Tracking system technology challenges and possible evolution Lucie Linssen, CERN Using slides from:...

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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 !


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)


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


tracking + impact parameter resolution

Momentum resolution

=> to get pT resolution similar to LHC => try to gain a factor 7 in σ/(BR2)


dominated bysingle-point resolution

multiple-scattering term => low material!

=> impact of #material on accuracy is most important in the vertex region


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)


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 (??)


dominated bysingle-point resolution

multiple-scattering term => low material!

CLIC goal a = 5 μm b = 15 μm

goal


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


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 ??


• Hybrid detector technology


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


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


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.

!


effect of sensor thickness on charge sharing

55 μm pixel size


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


• Monolithic detectors


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


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


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)


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


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


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


• 3D integrated detectors


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


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


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


SPARESLIDES


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


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 !


CLIC pixel detector and flavour tagging


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 !


SOI

Tracking system technology challenges and possible evolution Lucie Linssen, CERN Using slides from:...

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