The Belle II Silicon Vertex Detector Florian Buchsteiner (HEPHY Vienna)

Introduction Ladder Support Structure Cooling Summary 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector2

Introduction Ladder Support Structure Cooling Summary 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector3

Overview 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector4 LayerRadius [mm] LaddersSensors / Ladder Slanted?Windmill angle [°] Overlap [%] x67.1

Components  Not shown: Outer shell (CF) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector5 Ladders End rings (SUS) Carbon fiber (CF) cone End flange (aluminum)

Requirements & Features  Support for detectors with readout and cooling  Light-weight (minimal radiation length)  Stable in time (no vibrations except during earthquake)  Absorb thermal gradients  Fully assembled SVD can be split into halves  Important for quick assembly/disassembly around beam pipe and pixel detector (PXD)  PXD + SVD = VXD (Vertex Detector)  Also includes beam pipe and heavy metal masks (enclosed) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector6

Introduction Ladder Support Structure Cooling Summary 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector7

 The basic element (“atom”) of the SVD  Consists of  Double-sided silicon detectors  Readout electronics  Support structure  Cooling infrastructure  One distinct type for each layer Ladder 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector8

 Longest ladder type (L6) shown here Exploded Ladder 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector9 Origami flexes APV25 chips Airex spacer Silicon Sensors PCB Hybrid Pitch adapters Ribs FWD End Mount BWD End Mount

01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector10 Origami prototype module Silicon sensor Flex hybrid Pitch adapter for top side of sensor Pitch adapter for bottom side of sensor APV25 readout chip

Ladders and Layers  Ladders of L4,5,6 are similar  Different number of rectangular sensors with Origami readout  1 slanted sensor (different angles)  Ladders of L3 are more conventional  Straight design (no slanted part)  Just PCB hybrids on sides (no Origami readout) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector11 L3 ladder L3 bridges

Ladder Support Structure  2 Ribs + End Mount (aluminum) on each side  Rib structure: 3mm Airex core with laminated 0.15mm CF sheets  End mounts serve as  Mounting points to end ring  Heat sinks for readout electronics on PCB hybrids 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector12

Mounting a Ladder  Ladders are positioned by two precision pins  Fixed on backward side  Sliding on forward side to allow thermal movement 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector13

Slide Lock Mechanism (SLM)  SLM is used in layers 4,5,6  No screw driver access from top  Pin fits into precision hole in end ring  Locked by set screw  Also provides cooling contact 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector14 BWD FWD APV25 cover End mount Kokeshi pin = origin of ladder Swallow tail Spring Precision hole Set screw hole

Ladder Mount of Layer 3  L3 uses a different approach  Very limited space  Screwdriver access from top possible (unlike L4,5,6)  Oblong holes for precision pin and washer + screw (forward side)  Precision pin defines position  Washer + screw push bridge against end ring  Simple holes for fixed mounting (backward side) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector15 Precision pin Washer + screw L3 forward side

Issues Addressed 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector16  Rev. 0.12: Screwed connection between ribs and end mounts  Torque to tighten screws caused deformations of rib  Rev. 1.0: new joint without screws  Re-design of ribs and end mounts  Rev. 0.12: Individual end mount design in each layer  Complex shape  Difficult (& expensive) to manufacture  Rev. 1.0: unified end mount design for L4-L6  General improvement (simplification) of all parts

Modified End Mounts 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector17  Glued joint between ribs and end mounts  Secured by pin with  1 mm  Tested with simple mockup  Assembly done with gluing jig  No distortion during assembly  Slimmer ribs at joint  More space to route pitch adapters  New design is easier (& cheaper) to manufacture

FWD Sliding Mechanism Rev  Tricky task: provide thermal contact and allow linear motion  Design with undulated spring was too loose  Improved the design 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector18 Swallow tail Spring

New Sliding Mechanism Version 1  Components  End mount with swallow tail  Prism rail (brass)  Adjustment insert (brass)  Ball plungers  Various spring forces  Mockup exists  Works very well  Good thermal contact 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector19

New Sliding Mechanism Version 2 (Final)  Components  End mount with swallow tail  Prism rail (brass)  Coil spring (various forces)  1.5mm stainless steel ball  Grub screw  Easier to machine  Preferred solution  Mockup exists  Works even better!  Good thermal contact  Cheaper than Version 1 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector20

Ribs Rev July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector21 RibDisplacementVolume [cm 3 ]D max [mm] L L L  D max under (non-realistic) conditions – only for comparison between variants

Stiffness Improved Ribs (Final)  Significant D max improvement in all cases  L5: very limited space towards L4  <1mm clearance to PA1/PA2 in some cases 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector22 RibDisplacementVolume [cm 3 ]D max [mm] L L L

Introduction Ladder Support Structure Cooling Summary 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector23

End Rings  Supporting Ladders  Cooling for PCB hybrids 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector24  Individual rings for L5, L6  Combined L3+4 end rings

Integrated Cooling Channel  Made from two halves (SUS) with diffusion welding 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector25

Carbon Fiber Cones  End Rings are glued onto Carbon Fiber Cones  Separation between PXD and SVD regimes  Made from CF because its CTE~0 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector26

End Flanges  Supports SVD  End flanges are screwed to CDC  Feed-through openings for cables & pipes 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector27  Material  Aluminum

Outer Shell  Only mechanical connection between forward & backward sides (total VXD ~80kg + part of cable weight) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector28  Has to tightly seal the VXD volume (temperature, dew point)

Introduction Ladder Support Structure Cooling Summary 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector29

SVD Cooling  Total dissipated power  1748 APV25 chips  ~ 0.4W / chip  ~ 700W in total  Cooling of APV25 chips required  Common CO2 (IBBelle) system with PXD  Operated at -20°C  Dry volume with due point of -30°C  Ambient temperature inside dry volume: ~20°C  Thermal mockup of VXD  Under construction at DESY to study thermal behavior 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector30 MARCO DESY

Overview of Heat Transfer Points 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector31 Origami Cooling Backward PCB Hybrid Forward (Sliding) SLM L3 Bridge  Sufficient heat transfer measured with mockups  ΔT~10°C for Origami  ΔT~20°C for edge hybrids

Cooling of APV25 Chips  Edge hybrids  APV25 chips cooled by end rings  End mount / L3 bridges used as heat sink  Origami flexes  100µm thin pre-bent SUS pipe   1.6mm  Directly attached to APV25 chips 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector32 APV25 chips End mount End ring APV cover

Setup (1/2)  Dummy end ring with big metal block in water bath  Final SLM with weak or strong springs  Heater wires simulating APV25 power (4W total) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector33

Setup (2/2)  SLM must also work in upside-down position loaded with the weight of a ladder  Adding 100 g to simulate this condition 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector34

Result With Weak Spring  Larger  T with 100 g load  spring too weak 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector35 No weight With 100 g

Result With Strong Spring   T always around 15°C  spring is strong enough 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector36 No weight With 100 g

L3 Bridge (1/3)  Thermal simulation  End ring contact surface of bridge is held at -20°C  APV25 bar sinks 4.8W of heat (=12 APV25 chips)  Result of long bridge (backward side) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector °C -20°C ΔT~15°C

L3 Bridge (2/3)  Thermocouples: 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector38 0 water bath 1 heat sink 2 bar back 3 bar front 4 APV center 5 APV end 4.8W (dummy APVs)

L3 Bridge (3/3) 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector39 ΔT~17°C Consistent with simulation

Origami Cooling (1/3)  Simulation 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector40 CO 2 cooling pipe APV25 chip “GapPad”: 1mm Keratherm Softtherm 86/125 ΔT~10°C pre-amp)

Origami Cooling (2/3)  Thermal test using 2-sensor-Origami module (20 APV25 chips)  Tested in a dry box with blow CO 2 system  Placed a few thermocouples  Watched by infrared camera  Unfortunately, no absolute readings 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector41

Origami Cooling (3/3)  room temperature  APV chips much hotter 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector42 APVs on without cooling APVs on with cooling Pipe has -16°C (thermocouple) APV chips have similar temp. Camera does not provide correct absolute values!

DESY Beam Test – SVD Cooling  Installed 4 SVD modules  Layer 3 module with conventional hybrids  3 Origami modules with  1.6 mm cooling pipe  Cooling pipe tested up to 150 bar  SVD modules operated  Without cooling  at 0°C  at -10°C (humidity minimum)  Sensor bias current followed CO2 temperature  Indicates proper cooling contact 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector43

01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector44 Introduction Ladder Support Structure Cooling Summary

 Mechanics  Revised ladder design  Ribs and end mounts  FWD sliding mechanism  Fine tuning of end ring design  Cooling  Common CO2 cooling with PXD  Overall performance will be verified with thermal VXD mockup  DESY test beam: SVD modules cooled down to -10°C (humidity minimum)  Significant decrease of sensor bias current indicates proper heat transfer  Air temperature in box close to that of ambient air 01 July 2014F. Buchsteiner: The Belle II Silicon Vertex Detector45