1. R&D status of FPCCD VTX for ILD
Yasuhiro Sugimoto
KEK
2011/9/27
@LCWS2011 in Granada 1

2. Outline Introduction FPCCD sensor R&D Engineering R&D R&D goals
Prototypes
Engineering R&D
Wafer thinning
CO2 cooling system
Engineering common design

3. Performance goal of ILC VTX
Impact parameter resolution: sIP<510/(pbsin3/2q ) mm
Measurement accuracy < 3mm
Material budget < 0.1%X0/layer
Tolerance against beam background
Pixel occupancy < few%
Radiation immunity: 1x1012e/cm2/y
Tolerance against RF noise
RF noise is induced by bunched beam
It was a serious problem at SLD
There are many sensor options proposed to solve these challenges
One possible solution for these issues：FPCCD
Fine Pixel CCD: ~5mm pixel
Read out in 200ms between beam trains

4. R&D goal FPCCD sensors Readout ASIC Peripheral circuit Engineering R&D
Pixel size; 6um
Chip size;1cmx6.5cm
Speed >10Mpix/s
F.W.C. > e(?)
Power <10mW/ch
Rad. Tolerance >1x1013e/cm2 (=1x1012/cm2/y x 3y x safety factor 3)
Readout ASIC
Speed > 10Mpix/s
Power < 6mW/ch
Noise < 30 electrons
Peripheral circuit
Clock driver
Data suppression
Etc.
Engineering R&D
Over-all design
Low-mass ladder
Cooling system (~-40℃)
Support structure
Engineering prototype
Software tools
Track reconstruction
Cluster shape analysis

5. FPCCD sensor R&D

6. History in ILC era FY Sensor ASIC 2004 Fully depleted CCD 2005 2006
2007
1st FPCCD:12um
1st ASIC
2008
2nd FPCCD:12um (modified output amp)
2009
3rd FPCCD:12, 9.6, 8, 6um
2nd ASIC
2010
4th FPCCD:12, 9.6, 8, 6um (modified process)
Thin wafer:50um

7. Sensor R&D FPCCD prototype-3 Pixel size：12, 9.6, 8, 6mm
12, 9.6, and 8mm pixels work, but 6mm pixels do not work at all
12mm　 9.6mm　 8mm　 6mm

8. Sensor R&D FPCCD prototype-4
Same parameters as prototype-3
Improvement of potential profile based on device simulator
x2 improvement of the depth of the potential well is expected
6mm pixel works, but not properly
FPCCD prototype-5 (to be delivered FY2012)
First large size (~1cmx6cm) prototype
Horizontal shift register for 6mm pixel has a size of 6mmx12mm to improve full-well capacity and to decrease resistance of gate line
Multiple wire for gate: Many bonding pads along the longer side of the chip

9. Engineering R&D

10. Wafer thinning 50mm thick prototype Thinned by mechanical grinding
Dicing by “stealth dicing” technology
No increase of dark current was observed
Sag ~ mm over 60mm
60mmx9.7mmx50mm
Before expansion
After expansion

11. CO2 cooling system
FPCCD will be operated at low temperature (-40 degree) to minimize CTI
Power consumption
Inside cryostat: 4224 readout channel  ~100W
Cooling with cold air (nitrogen) flow would not be enough
Cooling system using 2-phase CO2 is a very attractive alternative because of its large cooling capacity (~300J/g)
Cooling tube is attached to VTX end-plate and heat produced by CCD output amp and ASIC is removed by conduction through CFRP ladder (simulation study for thermal design is necessary)
Return line of CO2 will be used to cool the electronics outside the cryostat (~200W/side)
Inner support tube should be air-tight and filled with dry air/nitrogen in order to prevent condensation on the CO2 tube

12. CO2 cooling system CO2 collaboration in Japan
ILC VTX, ILC TPC, Belle-II VTX, and KEK cryogenic group
We constructed “blow system” and temperature was successfully controlled between -40 and +15 degrees

13. CO2 cooling system

14. Common engineering design
A tentative engineering design of VTX which is common to all sensor options have been made to be used in ILD detector simulation (MOKKA) for DBD
GEANT4 simulation is common to all sensor options (50mm thick Si), and the study of different sensor option can be done at digitization phase
The design is based on SLD VTX
Double sided ladder option is assumed
Compared with old model (ILD00), material budget in forward region is increased
Implementation into MOKKA will be done by Gabriel Musat and Georgios Gerasimos Voutsinas

15. Common engineering design
t (mm)
Total t (mm)
X0 (%) Si 50
0.0534
Epoxi 10
2000
0.0028
FPC Cu 9
0.0125
Kapton 51
0.0179
CFRP
100
0.0383 20
0.0056
RVC
1600
0.0300
Total
2100
0.2966
Ladder
Ladder has a tricky shape to allow overlapping of sensors with adjacent ladder
Material budget ~0.3%X0/ladder = 0.15%X0/sensor layer

16. Common engineering design
Overall design

17. Common engineering design
Junction box
Flexible printed circuit (FPC) cables from the ladders are connected to the junction box using micro connectors
The junction box (PCBs) are placed surrounding beam pipe
Electronics parts on the PCB are represented by uniform 0.2mm-thick Si
Power cables to the junction box have cross section of 30mm2 in total

18. Common engineering design
Cooling pipe + Support shell

19. Summary
So far, starting from 24mm-pixel fully depleted CCD, small (6mmx6mm) FPCCD prototypes have been manufactured 4 times, and finally 6mm-pixel FPCCD has been developed
Design of the first large prototype of FPCCD is in progress and the prototype chips will be delivered in FY2012
Technology to make CCD wafers thinned down to 50mm has been established by HPK
R&D for cooling system using 2-phase CO2 is being carried out in collaboration with LC-TPC, Belle-II VTX, and KEK cryogenic groups
A tentative common engineering design has been made to be implemented into ILD simulation model

20. Backup slides

21. ASIC R&D ASIC Prototype Evaluation of prototype ASICs
Amp, LPF, CDS, ADC, LVDS driver
Charge-sharing successive approximation register array ADC  Low power consumption and medium speed
Alternative operation of two 5MHz ADCs  10MHz readout speed
8-channel/chip
Evaluation of prototype ASICs
Test system at Tohoku Univ.
SiTCP, DAQ-middleware
Expected performance is not achieved
 Improved prototype in FY

22. Beryllium support shell
FEA calculation of deformation
1kgf is applied in z-direction
Maximum deformation is less than 2mm
Total weight is less than 500g  max force caused by the friction at the kinematic mount would be less than 500gf
(mm)

23. Ladder
Structure
Layer-1
Layer-2,3

24. Endplate annulus
Without ladders
With ladders

25. Cooling system Cooling tube
Titanium tube 2mm o.d. and 1.5mm i.d. is attached to the VTX endplate near the endplate annuli
The return line of the cooling tube is also used for the cooling of the junction box
4 tubes/side run along the beam pipe between the vertex detector and the end of the inner support tube