The ALICE TPC an innovative device for heavy ion collisions at LHC

1
The ALICE TPC an innovative device for heavy
ion collisions at LHC
Bergen, Bratislava, CERN, Copenhagen, Krakow,
Darmstadt TU, Darmstadt GSI, Frankfurt,
Heidelberg, Lund

• Introduction
• Problems and Solutions
• TPC parts
• Performance (simulation)
• Test results
• Installation
• Commissioning status
• Outlook

Outline
2
ALICE Setup
TOF
TRD
TPC
RICH
ITS
L3-Magnet
PMD
PHOS
µ-ARM
3
Central event
Central event Pb-Pb _at_ dN/dy 4000
4
The Challenge

• High multiplicity
• space charge limitations
• occupancy large rmin
• optimize track recognition ? pad sizes
• FEE pile-up and baseline problems
• Momentum resolution goal dp/p ? 1
• low multiple scattering in structure and gas
• Event rate
• max drift time
• dE-resolution for PID

5
The Solution and the Consequences

• Thin cold gas with low diffusion Ne/CO2
  mixture
• high sensitivity to E and T
• tolerances ?E/E ? 10-4, ?T ? 0.1 K
• Low dE/dx high gas gain needed (2104 _at_ 1000 e
  rms)
• ?E-resol 159 samples ( pad rows)
• Minimize FEE channel count
• 3 pad sizes 4 x 7.5, 6 x 10, 6 x 15 mm2
  (pointing to vtx
• width tuned to pad response function and
  diffusion
• ? 557,568 pad channels
• FEE digital signal shaping and baseline
  restoration

6
TPC Dimensions and Specs

• ? lt 0.9 (full length tracks)
• 845 lt r lt 2466 mm (cf. STAR 600 to 1892)
• drift 2 x 2.5 m, 100 kV, 92 ?s
• Ne/CO2/N2 (90/10/5)
• occupancy 40 to 15 _at_ dN/dy 8000
• Today expect dN/dy ? 4000
• event rate 100 200 Hz
• material budget 3.5 X0 near ? 0

7
Advantages of N2 admixture

• Stable gain about 2 times higher
• Less sensitive to N2 accumulation
• Higher absolute voltage no problem

8
TPC Field Cage Overview

• Inner and outer isolation vessels
• flushed with CO2
• End plates housing 2x2x18 ROCs
• Field defining system aluminized mylar strips
  (166) supported by rods
• Central membrane
• 100 kV
• 5 x 5.6 m diameter,
• 95 m3 drift volume

9
Inside the TPC
10
Readout Chambers (ROC)

• 18 sectors each side, 2 chambers/sector
• Smaller IROC, larger OROC
• MWPCs, 557568 cathode pads
• gas gain 20000
• gated
• pad sizes 4x7.5, 6x10, 6x15 mm2
• 5.7 MHz 10 bit ADC sampling, 512 samples
• position resolution 800 1250 ?m (r?, z)

11
Frontend Electronics Architecture
FEC (Front End Card) - 128 CHANNELS (CLOSE TO THE
READOUT PLANE)
DETECTOR
Power consumption lt 40 mW / channel
L1 5ms 200 Hz
8 CHIPS x 16 CH / CHIP
8 CHIPS x 16 CH / CHIP
drift region 88ms
L2 lt 100 ms 200 Hz
gating grid
PASA
ADC
RAM
anode wire
DDL (4096 CH / DDL)
570132 PADS
CUSTOM IC (CMOS 0.35mm)
pad plane
CUSTOM IC (CMOS 0.25mm )
CSA SEMI-GAUSS. SHAPER
1 MIP 4.8 fC S/N 30 1 DYNAMIC 30 MIP

• BASELINE CORR.
• TAIL CANCELL.
• ZERO SUPPR.

10 BIT lt 10 MHz
MULTI-EVENT MEMORY
GAIN 12 mV / fC FWHM 190 ns
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Digital circuit ALTRO PrincipleALICE TPC
READOUT
10-bit arithmetic
10- bit 20 MSPS
11- bit CA2 arithmetic
18- bit CA2 arithmetic
11- 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

13
Front-end Card
128 ch
14
Inner Readout Chamber Connected to FE Card
FEC in Cu sandwich
6 cables per FEC

• 128 ch/FEC

15
Cooling Temperature Stabilization and
Homogeneity

• Clearly a challenging item we aim at ?T ? 0.1 K
• Thermal screens toward TRD and ITS
• Readout chamber Al bodies and pad planes
  water-cooled
• Water cooling of FEE boards (total power 27 kW)
• Leakless cooling systems

HV resistive divider rod 4 x 8 W, water-cooled
16
Laser System

• Rays perpendicular
• to beam axis
• 2 x 4 z-planes of 42 rays
• Strategic boundary crossings
• Effective ray ? 1mm
• Additional signal from
• central electrode

17
Performance (simulated)

• gt 97 efficiency _at_ dN/dy 8000

• Note standard field 0.5 T
• dp/p vs dN/dy 16 ? 9
• _at_ 100 GeV, dN/dy 2000

dp/p

• dE/dx resolution
• 5.3 6.8
• depending on multiplicity

18
IROC test facilityHigh Occupancy Events from
Cosmic Rays
ADC signal, only pedestal-subtracted
19
ALTRO digital tail cancellation and baseline
restoration
20
Energy Resolution and PID
Halo muons, pgt10 GeV/c

• dE/dx resolution obtained 9-10 (63 rows)
• for full length track 5-6 TDR 5.5

21
ROC installationHydraulic Platform Mounting
Tool in clean room
Mounting tool
22
Installation of last OROC
23

• View into TPC through last ROC opening
• ROC pad planes mirrored in central membrane

• 200 µm planarity of electrodes achieved

24
FEE installation highlights
25
The FEE installation team
2006-02-17
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Preparations for commissioning (above ground)

• Leak tests
• 10 ppm O2 reached at reduced flow
• ? 2 ppm in final sys
• Ternary gas system works
• filling with Ne/CO2/N2 mixture from 100 CO2 in 7
  days
• Acorde trigger for cosmics
• Laser system operational, one side

27
1st sector IROC, electronics test results
Characterization of Sector A09 - IROC
sum of samples
baseline rms
baseline
28
TPC status as of today

• Field cage assembly completed
• Readout chambers installed
• FEE completed
• Cooling and gas system running
• Field cage running at 100 kV with final gas
  mixture
• Commissioning (above ground) has started

29
Cosmic tracks in OROC 13
Start with moderate gain about 2 to 3000
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First Laser tracks in OROC 13

• ROC gain lowered
• Laser not full power

31
3D displays of one sector
Laser tracks
Cosmic tracks
32
A very busy shower event
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Summary and Outlook

• 2004 Field Cage assembly and ROC production
• 2005 Integration tests, ROC installation
• 2006 1st quarter installation of FEE
• Present status
• Full TPC is running with gas and 100 kV drift
  field
• Commissioning sectors one by one
• Sept 2006 Installation underground
• 2007 LHC start

34
ALICE TPC Collaboration
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, Ch. Garabatos, P. Glässel, Ch.
Gregory, H.A. Gustafsson, J. Hehner, H. Helstrup,
M. Hoch, M. Ivanov, R. Janik, K. Kadija, R.
Keidel, W. Klempt, E. Kornas, M. Kowalski, S.
Lang, J. Lien, V. Lindenstruth, C. Loizides, L.
Lucan, P. Malzacher, 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
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---------- Additional Slides -----------
36
ROC insertion, the last few cm
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Laser Tracks

• Pad response function
• ? 2 mm as expected
• Double track resolution
• Separated maxima down to
• two pad distance
• Two-gauss fit down to 1 pad

38
Test sector IROC results, preliminary
Characterization of Sector A09 - IROC
sum of charges, pad row 46
sum of charges
baseline
noise rms (ADC counts)
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Test sector OROC results, preliminary
Characterization of Sector A09 - OROC
sum of charges
sum of charges, pad row 11
baseline
noise rms (ADC counts)
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Test sector OROC results, preliminary
Characterization of Sector A09 - OROC
sum of samples
sum of samples
baseline rms
baseline rms
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TPC-ITS integration test
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Survey result of ROCs, A-side
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Argon test

• Flow 2.6 m3/h
• 4x less than with final system ? 4x more
  sensitive
• 11 ppm O2 reached 24.2.06, still not asymptotic
• extrapolated lt 3 ppm for final flow

44
FEE Row with Readout Bus

• Innermost row, closest spacing

45
The Environment of the TPC
TRD module
Space Frame
TPC
Service Support Wheel
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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

47
Readout Chamber Wire Geometry

• gate wires

cathodes
anodes
pads
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End plate
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Laser Rod with Mirrors
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Field Cage Assembly
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Field Cage Outer Containment Vessel
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Closing the end plate
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Drehen der TPCzurBestückung deranderen
Hälftebzw. in dieEndlage
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Laser Calibration and Monitoring System Principle
4 micro mirrors along z, alignment check with CCD
at other TPC end
55
Comparison SPC - RHIC LHC
PbPb, central

• The LHC is the ideal place to study the QGP
• hotter - bigger longer-lived
• 104 particles per event Event-by-event
  physics