The Silicon Inner Tracker for LHCb - LHCb - CERN

LHCb Inner Tracker Memo 2002-003
8 International Conference
on Instrumentation for Colliding Beam Physics
¡
Novosibirsk — February 28 - March 06, 2002
The Silicon Inner Tracker for LHCb
¢
¢
¢
¢
Olaf Steinkamp
Requirements and Layout
Silicon Sensors and Ladders
Read-Out Chip
Outlook
Physik Institut der Universität Zürich
Winterthurerstrasse 190 CH-8057 Zürich
olaf.steinkamp@physik.unizh.ch

LHCb Experiment
Dedicated experiment for B-physics at LHC
CP Violation and rare decays
production at LHC strongly forward peaked
¡
Special attention on:
forward spectrometer 250 mrad ¢ 300 mrad
£ vertexing: VELO ( ¤ talk by J.Libby )
£ particle identification: RICH detectors ( ¤ talk by C.Matteuzzi )
£
£
triggering: VELO, calorimeters, muon detector
tracking, momentum reconstruction: dipole spectrometer
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

LHCb Spectrometer
4 Tm dipole magnet ( bending plane horizontal )
Nine planar tracking stations
positions optimized for “upstream” tracking
Each station four detection layers
δp/p (per mille)
8
7
6
5
4
3
2
1
0
wire/strip orientation vertical, +5 ¡ , -5 ¡ , vertical
optimized for momentum resolution, pattern recognition
0 20 40 60 80 100 120 140 160 180 200
p (GeV)
– track reconstruction efficiency ¢ 95 %
for B decay tracks
– average momentum resolution £ 0.4 %,
dominated by mult.scatt. up to 100 GeV
¤
watch material budget!
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

( largest station 6 m
5 m )
Inner Tracker: cross-shaped layout
¡
¡
¡
¡
¡
four detector boxes
each box four detection layers
each layer seven silicon ladders
each ladder two 6” silicon sensors
¤
total surface 9 stations 14 m£
Tracking Stations
©
Track density strongly forward peaked
¡
¡
¡
¡
¡
up to 10¢
charged part./ cm£
near beam pipe
falling off with ¤
each station: two detector technologies
borderline determined by track density
“Outer Tracker”: straw drift chambers
¦¨§ ¥
“Inner Tracker”: silicon-strip detector
34.53 52.9 34.53
121.96
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp
21.8
59.76

Fraction of charge
1
0.8
0.6
0.4
0.2
0.7523E-02/ 11
P1 0.9481
P2 31.20
P3 61.79
0
0 25 50 75 100 125 150 175 200 225
Position
Amplitude, a. u.
1
0.8
0.6
0.4
0.2
0
Detector Simulation
GEANT description of active and dead material
Digitization within LHCb Gaudi framework:
0 20 40 60 80
Time, ns
signal generation
charge sharing ( from laser tests )
amplifier response ( from Beetle prototype )
gaussian noise
clustering
Cluster size
3
2.5
2
1.5
1
0.5
0
0 2 4 6 8 10 12
Station number
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0 2 4 6 8 10 12
eta function signal shape cluster size occupancies
Occupancy
Station number
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Radiation Dose and Particle Fluxes
Detailed Fluka description of detector
and cave
careful analysis of Inner Tracker region
to be done
From previous study:
integrated dose 20 Mrad
5 ¡
£¥¤
¢
¦
1-MeV equiv. neutrons / cm§
after 10 years of operation in hottest spot
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Cost read-out electronics:
“long” ladders, “large” pitch
Tracking performance, station layout:
22 cm long ladders
readout pitch about 250¡ m
Material budget:
“thin” sensors
LHC bunch crossing frequency:
Silicon Sensor Design
shaping time 25 ns to avoid pile-up
¢
small £
/¤
Radiation environment:
¥
5
§©¨
¦
to minimize capacitance
1-MeV equiv. n / cm
/ year
locally ( not our biggest worry )
110
108
78
76
135
150
Technology p
-on-n
Thickness 320 m
Sensitive 108 mm 76 mm
Number strips 320 (384)
Strip pitch 237.5 m (198 m)
Implant width 0.2
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp
0.3

Design aims:
Sensor
Support
simple, robust construction
modularity
material budget
cooling ( sensors at -5
¡
C )
Ladder Design
Pitch Adaptor
Front−End Chip
Layout:
Readout Hybrid
Balcony
U-shaped carbon-fibre support
ceramic pitch adaptor
kapton read-out hybrid
cooling “balcony”
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

2.5
Detector Box Design
78
one box for four detection layers
common “cooling plate” carrying
cooling pipe
thermal contact and positioning via
individual balconies
cold, dry nitrogen atmosphere
insulation box (not shown)
– light-weight foam for thermal
insulation
– thin aluminium foil for electrical
shielding
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

¡
four-layer Amoco K1100 shelf
dummy silicon sensors and hybrid
Kapton heat elements
Ladder Prototype
temperature probes / thermal camera
test mechanical and thermal properties
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Detector Box Prototype
¤
First prototype for thermal tests:
box from mold-injected polyurethane
foam
C¡ F¢ £
liquid cooling
aluminium cooling plate / balconies
mock-up ladders with kapton heat elements
validate cooling concept
Next: identify low-weight materials
balconies magnesium matrix composite
(magnesium-infiltrated carbon fibres)
cooling plate carbon-carbon material
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

leakage current [nA]
3000
2500
2000
1500
1000
500
0
1st Prototype Sensors from SPA-Detector, Kiev
0 20 40 60 80 100 120 0
bias voltage [V]
p¡
-on-n, 300 m thick ¢
64 strips, 6.66 cm long, 240 m pitch ¢
implant width 48, 60, 72 m ¢
fast turnaround, attractive price!
sensors work fine, except junction
breakdown at too low bias voltages
signal right strip [mV]
200
150
100
50
£
IR laser test
80 V
¤¥
§ ¦
0 50 100 150 200
signal left strip [mV]
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp
¨

N
6000
4000
2000
£
1st Test Beam with SPA Prototype Sensors
resolution:
m
¢
¥ ¤
¦
Constant 4870.
Mean -0.2990E-02
Sigma 0.1959
0
-2 -1 0 1 2
Δ [strips]
Cluster Charge [ADC]
9 GeV pions ( CERN-T7 test beam )
one-sensor and three-sensor ladders
¡
6.7 cm and 20 cm long
unirradiated sensors at room temp.
Helix read-out chip (HERA-B)
¡
30
20
10
¢
fastest shaping time 50 ns
short ladder
long ladder
0
0 100 200
trigger delay [ns]
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

As function of
efficiency
1
0.95
0.9
0.85
Detection Efficiency 20 cm-long Ladder
sensor 2 w/p=0.2
¡¢
( for £
0 0.2 0.4 0.6 0.8 1
track position
As function of £
efficiency
1.02
1
0.98
0.96
¡¢
80 V w/p=0.2
¨
0.2
0.94
0 0.2 0.4 0.6 0.8 1
track position
£
¤¥
§ ¦
¨
¤¥
§ ¦
( for
efficiency
1.02
0.98
0.96
80 V £
1
¡¢
¤¥
§ ¦
efficiency
¨
1
0.95
0.9
0.85
¨
90 V w/p=0.2
90 V ):
sensor 2 w/p=0.25
0 0.2 0.4 0.6 0.8 1
track position
0.2 ):
0.94
0 0.2 0.4 0.6 0.8 1
track position
¤¥
§ ¦
¨
¡¢
¨
efficiency
90 V £
0.25
1.02
1
0.98
0.96
100 V w/p=0.2
efficiency
1
0.95
0.9
0.85
0.94
0 0.2 0.4 0.6 0.8 1
track position
¤¥
§ ¦
¨
sensor 2 w/p=0.3
0 0.2 0.4 0.6 0.8 1
track position
efficiency
100 V £
¡¢
1.02
1
0.98
0.96
¨
0.3
110 V w/p=0.2
0.94
0 0.2 0.4 0.6 0.8 1
track position
¤¥
§ ¦
¨
110 V
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

S/N
60
40
20
Charge Collection Efficiency
0
30 31 32 33 34 35
strip number
S/N
60
40
20
0
30 31 32 33 34 35
strip number
one-strip clusters two-strip clusters
Reduced charge collection efficiency in between strips
¢¤£
effect decreases ¡
with increasing
effect decreases with increasing overbiassing
Interpretation:
Cure:
low-field region in between strips
charges get trapped or arrive too late ( fast shaping time! )
( simulation in preparation )
optimized strip geometry
higher overbiassing
¥
new sensors with better HV performance !
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

110mm
108mm
Region
Strips
Pitch
Width
Prototype Sensors from Hamamatsu
38mm
78mm
76mm
A B C D E
1−64 65−128 129−192 193−272 273−352
197.9 197.9 197.9 237.5 237.5
50 60 70 70 85
Full-size multi-geometry sensors:
p¡
-on-n, 320 ¢ m thick
198 ¢ m and 237.5 ¢ m pitch
£¤
¥
¦
§
¨©
Sensors received last Friday:
¦
testbeam at CERN end May
£¤
select strip geometry for LHCb
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Beetle Readout Chip
128-channel pipelined r/o chip, custom design at ASIC lab Heidelberg
basic RD20 front-end architecture
0.25 m CMOS ¡
analog and binary pipeline
prompt binary readout
programmable via I
¢
C interface
LHCb front-end requirements
40 MHz sampling rate
1 MHz read-out rate
160 cell analog pipeline
16 event internal buffer
900 ns max. read-out time
Beetle 1.1 submitted March 2001
Test
Input
Analog
In
6.1 mm
Itp
Testpulse
Generator
Vfp
Ipre
preamplifier
128 Analogue Input Pads
FETestOut PipeampTestOut
Vfs
Isha Ibuf
shaper
Vfp
Vfs
Ipre
Isha
Ibuf
Icomp
Ithmain
Ithdelta
Itp
Frontend
Bias−Generator
Frontend Amplifiers
Comparators
buffer
Testchannel
Pipeline
Control
comparator
Polarity
Icomp
Ithmain
Ithdelta
5.5 mm
D Q
CompClk
1 of 160+16+10 cells
Write
Read
I2C Interface
Pipeline
Pipeline/
Readout
Control
pipeline
Vd
Or Mux LVDS @ 80 MHz
Vdcl
Ivoltbuf
Vd
Dummy channel
1 of 128 channels
pipeline
readout−amplifier
Vdcl
Reset
Reset
Ipipe Ivoltbuf
1 of 16 channels
CompOut
notCompOut
Ipipe
Icurrbuf
Isf
Backend
Bias−Generator
multiplexer
4 x (32 to 1)
Isf
current
buffer
Icurrbuf
Out[3:0]
notOut[3:0]
8 Comparator Outputs
Pipeline Readout
Amplifiers
Multiplexers
Backend Bias Block
8 Comparator Outputs
Frontend Bias Block
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Beetle 1.1 Total Ionizing Dose Irradiation
Four chips irradiated at CERN X-ray facility
[V]
full functionality up to 45 Mrad
trigger / readout and slow control
performance degradation small
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
−0.02
0 Mrad
15 Mrad
30 Mrad
45 Mrad
−0.04
0 25 50 75 100
time [ns]
125 150 175 200
Pulse shape at C¡
£ ¤ ¢
¥
[%]
80
70
60
50
40
30
Cp = 3 pF
Cp = 7 pF
Cp = 10 pF
Cp = 13 pF
Cp = 25 pF
Cp = 36 pF
0 5 10 15 20 25 30 35 40 45
dose [Mrad]
¦pF Amplitude remainder after 25 ns
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

45
40
35
30
25
20
15
10
5
0
1st Test Beam with Beetle 1.1 Read-Out Chip
resolution:
¢¤£
¥¦
§ m
-0.04 -0.02 0 0.02 0.04
Residual [cm]
¡
120 GeV muons ( CERN-X7 test beam )
SPA prototype sensor ladders
6.7 cm and 20 cm long
successful, reliable operation of chips
14
12
10
8
6
4
2
( S / N limited by DAQ setup )
0
150 151 152 153 154 155 156 157 158 159
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Beetle 1.2, submission April 2002:
few bug fixes
SEU redundant logic
fully differential output driver
improved front-ends
Beetle — Next Steps
Measured on test chips (Beetle-FE 1.1):
remainder after 25 ns
ENC
§
¡
30% for ¢
¨©
S/N §
£
¥ ¦ ¤
up to 30 pF
¢
£
¥ ¦ ¤
/ pF
for 22 cm long ladder
gain (1 MIP = 23.200e) [mV]
ENC [e]
60
50
40
30
20
10
0
3000
2500
2000
1500
1000
BeetleFE 1.1 - Set 2c
(Vfp=0V, Vfs=0V, Ipre=600uA, Isha=80uA, Ibuf=80uA)
cp = 0pF
cp = 3pF
cp = 10pF
cp = 20pF
cp = 30pF
cp = 40pF
0 50 100
time [ns]
500
ENC BeetleFE 1.1 - Set 2c
(Vfp=0V, Vfs=0V, Ipre=600uA, Isha=80uA, Ibuf=80uA)
0
0 10 20
cp [pF]
30 40
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Read-Out Hybrid
Four-layer kapton hybrid for three Beetle chips
1. digital/analog power 3. traces
2. digital/analog ground 4. components
Two-layer “tails” for control signals and read-out of analog signals
Separate pitch adaptor ( thin-film ceramic? )
prototypes in production
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

Read-Out Link
Readout rate (L0-trigger accept rate): 1.1 MHz
Beetle output: 4¡
40 MHz analog
8-bit digitization:
1.28 Gbit/s per Beetle, 3.84 Gbit/s per ladder, 134 Gbit/s per Box
Design criteria read-out link:
radiation hardness components, material budget, cost
BEETLE
40 MHz
analog
FADC
FADC
FADC
FADC
8
8
8
8
CERN GOL
1 of 12
12x VCSEL
fibre transmitter
5−10 m
Silicon ladder Service box on Outer Tracker frames
19,2 Gbit/s
digital
100 m
to counting room
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp

¡
“LHCb-Light”
Common effort for overall re-optimization of LHCb detector
Two major changes to tracking system under investigation:
a) reduce number of tracking stations
improved performance
due to lower material budget
baseline scenario: four stations
very promising results
¡
8.84
23.17 52.9 23..17
143.5
144.84
b) use station in Level-1 trigger
1¢
£
improved performance
from momentum information
may need all silicon (6.8 m
careful study still needed
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp
10.8
¤
21.8
52.14
)
117.04

Main requirements:
22 cm long ladders,
Summary and Outlook
large pitch ( 80 ¡ m resolution sufficient )
fast shaping for 25 s bunch crossing rate
material budget!!!
Main D: R¢
sensors: 6” p
readout chip: Beetle
£
-on-n , 320 ¡ m thick, 198 ¡ m or 237.5 ¡ m pitch
ladder supports, detector boxes: modular design, low-weight materials
digital optical read-out link
Upcoming:
May/June — testbeam with full-size prototype sensors
¤
validation of sensor design, choice of strip geometry
October — submission Technical Design Report
March 02, 2002 The Silicon Inner Tracker for LHCb Olaf Steinkamp