27 January 2010 Immanuel Gfall (HEPHY Vienna) Belle II SVD Mechanics and Cooling DEPFET Meeting Prag

27 January 2010

Immanuel Gfall (HEPHY Vienna)

Belle II SVD Mechanics and Cooling

DEPFET Meeting Prag


2Immanuel Gfall (HEPHY Vienna)27 January 2010

Origami Concept• Thinned readout chips (APV25)

on sensor• Strips of bottom side are

connected by flex fanouts wrapped around the edge

• All readout chips are aligned single cooling pipe

• Shortest possible connections high signal-to-noise ratio

• Total material budget: 0.58% X0

3-layer kapton hybrid

DSSD

Single-layer fanouts Rohacell

APV25

Cooling Pipe


Mechanical Structure

• Composite sandwich rib design• Gravitational sag <100 µm• Sag is equal in horizontal and vertical sensor

position


Composite ribs

Sensor mounting points

DSSD

Origami Sensors

Endring Mount


Assembled Barrel


Cooling Loop Outlets

Capillary Evaporators

Layer 6,5,4

Endring Mounts


Space Issue Forward Region

• Slanted sensor design strongly limits available space

• Cables density• Hybridboards need

space• Coolingpipes space

problem


Cooling pipe loops

Ø Layer 4: 7.6 cm Ø Layer 5: 12.2 cm

Ø Layer 6: 15.6 cm


Thermal Conditions

# of Origamis/Ladder Number of ladders Number of APV25‘s

Layer 6 3 18 540

Layer 5 2 14 280

Layer 4 1 10 100


• Power dissipation/APV: 0.4 W• 1 Origami sensor features 10 APV‘s

• Total Origami power dissipation: 368 W• Total SVD power dissipation: 761 W• 393 W dissipated at the endrings


Observations

• Little power dissipation• Heat distribution focused on

small strips• Cooling pipes are sufficient,

no heatspreaders needed

• Heat transport is ensured by any solution (singlephase and dualphase)

• Relative SNR improvement of ~20% @ -8°C



Requirements for Cooling the SVD

• Low temperature ~ -20°C

• Dry air / nitrogen environment

• Air / Gasflow through SVD not necessary for cooling

• Exchange of gas at a slow rate is welcome (< 1 m/s)

• Temperature stability

• Warm supplylines to avoid water condensation



The CO2 Solution

• Requirements are met by CO2

• Warm supplylines @ ~ +20°C

• CO2 Radiationhard gas

• Low cost dualphase system

• Technology successfuly proven (LHCb-VELO)

• Existing experience from industrial solutions

• It is a „green“ solution



The CO2 Problems„Pressure Issue“

• High pressure in supplylines (~70 bar)

• High pressure in evaporator (~20 bar)

• Pressurelines and connectors are tested to over 100 bar : no problem!

• Complex system requires skilled engineering and human resources



Engineering Challenges

• Calculation of the capillary evaporator or finding/ building a suitable expansion valve

• Calculation of pressuredrop in the circuit

• Compensating pressure bending of the pipes

• Fitting the cooling circuit into the SVD volume

• Developing a monitoring and regulation system

• Subcooling the fluid state CO2 at expansion valve



Design Study Layer 6


Coolingloop Outlet (Detachable)

Outlet Circular Line

Evaporator (Dummy) Detachable

Inlet Circular Line

Source (Liquid)

Drain (~70% Gas)


Cooling Plant


• Sanyo unit with 900 W output available• Evaporating temperature adjustable between -

30°C and -5°C• Small package outline (630x520x245 mm)• Relatively cheap unit • Several different units from CERN and Italy

available but more expensive


Outlook

• Obtaining a cooling unit and evaluating it

• Calculating pressure drop and thermodynamical parameters for the coolingcircuit

• Building the unit

• Testing

• Tuning


Documents

27 January 2010 Immanuel Gfall (HEPHY Vienna) Belle II SVD Mechanics and Cooling DEPFET Meeting Prag