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

Immanuel 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 19.11.2009 Immanuel 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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel 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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Origami Module Sensor Side Rigid contact surface Conventional rib design is possible Wire bonds and fanouts limit the contact area 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Two Design Options Option 1: Sandwich Option 2: Ribs 19.11.2009 Immanuel 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) CFRP Sandwich Sensor 19.11.2009 Immanuel Gfall (HEPHY Vienna) 7

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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Option 1 - Simulation Max. sag: 0.084 mm Avg. sag: 0.05 mm 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Option 2 – Rib Design Sandwich composite ribs CFRP ribs support horizontally arranged sensors Sandwich rib structure supports vertically arranged sensors 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Option 2 – Mounting Points Elevated Rohacell mounting points Serve as contact area and isolation for the sensors 19.11.2009 Immanuel 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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Option 2 – Simulation Horizontal Sensors Max sag: 0.084 mm Avg sag: 0.05 mm 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Option 2 – Simulation Vertical Sensors Max sag: 0.087 mm Avg sag: 0.067 mm 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Radiation Length Option 1 “Batman” distribution of pipe and coolant Pipe Coolant APV Kapton Sensor CFRP Rohacell 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Radiation Length Option 2 APV Kapton Pipe Coolant Sensor CFRP Rohacell 19.11.2009 Immanuel Gfall (HEPHY Vienna)

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 Immanuel Gfall (HEPHY Vienna)

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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel 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 19.11.2009 Immanuel Gfall (HEPHY Vienna)

Immanuel Gfall (HEPHY Vienna) Outlook Construction of mechanical mockup Thermal simulation / measurements Integration of cooling Construction of outermost ladder Endring design 19.11.2009 Immanuel Gfall (HEPHY Vienna)