate in beam~ 30 Hz/cm2


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Dark counting rate a few Hz/cm2

Dark current < 1 microamp


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Tails = (all hist- gaus)/all hist


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N.B.Total counting rate for6 gap RPC is six times higher


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At maximal 90Srirradiation


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ConclusionConclusion It seems reasonable to play with ultra-thin glasses It seems reasonable to play with ultra-thin glasses

for high rates, indeed h.r. capability ~ 1/dfor high rates, indeed h.r. capability ~ 1/d Is it possible to reach 20 kHz/cmIs it possible to reach 20 kHz/cm22 with it ? with it ? actionaction factor factor 170 170 m m 50 50 m ~ 3 m ~ 3 slips are not availableslips are not available cathode = metal ~ 2 cathode = metal ~ 2 thinner gap(Qthinner gap(Q) ~2-3) ~2-3 totally >10 totally >10 May be possibleMay be possible

Intend to study these factors during April09 IHEP runIntend to study these factors during April09 IHEP run • and also 6 indep. gaps v.s. 6 floating gapsand also 6 indep. gaps v.s. 6 floating gaps will be testedwill be tested


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Plans with a 96 ch. prototypePlans 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


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Plans with a 96 ch. prototypePlans with a 96 ch. prototype

It is planned to have 8x12 overlapped cells

Why 96 channels = 4x24chIt 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 ?

Documents

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