the alice tpc c. garabatos, gsi. vienna 2004c. garabatos, gsi darmstadt2 tpc | | < 0.9 (full...

The ALICE TPCThe ALICE TPCC. Garabatos, GSIC. Garabatos, GSI

• Description, tasksDescription, tasks

• A challenging designA challenging design optimise the drift gasoptimise the drift gas

• ConstructionConstruction– Readout chambersReadout chambers– Field CageField Cage– ElectronicsElectronics– CoolingCooling– Laser systemLaser system

• OutlookOutlook

Vienna 2004 C. Garabatos, GSI Darmstadt 2

TPCTPC

• ||| < 0.9 (full length tracks)| < 0.9 (full length tracks)• 845 < r < 2466 mm845 < r < 2466 mm• 2 2 2500 mm drift 2500 mm drift• 88 m88 m33

• 557568 readout pads557568 readout pads


Layout

Inner and Outer Inner and Outer Containment VesselsContainment Vessels(150 mm, CO(150 mm, CO22))

Central electrodeCentral electrode100 kV100 kV

Suspended fieldSuspended fielddefining stripsdefining strips400 V/cm400 V/cm

Endplates housingEndplates housing2 2 2 2 18 chambers 18 chambers


Challenging requirements for the gas

HighMultiplicities

MomentumResolution

High Rate(200 Hz)

dE/dxResolution

Occupancy2 track res.

FieldDistortions

MultipleScattering

Drift speed(max. HV)

Signal/Noise

ArgonNeon HydrocarbonsCO2

CF4

Ageing

Flammability

Neutrons

Concentration:90-10

Gain:2 104

????

?

Small pads:4 7.5 mm2


Characteristics of the gasNe-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?


Yes: add Nitrogen

0 100 200 300 400 500 600 700 8000

1

2

3

4

5

Vdr

ift (

cm/

s)

E (V/cm)

Ne-CO2 [90-10]

Ne-CO2-N

2 [90-10-5]

5% lower drift velocity or ~5% higher drift field


Drift velocity changesof no N2 vs. N2

Ne-CO2-N2 90-10-0 90-10-5

Temperature +0.37 % / K +0.34 % / K

Pressure -0.15 % / mbar -0.15 % / mbar

CO2 concentration -7.6 % / %CO2 -6.4 % / %CO2

N2 contamination -1 % / %N2 -1 % / %N2

... and same diffusion coefficients, same electron absorption.


Gain changesof 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


N2 vs. no N2: StabilityInstantaneous maximum gain

1200 1300 1400 1500 1600

10000

100000

Ne-CO2-N

2 (90-10-5)

IROC 10

Ga

in

Anode voltage (V)

Ne-CO2 (90-10)

Operatinggain


Why N2 helps with Neon:quenching (by ionisation) of Neon

excited states in the avalanche

5 10 15 20 25 30 350

10

20

30

40

Ne*

N2

CO2

Ab

so

rpti

on

cro

ss

se

cti

on

(M

b)

Energy (eV)

20001500 1000 500 Wavelength (Å)


Chamber gain

1100 1150 1200 1250 1300 1350 14001000

10000

100000

Ga

in

Anode voltage (V)

Measured 40 % Penning 50 % Penning

IROC Ne-CO2 [90-10]

PCmonte simulations (S. Biagi) with Penning transfer, and measurements

1350 1400 1450 15001000

10000

100000

Ga

in

Anode voltage (V)

Measured 34 % Penning

IROC Ne-CO2-N

2 [90-10-5]


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


The Field Cage vesselswith field-shaping strips

Macrolon rodsMacrolon rods• to support the stripsto support the strips

(à la NA49)(à la NA49)• to supply the HVto supply the HV

and degrade it alongand degrade it along• to distribute the gasto distribute the gas

(radially in/out)(radially in/out)• to distribute laser tracksto distribute laser tracks

((àà la STAR) la STAR)

• Suspended Al-mylar stripsSuspended Al-mylar strips• Stretched Al-mylar central Stretched Al-mylar central

electrodeelectrode• Endplates to hold ROCsEndplates to hold ROCs• Mechanical precision:Mechanical precision:

~200 ~200 mm

Ready for gas and volts: summer 2004Ready for gas and volts: summer 2004


anode wire

pad plane

drift region88s

L1: 5s 200 Hz

DETECTOR

570132PADS

gat

ing

gri

d

cath

od

es

1 MIP = 4.8 fC

S/N = 30 : 1

DYNAMIC = 30 MIP

CSA SEMI-GAUSS. SHAPER

GAIN = 12 mV / fCFWHM = 190 ns

10 BIT

< 10 MHz

• BASELINE CORR.

• TAIL CANCELL.

• ZERO SUPPR.

MULTI-EVENT

MEMORY

PASA ADC DigitalCircuit

(ALTRO)

RAM

8 CHIPS x

16 CH / CHIP

8 CHIPSx

16 CH / CHIP

CUSTOM IC(CMOS 0.35m) CUSTOM IC (CMOS 0.25m )

FEC (Front End Card) - 128 CHANNELS(CLOSE TO THE READOUT PLANE)

FEC (Front End Card) - 128 CHANNELS(CLOSE TO THE READOUT PLANE)

L2: < 100 s 200 Hz

DDL(4096 CH / DDL)

Powerconsumption:

< 40 mW / channel

Powerconsumption:

< 40 mW / channel

Front-end Electronics: Architecture


ALTRO: digital tail cancellation and baseline restoration

Cosmic ray eventin prototype FC


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


Cooling: Temperature Stabilization and Homogeneity

• HV resistor rod: 4 x 8 W water-cooled removable electrolysis, corrosion

... all under control

• 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


• Rays perpendicular • to beam axis• Effective ray ~1mm• 2 x 4 z-planes• Strategic boundary

crossings• Additional signal from

central electrode

Laser System


Performance simulations> 97 % efficiency @ dN/dy = 8000

• dE/dx resolution: 5.3 – 6.8 % depending on multiplicity

p/p

• Magnetic field 0.5 T• p/p (100 GeV) vs dN/dy:

16% 9% at dN/dy=2000


Space resolution from cosmic ray data

Resolution in drift direction

Resolution in bend direction

PRELIMINARYPRELIMINARY


Summary

• A challenging, large TPC is thoroughly being constructed for ALICE• High multiplicities, high occupancy, high gain 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


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


Additional slides


Absorption cross-section of quenchers

5 10 15 20 25 30 350

40

80

120

160

C2H

6

C4H

10

CH4

CO2

Ab

so

rpti

on

cro

ss

se

cti

on

(M

b)

Energy (eV)

20001500 1000 500 Wavelength (Å)


Unprecedented gain?

950 1000 1050 1100 1150 12001000

10000

G

ain

Anode voltage (V)

50 % Penning 40 % Penning

NA49 VTPC1 PCmonte simulation


TPC test facility measurementsrms noise statistics, mean 700 e

time bin

pad

#

time bin

Cosmics tracks


Field Cage: Central Electrode

• 6m wide mylar foil, glued from 3 sheets


010011010001011101010011010001011110010011010001011010

01001101000110111010110011000111001010011010 010011010001101110010 010011010001101110010 010011010001101110010

BaselineCorrection

I

+

–

TailCancellation

BaselineCorrection

II

ZeroSuppression

010011010001101110010010011010001101110010010011010001101110010

DataFormat

Memory+

Multi-EventBuffer

010011010001011101010011010001011110010011010001011010

01001101000110111010110011000111001010011010 010011010001101110010 010011010001101110010 010011010001101110010

BaselineCorrection

I

+

–

TailCancellation

BaselineCorrection

II

ZeroSuppression

010011010001101110010010011010001101110010010011010001101110010

DataFormat

Memory+

Multi-EventBuffer

SAMPLING CLOCK up to 20 MHz (5.7 MHz used)

READOUT CLOCK 40 MHz

10- bit20 MSPS

11- bit CA2arithmetic

18- bit CA2arithmetic

11- bitarithmetic

40-bitformat

40-bitformat

10-bitarithmetic

ALICE TPC READOUT CHIP – Principle

16 ADCs and Digital Filter channels in one chip Algorithms and parameters reconfigurable


Field Cage Outer Containment Vessel


Readout Chamber Wire Geometry

gate wirescathodes

anodespads


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


Outer chamber test status

0 5 10 15 20 250

20000

40000

60000

2

4

51

6

8

10

712

1617

15

19

18

20

21

2522 26

29 3331

35

Gain Summary - OROC

Ga

in a

t 1

55

0 V

Chronological order


Tightness

0 10 20 300.1

1

10

100 OROC 29

Oxy

gen

(p

pm)

Time (hours)


Gain curve

1300 1350 1400 1450 1500 1550 16001000

10000

100000

OROC 29

Ga

in

Anode voltage (V)

Gain (anodes) Gain (cathodes)


Gain uniformity test

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

Y

Po

sitio

n

X position

5.0006.4177.8339.25010.6712.0813.5014.9216.3317.7519.1720.5822.00

Module 29


Long-term test

0 10 20 30 40 50800

850

900

950

1000

1050

1100

OROC 26

Time (hours)

Co

rre

cte

d p

ea

k P

osi

tion

0

5

10

15

20

25

30 FW

HM

(%)


Ageing tests

• Tested many assembly materials:– Glues:

• Araldit 2012, 2013, dp190, 116

– Tedlar foil– Vacuum grease

• Lithelen• Apiezon

– Stesalit-like insulator


Rate of ageing in ALICE with P10

qRGG '0 exp

0.01 0.1 1 10 100 10000.1

1

10

100

ALICE TPC(max)

R' [

(C/c

m)-1

/2]

Initial intensity (nA/cm)

Fischer et al. Au wire Au, Graphite cathode SS wire SS, CH

4 45

Au, 1 % water ALICE ROC, P10


Ageing predictions with P10

1E-3 0.01 0.1 1 100.3

0.4

0.5

0.6

0.7

0.8

0.9

1

ALICE10 years

STAR3 months

G/G

0

q (mC/cm)

R' = 0.1 (C/cm)-1/2

R' = 0.5 R' = 1 R' = 5 R' = 10

1E-3 0.01 0.1 1 10 100 10000.1

1

10

100

STAR TPC(max)

ALICE TPC(max)

R' [

(C/c

m)-1

/2]

Initial intensity (nA/cm)

Fischer et al. Au wire Au, Graphite cathode SS wire SS, CH

4 45

Au, 1 % water ALICE ROC, P10


Challenging requirements

• High multiplicities (dN/dy = 8000 originally)– High occupancy Small pads (down to 4 7.5 mm2)

– E (and E B) distortions in drift volume No Argon

• Momentum resolution goal dp/p 1%– low multiple scattering gas No Argon

• Event rate (up to 200 Hz)– 100 s max. drift time but 100 kV max Not much

quencher allowed

• Good particle ID through dE/dx– signal/noise, uniformity High enough gain


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/s)

• Low primary ionisation + small pads:

Unprecedented high gain: 2 104 (for TPCs)


Front End Card connection and cooling

FEC in cooledCu sandwich

Flexible cablesto PASA input

Extra structureExtra structure(Service Support Wheel)(Service Support Wheel)to hold weight of electronicsto hold weight of electronics


25 Front End Cards

ALTRO

PASA

Power Connector

Readout and Control

Backplane

(300 MB /sec)

Readout Partition (3200 channels)

FEE Components Assembly

the alice tpc c. garabatos, gsi. vienna 2004c. garabatos, gsi darmstadt2 tpc | | < 0.9 (full...

Documents

gain changesof n2

saturated drift velocity

lower drift velocity

readout chamber al bodies

field cage vesselswith

strong dependence of

temperature stabilization

chamber constructionis