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presented by Bert Koene

October 3, 2001 /1

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Topics

Introduction

Tracker layout

Straw tube drift cells

Detector modules

Performance

Stations

Electronics

HV, gas, alignment

Project organization

Summary

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INTRODUCTION

Momentum spectrometer T2 – T9Track slopes in RICH T1 - T2

T6 - T9Link vertex⇐⇒ CAL/muon

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Tracker = Inner Tracker + Outer Trackerfine grained coarse grained

surface 2 % 98 %

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Boundary IT - OT:cell occupancy←− track density ⊗ granularity

x position (cm)

y po

sitio

n (c

m)

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TRACKER LAYOUT

Detection elements5 mm diameter straw tubes packed in double-layeredmodules

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Module cross section

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Station = 4 planes of modules arranged as X U V Xviews

active area

station zmax xmax ymax channels

(mm) (mm) (mm)

2 2275 704 581 4.3 k

3 3635 1125 929 6.8 k

4 6035 1867 1541 11.4 k

5 7035 2176 1796 13.1 k

6 8038 2486 2052 15.1 k

7 8497 2628 2170 16.0 k

8 8956 2770 2287 16.8 k

9 9415 2912 2404 17.5 k

101.0 k

Stereo angle ±5o optimised for

εseeding ⊗ εfollowing⊗ RICH slopes

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z (cm)0 200 400 600 800 1000 1200

B (

Tes

la)

-1

-0.8

-0.6

-0.4

-0.2

0

yB

z and BxB

=0yθ=xθ

R1← following → seeds R2

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Economised since Techn. Proposal:

• No station behind RICH 2

• No Y planes at RICHes

• One magnet station less

Without T11, extended RICH

With T11

Momentum (GeV)

π -K

sep

arat

ion

(si

gma)

π-K separation for true pions

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STRAW TUBES

Cell size limited by:occupancysignal collection time

clean electrostatics (tube)fast drift gas

Tmax < 25 ns idealTmax < 50 ns realistic

consequence: time overlap with hits fromneighbouring BX

Detector sample

25ns 25ns 25ns 25ns 25ns 25ns

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Use Ar / CF4 / CO2 for fast driftLarge electron capture c.s. of CF4 at few eV:

• degrades drift resolution insignificant

• breakup to free fluorine radicals

Cathode surface of noble metal or carbon loaded polymer(ATLAS, HERA-B, COMPASS)

Technical Proposal: “drift cells of straw tube geometry builtwith honeycomb chamber technique”

HC proto’s of C-doped polycarbonate foil (Pokalon)Switched to real straw tubes of C-doped Kapton because:

1. Pokalon-C very expensive

2. doubts about Pokalon-C ‘aging’ in Ar / CF4 / X

3. slow drift in HC cell corners

4. better precision of cell shape

Channel density increase: 5 + 1 mm HC cell pitch5.25 mm tube pitch

Less planes =⇒ stayed at 100 k channels

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Inner layer = 40 µm Kapton XC with 30 % volume doping

Tested in Ar / CF4 / CO2 to1.2 C/cm (realistic: p beam)

several C/cm (extreme: glow discharge)

Estimate hottest OT regions: 0.25 C/cm per year

Module aging tests in HERA-B and with X-ray source

realism accelerated

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Outer layer = 25 µm Al⇐= X-talk suppression

Tested 1. Kapton XC2. aluminium3. pure Kapton4. aluminised Mylar

1 & 2 cathode to HV GND via outer layer

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X talk by amplitude:0.5 % aluminium1.8 % Kapton XC

stays worse with shielding foils

Pair of Al-XC tubes acts as 1/4λ resonator if onlysees GND at preampL = O (2 m) =⇒ ν = O (40 MHz), inside preampbandwidth

Remedy: tube grounding at short intervals

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STRAW TUBE MODULES

64 cells widesandwich plates of HC core + 100 µm carbon facings + 20µm Al foil

no module overlap =⇒ loose 1/2 cell at border

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drift gas flows through and around the tubes

gas distribution into tubes

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Electrical split near y = 0 to limit cell occupancy andsignal propagation time

Wire centering supports every 80 cm

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midway splitterboost far-end amplitude: no terminating impedance

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signal round trip ≤ 20 ns ' shaping time

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10 mm long wire support =⇒ 12 mm insensitiveregion

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assembly of end piece and front end boards

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MATERIAL BUDGET

Module elements: 0.67 % X0

2 tube layers 0.276 %4 x 0.1 mm facing 0.14 %2 x 10 mm HC core 0.11 %2 x 20 µm Al foil 0.045 %gluings (est.) 0.1 %

Break down for tube layers:

aluminium 0.165 %glue 0.02 %Kapton XC 0.091 %

Add localised materials =⇒ 0.75 % per module4 x 0.75 % = 3.0 % X0 per stationSum for Outer Tracker:

24 % X0

10 % λI

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TEST BEAM RESULTS

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plateau curves and cell resolution at different CF4

concentrations

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Tmax vs B field: 15 % CF4 is enough

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smallish effect of CF4 concentration on resolution

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homogeneous response along 3.3 metre long and fullyrealistic prototype

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PERFORMANCE STUDIES

OT configuration optimization

Track reconstruction on simulated bb̄ events + min.bias bkg events

pp interactions at√

s = 14 TeV Pythiaparticle decays QQ packagefollow through LHCb GEANT based SICBOuter Tracker response GAUDI

tuned to test data, incl. dead time etc.track reconstruction TRAIL package

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Background mixed into bb̄ events :

PILE UP: min. bias in same BX (average 0.53)

SPILL OVER: hits due to different BX

1. overlap of 50 ns OT time windows per BX

2. long-lived curling tracks

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quiet Bd → π+π− event

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busy Bd → π+π− event

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OCCUPANCY

Def: fraction of channels hit within the 50 ns eventwindowimportance:

• pattern recognition efficiency & ghost raterequires mean occupancy

seeding ≤ 10 %

other ≤ 15 %

• f.e. dead time ' 35 ns / hitoccupancy =⇒ inefficiency

0 2000 4000 6000 8000 10000

100

95

90

85

80

Hit multiplicity in OT

OT

see

ding

eff

icie

ncy

(%

)

seeding eff. vs number of hits in T6 – T9

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Tuning of IT - OT boundary

x position (mm)

aver

. occ

up. (

%)

average occupancy vs cell position in T7

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occupancy

# E

vent

s

event-to-event occupancy fluctuation in hottestregion of T3

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Station

Occ

upan

cy

TO

P

CO

RN

ER

SID

E

Average occupancies in the hottest regions of each stationat L = 2× 10

32cm−2s−1

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Track reconstructionOT ⊕ IT

Upstream tracking

• find track seeds in T6 – T9

• assume origin in vertex⇒ δp/p to O(2 %) from pt kick

• follow into the gently rising B field

Fast variant for L2 trigger

• match track seed with VELO track, p from kink

δp/p = 1.3 %matching eff. = 92 % for p > 5 GeV/c

Downstream tracking

• follow VELO track into the magnet (T4)δp/p ' 0.6 %

ε = 80 % – 90 % depending on p

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Upstream tracking

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100 120 140 160 180 200

p (GeV)

δp/p

(pe

r m

ille)

m.s. term (constant) and resolution term (∝ p) areequal at 100 GeV/c

< δp/p > = 0.39 % for p > 1 GeV/c

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Upstream tracking efficiencies

0 20 40 60 80 100

100

95

90

85

80

Momentum (GeV/c)

Seed

ing

effi

cien

cy (

%)

seeding

momentum(GeV/c)0 20 40 60 80 100

Fo

llow

ing

eff

icie

ncy

(%)

80

85

90

95

100

following

requiring > 70 % purity and efficiency of hit assignment

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momentum (GeV/c)0 20 40 60 80 100

com

bin

ed e

ffic

ien

cy (

%)

80

82

84

86

88

90

92

94

96

98

100

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Stereo angle

track following ≤ 5o

track seeding ≤ 10o

RICH slopes not too small, 5o still OK(⇒ 0.09 mrad on trackvs 0.58 mrad per photon)

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Stereo angle (degrees)

Seed

ing

effi

cien

cy (

%)

Processing time (seconds/event)

seeding eff. vs stereo angle

Stereo angle(degrees)0 2 4 6 8 10 12 14 16

Fo

llow

ing

eff

icie

ncy

(%)

90

95

100

Stereo angle(degrees)0 2 4 6 8 10 12 14 16

Gh

ost

rat

e(%

)

0.1

0.15

0.2

following eff. and ghost rate vs stereo angle

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Physics performance illustration

Tracking efficiency

Bd → ππ 94 % (⇐ 97 % per track)

Bs → Ds(KKπ)K 80 % (⇐ 95 % per track)

Mass resolution

(GeV)0Bm

5.2 5.40

10

20

30

40

50 σ =21.8 MeV

(GeV)sBm

5.3 5.35 5.4 5.450

10

20

30

40

50 σ =10.7 MeV

(GeV)sDm

1.94 1.96 1.98 20

10

20

30

40

50 σ =4.3 MeV

Bd → ππ Bs → DsK Ds → KKπ

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comment to mass resolution

Tracker =⇒ track momentaVELO =⇒ track angles

δM/M ∝ δp/p and ∝ δα/α

B → ππ hard tracks, large opening anglemomentum error dominates

Ds → KKπ soft tracks, small opening angleerrors on momenta and angles contributeequally

cp. Techn. Proposal:assumed δp/p = 0.3 %δM(Bs → DsK): unchangedδM(Bd → ππ): 17 MeV/c2 × (0.39 % / 0.3 %) = 22MeV/c2

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STATION DESIGN

seeding stations T6 – T9 are identical

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L/R station halvesmodules mounted on top/bottom precision bars

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10 cm between pole faces and ± 250 mradacceptance limit

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3734

3082

3924

340 170

200

581

(end of active region)

so cut sawtooth of stereo planes away

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T3 – T5 mounted on rails fixed to magnet yokeL/R halves separate when moving out

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ELECTRONICS

32x32x

2x

TTCrxECSslave

Powerregulator

L0 derandomizerL0 derandomizer

level 0bufferlevel 0buffer

serviceboards

~ 40

3250front−endboards

815 signaldistributionboards

102level 1boards

104000 channels

815 optical links

204 optical links

DLLDLL

DACsDACs

triggerlogic

triggerlogic

ECSslave

L1 Yesclock

I2CJTAG

level 1 logic &header generator

level 1 buffer(FIFO)

TTCrx

output FIFO

L1 derandomizer

straw tube signals

clock

L0−yes

8 I2C

ASDBLR

4xV threshold

32channels

LH

Cb

cav

ern

fine timefine time

zero−suppressor32:1 multiplexor

Co

un

tin

g r

oo

m

Front−End links to DAQ

Multiplexor 4:1

GOL

OTISTDC

Power

TTCECS

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Front end:

• Hit rates locally up to 4 MHz atL = 5× 1032cm−2s−1

• radiation dose O(10 krad/yr) =⇒ rad. tolerant /hard

Preamp: 8-channel ASDBLR chip

DMILL→ radiation hardpeaking time 8 nsshaping time 20 ns

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Custom designed TDCOTIS chip, ASIC lab Heidelberg

• rad hard 0.25 µm CMOS

• clock driven (via TTC system from LHC clock)

• DLL adds 5 bits fine time

• 32 channels / chip

• each channel has its own clock-synchronous L0buffer

• on L0 accept two buckets to derandomizer

OTIS development steps

submits of TDC core and memory tested July 2001first submit of full chip April 2002final evaluation May 2003

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fall-back solution: already existing HPTDC chip

• 32 channels share 1 L0 buffer⇒ in hot regionsuse only 16 channels/chip

• limited radiation tolerance⇒ not on f.e. boards(racks near detector)

• FPGAs convert data to OTIS format⇒ same L1electronics

Can do the job at added cost of crates and cabling

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HV DISTRIBUTION

2 × 64 ch per HV branch

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Drift gas system

recirculating⇐ CF4 cost

90 % regeneration per cycle

flow rate O(1 vol/ 2 h)

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Hardware alignment monitoring(if it fits in)

RASNIK system logs movements within station tripletsMASK (1) → LENS (2) → CCD CAMERA (3)

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PROJECT ORGANISATION

Milestone Date

Mechanics

Engineering design of modules completed 12/2001

Engineering design of frames completed 6/2002

Start of module production 6/2002

Start of frame production 3/2003

All frame parts at IP8; start of station assembly 6/2004

Last modules to IP8 4/2005

Last station installed 6/2005

Electronics

TDC choice 5/2003

Start of electronics production 6/2003

All electronics produced and tested 3/2005

Project

Commissioning completed 3/2006

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Task Institutes

Mechanics

T2 – T5 Heidelberg, Krakow

T6 – T9 Beijing, NIKHEF, Warsaw

Electronics

Before TDC NIKHEF

From TDC to DAQ

Baseline design Dresden, Heidelberg, NIKHEF

Fall-back design Krakow, NIKHEF

Production & testing Beijing, Dresden,

Heidelberg, NIKHEF

Services

Drift gas CERN, Krakow

High voltage CERN, NIKHEF

Alignment Warsaw

Controls NIKHEF

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Comments

620 modules includes 10 % spares

assembly of large stations at CERN

tracking software and performance studies:common for OT + IT by Tracking Task Force

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PROJECT COST

detector modules 2720 kCHFelectronics 5570frames and installation 560services 450

TOTAL 9300 kCHF

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SUMMARY

• Module design: ready and proven

• Known how to assemble into stations

• Electronics is designed; TDC still underdevelopment, fall-back is on the shelf

• Tracker layout simplified: two stations less thanin Technical Proposal

• Track reconstruction efficiency through entirespectrometer ≥ 90 %

• Momentum resolution 0.39 %(T.P. assumed 0.3 %)

• Outer Tracker represents 0.24 X0

(T.P. idealized design 0.18 X0)

• Resources of people, time and money match thepresent project size

Further LHCb optimization: trend to ‘less is evenbetter’May drop another station, but no effect on technicaldesign

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