Analysis for J2 chamber

Yousuke Kataoka (University of Tokyo)Atsuhiko Ochi, Yuki Edo (Kobe University)

11 / 12 / 2012 Micromegas weekly meeting

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Introduction• J2 chamber is made in Kobe (with Raytech)

– Print screen 400um pitch– 1 dimentional readout (2d for Z1,Z2)– 100um mesh gap (128um for Z1,Z2)– 15mm drift gap (5mm for Z1,Z2)

• H6 test beam 19~25 Nov.– Run 8325~8500 by APV– 0,+10,+20,+30,+40 degree– HV_strip, HV_drift scan– some time with Z1, Z2

J2

Tmm5,6

Z1 Z2

Tmm2,3

beam

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Chamber efficiency

at least 1 cluster on J21 cluster on Tmm2,3,5,6

chamber efficiency =

conditions- ZS factor = 0.8-reject 1 strip cluster-require cluster Q > 100-allow gap up to 12 in cluster

• J2 reach >99% at 430V, Zebra at 550V• The difference come from mesh gap, drift gap, 1D or 2D• drop at larger angle due to smaller Q / strip

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Strip efficiency

strip efficiency == strip at center hit ?

At larger angle, some drops of strips within cluster

- even when chamber efficiency is 100%, strip efficiency could be much low impact on perfomance

40

30

20

Number of hits (40 degree)

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Comparison to Garfield

APV25CR-RC shaper τ = 50nst/50 x exp(- t/50)

25ns bin

400u

m b

in

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1. Garfield 9 (fortran) 2. assign gas gain 3. assign shape

5. digitize4. give jitter

~51 electrons (5mm,0 deg.)

drift timing &position

PDF from Garfield

6. threshold

T T + random(25ns)X X + random(profile)

basically every plots(full simulation)

7. compare to data

threshold for charge ~ strip efficiency

Cluster width

good agreementswider than Zebra

6

assume 100% strip effi.

Timing width drift velocity

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T_qmax

roughly consistent(need to check)

width [Tbin]

Position resolutionCenter = (left + right) /2.

J2 x 400um – (Tmm2 + Tmm3 + Tmm5 + Tmm6)/4 x 250um / cos(theta)

resolution = sigma / sqrt(1+1/4)

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after introducing strip efficiency,agreement is good

Time resolutionConstant fraction threshold = 50%

J2 x 25ns – (Tmm2 + Tmm3 + Tmm5 + Tmm6)/4 x 25ns

resolution = sigma / sqrt(1+1/4)

CFD=25%

CFD=50%

delay was not enoughprobably optimistic9

pile up effect at 0 degree(CDF not work)

TPC Angle

J2(0) … 0.100 1.9 degreeJ2(10) … -0.639 12.1J2(20) … -1.097 20.2J2(30) … -1.678 29.4J2(40) … -2.386 38.7Z1(20) … -1.296 23.5Z2(20) … -1.290 23.4

~ 1 degree

4.7cm/us

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wide gap is good for TPC

Summary

• J2, Z1, Z2 are working fine and in good agreement with Garfield simulation (many points need to be understood …)• strip efficiency affects performance, so higher voltage (lower threshold) is better (not just chamber 100% efficiency)• wider drift gap (wrt. pitch) is not good for strip efficiency and

clustering, but better for TPC reconstruction

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backup

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CFD=25% log scaleCFD=50%

CFD=25%CFD=25% (log)

CFD=50% (log)

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Time resolutionConstant fraction threshold = 25%

J2 x 25ns – (Tmm2 + Tmm3 + Tmm5 + Tmm6)/4 x 25ns

resolution = sigma / sqrt(1+1/4)

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