The ATLAS Silicon Microstrip Tracker introduction system design sensors module design electronics hybrids status Lutz Feld, Freiburg University, for the ATLAS SCT Collaboration 9th Vienna Conference on Instrumentation, February 2001

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Large Hadron Collider at CERN pp collisions at 14 TeV centre of mass energy two multi purpose experiments: ATLAS and CMS two specialised experiments: ALICE (heavy ions) and LHC-B (b physics and CP) first beam in 2005, first collisions in 2006

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb ATLAS-Detector 22m 46m

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb LHC means high rate and high multiplicity at full luminosity L=10 34 cm -2 s -1 : ~23 overlapping interactions in each bunch crossing every 25 ns ( = 40 MHz ) inside tracker acceptance (|  |<2.5) 750 charged tracks per bunch crossing per year: ~5x10 14 bb; ~10 14 tt; ~20,000 higgs; but also ~10 16 inelastic collisions severe radiation damage to detectors detector requirements: speed, granularity, radiation hardness a H->bb event plus 22 minimum bias interactions a H->bb event as observed at high luminosity

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb ATLAS Inner Tracker Performance: rapidity coverage: |  | < 2.5 momentum resolution for isolated leptons:  p T / p T ~0.1 p T (TeV) track reconstruction efficiency (high-p T ) for isolated tracks  > 95%, within jests  > 90%, ghost tracks < 1% (for isolated tracks) impact parameter resolution at high-p T  r-  < 20  m,  z < 100  m low material budget for tracker and ECAL performances lifetime > 10 LHC years 2.3m 7m inside a solenoid providing 2T magnetic filed

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb ATLAS Silicon Microstrip Tracker SCT o4 barrel layers obarrel radii: 300, 371, 443 and 514 mm; length 1600 mm oin total 2112 modules o2 x 9 forward disks odisk distance from z = 0: mm, radii: mm oin total 1976 modules (3 rings: 40, 40, 52 modules each) oall 4088 modules double sided o15,392 sensors of total 61.1m² ototal length of diode: 716 km o49,056 front-end chips, total 6.3 Mio. channels ooptical command and data links 5.6m 1.2m

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Radiation Environment in SCT volume up to 1.3x MeV-n/cm² and 5 Mrad for 10 years of operation damage to sensors obulk damage: displacement of Si atoms from lattice sites oincreasing leakage current I leak ~fluence oinversion from n-type to p-type and depletion voltage changes, increasing up to ~300V odeterioration of charge collection osurface damage: creation of charge carriers in silicon oxide omodification of electron accumulation layer and change of interstrip capacitance damage to electronics omodification of oxide charge changes threshold voltages of MOS transistors omid-gap states degrade current gain in bipolar transistors oparasitic currents osingle event upset

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb ATLAS SCT Sensors p-on-n single sided detectors 285µm thick 2-8 k .cm 4“ substrate barrel o64x64mm² o80µm pitch forward o5 different wedge shaped sensors oradial strips o µm pitch 768 read-out strips AC coupled to read-out polysilicon or implanted resistors multiguard structure for HV stability ~20000 sensors needed ordered from Hamamatsu, CIS (and Sintef)

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Leakage Current after Irradiation IV curves for CiS wedge detectors after 3x10 14 p/cm 2 (7 days annealing at 25°C) Spec: <250 µA at 450V and -18°C MPI/HLL

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Depletion Voltage after Irradiation beneficial annealing: few days at room temperature decreases depletion voltage reverse annealing: longer time at temperatures >0°C increases depletion voltage -> need to keep irradiated silicon cold (<0°C) oxigenated detectors: less damage and slower reverse annealing, will be used in parts of the inner region MPI Munich

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Barrel Modules double sided module as back-to-back build-up of 2 pairs of rectangular sensors 40 mrad stereo angle to measure second co-ordinate centre-tapped electronics hybrid

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb SCT Forward Disk outer modules inner modules cooling block power tapes optical fibres middle modules (on backside)

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Forward Module in Transport Frame

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Forward Module double sided module as back-to-back build-up of 2 pairs of wedge shaped sensors 40 mrad stereo angle to measure second co-ordinate double sided, end-tapped electronics hybrid alignment: 4µm sensor-to-sensor on each side, 8µm front-to-back

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Leakage Current and Thermal Stability I leak =   x volume x fluence    3x A/cm at 20 o C, fluence in 1MeV equiv. oindependent of material or radiation type after 10 years of LHC running: oa 12 cm long strip at 100 mm pitch draws ~1 µA, oa detector module (160 cm 2 ) draws ~2mA, (both at -10 o C). given the high bias voltage this leads to a significant power dissipation of the silicon itself -> need efficient cooling to avoid thermal runaway remedies: oleakage current strongly temperature dependent oI=I 0 T 2 exp(-E g /kT) ocurrent doubles every 7°C othermal split between hybrid and sensors oreduce thermal resistance in the module C 3 F 8 evaporative cooling system at ~ -20°C, keeping silicon temperature around -7°C expected power dissipation after 10 years

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Front-End ASIC ABCD3T binary read-out 128 channels DMILL radiation hard process bipolar input transistor shaping time ~20ns comparator threshold trimmable for each channel 132 cell pipeline edge detection, data reduction and multiplexing expected ENC ~ 1500 e for 12 cm strips, increasing to ~1800 e after 10 years of irradiation ~4 mW/channel preamp shaper comparator pipeline data reduction read-out buffers control logic digitalanalogue 128 channels

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Forward Electronics Hybrid requirements: double sided distribute and filter analogue and digital currents (~4V, 1.8A) route/filter detector bias (500V) filter/shield noise/pick-up route commands and data full redundancy provide electrical/optical connectivity remove heat (~7.2W) low mass implementation: 4 layers of copper traces in Kapton flex trace width/gap ~75µm layer thickness ~15µm ~3000 micro vias for connections between planes produced at DYCONEX AG flex folded around a metallised carbon fibre substrate similar technology used for barrel hybrid

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb System Test: Forward Mini-Sector 3 outer modules inner module power cables optical fibres Bench: Sector: with proper grounding scheme no extra noise on the disk

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Test Beam: Median Charge Collection vs. Bias Voltage analysis: N. Unno PRELIMINARY full module irradiated to 3x10 14 p/cm 2 non-irradiated module uncertainty on charge calibration is about 20%

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Test Beam: Hit Efficiency and Noise Occupancy noise occupancy vs. thresholdefficiency at 1 fC vs. bias voltage analysis: N. Unno PRELIMINARY non-irradiated module full module irradiated to 3x10 14 p/cm 2 full module irradiated to 3x10 14 p/cm 2 non-irradiated module

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Production Scheme distributed, parallel production module production ( ): obarrel: KEK, RAL, Berkeley, Oslo oforward: Manchester, Valencia, Geneva, MPI, Freiburg, Prague, NIKHEF, Melbourne mounting modules onto structures ( ): obarrel: KEK, Oxford oforward: Liverpool, NIKHEF, Melbourne macro-assembly ( ): ointegration of 4 barrels at CERN omounting of disks into support cylinders at NIKHEF and CERN/UK SCT ready for installation in ATLAS: 2004

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Summary and Current Status the ATLAS SCT is now preparing the production phase sensors are under fabrication front-end electronics chosen and pre-production has started electronics hybrids close to final design review module design close to final design review several close-to-final modules built and tested (incl. irradiation) module assembly procedure defined and production centres in qualification step off-detector electronics and services in prototyping cooling tested on prototypes barrel support structure under construction forward support structure in prototyping

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb ATLAS Inner Tracker

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Charge Collection Efficiency standard material oxygenated material signal seen on single strip with ~20ns shaping after 32 days annealing at 25°C (MPI Munich) sensors irradiated to 3x GeV-p/cm 2

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb SCT Material Budget

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Magnetic Field and p t Resolution p t resolution as a function of |  | for muons of various momenta circles and squares show simulation for ATLAS solenoidal field, triangles for uniform field

Lutz Feld, Uni FreiburgVienna Conference on Instrumentation, Feb Impact Parameter Resolution