The ALICE TPC C. Garabatos, GSI Description, tasks A challenging design optimise the drift gas Construction Readout chambers Field Cage Electronics Cooling Laser system Outlook

C. Garabatos, GSI Darmstadt TPC || < 0.9 (full length tracks) 845 < r < 2466 mm 2 ´ 2500 mm drift 88 m3 557568 readout pads Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Layout Inner and Outer Containment Vessels (150 mm, CO2) Central electrode 100 kV Suspended field defining strips 400 V/cm Endplates housing 2 ´ 2 ´ 18 chambers Vienna 2004 C. Garabatos, GSI Darmstadt

Challenging requirements for the gas High Multiplicities High Rate (200 Hz) Momentum Resolution dE/dx Resolution Occupancy 2 track res. Field Distortions Drift speed (max. HV) Multiple Scattering Signal/ Noise Argon CO2 Hydrocarbons Neon CF4 Small pads: 4 ´ 7.5 mm2 Neutrons Ageing Flammability ? ??? Gain: 2 ´ 104 Concentration: 90-10 Vienna 2004 C. Garabatos, GSI Darmstadt

Characteristics of the gas Ne-CO2 [90-10] Non saturated drift velocity (as with Ar): strong dependence of Vd on everything Very 'sensitive' Townsend coefficients: strong dependence of Gain on everything (Everything: T, P, E, composition, purity, ...) Poor stability: tendency to undergo self-sustained glow discharges due to minor imperfections in chamber construction Is there any other quencher out there? Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Yes: add Nitrogen 5% lower drift velocity or ~5% higher drift field Vienna 2004 C. Garabatos, GSI Darmstadt

Drift velocity changes of no N2 vs. N2 Ne-CO2-N2 90-10-0 90-10-5 Temperature +0.37 % / K +0.34 % / K Pressure -0.15 % / mbar CO2 concentration -7.6 % / %CO2 -6.4 % / %CO2 N2 contamination -1 % / %N2 ... and same diffusion coefficients, same electron absorption. Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Gain changes of N2 vs. no N2 90-10 90-10-5 Temperature +0.9 % / K ? % / K Pressure -0.34 % / mbar ? % / mbar CO2 concentration +67, -20 % / %CO2 +17, -14 % / %CO2 N2 contamination +34 % / %N2 +6.3 % / %N2 Vienna 2004 C. Garabatos, GSI Darmstadt

N2 vs. no N2: Stability Instantaneous maximum gain Operating gain Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Why N2 helps with Neon: quenching (by ionisation) of Neon excited states in the avalanche Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Chamber gain PCmonte simulations (S. Biagi) with Penning transfer, and measurements Vienna 2004 C. Garabatos, GSI Darmstadt

Readout Chamber Production About 2/3 of the –not that conventional– wire chambers assembled and thoroughly tested Material ageing tests End of production/testing: Spring 2004 Vienna 2004 C. Garabatos, GSI Darmstadt

The Field Cage vessels with field-shaping strips Macrolon rods to support the strips (à la NA49) to supply the HV and degrade it along to distribute the gas (radially in/out) to distribute laser tracks (à la STAR) Suspended Al-mylar strips Stretched Al-mylar central electrode Endplates to hold ROCs Mechanical precision: ~200 mm Ready for gas and volts: summer 2004 Vienna 2004 C. Garabatos, GSI Darmstadt

FEC (Front End Card) - 128 CHANNELS (CLOSE TO THE READOUT PLANE) Front-end Electronics: Architecture anode wire pad plane drift region 88ms L1: 5ms 200 Hz DETECTOR 570132 PADS gating grid cathodes PASA ADC Digital Circuit (ALTRO) RAM 8 CHIPS x 16 CH / CHIP CUSTOM IC (CMOS 0.35mm) CUSTOM IC (CMOS 0.25mm ) FEC (Front End Card) - 128 CHANNELS (CLOSE TO THE READOUT PLANE) L2: < 100 ms 200 Hz DDL (4096 CH / DDL) Power consumption: < 40 mW / channel CSA SEMI-GAUSS. SHAPER 1 MIP = 4.8 fC S/N = 30 : 1 DYNAMIC = 30 MIP BASELINE CORR. TAIL CANCELL. ZERO SUPPR. 10 BIT < 10 MHz MULTI-EVENT MEMORY GAIN = 12 mV / fC FWHM = 190 ns Vienna 2004 C. Garabatos, GSI Darmstadt

ALTRO: digital tail cancellation and baseline restoration Cosmic ray event in prototype FC Vienna 2004 C. Garabatos, GSI Darmstadt

Electronics production status PASA 40 000 chips (18000 produced), end of production: March 04 ALTRO (digital chip): 44000 chips produced by March 04 FEC 4800 boards (50 produced). Production finished Oct. 04. Automatic (robot) tests running: 1200 chips/day Vienna 2004 C. Garabatos, GSI Darmstadt

Cooling: Temperature Stabilization and Homogeneity Very challenging: we aim at T  0.1 K in the whole volume Thermal screens towards TRD (outer) and ITS (inner) Water-cooling of Readout Chamber Al bodies and pad planes Water cooling of FEE boards (total power 27 kW) All leakless (P < Patm) cooling systems >400 temperature probes HV resistor rod: 4 x 8 W water-cooled removable electrolysis, corrosion ... all under control Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Laser System Rays perpendicular to beam axis Effective ray  ~1mm 2 x 4 z-planes Strategic boundary crossings Additional signal from central electrode Vienna 2004 C. Garabatos, GSI Darmstadt

Performance simulations > 97 % efficiency @ dN/dy = 8000 Magnetic field 0.5 T dp/p (100 GeV) vs dN/dy: 16%  9% at dN/dy=2000 dp/p dE/dx resolution: 5.3 – 6.8 % depending on multiplicity Vienna 2004 C. Garabatos, GSI Darmstadt

Space resolution from cosmic ray data PRELIMINARY Resolution in bend direction Resolution in drift direction Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Summary A challenging, large TPC is thoroughly being constructed for ALICE High multiplicities, high occupancy, high gain à Optimised gas: Ne-CO2-N2 [90-10-5] (If you can't beat her, join her) Outlook: Dec. 04 - Aug. 05: Full TPC assembly in surface 2006: TPC Installation underground 2007 START OF LHC Vienna 2004 C. Garabatos, GSI Darmstadt

ALICE TPC Collaborators T. Alt, Y. Andres, T. Anticic, D. Antonczyk, H. Appelshäuser, J. Bächler, J. Bartke, J. Belikov, N. Bialas, U. Bonnes, R. Bramm, P. Braun-Munzinger, R. Campagnolo, P. Christakoglou, E. Connor, H. Daues, C. Engster, Y. Foka, F. Formenti, A. Förster, U. Frankenfeld, J.J. Gaardhøje, C. Garabatos, P. Glässel, C. Gregory, H.A. Gustafsson, J. Hehner, H. Helstrup, M. Hoch, M. Ivanov, R. Janik, K. Kadija, R. Keidel, W. Klempt, E. Kornaś, M. Kowalski, S. Lang, J. Lien, V. Lindenstruth, C. Loizides, L. Lucan, P. Malzacher, T. Meyer, D. Miskowiec, B. Mota, L. Musa, B.S. Nielsen, H. Oeschler, A. Oskarsson, L. Osterman, A. Petridis, M. Pikna, S. Popescu, S. Radomski, R. Renfordt, J.P. Revol, D. Röhrich, G. Rüschmann, K. Safarik, A. Sandoval, H.R. Schmidt, K.E. Schwarz, B. Sitar, H.K. Soltveit, J. Stachel, T.M. Steinbeck, H. Stelzer, E. Stenlund, R. Stock, P. Strmen, T. Susa, I. Szarka, H. Tilsner, G. Tsiledakis, K. Ullaland, M. Vassiliou, A. Vestbo, D. Vranic, J. Westergaard, A. Wiebalck, B. Windelband Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Additional slides Vienna 2004 C. Garabatos, GSI Darmstadt

Absorption cross-section of quenchers Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Unprecedented gain? Vienna 2004 C. Garabatos, GSI Darmstadt

TPC test facility measurements rms noise statistics, mean 700 e Cosmics tracks pad # time bin time bin Vienna 2004 C. Garabatos, GSI Darmstadt

Field Cage: Central Electrode 6m wide mylar foil, glued from 3 sheets Vienna 2004 C. Garabatos, GSI Darmstadt

ALICE TPC READOUT CHIP – Principle 10- bit 20 MSPS 11- bit CA2 arithmetic 18- bit CA2 arithmetic 11- bit arithmetic 10-bit arithmetic 40-bit format 40-bit format SAMPLING CLOCK up to 20 MHz (5.7 MHz used) READOUT CLOCK 40 MHz 16 ADCs and Digital Filter channels in one chip Algorithms and parameters reconfigurable Vienna 2004 C. Garabatos, GSI Darmstadt

Field Cage Outer Containment Vessel Vienna 2004 C. Garabatos, GSI Darmstadt

Readout Chamber Wire Geometry gate wires cathodes anodes pads Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Pad Plane optimized pad sizes 4 x 7.5 mm 6 x 10 mm 6 x 15 mm segmented: IROC and OROC total 557 568 pads Vienna 2004 C. Garabatos, GSI Darmstadt

Outer chamber test status Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Tightness Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Gain curve Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Gain uniformity test Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Long-term test Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt Ageing tests Tested many assembly materials: Glues: Araldit 2012, 2013, dp190, 116 Tedlar foil Vacuum grease Lithelen Apiezon Stesalit-like insulator Vienna 2004 C. Garabatos, GSI Darmstadt

Rate of ageing in ALICE with P10 Vienna 2004 C. Garabatos, GSI Darmstadt

Ageing predictions with P10 Vienna 2004 C. Garabatos, GSI Darmstadt

Challenging requirements High multiplicities (dN/dy = 8000 originally) High occupancy ð Small pads (down to 4 ´ 7.5 mm2) E (and E ´ B) distortions in drift volume ð No Argon Momentum resolution goal dp/p  1% low multiple scattering gas ð No Argon Event rate (up to 200 Hz) 100 ms max. drift time but 100 kV max ð Not much quencher allowed Good particle ID through dE/dx signal/noise, uniformity ð High enough gain Vienna 2004 C. Garabatos, GSI Darmstadt

C. Garabatos, GSI Darmstadt The gas: what is left Noble gas cannot be Argon Positive ions too slow, Multiple scattering Noble gas must be Neon Quencher cannot be a hydrocarbon Flammability, Ageing, Slow proton production Quencher cannot be CF4 (not well understood) Quencher must be CO2 Composition not different from [90-10] (Vd=2.8 cm/ms) Low primary ionisation + small pads: Unprecedented high gain: 2 ´ 104 (for TPCs) Vienna 2004 C. Garabatos, GSI Darmstadt

Front End Card connection and cooling FEC in cooled Cu sandwich Flexible cables to PASA input Extra structure (Service Support Wheel) to hold weight of electronics Vienna 2004 C. Garabatos, GSI Darmstadt

FEE Components Assembly Readout and Control Backplane (300 MB /sec) 25 Front End Cards Power Connector PASA Readout Partition (3200 channels) ALTRO Vienna 2004 C. Garabatos, GSI Darmstadt