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Beam Test Result. Jeewon SEO World lab fellow. T10 Beam Test . 14. Oct. ~ 20. Nov. 2009 ALICE TOF 10 gap chamber and 24 gap MRPC was tested with different percentages of SF 6 . SF 6 Property : Highly electronegative Disadvantages Expensive cost Global warming gas. 10 Gap MRPC. - PowerPoint PPT Presentation
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Beam Test Result
Jeewon SEO
World lab fellow
T10 Beam Test 14. Oct. ~ 20. Nov. 2009ALICE TOF 10 gap chamber and 24 gap MRPC
was tested with different percentages of SF6.SF6
◦ Property : Highly electronegative◦ Disadvantages
Expensive cost Global warming gas
10 Gap MRPC Gap size : 250 ㎛
Aluminum box volume : 200ℓ Gas flow rate : 20ℓ/h (O2 content was kept at 100 ppm)
Beam Test Setup
-5GeV/c beam of π-, μ- . Trigger selected 10 ㎜ⅹ 10 ㎜ beam spot
(130 triggers/spill in every 20 seconds)
Data Acquisition
Slewing Correction
Time = Tchamber – Tave Tave : average time of the timing scintillators
Time Resolution
σres = √( σch2-σsc
2)
σres : time resolution σch : measured time of signals σsc : jiter of scintillators
Ave(S1,S2)-Ave(S3,S4)
Efficiency and Streamer Plateau
SF6 0 % 2 % 4 % 6 % 8 % 10 %Streamer
free and ef -ficient >90%
operation range
10.6~11.6 kV
10.8~13 kV
11~13.2 kV
11.2~13.4 kV
11.4~13.6 kV
11.6~13.8 kV
1 kV 2.2 kV 2 .2kV 2.2 kV 2.2 kV 2.2 kV
The knee of the effi-ciency plateau moves to high voltage when the percentage of SF6 in-crease.
Breakdown at 11.8 kV with the pure freonBreak down at
11.8kVwith pure freon
Time resolution with various percentage of SF6
Time resolution is independent of the fraction of SF6.
24 Gap MRPC
160 ㎛ gaps (total thickness : 3.84 ㎜ )
Gas flow rate : 20ℓ/h (box volume : 30ℓ)
-> O2 content was kept at
20 ppm
Threshold : 40 fC
Data Acquisition
NINO mounted on chamber inside gas volume
Compare time of one MRPC with another
Time resolution obtained by measuring time difference between two chambers
Timing scintillators are not used.
Efficiency and Time resolution
Tdiff = (Tmean)MRPC1-(Tmean)MRPC2
The best resolution is 20.8 ps with pure freon and 19.1 ps with added 5% SF6.
Efficiency plateau is shifted to a lower voltage with the pure freon.
The streamer-free and efficient operation range
Pure freon : 1.6 kV (10.6kV ~ 12.2kV)
5% SF6 : 2 kV (11kV ~ 13 kV)
Conclusion 10 gap MRPC
◦ Break down at 11.8kV with pure freon.◦ Work with 2% SF6, obtaining the time resolution below 50 ps with a
2.2 kV range.-> Seems to need the SF6 to avoid breakdown
24 gap MRPC◦ Work satisfactorily with pure freon
SF6 effect◦ Shift the efficiency plateau to a higher voltage ◦ Shift in streamer production to higher voltage◦ For 24 gap MRPC, the efficient operation range without streamer is
broader when SF6 added.
Time resolution is independent of SF6 fraction.