Astrophysics Detector Workshop – Nice – November 18 th, David Attié — on behalf of the LC-TPC Collaboration — Beam test of the Micromegas ILC-TPC Large Prototype MPGD2009 – Kolimpari, Crete - June 12-15, 2009

Outline MPGD2009 – Crete – June 13 th, Introduction, technological choice for ILC-TPC The ILC-TPC Large Prototype Bulk Micromegas with resistive anodes Beam test conditions, T2K electronics Data analysis results –drift velocity –pad response function –resolution Comparison between two resistive modules Conclusion

How to improve the spatial resolution? 3 Need for ILC: measure 200 track points with a transverse resolution ~ 100 μm - example of track separation with 1 mm x 6 mm pad size:  1,2 × 10 6 channels of electronics   z=0 > 250 μm amplification avalanche over one pad Spatial resolution σ xy : - limited by the pad size (  0 ~ width/√12) - charge distribution narrow (RMS avalanche ~ 15 μm)  1. Decrease the pad size: narrowed strips, pixels + single electron efficiency –need to identify the electron clusters  2. Spread charge over several pads: resistive anode + reduce number of channels, cost and budget + protect the electronics –limit the track separation –need offline computing –time resolution is affected 2. Resistive anode Calculation for the ILC-TPC D.C. Arogancia et al., NIMA 602 (2009)  m 1. Pixels MPGD2009 – Crete – June 13 th, 2009

ILC-TPC Large Prototype 4 Built by the collaboration Financed by EUDET Located at DESY: 6 GeV e- beam Sharing out : - magnet : KEK, Japan - field cage : DESY, Germany - trigger : Saclay, France - endplate : Cornell, USA - Micromegas : Saclay, France, Carleton/Montreal, Canada - GEM : Saga, Japan - TimePix pixel : F, D, NLc MPGD2009 – Crete – June 13 th, 2009

ILC-TPC Large Prototype 5 MPGD2009 – Crete – June 13 th, 2009

ILC-TPC Large Prototype 6 60 cm long TPC Endplate ø = 80 cm of 7 interchangeable panels of 23 cm: –Micromegas –GEMs (See Takeshi Mastuda’s talk) –Pixels: TimePix + GEM or Micromegas 80 cm 24 rows x 72 columns ~ 3x7 mm 2 MPGD2009 – Crete – June 13 th, 2009

Three panels were successively mounted and tested in the Large Prototype and 1T magnet: -standard anode -resistive anode (carbon loaded kapton) with a resistivity ~ 4-8 MΩ/□ -resistive ink (~1-2 MΩ/□) Bulk Micromegas panels tested at DESY 7 Standard bulk Micromegas module Carbon loaded kapton Micromegas module MPGD2009 – Crete – June 13 th, 2009 May-June 2009 November 2008

Beam test conditions at B=1T 8 Bulk Micromegas detector: 1726 (24x72) pads of ~3x7 mm² AFTER-based electronics (72 channels/chip): –low-noise (700 e-) pre-amplifier-shaper –100 ns to 2 μs tunable peaking time –full wave sampling by SCA Beam data (5 GeV electrons) were taken at several z values by sliding the TPC in the magnet. Beam size was 4 mm rms. –frequency tunable from 1 to 100 MHz (most data at 25 MHz) –12 bit ADC (rms pedestals 4 to 6 channels) MPGD2009 – Crete – June 13 th, 2009

Determination of z range 9 MPGD2009 – Crete – June 13 th, 2009 cosmic run at 25 MHz of sampling frequency  time bin = 40 ns TPC length = 56.7 cm agreement with survey 190 time bins

Pad signals: beam data sample 10 RUN 284 B = 1T T2K gas Peaking time: 100 ns Frequency: 25 MHz MPGD2009 – Crete – June 13 th, 2009

Two-track separation 11 MPGD2009 – Crete – June 13 th, 2009 r φ z

Offset per row 12  rms offset ~9 microns MPGD2009 – Crete – June 13 th, 2009 B = 0T

Drift velocity measurement 13 Measured drift velocity (E drift = 230 V/cm, 1002 mbar): 7.56 ± 0.02 cm/ μ s Magboltz: ± for Ar/CF 4 /iso-C 4 H 10 /H 2 O (95:3:2:100ppm) B = 0T MPGD2009 – Crete – June 13 th, 2009

Drift velocity vs. peaking time 14  E drift = 230 V/cm  V d Magboltz = 76 μm/ns B=1T data For several peaking time settings: 200 ns, 500 ns, 1 μ s, 2 μs  E drift = 140 V/cm  V d Magboltz = 59 μm/ns Z (cm) Time bins MPGD2009 – Crete – June 13 th, 2009

Determination of the Pad Response Function 15 Fraction of the row charge on a pad vs x pad – x track (normalized to central pad charge)  Clearly shows charge spreading over 2-3 pads (data with 500 ns shaping) Then fit x(cluster) using this shape with a χ² fit, and fit simultaneously all lines x pad – x track (mm)  Pad pitch  MPGD2009 – Crete – June 13 th, 2009 See Madhu Dixit’s talk x pad – x track (mm)

Residuals (z=25 cm) 16 Residuals (x row -x track ) are gaussians row 1row 2row 3 row 4 row 5row 6 MPGD2009 – Crete – June 13 th, 2009

Residual bias (z=25 cm) 17 Bias remaining after correction: mean of residual x row -x track = f(x track ) Variation of up to 50 μ m with a periodicity of about 3mm (pad width) row 0 row 3 row 8 MPGD2009 – Crete – June 13 th, 2009 row 1 row 2row 4 row 5

Spatial resolution 18 MPGD2009 – Crete – June 13 th, 2009 Resolution at z=0: σ 0 = 54.8±1.6 μm with mm pads (w pad /55) Effective number of electrons: N eff = 31.8±1.4 consistent with expectations Preliminary

Field distortion measurement using laser 19 MPGD2009 – Crete – June 13 th, 2009 Beam position 5 cm two laser devices installed on the endplate to light up photosensitive pattern on the cathode (spots and line) deterioration of resolution at z > 40 cm : due to low field 0.9 to 0.7 T in the last 20 cm (significant increase of transverse diffusion) 30 cm50 cm B field map of the magnet Photoelectrons from the cathode pattern

Description of the resistive anodes DetectorDielectric layerResistive layerResistivity (MΩ/□) Resistive Kapton Epoxy-glass 75 μm C-loaded Kapton 25 μm ~4-8 Resistive Ink Epoxy-glass 75 μm Ink (3 layers) ~50 μm ~1-2 Resistive KaptonResistive Ink PCB Prepreg Resistive Kapton PCB Prepreg Glue 1-2 μm Glue 1-2 μm 20MPGD2009 – Crete – June 13 th, 2009 Resistive Ink

Comparison at B=1T, z ~ 5 cm Resistive KaptonResistive Ink RUN 310 v drift = 230 cm/μs V mesh = 380 V Peaking time: 500 ns Frequency Sampling: 25 MHz RUN 549 V drift = 230 cm/μs V mesh = 360 V Peaking time: 500 ns Frequency Sampling: 25 MHz 21MPGD2009 – Crete – June 13 th, 2009

Pad Response Functions, z ~ 5 cm Resistive Kapton MPGD2009 – Crete – June 13 th, 2009 Resistive Ink Γ = 7 mm δ = 10 mm Γ = 11 mm δ = 13 mm 22 x pad – x track (mm)  σ z=5 cm = 68 μm  σ z=5cm = 130 μm !

2.2 GeV Momentum 23MPGD2009 – Crete – June 13 th, 2009

Further tests for Micromegas In 2008/2009 with one detector module In 2010 with 7 detector modules. Reduce the electronic with possibility to bypass shaping Resitive technology choice 4 chips Wire bonded Front End-Mezzanine 24MPGD2009 – Crete – June 13 th, 2009

Conclusions Two Micromegas with resistive anode have been tested within the EUDET facility using 1T magnet to reduce the transverse diffusion C-loaded Katpon technology gives better result than resistive ink technology First analysis results confirm excellent resolution at small distance with the resistive C-loaded Kapton: 55 μ m for 3 mm pads A moving table for the magnet will be installed in a few weeks which fixes the inhomogeneous B field at high z Plans are to test several resistive layer manufacturing process and capacitance/resistivity, then go to 7 modules with integrated electronics 25MPGD2009 – Crete – June 13 th, 2009

Acknowledgments 26 MPGD2009 – Crete – June 13 th, 2009 Saclay, France: –D. A. –P. Colas –M. Riallot Carleton Univ., Canada: –M. Dixit –Y.-H. Shin –S. Turnbull –R. Woods Montreal Univ. Canada –J.-P. Martin Victoria Univ., Canada –P. Conley –D. Karlen –P. Poffenberger DESY/EUDET