1. 27 January 2010 Immanuel Gfall (HEPHY Vienna) Belle II SVD Mechanics and Cooling DEPFET Meeting Prag

2. Belle II SVD Mechanics and Cooling 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% X 0 3-layer kapton hybrid DSSD Single-layer fanoutsRohacell APV25 Cooling Pipe

3. Belle II SVD Mechanics and Cooling Mechanical Structure Composite sandwich rib design Gravitational sag <100 µm Sag is equal in horizontal and vertical sensor position 3Immanuel Gfall (HEPHY Vienna)27 January 2010 Composite ribs Sensor mounting points DSSD Origami Sensors Endring Mount

4. Belle II SVD Mechanics and Cooling Assembled Barrel 4Immanuel Gfall (HEPHY Vienna)27 January 2010 Cooling Loop Outlets Capillary Evaporators Layer 6,5,4 Endring Mounts

5. Belle II SVD Mechanics and Cooling Space Issue Forward Region Slanted sensor design strongly limits available space Cables density Hybridboards need space Coolingpipes space problem 5Immanuel Gfall (HEPHY Vienna)27 January 2010 Cooling pipe loops Ø Layer 4: 7.6 cm Ø Layer 5: 12.2 cm Ø Layer 6: 15.6 cm

6. Belle II SVD Mechanics and Cooling Thermal Conditions # of Origamis/LadderNumber of laddersNumber of APV25‘s Layer 6318540 Layer 5214280 Layer 4110100 6Immanuel Gfall (HEPHY Vienna)27 January 2010 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

7. Belle II SVD Mechanics and Cooling 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 7Immanuel Gfall (HEPHY Vienna)27 January 2010

8. Belle II SVD Mechanics and Cooling 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 8Immanuel Gfall (HEPHY Vienna)27 January 2010

9. Belle II SVD Mechanics and Cooling The CO 2 Solution Requirements are met by CO 2 Warm supplylines @ ~ +20°C CO 2 Radiationhard gas Low cost dualphase system Technology successfuly proven (LHCb-VELO) Existing experience from industrial solutions It is a „green“ solution 9Immanuel Gfall (HEPHY Vienna)27 January 2010

10. Belle II SVD Mechanics and Cooling The CO 2 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 10Immanuel Gfall (HEPHY Vienna)27 January 2010

11. Belle II SVD Mechanics and Cooling 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 CO 2 at expansion valve 11Immanuel Gfall (HEPHY Vienna)27 January 2010

12. Belle II SVD Mechanics and Cooling Design Study Layer 6 12Immanuel Gfall (HEPHY Vienna)27 January 2010 Coolingloop Outlet (Detachable) Outlet Circular Line Evaporator (Dummy) Detachable Inlet Circular Line Source (Liquid) Drain (~70% Gas)

13. Belle II SVD Mechanics and Cooling Cooling Plant 13Immanuel Gfall (HEPHY Vienna)27 January 2010 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

14. Belle II SVD Mechanics and Cooling Outlook Obtaining a cooling unit and evaluating it Calculating pressure drop and thermodynamical parameters for the coolingcircuit Building the unit Testing Tuning 14Immanuel Gfall (HEPHY Vienna)27 January 2010