Post on 20-Jan-2016
19.11.2009
Immanuel Gfall (HEPHY Vienna)
The Mechanical Structure for the SVD Upgrade
The Mechanical Structure for the SVD Upgrade
19.11.2009 2Immanuel Gfall (HEPHY Vienna)
Design Goals
• Lowest possible material budget
• Gravitational sag equal or lower than 100µm
• Minimum coefficient of thermal expansion
• Low moisture susceptibility
• Radiation hardness up to 10 Mrad
• Compliant with the Origami concept
The Mechanical Structure for the SVD Upgrade
19.11.2009 3Immanuel Gfall (HEPHY Vienna)
Origami Module Readout Side
• High component density
• Sensitive wirebonds
• Flexible structure
• Thermal expansion
• Bad attributes for mounting the structure on top side
The Mechanical Structure for the SVD Upgrade
19.11.2009 4Immanuel Gfall (HEPHY Vienna)
Origami Rohacell Core
• Rohacell core is an already existing volume
• Electrical and thermal separation from sensor
• Evenly distributed material
• Small modifications of the core can lead to good structural strength
The Mechanical Structure for the SVD Upgrade
19.11.2009 5Immanuel Gfall (HEPHY Vienna)
Origami Module Sensor Side
• Rigid contact surface
• Conventional rib design is possible
• Wire bonds and fanouts limit the contact area
The Mechanical Structure for the SVD Upgrade
19.11.2009 6Immanuel Gfall (HEPHY Vienna)
Two Design Options
Option 1: Sandwich Option 2: Ribs
The Mechanical Structure for the SVD Upgrade
19.11.2009 7Immanuel Gfall (HEPHY Vienna)
Option 1- Sandwich Design
• Carbon Fiber Reinforced Plastic (CFRP) layers cover Rohacell core
• Separating Sensor from CFRP using a thin isolating film (eg. Sil-Pad strips)
• Origami hybrid sits on top of Sandwich (not drawn in this sketch)Sensor
CFRP Sandwich
The Mechanical Structure for the SVD Upgrade
19.11.2009 8Immanuel Gfall (HEPHY Vienna)
Option 1 – Simulation Boundary Conditions
• Rohacell: 2 mm thickness
• CFRP: 2 x 0.14 mm plies
• 40 mm wide, 2.28 mm thick, 698 mm long
• Sensor weight: 23.90 g
• Structure weight: 15 g
• Fixed support at both ends
• Average radiation length: 0.629% X0
The Mechanical Structure for the SVD Upgrade
19.11.2009 9Immanuel Gfall (HEPHY Vienna)
Option 1 - Simulation
• Max. sag: 0.084 mm
• Avg. sag: 0.05 mm
The Mechanical Structure for the SVD Upgrade
19.11.2009 10Immanuel Gfall (HEPHY Vienna)
Option 2 – Rib Design
• Sandwich composite ribs
• CFRP ribs support horizontally arranged sensors
• Sandwich rib structure supports vertically arranged sensors
The Mechanical Structure for the SVD Upgrade
19.11.2009 11Immanuel Gfall (HEPHY Vienna)
Option 2 – Mounting Points
• Elevated Rohacell mounting points
• Serve as contact area and isolation for the sensors
The Mechanical Structure for the SVD Upgrade
19.11.2009 12Immanuel Gfall (HEPHY Vienna)
Option 2 – Simulation Boundary Conditions
• Rohacell: 1.2 mm thickness
• CFRP: 2 x 0.14 mm plies per rib
• 6.5 mm high, 1.48 mm wide, 698 mm long
• Structure weight: 4.8 g (both ribs)
• Fixed support at both ends
• Average radiation length: 0.579 % X0
The Mechanical Structure for the SVD Upgrade
19.11.2009 13Immanuel Gfall (HEPHY Vienna)
Option 2 – Simulation
• Horizontal Sensors• Max sag: 0.084 mm• Avg sag: 0.05 mm
The Mechanical Structure for the SVD Upgrade
19.11.2009 14Immanuel Gfall (HEPHY Vienna)
Option 2 – Simulation
• Vertical Sensors• Max sag: 0.087 mm• Avg sag: 0.067 mm
The Mechanical Structure for the SVD Upgrade
19.11.2009
Radiation Length Option 1
15Immanuel Gfall (HEPHY Vienna)
0 10 20 30 40 50 600
0.5
1
1.5
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Profile [mm]
Radi
atio
nLe
ngth
[%]
Sandwich Design
CFRP
Pipe APV Kapton
RohacellSensor
Coolant
“Batman” distribution of pipe and coolant
The Mechanical Structure for the SVD Upgrade
19.11.2009
Radiation Length Option 2
16Immanuel Gfall (HEPHY Vienna)
Kapton
0 10 20 30 40 50 600
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1
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Profile [mm]
Radi
atio
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ngth
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Rib Design
CFRP Rohacell
Pipe APVCoolant
Sensor
The Mechanical Structure for the SVD Upgrade
19.11.2009
Pros & Cons of Option 1 (Sandwich Design)
+ Even distribution of material budget
– High fabrication effort & cost
– Connector issues with bent kapton
– Additional capacitance decreases signal to noise by ~ 2.5%
– Bonding potentially more complicated
17Immanuel Gfall (HEPHY Vienna)
The Mechanical Structure for the SVD Upgrade
19.11.2009
Pros & Cons of Option 2 (Rib Design)
+ Significantly easier to build
+ High assembly precision
+ Gravitational sag constant in φ
– Particles could hit the structure before they hit the sensor (although unlikely)
– Uneven material distribution
18Immanuel Gfall (HEPHY Vienna)
The Mechanical Structure for the SVD Upgrade
19.11.2009 19Immanuel Gfall (HEPHY Vienna)
Discussion
• Homogeneous design vs. lower average radiation length
• Construction effort of sandwich vs. rib design
• Higher costs of sandwich design
• Problem of twist resulting from slanted sensors
The Mechanical Structure for the SVD Upgrade
Outlook
• Construction of mechanical mockup
• Thermal simulation / measurements
• Integration of cooling
• Construction of outermost ladder
• Endring design
20Immanuel Gfall (HEPHY Vienna)19.11.2009