1. SVD Electronics Constraints
DESY Meeting, April 2012
SVD Electronics Constraints
Markus Friedl (HEPHY Vienna)

2. Readout Chain Overview
Analog APV25 readout is through copper cable to FADCs
Junction box provides LV to front-end
1748 APV25 chips
Front-end hybrids
Rad-hard DC/DC converters
Analog level translation, data sparsification and hit time reconstruction
Unified Belle II DAQ system
~2m copper cable
Junction box
~10m copper
cable
FADC+PROC
Unified optical data link (>20m)
Finesse Transmitter
Board (FTB)
COPPER
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

3. Constraints: Sensors L4…L6: sensors are ordered and in production
Sensor design (size, strips, pitch) is thus frozen
L3: tentative design in TDR, but not ordered yet
Sensor design (size, strips, pitch, number of sensors) can be adapted
Should be similar to TDR to achieve same (or better) performance
Pitch adapter must be placed between sensor and hybrid
minimum length given by line width/spacing requirements of manufacturing process
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

4. Constraints: APV25 Chips
APV25 has fast shaping (50ns), thus noise figure strongly depends on capacitive load
Must read out each sensor individually (no ganging possible)
Achieved by Origami scheme, which allows double-sided readout at minimum material budget (0.55% X0 per layer)
Implies one or more layers of Kapton with connectors in parallel to edge hybrids
Stack of connectors needs mechanical strain relief
Thus screwing like SVD2 is not possible for ladder mounting, because the Kapton flexes cover the hybrids
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

5. Constraints: APV25 Chips & Edge Hybrids
Chip size = (long) x 7.1 (wide) mm2
In fact, a margin for die cutting tolerance must be added
Closest realistic APV25 “pitch” is 7.5 mm
Defines the hybrid width (6 chips wide)
In L4…L6, sensor is wider than 6 APV25 chips
In L3, the sensor pitch is lower, thus 6 chips are wider than the sensor
Potential problem due to space constraints
Might try a 2-tier option (3+3 APV25 chips; experimental) to overcome this limitation
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

6. Constraints: Edge Hybrids
Hybrid width given by
6 APV25 chips width
Hybrid length given by
pitch adapter gluing area
APV25 chips including wire bonding
Mechanical mounting holes on hybrid
Line routing to back end
Connector
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

7. Constraints: Hybrid Connector
Connector must have
Locking mechanism
Halogen-free (no PVC)
Gold plated contacts
50 pins
Small feature size
Nanonics (SVD2): expensive, fragile, two solder rows
JAE: cheap, one solder row, but also larger
Connector is practical, but not mandatory
Could also solder wires directly if needed (option for L3)
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

8. Constraints: Cables
= 12m analog signal path directly driven by APV25
Connectors at Junction Box are inevitable (installation, power)
Need same cable on both legs to guarantee same impedance
Cable must have
Twisted pairs (25 for 2m, 34 for 10m part) = no Kapton
Low resistance to minimize power drop (OK with 30 AWG)
Halogen-free (no PVC)
Suitable cables:
0.635 mm pitch twisted flat IDC cable 30 AWG
3M P-270A / P-270A
(CERN SCEM: / )
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

9. Constraints: Cooling Each APV25 dissipates ~0.35w
Heat must be removed from closed SVD volume
Air flow is not sufficient (or storm blows off bond wires)
No hard requirement for APV25 operating temperature
But low temperature lowers noise figure
Thus -20°C is our choice together with PXD (approximately +15% for S/N compared to room temperature)
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012

10. Constraints: Position Accuracy
Mechanical tolerances do not allow perfect positioning
Gravitational sag of a ladder adds deviation
dependent on position in f
up to 100 µm according to simulation
Can only be reduced at cost of material budget
Perfect mechanical precision is not needed if we can do online alignment
CMS experiment does it successfully with many more degrees of freedom
Does not require 10 µm mechanical precision (anyway useless with 100 µm gravitational sag)
M.Friedl (HEPHY Vienna): SVD Electronics Constraints
12-13 Apriil 2012