C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 1

VETO AND XPC: Preliminary ideasVETO AND XPC: Preliminary ideas

Outline:

•Mechanical structure•Gas mixture study•Aging tests•Glass RPC R&D•Conclusion

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 2

Mechanical structureMechanical structure

•The XPC frame drawing is ready (E.Tatananni). •A real scale prototype (1,46x9 m2) is foreseen

for the end of the year.•Frame calculations (C. Zarra) NOT concluded

because personal problems of Chiara.•We need an engineer for it (XPC, VETO and

glass RPC)

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 3

Float Glass:

Bakelite

Stable resistivity (hopping conductivity)=1012-1013 cm at normal temperatureResistivity depends only on temperature

=010(T-20)/25

Well known industrial technologyBELLE EXPERIMENT

=1010-1012 cm at normal temperatureresistivity increases with the integrated charge (ionic conductivity)Need a surface treatment with linseed oil L3, BaBar ARGO EXPERIMENTS

2 kV

compound

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 4

gas study (1)gas study (1)

We have been tested 4 components gas mixture (argon+TFE+Isobutane+SF6)With this choice the presence of an avalanche precursor is apparentThe precursor is prompt (good timing), the streamer is not (large jitter)The electronics exploit the good timing of precursor (low thr) and the big amplitude of streamer (high thr=noise suppressor)

Trigger, ADC gate, TDC start

Scintillators

Glass RPC

FANOUT

ADC

Lowthreshold

TDC, Scaler

20 ns

TDC

Highthreshold

precursor

streamer

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 5

gas study (2)gas study (2)

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 6

gas study (3)gas study (3)

single streamer peak

Multistreamer peaks

Efficiency knee

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 7

gas study (time resolution)gas study (time resolution)

By using SF6 + proper electronics: 1 ns resolution “everywhere” (safe operation)

Efficiency kneeEfficiency knee

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 8

gas study (time resolution)gas study (time resolution)

Single thr time distribution (knee voltage)Double thr time distroibution (knee voltage)Gaussian shape

TFE+argon +isobutane+SF6=48+47+4+1 %

Single thresholddistribution

Precursordrivendistribution

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 9

OPERA: gas study (charge)OPERA: gas study (charge)

With SF6 the peak charge is 1/3 than w/o. The afterpulses increases for TFE<48% and/or Isobutane<4%

No SF6

No SF6

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 10

OPERA: gas study (summary)OPERA: gas study (summary)

No SF6

SF6>0.6% small streamer, big precursorISO-butane>4% photon absorptionTFE>48% little afterpulsingTFE>36% good timing

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 11

Aging: long term operationAging: long term operation

After 5 months of operation, better performance (lower counting level). Tests are still in progress

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 12

Aging: GIF irradiationAging: GIF irradiation

Good efficiency after 7 mC/cm2(corresponding to more than 30 years of operation in the hall C)

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 13

Aging: temperature testsAging: temperature tests

Avalanche modeStreamer mode

Differently from Bakelite, Glass RPC do not suffer high temperatures

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 14

Aging: humidity testAging: humidity test

Water vapour seriously damages the Glass RPC: It is a threshold effect

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 15

Aging: Glass RPC recoveryAging: Glass RPC recovery

Bubbling the gas through 28% ammonia there is a full recovery after 2 weeks

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 16

RPC design: new spacersRPC design: new spacers

No glue overflowing

electrode

glue

spacer

Field lines never cross the spacer(no charging up)

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 17

RPC productionRPC production

Real scale prototype from:GT (glass and bachelite)G&A (glass)LNGS (reference detectors)

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 18

Time schedule (XPC):Time schedule (XPC):

Mechanical structure XPC):Mechanical structure XPC):

Final design ready: to be discussed withFinal design ready: to be discussed with

magnet, TT and PT people.magnet, TT and PT people.

december: real scale modeldecember: real scale model

Glass RPC R&D Glass RPC R&D

July: large area prototype with 2 and 3 mm glass July: large area prototype with 2 and 3 mm glass electrodes.electrodes.

End of the year: choice between glass and bachelite End of the year: choice between glass and bachelite

C.Gustavino, XPC and VETO, LNGS OPERA meeting, may 2003 19

VETO System:VETO System:

Same conceptual structure and detectors as XPC.Same conceptual structure and detectors as XPC.

Schedule and responsability must be defined soon.Schedule and responsability must be defined soon.