19.11.2009 Immanuel Gfall (HEPHY Vienna) The Mechanical Structure for the SVD Upgrade.

19.11.2009

Immanuel Gfall (HEPHY Vienna)

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



Origami Module Readout Side

• High component density

• Sensitive wirebonds

• Flexible structure

• Thermal expansion

• Bad attributes for mounting the structure on top side



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



Origami Module Sensor Side

• Rigid contact surface

• Conventional rib design is possible

• Wire bonds and fanouts limit the contact area



Two Design Options

Option 1: Sandwich Option 2: Ribs



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



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



Option 1 - Simulation

• Max. sag: 0.084 mm

• Avg. sag: 0.05 mm



Option 2 – Rib Design

• Sandwich composite ribs

• CFRP ribs support horizontally arranged sensors

• Sandwich rib structure supports vertically arranged sensors



Option 2 – Mounting Points

• Elevated Rohacell mounting points

• Serve as contact area and isolation for the sensors



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



Option 2 – Simulation

• Horizontal Sensors• Max sag: 0.084 mm• Avg sag: 0.05 mm



Option 2 – Simulation

• Vertical Sensors• Max sag: 0.087 mm• Avg sag: 0.067 mm


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


19.11.2009

Radiation Length Option 2


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


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



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




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


Outlook

• Construction of mechanical mockup

• Thermal simulation / measurements

• Integration of cooling

• Construction of outermost ladder

• Endring design

20Immanuel Gfall (HEPHY Vienna)19.11.2009

19.11.2009 Immanuel Gfall (HEPHY Vienna) The Mechanical Structure for the SVD Upgrade.

Documents

Transcript of 19.11.2009 Immanuel Gfall (HEPHY Vienna) The Mechanical Structure for the SVD Upgrade.