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David Attié — on behalf of the LC-TPC Collaboration —

Micromegas TPC Large Prototype beam tests. David Attié — on behalf of the LC-TPC Collaboration —. TILC09 – Tsukuba – April 17-21, 2009. Outline. Introduction, solutions for ILC-TPC Micromegas with resistive anode description previous results The Large Prototype (LP)

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David Attié — on behalf of the LC-TPC Collaboration —

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  1. Micromegas TPC Large Prototype beam tests David Attié — on behalf of the LC-TPC Collaboration — TILC09 – Tsukuba – April 17-21, 2009 Astrophysics Detector Workshop – Nice – November 18th, 2008

  2. Outline • Introduction, solutions for ILC-TPC • Micromegas with resistive anode • description • previous results • The Large Prototype (LP) • Micromegas panels in the LP • drift velocity • pad response function • resolution • Conclusion TILC09 – Tsukuba – April 18th, 2009

  3. How to improve the spatial resolution? • 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 × 106 channels of electronics • sz=0 > 250 μm amplification avalanche over one pad • Spatial resolution σxy: • limited by the pad size (s0 ~ width/√12) • charge distribution narrow (RMSavalanche ~ 15 μm) Simulation for the ILC-TPC •  1. Decrease the pad size: narrowed strips, pixels • + single electron efficiency • need to identify the electron clusters 55 mm 1. Pixels • 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 TILC09 – Tsukuba – April 18th, 2009

  4. Micromegas Best technology for gaseous detector readout: Micro Pattern Gaseous Detector • better ageing properties • easier to manufacture • more robust than wires • no E×B effect • fast signal & high gain • low ion backdrift Micromegas • MICROMEsh GAseous StructureY. Giomataris et al., NIM A 376 (1996) 29 • metallic micromesh (typical pitch 50μm) • sustained by 50-100 μm pillars cathode ~50 µm ~50 kV/cm ~1 kV/cm • simplicity • single stage of amplification • fast and natural ion collection • discharges non destructive TILC09 – Tsukuba – April 18th, 2009

  5. Resistive anode (r) Q(t) • One way to make charge sharing is to make a resistive anode • Equivalent to adding a continuous RC circuit on top of the pad plane. • Charge density ρ(r,t) obeys 2D telegraph equation: M.S.Dixit et.al., NIM A518 (2004) 721 (r,t) integrate over pads r (mm) t (ns) Current generators R R R R R R R R Resistive foil C C C C C C C Signal pickup pads Rp Rp Rp Pad amplifiers TILC09 – Tsukuba – April 18th, 2009

  6. Resistive anode Simulation Data 2 x 6 mm2 pads (r) Q(t) (r,t) integrate over pads r (mm) t (ns) M.S.Dixit and A. Rankin NIM A566 (2006) 281 TILC09 – Tsukuba – April 18th, 2009

  7. Micromegas with resistive anode • TPC COSMo (Carleton-Orsay-Saclay-Montreal) at DESY in 2006 • + Micromegas 10 x 10 cm² (gap 50 μm) • + resistive anode used to spread charge over • 126 pads (7x18) of 2x6 mm² • 15 cm drift space • 25 µm mylar with Cermet (Al-Si) of 1 MW/□glued onto the pads with 50 µm thick dry adhesive mesh Resistive foil Glue pads PCB Micromegas TPC COSMo Resistive anode 5 T magnet at DESY + TPC COSMo TILC09 – Tsukuba – April 18th, 2009

  8. Spatial resolution at 0.5T • B = 0.5T, resolution fitted by where • Resolution 0( at z = 0) ~50 µm still good at low gain (will minimize ion feedback) • Mean of Neff = 27 (value measured before ~ 22)  s0 = 1/40 of pad pitch Gain = 4700 Gain = 2500 Neff=25.2±2.1 Neff=28.8±2.2 TILC09 – Tsukuba – April 18th, 2009

  9. Spatial resolution at 5T Ar Iso (95:5) B = 5T Extrapolate to B = 4T with T2K gas for 2x6 mm2 pads: • DTr = 23.3 μm/cm, • Neff ~ 27, • 2 m drift distance,  Resolution of Tr  80 m will be possible !!! • Analysis: - Curved track fit • - EP < 2 GeV • - |f| < 0.05 (~3°)   ~ 50 µm independent of the drift distance 50 mm TILC09 – Tsukuba – April 18th, 2009

  10. ILC-TPC Large Prototype • Built by the collaboration • Financed by EUDET • Sharing out : • - magnet : KEK, Japon • - field cage : DESY, Allemagne • - trigger : Saclay, France • - endplate : Cornell, USA • - Micromegas : Saclay, France • - GEM : Saga, Japon • - TimePix pixel : F, D, NLc TILC09 – Tsukuba – April 18th, 2009

  11. ILC-TPC Large Prototype • Endplate ø = 80 cm of 7 interchangeable panels of 23 cm: • Micromegas • GEMs • Pixels (TimePix + GEM or Microgemgas) 24 rows x 72 columns <pad size> ~ 3x7 mm2 80 cm TILC09 – Tsukuba – April 18th, 2009

  12. Bulk Micromegas panels tested at DESY Standard bulk Micromegas module Carbon loaded kapton Micromegas module • Two panels were successively mounted in the Large Prototype and 1T magnet • standard anode • resistive anode (carbon loaded kapton) with a resistivity ~ 5-6 MΩ/□ • Two other resistive technology are planned to be tested: • resistive ink (~1-2 MΩ/□) ready for next beam tests in May • a-Si thin-layer deposit (N. Wyrsch, Neuchatel) in preparation TILC09 – Tsukuba – April 18th, 2009

  13. Beam test conditions • frequency tunable from 1 to 100 MHz (most data at 25 MHz) • 12 bit ADC (rms pedestals 4 to 6 channels) • 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. TILC09 – Tsukuba – April 18th, 2009

  14. ILC-TPC Large Prototype TILC09 – Tsukuba – April 18th, 2009

  15. 5 GeV e- beam data in T2K gas • Frequency sampling: 25 MHz • T2K gas: Ar/CF4/iso-C4H10 (95:5:3) • Peaking time: 500 ns • B = 1T TILC09 – Tsukuba – April 18th, 2009

  16. Pad signals: beam data sample • RUN 284 • B = 1T • T2K gas • Peaking time: 100 ns • Frequency: 25 MHz TILC09 – Tsukuba – April 18th, 2009

  17. Pad signals: cosmic-ray data sample • RUN 294 • B = 1T • T2K gas • Peakingtime: 1 μs • Frequency: 100 MHz TILC09 – Tsukuba – April 18th, 2009

  18. Systematics Displacement / vertical straight line (μm) B = 0T Pad line number  rms displacement: ~9 microns TILC09 – Tsukuba – April 18th, 2009

  19. Drift velocity measurement • Measured drift velocity (Edrift = 230 V/cm, 1002 mbar): 7.56 ± 0.02 cm/μs • Magboltz: 7.548 ± 0.003 for Ar/CF4/iso-C4H10/H2O (95:3:2:100ppm) B = 0T TILC09 – Tsukuba – April 18th, 2009

  20. Drift Velocity vs. Peaking Time • B=1T data • For severalpeaking time settings: 200 ns, 500 ns, 1 µs, 2µs • Edrift = 220 V/cm • VdMagboltz = 76 m/ns • Edrift = 140 V/cm • VdMagboltz = 59 m/ns Time bins Time bins Z (cm) Z (cm) TILC09 – Tsukuba – April 18th, 2009

  21. Determination of the Pad Response Function  Pad pitch • Fraction of the row charge • on a pad vs xpad – xtrack • (normalized to central pad charge) • Clearly shows charge spreading • over 2-3 pads • (use data with 500 ns shaping) • Then fit x(cluster) using this • shape with a χ² fit, • and fit simultaneously all lines • to a circle in the xy plane xpad – xtrack (mm) TILC09 – Tsukuba – April 18th, 2009

  22. Residuals (z=10 cm) row 5 row 6 row 7 row 8 row 9 row 10 • Lines 0-4 and 19-23 removed for the time being • (non gaussian residuals, magnetic field inhomogeneous for some z positions?) TILC09 – Tsukuba – April 18th, 2009

  23. Residuals (z=10 cm) row 6 • There is a residual bias of up to 50 micron, with a periodicity of about 3mm. • Unknown origin: • Effect of the analysis? • Or detector effect: • pillars? • Inhomogeneity of RC? row 7 row 8 TILC09 – Tsukuba – April 18th, 2009

  24. Spatial resolution at 1T • Resolution (z=0): σ0 = 46±6 microns with 2.7-3.2 mm pads • Effective number of electrons: Neff = 23.3±3.0 consistent with expectations TILC09 – Tsukuba – April 18th, 2009

  25. Further tests for Micromegas Resitive technology choice In 2009 with 7 detector modules. In 2008 with one detector module Compact the electronics with possibility to bypass shaping Front End-Mezzanine 4 chips Wire bonded TILC09 – Tsukuba – April 18th, 2009

  26. Conclusions • Excellent start for the Micromegas TPC tests within the EUDET facility. Smooth data taking. • First analysis results confirm excellent resolution at small distance: 50 μm for 3mm pads • Expect even better results with new (bypassed shaper) AFTER chips • Plans are to test several resistive layer fabrication, then go to 7 modules with integrated electronics TILC09 – Tsukuba – April 18th, 2009

  27. Backup slides TILC09 – Tsukuba – April 18th, 2009

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