Post on 04-Jan-2016
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Tracking system technology challengesand possible evolution
Lucie Linssen, CERN
Using slides from: Tony Affolder, Saverio D’Auria, Dominik Dannheim, Erik van der Kraaij, Sandro Marchioro, Luciano Musa, Ivan Peric, Petra Riedler, Walter Snoeys, etc.
FCC workshop, March 25th 2015
Lucie Linssen, March 25th 2015 2
outline
• Tracking requirements for FCC-hh• Parameters defining in tracking performance• Comparison of LHC / HL-LHC / CLIC / FCC-hh requirements • Overview of solid-state tracker technologies• Technology examples• Summary
DISCLAIMERThis presentation is subjective and incomplete
Not paying justice to the broad field of ongoing tracker R&D
MAIN TAKE-HOME MESSAGEBe optimistic about what can be achieved in 2 decades of R&D !
Lucie Linssen, March 25th 2015 3
FCC-hh tracking environmentSome basic assumptions:• pp centre-of-mass energy: 100 TeV
• Luminosity: 5×1034 in the 1st phase
30×1034 in a 2nd phase
• Pile-up: [170, then 1020] events at 25 ns spacing
[34, then 204] events at 5 ns spacing
• Average/maximum occupancy: ~50% higher than at 14 TeV
• Integrated luminosity 3 ab-1 for the 1st phase
30 ab-1 for a 2nd phase
• Expected radiation level 3x1016 cm-2 1MeVneq fluence (1st phase)10MGy Dose (1st phase)
• η coverage up to η= 4 (~2 degrees) or η= 6 (~0.3 degrees)
Lucie Linssen, March 25th 2015 4
FCC-hh tracking performance requirements
Time resolution
• a few ns hit timing accuracy assumed
Momentum resolution
• Assume σ(pT)/pT of ~10% needed for isolated objects of very high energy• What resolution will be needed for lower pT, e.g. particle in jets ???
Impact parameter resolution
• Aim for significantly better than current LHC performances ???σ(rϕ) << 70 μm at 1 GeV σ(rϕ) << 10 μm at 1 TeV
Lucie Linssen, March 25th 2015 5
tracking + impact parameter resolution
Momentum resolution
=> to get pT resolution similar to LHC => try to gain a factor 7 in σ/(BR2)
Impact parameter resolution
dominated bysingle-point resolution
multiple-scattering term => low material!
=> impact of #material on accuracy is most important in the vertex region
Lucie Linssen, March 25th 2015 6
momentum resolution at high pT
Momentum resolution (assuming CMS-like solenoid geometry)
to get pT resolution similar to LHC => try to gain a factor 7 in σ/(BR2)
Increase B-field ?: =>=> very challenging/risky/expensive to go above 4T (CMS)
Increase single-point resolution ?:Current CMS/ATLAS =>=> ~20-25 μmRoom for improvement =>=> factor ≥4 (10??) in central region
=>=> Resulting increase in tracker radius would be: < √7/4 ≈ <30%
What is the pT resolution needed at large η ?• Worth studying to stretch coil and tracker in z to increase coverage• Penalty on #material (e.g. longer/stronger supports and longer cables)
Lucie Linssen, March 25th 2015 7
resolution in vertex detector ?
CLIC aims for: ~25 times smaller pixel size than current CMS/ATLAS~10 times less material/layer than current CMS/ATLAS
Given the long time-scale, one can assume a CLIC-like accuracy goal for FCC-hh (??)
Impact parameter resolution
dominated bysingle-point resolution
multiple-scattering term => low material!
CLIC goal a = 5 μm b = 15 μm
goal
Lucie Linssen, March 25th 2015 8
comparison of requirements
CLIC ALICE upgrade HL-LHC FCC-hh Radiation hardness
Position resolution
Timing accuracy
Low massHL-LHC ALICE upgrade FCC-hh CLIC
ALICE upgrade HL-LHC CLIC FCC-hh
HL-LHC ALICE upgrade FCC-hh CLIC
weaker very strong
The 4 listed projects have many individual requirements in common, though their combination is different
Lucie Linssen, March 25th 2015 9
Si technology types
Hybrid Monolithic 3D-integrated
Examples ATLAS, CMS, LHCb-Velo, Timepix3/CLICpix
HV-CMOS, MAPS SOI, wafer-wafer bonded devices
Technology Industry standard for readout; special high-Ω sensors
R/O and sensors integrated, close to industry standards
Currently still customised niche industry processes
Interconnect Bump-bonding required
Connectivity facilitated
Connectivity is part of the process
Granularity Max ~25 μm Down to few-micron pixel sizes
Down to few-micron pixel sizes
Timing Fast Coarse, but currently improving with thin high-Ω epi-layers
Fast
Radiation hardness
“Feasible” To be proven ??
Lucie Linssen, March 25th 2015 10
• Hybrid detector technology
Lucie Linssen, March 25th 2015 11
ATLAS/CMS tracker upgrades
z [m]
Significant progress in:• Integration, production, radiation hardness• Powering and services• Less material (gain >2)• Smaller cell sizes
Due to lack of time, and given well-informed audience, CMS/ATLAS work not further addressed in this talk
Lucie Linssen, March 25th 2015 12
CLIC vertex/tracker requirements
1 m
(calorimeter)pixel
detector
tracker
CLIC vertex detector requirements• 3 μm single point accuracy• 25*25 μm2 pixels • Pulse height measurement
• Time measurement to 10 ns• Ultra-light => 0.2%X0 per layer
• Power pulsing, air cooling• Aim: 50 mW/cm2
• Radiation level ~104 lower than LHC
ongoing R&D covering several disciplines
CLIC tracker requirements• Radius 1.5 m, half-length 2.3 m• 7 μm single point accuracy• Large pixels/short strips
• Time measurement to 10 ns• Ultra-light => 1%X0 per layer• Radiation level ~104 lower than LHC
R&D just starting
FCC-hh accuracy requirementsmay be quite similarWith in addition:• Radiation hardness• Buffering/Triggering ?• Large data rates
Lucie Linssen, March 25th 2015 13
CLIC vertex detector => hybrid baselineCLICpix demonstrator ASIC64×64 pixels, fully functional• 65 nm technology• 25×25 μm2 pixels• 4-bit ToA and ToT info• Data compression• Pulsed power: 50 mW/cm2
Hybrid baseline option:• Thin ~50 μm silicon sensors• Thinned high-density readout ASIC, ~50 μm
• R&D within Medipix/Timepix effort• Low-mass interconnect (TSV)
Very thin sensorsTested with Timepix ASICs (55 μm pitch)
1.6 mm
64×64 pixels
RD53collab.
!
Lucie Linssen, March 25th 2015 14
effect of sensor thickness on charge sharing
55 μm pixel size
Lucie Linssen, March 25th 2015 15
position resolution and charge sharing
Charge-sharing is important to achievePosition accuracy• Holds both for analog and digital
readout• Conflict of low mass charge sharing
( Charge-sharing can be enhanced with signal collection through diffusion, but this is in conflict with timing requirements and radiation requirements. )
50 μm thin sensor55 μm pixel pitch
2-hit clusters
1-hit clusters
Beam test with accurate reference telescope
Ultimately, a strong limit to the hybrid solution is the bump-bonding pitch (and cost!).=> Currently prevents pushing to ever smaller pixel sizes
Lucie Linssen, March 25th 2015 16
• Monolithic detectors
Lucie Linssen, March 25th 2015 17
integrated MAPS technology
MAPS:• Integrated electronics functionalities• Allows for small pixel sizes• No need for expensive bump-bondingHV-CMOS:• Possible in advanced 180 nm (350 nm)
High Voltage process• Vbias ~100 V, 10-20 μm depletion layer• Fast signal collection from depleted layer
Radiation hardness improves when fully depleted, needs further R&D
Lucie Linssen, March 25th 2015 18
MAPS, early application (1994)
34μm
125 μm
2 μm technology300 μm thick, high resistivityP-type
σ = 2 μm
Excellent S/N of 150 for MIPCharge sharing with analog readout
C. Kenney et al. NIM A 342 (1994) 59-77
Lucie Linssen, March 25th 2015 19
ALICE inner tracker upgrade
3 cm
1.5
cm
Soldering pads
~ 500 000 pixels of 28 x 28 μm2
180 nm Tower Jazz processMAPS-type
3 inner barrel layer (IB)4 outer barrel layers (OB)
Radial coverage 21-400 mm
12.5 Giga-pixel tracker
10 m2
4.5 cm2
Large single cell of 4.5 cm2
Few contacts, laser bonded to flex
For installation in ALICE in LS2 (2019)
Lucie Linssen, March 25th 2015 20
ALICE inner tracker upgrade
• All-pixel design, pixel pitch 28 μm• Single-point resolution 5 μm
• Sensors not fully depleted, not a fast signal• ~2 μs hit time resolution
Radiation level: 700 krad / 1013 MeV neq(includes safety factor 10)
Low-mass design:
0.3%X0 in inner layers0.8%X0 in outer layers
Power density <100 mW/cm2
Lucie Linssen, March 25th 2015 21
hybrid of HV-CMOS with readout ASIC
Hybrid option:Capacitive Coupled Pixel Detector (CCPD)• HV-CMOS chip as integrated sensor+
amplifier• Capacitive coupling to complex readout ASIC
through layer of glue => no bump bonding
Lucie Linssen, March 25th 2015 22
hybrid vertex detector with HV-CMOS
Hybrid option with HV-CMOS:Capacitive Coupled Pixel Detector (CCPD)• HV-CMOS chip as integrated sensor + amplifier• Capacitive coupling to CLICpix (or FEI4) ASIC
through layer of glue => no bump bonding
CCPDV3
R&D pursued by e.g. ATLAS and CLICsuccessful initial beam tests in 2014Further beam tests in 2015
HV-CMOS + CLICpix, AC coupled
Lucie Linssen, March 25th 2015 23
• 3D integrated detectors
Lucie Linssen, March 25th 2015 24
3D detectors, wafer-to-wafer bonding
SOI3D-integrated, 3 tiers
3D technologies, wafer-to-wafer bonded ASIC + sensorMain advantages:
Combining optimal sensor material (high-Ω) with high performance ASICAvoid bump-bondingProfit from industrial CMOS trends towards very small feature sizes
Drawbacks:Currently either still niche application (e.g. SOI) or fast-changing industrial
R&D (e.g. R&D for cameras with very small pixels)
Generally too high cost for particle physics R&D budgetsWe have to stay open to grab future opportunities in such domains
Lucie Linssen, March 25th 2015 25
engineering….
Talk is too short to cover important (engineering) issues:• Interconnect technologies• Powering• Services• Cooling• Light-weight supports• New materials• Detector stability and alignment
These engineering items are crucial parts of the R&DRequiring fully integrated apparoach
Lucie Linssen, March 25th 2015 26
conclusionsMostly copied/adapted from Saverio d’Aurio, Feb 2015
• Detectors for FCC-hh inner tracking are considered feasible• ~ns time resolution, ~micron-level space resolution and radiation
tolerance to ~30x1016 appear as natural evolution of present technologies.• Minimal FCC-hh target specifications are almost already achieved in
dedicated detectors.• However, no single technology reaches all design specs at the same time. • The main issue: coverage at small radius with radiation hardness, fine
granularity.• Several sensor technologies are promising => consider them all• Microstrips will most likely be replaced by pixels everywhere.• Big technology step: integrated electronics => to be pursued closely• Important to develop all integrated design details among physicists,
microelectronics experts, mechanical engineers and material scientists
Room for several future projects to join forces
Lucie Linssen, March 25th 2015 27
SPARESLIDES
Lucie Linssen, March 25th 2015 28
comparison main tracker LHC vs. CLIC
Momentum resolution for high pT
(η=2)
CLIC tracker requirements7 μm single point accuracytime-stamping 10 ns
~5-6 tracking layersRadius ~1.5 m, half-length ~2.3 m
High occupancies in certain regions:• Requires large pixels and/or short-strips
Very light => ~1%X0 per layer
Lucie Linssen, March 25th 2015 29
CLIC vertex detector optimisation
Spiral disksSingle layers
Spiral disksdouble layers
Using flavour tagging as a gauge1. Test single vs. double layers2. More realistic material (0.2% X0/layer)3. Vary inner radius (for 4 T or 5 T B-field)
double layer better
single layer better
larger inner radius better
Inner radius 27 mm / 31 mm0.1% X0/layer / 0.2%X0/layerSingle layers / double layers
more material better
1. 2. 3.
Work in progress !
Lucie Linssen, March 25th 2015 30
CLIC pixel detector and flavour tagging
Lucie Linssen, March 25th 2015 31
CLIC main tracker and B-field choice1
x
BR2
Large tracker size has advantage• R =1.5 m• Half-length = 2.3 m (stretched wrt CDR)B-field gives +10% improvement for +0.5 TCompromise: 4 T (inner bore radius ~3.2 m)
Jet performance was checked for those values
θ=90o θ=20o
Work in progress !
Lucie Linssen, March 25th 2015 32
SOI