1. Tracking Detector Mechanics
CEPC Meeting
Beijing, November 2019
Tracking Detector Mechanics
Tim Jones
Liverpool PP Group

2. CEPC Workshop - Beijing - November 2019
Overview
Mechanics Development for ATLAS
Lessons from current ATLAS SCT
ATLAS ITk “Local Supports”
Multi-functional structures
Liverpool HV-CMOS Demonstrator Programme
Mu3e
LHCb Mighty Tracker
Tracker Mechanical concepts for Future GPDs
Size matters
Services
Materials
Development themes
23/01/2020
CEPC Workshop - Beijing - November 2019

3. CEPC Workshop - Beijing - November 2019
ATLAS ITK Upgrade
Barrel Strips (4 barrels)
Endcap Strips (6 disks)
Outer pixel Endcap (11, 9, 10 rings)
Outer pixel Barrel ( barrels)
Inner pixels
23/01/2020
CEPC Workshop - Beijing - November 2019

4. ATLAS ITk – Local Supports
Current ATLAS strips
Individual back-to-back modules individually fastened to large structures with discrete services
Future ITk Strips
Single-sided modules glued to ~30 module structures with integrated services
6cm
23/01/2020
CEPC Workshop - Beijing - November 2019

5. ATLAS ITK Local Supports
Mechanical Support Structure
Positioning requirements from physics (placement & stability)
Assembly, transport & integration
Integrated Electrical Services
Serial / DCDC powering
Data I/O (strips only – data-rate too high for pixels)
Integrated Cooling
Evaporative CO2 (Tevap ~ -35°C) in Titanium tube
Materials
Low CTE/CME, high radiation tolerance, long radiation length
23/01/2020
CEPC Workshop - Beijing - November 2019

6. Mechanical LS Requirements
Geometric Stability
ASD < 10-9 g2/Hz in ATLAS
Translates into sub-µm RMS motions for f0 > 10Hz
Verified by in-situ FSI system
Large movements - cooling/power & magnet
Minimize sensitivity to ‘weak modes’
Coherent deformations of large-scale structures
Hits form a track but parameters are wrong
Robust enough to survive assembly, transport & integration
23/01/2020
CEPC Workshop - Beijing - November 2019

7. Thermal LS Requirements
ATLAS ITk Strip
Power = 60mW/cm2
ATLAS ITk Pixel
Power = 700mW/cm2
Support, electrical services & cooling: 0.7%Xo
Support, electrical services & cooling: 1.5%Xo
23/01/2020
CEPC Workshop - Beijing - November 2019

8. Liverpool HV-CMOS Programme
ATLASpix2
LHC
MuPix9
Mu3e
2014
2015
2016
2017
2018
2019
H35DEMO
MuPix8/ATLASpix1
Mu3e/LHC
ATLASpix-3
Start
LFATLASpix
LHC/Mu3e
LFR2
LHC/R&D
RD50-MPW2
R&D
RD50-MPW1 LHC/R&D
23/01/2020
CEPC Workshop - Beijing - November 2019

9. CEPC Workshop - Beijing - November 2019
HV-CMOS Deliverables
Mu3e experiment phase-II (2025)
Search for ultra-rare decays of muons (< 1 in 1016) to uncover new phenomena
Requires very thin detectors with < 1 ns time resolution
LHCb experiment upgrades (2024 and 2030)
Searching for explanation of matter-antimatter asymmetry
Operates at highest rates at the LHC
Requires accurate, fast and radiation tolerant sensors
Liverpool PP signed the Mighty Tracker SOI (Bowcock, Farry, Vilella, Vossebeld)
Beam instrumentation for proton cancer treatment
With a commercial partner (PPI), Liverpool are developing new instrumentation to improve the accuracy of therapy planning (better outcome for patients)
DMAPS instrument already under development (with FBK Trento) providing high rate capability and radiation tolerance at lower cost
Longer Term
Colliders (CEPC, FCC, CLIC)
Precision experiments (g-2, pEDM)
23/01/2020
CEPC Workshop - Beijing - November 2019

10. CEPC Workshop - Beijing - November 2019
Mu3e
Charged lepton flavour violation in µ→e+e+e-
Aiming for 4 orders of magnitude improvement in current limit
Radiation length budget = 0.1%X0 per layer – muon decays at rest so Ee ≤ 53 MeV
HV-CMOS sensors (P~0.3W/cm2, 3 x 1.25Gbit/s data links)
23/01/2020
CEPC Workshop - Beijing - November 2019

11. CEPC Workshop - Beijing - November 2019
Mu3e Ladders
50µm HVMAPS ~ 0.05%X0
100µm HDI ~ 0.05%X0
Doesn’t leave a lot for the stiffener, adhesive, etc !
0.1%X0 Kapton-based tracker…
Room temperature (gaseous helium cooling / tracking volume)
low multiplicity final state
Physics-friendly services routing - electrons absorbed in scintillating tiles in ‘Re-curl’ stations allowing services routing outside physics acceptance.
23/01/2020
CEPC Workshop - Beijing - November 2019

12. Mu3e Mechanical Evaluation
Liverpool’s role is the integration of Kapton ladders to form modules
Expertise being developed
Tooling to integrate ultra low-mass ladders
Supply of gaseous cooling to prototype ladders & assemblies
Measurement of mechanical deformation of ultra-light structures
Laser Vibrometry
Capacitance displacement sensors
23/01/2020
CEPC Workshop - Beijing - November 2019

13. LHCb Mighty Tracker Study
Gas-cooled ‘tile’ for LHCb MT
Rate of heat transfer given by;
𝑄=ℎ ×𝐴 × 𝑇 𝑤𝑎𝑙𝑙 − 𝑇 𝑏𝑢𝑙𝑘
Pressure drop through foams is predicted by Darcy-Forchheimer formula
Foam properties are wrapped up in 𝐶 𝑓 𝐾 term. Can be determined by measurements of pressure drop vs velocity.
Development work on gaseous cooling for Mu3e can be applied here too
Images from LHCb-INT (April 2019)
23/01/2020
CEPC Workshop - Beijing - November 2019

14. Tracker Mechanics for Future GPDs
Vertex Layers
Ultra low mass
High granularity
Likely to be dominated by data transmission – typical solution is to move services outside acceptance (eg ALICE ITS)
High(er) power per unit area
Outer Tracking System
Large geometric area
Simplicity of construction
Low(er) power per unit area
Physical size requires novel solutions
Surely cannot be lower %X0 than TPC?
23/01/2020
CEPC Workshop - Beijing - November 2019

15. CEPC Workshop - Beijing - November 2019
CFRP
Most low-mass support structures in PP experiments are made from CFRP.
High modulus carbon fibres embedded in a resin matrix
Cured under heat (say 120°C) and pressure (vacuum 1 bar, autoclave 7 bar)
Laminate built up from several laminae at different angles
But ….
Typically only half of the volume of a laminate is fibre. The resin plays an important role …
transfers stress from one fibre to another
drives the properties transverse to fibre direction (stiffness, CTE/CME, etc)
CFRP laminates cured at elevated temperature need to be symmetric to avoid distortions. Eg: [0], [0]n, [0/90/0], [0/90/90/0], etc…
Laminates may need to be balanced eg [0/90/90/90] vs [0/90/0] to give uniform in-plane properties (modulus, CTE)
Possible Solution ?
Spread-tow laminates
23/01/2020
CEPC Workshop - Beijing - November 2019

16. Spread-tow CFRP Laminates
Laminates either formed of UD layers in different orientations or woven material
UD laminates need to be symmetric to avoid distortion
3 or more layers
In spread-tow pre-preg, the fibre bundles are spread out into strips (typical commercial product >15mm wide)
Lower areal weight and higher fibre fraction
Lower mass for equivalent stiffness
Laminate is locally asymmetric (at short distance scales) but balanced and flat on larger scale
15-20mm
23/01/2020
CEPC Workshop - Beijing - November 2019

17. Single-shell Vertex Layer Support
Commercial spread-tow weave too large for vertex layer & use low modulus & poor thermal conductivity fibre
Develop manufacture of custom spread-tow woven pre-preg with weave ~ 5mm
OK for vertex-scale – too laborious for larger scales – would need commercial solution
Single woven layer of K13C2U/EX-1515
Thickness ~ 80µm
%X0 ~ 0.03%
Fabrication
3D printed master mould tool
CFRP mould made from 70°C cure tooling pre-preg followed by 130°C post cure
Production part made from K13C2U/EX-1515 using CFRP mould
Spread-tow laminate oriented at +/-45°
First prototype under evaluation
23/01/2020
CEPC Workshop - Beijing - November 2019

18. Prototype 10-sided Structure
Need to understand interfaces to global support structures & services connections to progress fully
23/01/2020
CEPC Workshop - Beijing - November 2019

19. CEPC Workshop - Beijing - November 2019
Spread-tow Ladders #1
Spread-tow woven laminates can be made ‘flat’
Can we make core structures using open woven structures ?
Started in collaboration with Jinju Fu
Ladder Design
Omega-shaped lattice core with [0]n facings
Gaseous cooling
Open/closed sides
Status
Several ladders constructed to develop process
Custom ‘end-pieces’ designed
Plan to use Mu3e gaseous cooling test rig & instrumentation to evaluate
23/01/2020
CEPC Workshop - Beijing - November 2019

20. CEPC Workshop - Beijing - November 2019
Spread-tow Ladders #2
Develop a version of the woven lattice support for contained fluid cooling (i.e. the fluid is in a tube)
Combine previous woven lattice with 1mm OD Kapton™ tube wrapped in CFRP
23/01/2020
CEPC Workshop - Beijing - November 2019

21. CEPC Workshop - Beijing - November 2019
Lattice Ladder FEA
Full thermo-mechanical FEA
ANSYS Mechanical (shell elements)
ACP (model composite properties)
Aim to …
Develop modelling techniques which correctly predict the properties of spread-tow (full and mesh) laminates
Calculate
The gravitational deflection and thermo-mechanical distortion of CEPC-scale vertex system ladders
The temperature distribution for HV-CMOS based sensors
Preliminary – still debugging !
Gravitational load: Deflection = -3µm
Thermal load +10°: Amplitude = 20µm
23/01/2020
CEPC Workshop - Beijing - November 2019

22. Outer Tracking Concepts
Homogeneous structure to maximize stiffness & minimize material
Combine support for 2 layers
Eliminate need for individual Global Support cylinders
One complete double-layer (R ~ 1m) formed from 14 interlocking super-modules in phi
Each super-module combines local and global supports for 7 ladders together in single structure.
Gaseous cooling
Co-cured electrical services
Co-development with Oxford University
Manufacture model of final outer shape in tooling board
Manufacture 4-part CFRP mould from tooling board model & assembly.
Layup CFRP on model & transfer into CFRP mould
Cure under vacuum with internal bag to consolidate pre-preg
23/01/2020
CEPC Workshop - Beijing - November 2019

23. Interlocking Super-module
Vacuum Bagging
Final component
Cooling
Envisage gaseous cooling flowing through box channels integrated into structure
New mould tool just received
3D printed inlet/exhaust manifold
Thermal Test Programme
Attach 10x10 heater pads
Vary power & air flow
Use IR to measure surface temperatures
23/01/2020
CEPC Workshop - Beijing - November 2019

24. CEPC Workshop - Beijing - November 2019
Tracker Volumes
ATLAS ITk
ALICE ITS
23/01/2020
CEPC Workshop - Beijing - November 2019

25. ALICE ITS - OB Integration
Low mass in active area
Chunky services but only for η>1.5
23/01/2020
CEPC Workshop - Beijing - November 2019

26. VTX System Environment
Lots to discuss ….
How are VTX, SIT & FTD supported ?
How are their services (plus LumiCal) routed ?
If the central silicon system is cooled by gas what is the required cross-section of the cooling inlet/outlet ?
How is the performance of the TPC affected by high (30°C plus) and possibly varying temperatures ? (eg drift velocity)
23/01/2020
CEPC Workshop - Beijing - November 2019

27. CEPC Workshop - Beijing - November 2019
Summary
Liverpool has a well motivated mechanical structures prototyping programme which is well aligned to our HV-CMOS sensor development work
Mu3e -> LHCb -> ???
Our work on Mu3e will allow us to develop the expertise and test equipment to evaluate the performance of gaseous cooling structures for future applications
The team in our Advanced Materials Lab are developing the techniques to manufacture CFRP structures, with either gas or liquid cooling which would be suitable for future applications in both vertex and outer tracking system geometries for CEPC.
Services management is key to achieving low %X0
The lowest %X0 tracking systems (Mu3e, ALICE ITS) only achieve goals by routing services outside physics acceptance.
We are beginning to build upon previous work modelling the ATLAS ITk Local and Global supports to incorporate spread-tow laminate structures. The data from the prototype structures will be used to verify the FEA so that we can simulate mechanical structures for future applications with confidence.
We welcome collaboration with teams with similar interests & have successfully hosted PhD students from external institutes at Liverpool to gain experience in the development of mechanical support structures in CFRP.
Low-mass mechanical structures, global supports & services routing
23/01/2020
CEPC Workshop - Beijing - November 2019