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The LHCb VELO Upgrade. Jianchun Wang Syracuse University For the LHCb VELO Group VERTEX 2009 Workshop,Veluwe, Netherlands, Sept 13-18, 2009. The LHCb Environment. b. doesn’t occur. b. b. b. b. b. A dedicated b-physics experiment. - PowerPoint PPT Presentation
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The LHCb VELO Upgrade
Jianchun Wang
Syracuse University
For the LHCb VELO Group
VERTEX 2009 Workshop,Veluwe, Netherlands, Sept 13-18, 2009
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 2
The LHCb Environment
Choose to run at <L>~21032 cm–2s–1 (2 fb–1/year), ~1012 bb pairs produced per year.
Maximize probability of single interaction per crossing.
Clean environment (average interactions per crossing <n>~ 0.5 ), easier to reconstruct.
Less radiation damage ( the closest tip ~7 mm away from beam).
Designed to maximize B-acceptance within cost and space constraints.
Forward spectrometer ( 1.9 < || < 4.9 ), where b are maximally boosted, benefits proper time measurement.
One arm is OK since bb directions are correlated. Production bb~500 b, Min. bias: inel ~ 80 mb.
A dedicated b-physics experiment
b
b
b
b
doesn’t occur b
b
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 3
VErtex LOcator
The LHCb Detector
VErtex LOcator• primary vertex• impact parameter• displaced vertex
Tracking StationsTrigger Tracker
(IP) ~ 14 m + 35 m / Pt
Primary vertex ~10 m in X/Y, ~50 m in Z.
B proper time resolution ~ 40 fs.
Ready
to g
o !
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 4
Limitation of Current Trigger System To improve the physics sensitivity LHCb plan to
increase the luminosity by a factor of 10.
Current trigger system has two stages: L0 hardware trigger, reduce to 1 MHz. HLT software trigger, reduce to 2 kHz.
L0 trigger limit is driven by 1 MHz maximum readout rate.
,
3.5
2.5
1
hadronT
eT
T
E GeV
E GeV
P GeV
With increased L, the L0 criteria has to be tighten to stay below 1 MHz. There is not much net gain, especially in hadron channel.
Increasing L to 1033 will not introduce too much complexity to event. Most events have 1 or 2 interactions. Increasing to 2x1033 the average number of interactions increases to ~ 4,
At L=2x1033, unacceptable increase in CPU time due to large combinatorics.
hadron trigger
muon trigger
Ra
te
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 5
LHCb Upgrade Strategy
Run at 2x1033 cm-2s-1 for 5 years (~100 fb-1). This plan is consistent with, but independent of the sLHC upgrade program.
LHCb will readout all sub-detectors at 40 MHz replace FE electronics of most detectors.
The trigger decision will be performed entirely on CPU farm. Removing L0 trigger, thus no limit on the data rate. Software trigger allows sophisticated triggering scheme with lower Pt cuts and
use of IP to maximize the signal yields. Preliminary studies show that at current L the hadronic channel efficiency
improves by ~2 (the goal), and the yield increases proportionally to L. Increases in statistics by ~20 for hadronic channels and ~10 for leptonic
channels. More complicated events significantly increase trigger processing time,
increasing granularity is mandatory.
Improve or maintain efficiency and resolution.
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 6
pile-up veto (R-sensors)
RF foil
interaction point
3cm separation
~ 1 m
Current Vertex Locator Silicon micro-strip, n+ in n-bulk sensors. Detector halves retractable (by 30mm) for
injection. 21 tracking stations per side. R-Φ geometry, 40–100μm pitch, 300m thickness. Optimized for
tracking of particles originating from beam-beam interactions.
fast online 2D (R-z) tracking. fast offline 3D tracking in two steps (R-z then ).
r = 8 mm( ~7 mm)
r = 42 mm
2048strips
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 7
Current VELO Detector for Upgrade?
Radius (cm)
Par
ticle
Hits
/ E
vent
/ c
m2
L(x1032cm-2s-1) 2 5 10 20
a
b
At L=2x1033 the occupancy will be high, especially at the inner region (particle/hit occupancy ~2%, strip occupancy ~4%). Higher granularity and lower noise are needed. Pixel architecture meets the need.
Analog readout of VELO data at 40MHz is unrealistic. Signals need to be digitized and sparsified at FE.
The data rates are enormous. Clustering reduces the data rates out of FE.
This triggered a dedicated R&D on radiation hard FPGAs.
Pixel architecture reduces pattern recognition difficulty.
Inn
er
Ra
diu
s
Start upgrade studies from the current VELO
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 8
Pixel Detector
Two main thrusts of R&D required for the upgrade are: Front-End Electronics Sensor
We had studied different types of sensors and readout schemes. We decide to focus on an upgrade solution based on pixel architecture.
Electronics
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 10
Front-end Electronics
Must provide digitized data to trigger processor in real time: digitization, data sparsification, and pushing data to storage buffer.
Withstand same radiation environment as sensor TID: ~400 MRad.
Modern fabrication technologies may allow larger radiation tolerance – 130 nm, 90 nm.
Issues to be investigated Analog electronics optimization: noise, peaking time, stability of
performance with irradiation, leakage current compensation Digitization: speed, effective number of bits. Zero suppression: effective threshold, time walk, discriminator stability Digital section: data rate capability, stability of performance with
irradiation.
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 11
Timepix Readout Chip
Pixel readout chip based on Medipix2
256 x 256 pixels 55 m square, and chip is 3 side buttable. Single Layer Modules Possible!! (X0)
By using TSV (through silicon vias) dead side can be reduced to 0.8 mm in Medipix3 (out of 1.5 mm)
Analogue power consumption 6 W per pixel. TOT provides better than 6 bit equivalent ADC resolution
Upgrade being considered to 90 nm technology (power consumption, density of logic and radiation hardness benefits)
Specifications for Timepix adaptation to VELO upgrade needs are under study.
14100
14
10
0
800Medipix3Chip dimensions
See Richard Plackett’s presentation for more details
Q
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 12
Conceptual Design
Silicon (1-3 pieces)55x55 m pixels+ 800 m pixels inareas under chip periphery
10 Tiimepix chips(periphery indicated in white)
Ground plane(aluminised directly onto diamond)
Diamond thermal plane withcutouts immediately above TSV regions
Power strips andsignal routing area
Cooling channel
Cross section cutout region
Advantage: Single layer, less material, very important for IP.
Challenges: power tape + TSV, Thinned electronics / sensor.
Beam position
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 13
Timepix In Real Beam
A telescope was constructed with 6 double rotated (9o) around both axes. 4 Timepix and 2 Medipix sensors were used.
The DUT (in this case another Timepix chip) position and angle are controlled by a stepper motor to reduce the number of interventions
6 plane Timepix/Medipix telescope
DUT
Track reconstructed
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 14
Quick Look at TimePix Testbeam Data
More to Be Studied Time walk, which could potentially affect physics. Non-linear gain curve. Investigate methods of moving data off chip at
required speeds (started, digital processing within pixel array may be necessary).
Testbench features of baseline module.
N=1
N=2
N=3 N=4
Angle (Degree)
(Npi
xel=
N)
/ All
Angle (Degree)
Unb
iase
d R
esid
ual (
m)
Normal Incidence
All
N=1 N=2
N=3 N=4
Indiv.pixel
Total Charge
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 15
Medipix3 X-ray Irradiation
Total ionizing dose measurement on a single chip up to 400Mrad (X-ray, continuously over 4 days)
Confirmation of previous single transistor studies on 130nm CMOS
Chip readout DACs, LVDS etc remained operational for full dose.
This needs to be followed up by hadron irradiation.
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 16
Current VELO
Pixel X/Y
Pixel X/Y
Pixel Y
~ 1 m
5 stations6 modules per station4 chips per moduleTotal 120 FPIX2 chipsAperture 35 x 35 mm2
Number of Rows
Num
ber
of H
its (
arb
Uni
t)
Residual (mm)
=11.3 m75.8%
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 17
Electronics Development
FPIX2
Features (selected): Derived from BTeV Columnar architecture (50m x 400 m) Flash ADC (3-bit) Data driven readout. Sensor and electronics successfully
thinned down to 200 m. Separate X/Y precision measurements.
Large digital periphery requires overlap material.
Need to Study (selected): Modern fabrication technology Radiation hardness study. Stability of front end electronics Readout speed, with designed for 132ns. Cooling.
Focus resources on a single chip development (still useful for sensor R&D).
TIMEPIX
Features (selected): Derived from MediPix Square pixel (55m x 55m) Time over threshold Single layer module possible, edgeless
possible
Need to Study (selected): Modern technology: 130nm or 90nm. Radiation hardness study. Optimization of analog front end Time walk Digitization precision and readout scheme Data flow and data rate TSV technology Detector and sensor thinning Cooling
Development continues.
Two main avenues of investigation in LHCb Upgrade
Sensors
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 19
Sensor
Sensor requirements Radiation hardness Low leakage current, heat dissipation High granularity Minimize material
Sensors investigated: Sensors of current type: n-type, strips Sensors with small modifications: p-type Sensors with large modifications: pixels Sensors using new technology: 3D Alternative material: diamond
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 20
Test of Irradiated Sensors
N type sensor
Preliminary VELO sensors of n-type and p-type
were differentially irradiated.
They were tested in the beam at Fermilab using FPIX2 pixel system for tracking (in collaboration with Dave Christian).
Irradiation particle flux ~ 0.86x1015 neq/cm2 (~6 years running of current L at inner radius).
More results on irradiated sensors are coming soon.
N-type
~ 25% drop
Measured in 120 GeV proton beam @ -10C
Preliminary
1 MIP Qmp
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 21
Double-sided 3D Sensor
Passivation
p+ doped
55m pitch
50m
300m
n+ doped
10m
Oxide
n+ doped
Metal
Poly 3m
Oxide
Metal
50m
TEOS oxide 2m
UBM/bump
n-type Si
Passivation
p+ doped
55m pitch
50m
300m
n+ doped
10m
Oxide
n+ doped
Metal
Poly 3m
Oxide
Metal
50m
TEOS oxide 2m
UBM/bump
n-type Si
Optimisation for SLHC: Nucl. Instr. Meth. A 592 (2008) 16 Glasgow / CNMTest beam results: Nucl. Instr. Meth. A 607 (2009) 89
• novel double sided structure• n-bulk and p-bulk detectors produced & tested
SEM after polysilicon deposition and etching
Pixel on Medipix detector
m
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 22
Double-sided 3D Sensor
Glasgow / CNM
P+
N+
1/Capacitance, Pad detector
0.0E+00
5.0E+08
1.0E+09
1.5E+09
2.0E+09
2.5E+09
3.0E+09
3.5E+09
4.0E+09
4.5E+09
5.0E+09
0.0 5.0 10.0 15.0 20.0
Bias (V)
1/C
(F
-1)
2.3V lateral depletion
~9V back surface depletion
Tesbeams at Diamond Light Source (X-rays), CERN (MIPs)
3D Planar
0 2 4 6 8 10 12 14 16 18 200
5
10
15x 10
6 3D - Signal spectrum vs Energy - 15keV
Energy (keV)
Ra
te o
f ch
an
ge
in c
ou
nts
3D, 15keV
Charge sharing
Noise Signal
Measurements of:• Charge loss in holes• Charge sharing• IrradiationsTwo presentations at IEEE NSS with full results
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 23
Sensor R&D
Diamond sensor Ultra radiation hard, Very low leakage current (~nA instead of A) Needs no guard ring and can be edgeless. CVD diamond can also be used as heat conductive
spine. Joined RD42 collaboration for investigate this option. Planning test beam studies of different solutions.
2551-6FZ ; 312 micron thick ; n on p
Bulk currents for 3 sensors
0.E+00
1.E-08
2.E-08
3.E-08
4.E-08
5.E-08
6.E-08
7.E-08
8.E-08
9.E-08
0 200 400 600 800 1000 1200
Voltage (V)
Cu
rre
nt
(A)
S1
S2
L P-type silicon sensor “BTeV style” single chip pixel devices.
Fabricated by Micron Semiconductor. Depletion voltage 20-80V before
irradition. Started examining performance of
irradiated detectors
Syracuse/RD50
Syracuse/RD42
Other Issues
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 25
POSSIBLE NEW RF FOIL for UPGRADE MAIN REQUIREMENTS
Separates accelerator and detector vacua (must be ultra-high vacuum compatible)
Should have the smallest radiation length possible, esp. before first measured point
Must shield against RF EMI pick-up effects Must carry beam image charge Must allow for sensor geometry and overlap Must withstand high radiation levels
CURRENT DESIGN Foil is 300 um AlMg3, coated with insulator and
getter Foil shape set by overlapping sensors, beam
clearance and beam effects Wakefield suppressors to adapt beam pipe
geometry Was a huge engineering effort (NIKHEF)
UPGRADE DESIGN Replace AlMg3 by Carbon Fiber composite
Use large-modulus fibers (stiff, low density) Resin with high rad tolerance, low outgassing
(space-qualified), micro-crack resistant Produce foil + box + flange as a single
integrated unit Avoids sealing problems
Can reduce mass thickness to ~50% current Similar material mechanically stable to above
500 MRad (CERN 98-01) Currently in development with industrial partner
CMA (Composite Mirror Applications, Inc.) Prototyping planned to start by End 2009,
testing to start in early 2010
CURRENTDESIGN
FOIL~200 mm x 1 m
Dominant contribution to the average X0 of particle traversing VELO at 2<<4.2
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 26
Conclusion
The LHCb detector is ready to take data. Initial plan is to collect 10 fb-1 in the first 5 years.
LHCb upgrade forseen for 2015/16, with luminosity increases to 2x1033 cm-2s-1, expected to collect 100 fb -1 in 5 years.
Key aspects of the upgrade are: Readout of the full detector at 40 MHz fully software-based trigger
flexibility. Improved granularity in sub-detectors needed to cope with larger
occupancies, provide better background suppressing and reduce CPU time/event.
Goal is to increase sample sizes by a factor of 10-20 with comparable or better S/B to current detector.
Many R&D projects associated with VELO upgrade are in progress: readout electronics, sensor, hybrid, mechanics, cooling cabling etc.
The VELO upgrade is feasible.
Backup Slides
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 28
Backup Mini Strip Plan
200 m Diamond heat planerouting out Beetle signals
20 Beetle40 chips
Inner radius at 7.5mm, 25-30 m pitch(edgeless sensors would bring 10% improvement)
200 m thin silicon sensor
Radiation length 0.6%.
Double sided module
Cooling channel
p-stop or p-spray.
Need to study more on data readout scheme.
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 29
Trigger Time in HLT Di-hadron
33 32
33 32
10 2 10
2 10 2 10
2.2
42x
x
t t
t t
L = 2 x 1032 cm-2s-1
L = 2 x 1033 cm-2s-1
L = 1 x 1033 cm-2s-1
At L=2 x 1032 cm-2s-1, the events are more complex. With current VELO-like detector, the pattern
recognition is very slow. And trigger can not be decided within 2.5 m latency.
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 30
Irradiation Issue
Operating up to ~120 fb-1
Flux: 0.8x1014 neqcm-2 per fb-1
TID (Electronics): 3.7 MRad per fb-1at tip~ 7mm
500
50
5
Radius (cm)
Dose after 100 fb-1
n eqc
m-2
x 1
016
TID
(M
Rad
)
•After this dose @ 900V we expect• 102 uA / cm-2 at -25o C • CCE of ~ 8.5 ke-
Thermal runaway at the tip is the issue
tip of current VELO
T. AffolderTIPP 09
Sept 13-18, 2009 Jianchun Wang, Vertex 2009 31
FPIX2 Readout Chip
FPIX2 Chip
22x400m
128x
50
m
10.3
mm
9.0 mm
I/O & Control pads from Chip to HDI
6.4
mm
0.7 mm