Beam test Analysis Micromegas TPC by Wenxin Wang
Beam test Analysis Micromegas TPC by Wenxin Wang CEA-Saclay
Micromegas module 2 • • Module size: 22 cm × 17 cm 24 rows × 72 columns Readout: 1726 Pads Pad size: ~3 mm × 7 mm 11/09/2013
3 2008~2011: Test with one module at the center of LP-TPC 2012~2013: Test with multi-modules at the endplate of LP-TPC 11/09/2013
4 Tests with one single module (2008~2011) At the center of LP-TPC 11/09/2013
5 Micromegas modules Module 3 Module 4 & Module 5 Module 1 Resistive Kapton ~3 MΩ/□ Standard (no resistive layer) Resistive Kapton ~5 MΩ/□ Module 2 Resistive ink ~3 MΩ/□ 11/09/2013
Uniformity 6 5 cm = Z Resistive CLK Module Resistive ink Module Mean Residual vs Row Number Z-independent distortions Distortions up to 50 microns for resistive ink (blue points) Z= Rms 7 microns for CLK film (red points) cm 5 3 m 0 c 5 = Z 11/09/2013 Row number
7 Spatial resolution (B = 0 T) Module 4 11/09/2013 Module 5
8 Spatial resolution (B = 1 T) Cd = 94. 2 µm/√cm (Magboltz MC) Module_CLK 11/09/2013 Module_INK
9 11/09/2013 Spatial resolution
10 Tests with multi-modules (2012~2013) Fully cover the endplate of LP-TPC 11/09/2013 Using a quasi-industrial production chain
Integrated electronics 11 Front-End Card (FEC) v Remove packaging and protection diodes v Wire-bond AFTER chips v Use two 300 -point connectors 25 cm 4. 5 cm 12. 5 cm AFTER Chip 14 cm 3. 5 cm 11/09/2013 2. 8 cm 3. 5 cm 0. 78 cm 0. 74 cm The resistive foil protects against sparks
Test bench 12 Test with collimator 11/09/2013 Test without collimator to check the map of missing pads
Modules comparison Energy Resolution (r. m. s) 13 20% 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% 0 1 2 3 4 5 6 7 Module number At Vmesh = 380 V, Energy resolution ~12% r. m. s 11/09/2013 8
Modules comparison 14 Gain 10000 100 0 1 2 3 4 5 6 7 8 Module number At Vmesh = 380 V, average gain ~ 2630, gain spread ~15% 11/09/2013
15 Gain Study using beam events Charge per row For 6. 84 mm pitch & 5 Ge. V e. Nelectron (MPV) expected = 45 (from HEED simulation) 11/09/2013 2500 at Vmesh=380 V ( 2700 at Vmesh=380 V From test bench)
16 Beam events display Online monitor 2 D or 3 D display from ILC software Offline monitor 11/09/2013
17 Analysis Framework: Marlin. TPC �Marlin. TPC Marlin based simulation, digitization, reconstruction and analysis code for the TPC. �Kal. Det &Kal. Test: (installed in Marlin) – – 11/09/2013 A ROOT-based Kalman Filter Package. Used to reconstruct tracks.
18 Spatial resolution Event selection 11/09/2013 only single track event
19 Spatial resolution Hit selection Fit track with all rows 11/09/2013
20 Spatial resolution Pad size (mm) Profile histogram of the residual with the track in one row before bias correction 11/09/2013 Profile histogram of the residual with the track in one row after bias correction
21 Spatial resolution Distribution of the residuals (z = 15 cm) 11/09/2013
Spatial resolution 22 B=1 T Cd = 94. 2 µm/√cm (Magboltz MC) 24 rows of a module 11/09/2013
23 Extrapolation of the spatial resolution Extrapolate to 2. 3 m & B=3. 5 T B=1 T ----- Micromegas with 3 mm width pads GEM with 1 mm width pads B=0 T B=1 T B=3. 5 T 11/09/2013
Distortions 24 B=1 T B=0 T 11/09/2013 After alignment B=0 T
Field distortions 25 Distortions in B=0 T or B=1 T at different drift distances z (15 cm~50 cm) B=0 T 11/09/2013 B=1 T
26 A measured 55 Fe spectrum (at Vmesh = 350 V and Vdrift = 400 V) 11/09/2013 Gain as a function of Vmesh (Edrift = 0. 2 k. V/cm at atmospheric pressure)
27 11/09/2013 Electron transparency
28 Conclusion • A lot of experience has been gained in building and operating Micromegas TPC panels. • The characteristics of the Micromegas modules, such as the uniformity, energy resolution, stability have been studied in detail. • 7 modules have been successfully tested with full integration of the electronics at the same time. • Thanks to the resistive technology, the measured resolution is about 60 microns at zero drift distance with 3 mm wide pads. This meets ILC needs. • Distortions are observed. Their detailed study will allow to correct them and improve the design to minimize them.
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