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

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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

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Two Design Options

Option 1: Sandwich Option 2: Ribs

The Mechanical Structure for the SVD Upgrade

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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

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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

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Option 1 - Simulation

• Max. sag: 0.084 mm

• Avg. sag: 0.05 mm

The Mechanical Structure for the SVD Upgrade

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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

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Option 2 – Mounting Points

• Elevated Rohacell mounting points

• Serve as contact area and isolation for the sensors

The Mechanical Structure for the SVD Upgrade

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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

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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

2

2.5

3

3.5

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

0.5

1

1.5

2

2.5

3

3.5

Profile [mm]

Radi

atio

nLe

ngth

[%]

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