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

Outline TILC09 – Tsukuba – April 18 th, 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

How to improve the spatial resolution? TILC09 – Tsukuba – April 18 th, 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 Simulation for the ILC-TPC 55  m 1. Pixels

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

Resistive anode TILC09 – Tsukuba – April 18 th,  (r,t) integrate over pads  (r) r (mm) Q(t) t (ns) M.S.Dixit et.al., NIM A518 (2004) 721 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: R R R R R R R R C C C C C C C RpRp RpRp RpRp Current generators Pad amplifiers Signal pickup pads Resistive foil

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

Micromegas with resistive anode TILC09 – Tsukuba – April 18 th, TPC COSMo (Carleton-Orsay-Saclay-Montreal) at DESY in 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 M  /□ glued onto the pads with 50 µm thick dry adhesive 5 T magnet at DESY + TPC COSMo Micromegas TPC COSMo Resistive foil Glue pads PCB mesh Resistive anode

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

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

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

ILC-TPC Large Prototype TILC09 – Tsukuba – April 18 th, Endplate ø = 80 cm of 7 interchangeable panels of 23 cm: –Micromegas –GEMs –Pixels (TimePix + GEM or Microgemgas) 80 cm 24 rows x 72 columns ~ 3x7 mm 2

Bulk Micromegas panels tested at DESY TILC09 – Tsukuba – April 18 th, 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 Standard bulk Micromegas module Carbon loaded kapton Micromegas module

Beam test conditions TILC09 – Tsukuba – April 18 th, 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)

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

5 GeV e - beam data in T2K gas TILC09 – Tsukuba – April 18 th, Frequency sampling: 25 MHz T2K gas: Ar/CF 4 /iso-C 4 H 10 (95:5:3) B = 1T Peaking time: 500 ns

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

Pad signals: cosmic-ray data sample TILC09 – Tsukuba – April 18 th, RUN 294 B = 1T T2K gas Peaking time: 1 μs Frequency: 100 MHz

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

Drift velocity measurement TILC09 – Tsukuba – April 18 th, 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

Drift Velocity vs. Peaking Time TILC09 – Tsukuba – April 18 th,  E drift = 220 V/cm  V d Magboltz = 76  m/ns B=1T data For several peaking time settings: 200 ns, 500 ns, 1 µs, 2µs  E drift = 140 V/cm  V d Magboltz = 59  m/ns Z (cm) Time bins

Determination of the Pad Response Function TILC09 – Tsukuba – April 18 th, 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 (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 x pad – x track (mm)  Pad pitch 

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

Residuals (z=10 cm) TILC09 – Tsukuba – April 18 th, 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 6 row 7 row 8

Spatial resolution at 1T TILC09 – Tsukuba – April 18 th, Resolution (z=0): σ 0 = 46±6 microns with mm pads Effective number of electrons: N eff = 23.3±3.0 consistent with expectations

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

Conclusions TILC09 – Tsukuba – April 18 th, Excellent start for the Micromegas TPC tests within the EUDET facility. Smooth data taking. First analysis results confirm excellent resolution at small distance: 50 μ m 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

Backup slides TILC09 – Tsukuba – April 18 th,