1. Analysis for J2 chamber Yousuke Kataoka (University of Tokyo) Atsuhiko Ochi, Yuki Edo (Kobe University) 11 / 12 / 2012 Micromegas weekly meeting 1

2. 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 2

3. Chamber efficiency at least 1 cluster on J2 1 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 3

4. 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) 4

5. Comparison to Garfield APV25 CR-RC shaper τ = 50ns t/50 x exp(- t/50) 25ns bin 400um bin 5 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

6. Cluster width good agreements wider than Zebra 6 assume 100% strip effi.

7. Timing width drift velocity 7 T_qmax roughly consistent (need to check) width [Tbin]

8. Position resolution Center = (left + right) /2. J2 x 400um – (Tmm2 + Tmm3 + Tmm5 + Tmm6)/4 x 250um / cos(theta) resolution = sigma / sqrt(1+1/4) 8 after introducing strip efficiency, agreement is good

9. Time resolution Constant 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 enough probably optimistic 9 pile up effect at 0 degree (CDF not work)

10. TPC Angle J2(0) … 0.100  1.9 degree J2(10) … -0.639  12.1 J2(20) … -1.097  20.2 J2(30) … -1.678  29.4 J2(40) … -2.386  38.7 Z1(20) … -1.296  23.5 Z2(20) … -1.290  23.4 ~ 1 degree 4.7cm/us 10 wide gap is good for TPC

11. 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 11

12. backup 12

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15. CFD=25% log scale CFD=50% CFD=25% CFD=25% (log) CFD=50% (log) 15

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17. Time resolution Constant fraction threshold = 25% J2 x 25ns – (Tmm2 + Tmm3 + Tmm5 + Tmm6)/4 x 25ns resolution = sigma / sqrt(1+1/4) 17