T2K TPC Micromegas Prototype: Test Results on Harp setup Marco Zito February 15 2006 ILC-TPC Jamboree DESY ILC-TPC Jamboree February 15, 2006 Marco Zito

Outline A TPC prototype based on Micromegas has been tested at Cern (Harp setup) in november 2005 Two Micromegas modules : 2x1000 pads 8x8 mm**2, 52 cm track length Modular and flexible detector concept NB: more relaxed detector resolution needed for T2K This talk : Highlights of the detector Methods and results from the data ILC-TPC Jamboree February 15, 2006 Marco Zito

Micromegas concept Micromesh Amplification region: 100μm, 40-70kV Anode : strips, pads ILC-TPC Jamboree February 15, 2006 Marco Zito

The T2K 280m TPC P0D TPC TPC TPC Pb-P0D Requirements : Active target Magnet + Side-MRD Instrument 6 read-out planes (0.6x2.5 m**2) Total drift distance 1.25 m B=0.2 T E=200V/cm Pad size: 0.6 to 0.8 cm EM calorimeter P0D TPC TPC TPC Pb-P0D FGD+H2O FGD EM calorimeter Muon ID hodoscope EM calorimeter Magnet + Side-MRD Requirements : σ(p)/p < 10 % @ 1 GeV/c dE/dx capability: separate e from μ ILC-TPC Jamboree February 15, 2006 Marco Zito

The proposed TPC readout plane Readout plane support 7x2x4 Front End Cards E Field cage strips Ref : J-Ph Mols ILC-TPC Jamboree February 15, 2006 Marco Zito

Exploded view of a 27x26 cm2 Micromegas module O-ring on the side of the support vacrel Woven mesh Pads PCB FEC vacrel FR4 « bulk » Micromegas seal support Ref : J-Ph Mols ILC-TPC Jamboree February 15, 2006 Marco Zito

T2K Micromegas 1020 pads PCB Done Ch. Coquelet, A. Delbart ~3.2 mm HV connector from backplane ! Done FR4 ~20 mm Passivated Cu ~3.2 mm 124 mm ILC-TPC Jamboree February 15, 2006 Marco Zito

Two Micromegas on the Saclay flange Saclay Interface Flange with O-ring groove Geneva Univ. HARP Cage interface Flange SHV HV connector #1 SHV HV connector #2 Gas connector Ref : P. Graffin Mounting stud ILC-TPC Jamboree February 15, 2006 Marco Zito

End plate for Harp in Saclay A. Delbart, J-L. Ritou Inner side Outer side Inner surface covered by PCB for E-field termination ILC-TPC Jamboree February 15, 2006 Marco Zito

Close-up of the two MM modules 12mm dead region ILC-TPC Jamboree February 15, 2006 Marco Zito

Micromegas endplate mounted and instrumented on the HARP TPC field cage CERN, november 8 2005 ILC-TPC Jamboree February 15, 2006 Marco Zito

Cosmic track display-B=0 Shades of blue to green <150ADC Black > 150, red>200 ADC ILC-TPC Jamboree February 15, 2006 Marco Zito

Cosmic track display-B=0 ILC-TPC Jamboree February 15, 2006 Marco Zito

Cosmic track display-B=0.2 ILC-TPC Jamboree February 15, 2006 Marco Zito

Cosmic track display-B=0.2 ILC-TPC Jamboree February 15, 2006 Marco Zito

Cosmic track display-B=0 Ar-CO2 ILC-TPC Jamboree February 15, 2006 Marco Zito

Entering the TPC from the cathode Vdrift = 6.42±0.05 cm/μs (Magboltz 6.5) ILC-TPC Jamboree February 15, 2006 Marco Zito

Digitized signals Charge (ADC) Ar-CF4-C4H10 Ar-CF4-C4H10 Time (tick=100ns) Fit with C(t/tau)**4exp(-4t/tau) Fourth order semi-gaussian filter Tau ≈200ns Longer pulses with Ar-CO2 Ar-CO2 ILC-TPC Jamboree February 15, 2006 Marco Zito

Data analysis New C++ package Oompa used (ROOT, Minuit, STL) Exercised and debugged using ILC TPC prototype data Build clusters in each row : adjacent pads close in time Track finder : full length across the two modules, based on a road from seeds in the top-bottom rows Track fitting : χ2 fit in the two projections (x-y, y-t) Crucial ingredient : how to compute the position for a cluster with two pads hit q1 The charges q1 and q2 can be computed from the integral of the track width ST over the pad boundaries Relation between r=q1/(q1+q2), ST and the track position x r measured, ST from Magboltz -> measure x for two pads clusters (numerical method) q2 ILC-TPC Jamboree February 15, 2006 Marco Zito

Track parameters Chi**2 N Cluster ILC-TPC Jamboree February 15, 2006 Marco Zito

Track parameters Same distributions from Geant4 MC X0 (cm) Phi (rad) A. Sarrat X0 (cm) Phi (rad) ILC-TPC Jamboree February 15, 2006 Marco Zito

Resolution study Consider these distributions for clusters with two pads only: Residual cluster-track : track refitted without the cluster info Residual cluster-track : cluster info in track fit [Residual cluster-track (row i)] - [Residual cluster-track (row i+2)] =double residual (divide width by sqrt(2)) The double residual is insensitive to track extrapolation uncertainty (200-300μm), alignment, track model systematics Fit gaussian width as a function of z ILC-TPC Jamboree February 15, 2006 Marco Zito

Resolution study Little information in clusters with one pad hit. Distribution integrated over z. Need to study residuals vs z Res 1 pad σ 1800 μm Res 2 pad σ 610 μm Res 3 pad σ 856 μm ILC-TPC Jamboree February 15, 2006 Marco Zito

Resolution study B=0 Ar-CF4-C4H10 Cumulative fraction of rows with no hit, 1 pad, two pad, three or more pad cluster Res width vs z (cm) 600μm Double residual ILC-TPC Jamboree February 15, 2006 Marco Zito

Resolution study B=0.2T Ar-CF4-C4H10 Cumulative fraction of rows with no hit, 1 pad, two pad, three or more pad cluster Res width vs z (cm) 600μm Clusters with two pads or more 1m Overall inefficiency≈5% including electronics, analysis ILC-TPC Jamboree February 15, 2006 Marco Zito

Resolution study B=0.4T Ar-CF4-C4H10 Cumulative fraction of rows with no hit, 1 pad, two pad, three or more pad cluster Res width vs z (cm) 600μm ILC-TPC Jamboree February 15, 2006 Marco Zito

Momentum resolution With Gluckstern formula we use σpoint=600μm, N=(2/3)*64=43, L=60cm and obtain σp/p<=10.9% at 1 GeV/c, 1 m drift distance for B=0.2 T NB: analysis still in progress, better use of all info, this result will improve lower noise in electronics (600 vs 2000 e RMS) -> lower threshold->more clusters with two pads-> better momentum resolution Other possible improvements for T2K : longer track length, smaller pads, elongated pads … ILC-TPC Jamboree February 15, 2006 Marco Zito

Ar-CO2 @ 70cm drift Cumulative fraction of rows with no hit, 1 pad, two pad, three or more pad cluster 0.6 First look at Ar-CO2 data, resolution comparable to Ar-CF4-C4H10 ILC-TPC Jamboree February 15, 2006 Marco Zito

First look at dE/dx Charge in row Ar-CF4-C4H10 80% truncated mean No momentum correction yet ! 80% truncated mean σ=11.6 % Charge in MM2 and 3 ILC-TPC Jamboree February 15, 2006 Marco Zito

Attenuation Ar-CF4-C4H10 Ar-CO2 0.5 m 1.5 m Attenuation length: 3.4m Micromegas works fine with Ar-CO2 but electron capture on oxygen traces is a serious problem ILC-TPC Jamboree February 15, 2006 Marco Zito

Conclusion A new package for TPC data reconstruction and analysis has been developed Excellent results obtained for the T2K TPC prototype Further development : 1) code improvement (cluster by cluster error from binomial and electronics noise) 2) interface to T2K reconstruction ILC-TPC Jamboree February 15, 2006 Marco Zito