1. Recents Analysis Results From Micromegas TPC
D. Attié, P. Colas, M. Dixit, M. Riallot, YunHa Shin, S. Turnbull, W. Wang
and all the LC-TPC collaboration
20/10/2010
Wenxin.Wang_IWLC meeting 2010

2. The EUDET facility at DESY Hamburg
See K.Dehmelt’s talk
PCMAG:
superconducting magnet, 1.2 T
e- test
(1GeV/c<p<6GeV/c)
KEK
SiPM Cosmic
Trigger Setup
Moving frame
DESY
Saclay
LP : part of a
TPC endplate
Cornell
20/10/2010
Wenxin.Wang_IWLC meeting 2010

3. Micromegas TPC
From December 2008 to March 2010 we tested 5 panels. One module was installed in the centre of the Large Prototype each time
Read out by T2K electronics
20/10/2010
Wenxin.Wang_IWLC meeting 2010

4. 5 Micromegas Modules for TPC
Resistive ink
~3 MΩ/□
Resistive Kapton
~5 MΩ/□
Standard
2 Resistive Kapton
Module 4&5
Module 1
Module 3
Module 2
20/10/2010
Wenxin.Wang_IWLC meeting 2010

5. Bulk technology (à la T2K)
The mesh is held by the pillars on the whole surface. There is not need for frame. Very robust.
A T2K ND280 TPC event (in operation since 1 year
9 m² of bulk Micromegas
Resistive bulk : continuous RC circuit to spread the charge to improve resolution
20/10/2010
Wenxin.Wang_IWLC meeting 2010

6. Test schedule
December 2009: tested modules 4 and 5 without magnetic field.
March 2010: tested modules 2 (ink) and 3 (kapton) with 1T magnetic field.
June-July 2010: data taken in a high intensity hadron beam at CERN.
20/10/2010
Wenxin.Wang_IWLC meeting 2010

7. 20/10/2010
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8. Data analysis results (B=0T)
Drift Velocity in T2K gas compared to Magboltz simulations for
- P=1035 hPa
- T=19°C
ppm H20
( T2K gas: Ar:CF4:iso=95:3:2)
Vdrift = cm/µs at E=230 V/cm
(Magboltz : (gas comp.))
The difference is %
B=0 data : Drift velocity measurements
20/10/2010
Wenxin.Wang_IWLC meeting 2010

9. Data analysis results PRF : Pad Response Function
A measure of signal size as a function of track position relative to the centre of the pad  
The PRF:
is not Gaussian.
can be characterized by its FWHM (z) & base Width (z), plus another shape parameter.
20/10/2010
Wenxin.Wang_IWLC meeting 2010

10. PRF(Pad Response Functions) fits, z ~ 5 cm
Data analysis results
Γ ~ 4 mm
δ ~ 14 mm
Γ ~ 2.6 mm
δ ~ 10 mm
B=1T data : comparison of resistive ink and Carbon-loaded Kapton
PRF(Pad Response Functions) fits, z ~ 5 cm
20/10/2010
Wenxin.Wang_IWLC meeting 2010

11. Bias Bias before Bias after
±50µm
Bias due to non-uniformity can be easily corrected.
(module 3 CLK, B=1T)
20/10/2010
Wenxin.Wang_IWLC meeting 2010

12. Residuals Position residuals xrow-xtrack 20/10/2010
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13. Uniformity MEAN RESIDUAL vs ROW number Z-independent distortions
Distortions up to 50 microns for resistive ink (blue points)
Rms 7 microns for CLK film (red points)
Z=5cm
Z=35cm
Z=50cm
20/10/2010
Wenxin.Wang_IWLC meeting 2010

14. Average charge by row using 5GeV e- beam (B = 1T)
Uniformity
Very Preliminary
Average charge by row using 5GeV e- beam (B = 1T)
20/10/2010
Wenxin.Wang_IWLC meeting 2010

15. Uniformity (B = 0T) Very Preliminary Using cosmic-ray
Average charge by row using cosmic-ray events
20/10/2010
Wenxin.Wang_IWLC meeting 2010

16. Data analysis results (B = 0T & 1T)
Carbon-loaded kapton resistive foil
B=0 T Cd = µm/√cm (Magboltz)
B=1 T Cd = µm/√cm (Magboltz)
Module 3
χ2 :     29.1
Ndf:        11
Module 4
χ2 :     10.6
Ndf:    10
20/10/2010
Wenxin.Wang_IWLC meeting 2010

17. Neff measurement with Micromegas
Averaging B=0T and B=1T data
(excluding ink module):
Neff = 38.0±0.2(stat) ±0.8 (Cd syst)
σ0= 59 ± 3 µm
Assuming Polya distribution, =3.2± Consistent with M. Lupberger’s thesis.
See Michael Lupberger’s talk in EUDET meeting in Hamburg
Note that 1/<1/N> = 47.1 from Heed for 5 Gev electrons on 6.84 mm long pads.
This demonstrates that gain fluctuations are not exponential (Neff would be 23) but smaller.
1/<1/N> = 34.9 for 5.4 mm pads (GEM case).
20/10/2010
Wenxin.Wang_IWLC meeting 2010

18. Test in a high intensity beam
27 cm
40 cm
35cm
B field
Top
11 cm
Bottom
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Wenxin.Wang_IWLC meeting 2010

19. Test at CERN (July 2010) at 180 kHz (5 x 2 cm² beam) showed no charging up and stable operation
Peaking time of 200 ns is enough to obtain the best resolution -> 300 ns suffice to distinguish 2 tracks on the same pad
20/10/2010
Wenxin.Wang_IWLC meeting 2010

20. Conclusions
A lot of experience has been gained in building and operating Micromegas TPC panels
The uniformity of the detector is excellent, with no distortions nor edge effects, and very small dead areas
The measured resolution meets LC needs : 60 microns at zero drift distance with 3 mm wide pads
The effective number of electrons per row is measured to be 38
The detector peformed perfectly normally in high intensity beam
Next step is to equip the whole endplate with full integration of the electronics flat behind the panels
20/10/2010
Wenxin.Wang_IWLC meeting 2010

21. Thank you
20/10/2010
Wenxin.Wang_IWLC meeting 2010