1. P326 Gigatracker Pixel Detector
Requirements
material budget, time resolution, radiation hardness,...
Hybrid pixels: sensor, readout chip, bump bonding
Electronics system
(Mechanics and) Cooling
Resources - Workplan
Possible interest in R&D for CLIC
04/10/06
G. Stefanini/LC WG/P326/GTK

2. G. Stefanini/LC WG/P326/GTK
P326 Proposal
10-11 branching ratio
high intensity K beam
high background rejection
≈ K decays/year
≈ 100 events by 2011
04/10/06
G. Stefanini/LC WG/P326/GTK

3. G. Stefanini/LC WG/P326/GTK
P326 Beam
Tracking, momentum, time stamp
modified NA48 K12 beam line
protons on target (400GeV) ==> 60% pions, 20% protons, 14% electrons, 6% kaons
overall particle rate ≈ 0.8GHz ==> “Gigatracker”
beam cross-section ≈ 12cm2 at GTK
04/10/06
G. Stefanini/LC WG/P326/GTK

4. G. Stefanini/LC WG/P326/GTK
GTK Si Pixels
P. Riedler
04/10/06
G. Stefanini/LC WG/P326/GTK

5. Required Gigatracker time resolution
P(>1hit in Dt) =1-exp(-Dt*rate)
Dt ( ±2s)
% %
% %
% %
K+ p+p0
Dependence of the signal to
background (from K+ p+p0 )
as a function of the gigatracker
time resolution
04/10/06

6. Material Budget Requirements
Full GEANT simulation
Impact of GTK material budget
beam momentum resolution
angular beam resolution
vertex resolution
missing mass
No significant degradation at ≈ 0.5%Xo per plane
04/10/06
G. Stefanini/LC WG/P326/GTK

7. Radiation Levels in Gigatracker (GTK)
Calculated fluence ≈ (1 MeV neq cm-2) 100 days
For comparison:
ATLAS SCT/CMS TK ≈ (1 MeV neq cm-2) 10 years
Safety factors in estimates
04/10/06
G. Stefanini/LC WG/P326/GTK

8. GTK Hybrid Pixel Design Parameters (Preliminary)
hybrid pixels
Pixel cell size 300mm x 300mm
Sensor thickness 200mm
charge collection time vs signal amplitude
Pixel chip thickness ≤ 100mm
Bump bonding Pb-Sn
Material budget ≈ 0.4% X0 (each station)
Operating temp. T ≤ 5 °C (in vacuum)
Cooling ≈ 120mm CF radiator/support with peripheral cooling
04/10/06
G. Stefanini/LC WG/P326/GTK

9. G. Stefanini/LC WG/P326/GTK
Si Sensors
Radiation effects
type inversion (higher Vb required)
leakage current increase
DIvol=a fne (a ≈ 5 x A/cm)
Remedies
M-CZ material (to be studied)
operation at low(er) temp (in vacuum...)
I  exp(-Eg/2kT)
(up to ≈ 25 °C )
DI reduction ≈ 16x @ 0 °C
periodic replacement of station
04/10/06
G. Stefanini/LC WG/P326/GTK

10. G. Stefanini/LC WG/P326/GTK
GTK Pixel ASIC
Technology: CMOS8 (0.13mm)
speed, density, power, (radiation hardness)
availability/obsolescence, MPW access
cost (prototyping, engineering run)
frame contract at CERN for applications within the HEP community
Conceptual study well advanced
definition of system architecture
noise (mixed-signal application)
upcoming MPW submission of functional blocks (amplifier, discriminator, TDC, ...)
ALICE pixel ASIC (CMOS mm)
8,192 pixel cells
04/10/06
G. Stefanini/LC WG/P326/GTK

11. G. Stefanini/LC WG/P326/GTK
Bump Bonding
Bump bonding of 150mm pixel chips to 200mm sensors: in volume production (ALICE SPD 107 pixels)
Pb-Sn (VTT/Finland)
Thinning of pixel wafers (D=200mm) is done after bump deposition
Thinning/bb to 100mm (or less) requires prototyping
Preliminary test under way with ALICE pixel dummy wafers
Key issue: flatness of sensors
©VTT
Pb-Sn
~20-25µm
04/10/06
G. Stefanini/LC WG/P326/GTK

12. Readout Wafer Thinning
200mm Si wafer thinned to 150 mm
J. Salmi/VTT
BOND’03
CERN
04/10/06
G. Stefanini/LC WG/P326/GTK

13. Chip Size - Power Management
Power dissipation up to 2W/cm2 (preliminary estimate)
Material budget constraints on coverage of beam area
Lowest material budget with only pixel matrix in beam
I/O pads and cooling at periphery
This leads to power management problems
Beam cross section adjusted (≈ rectangular) to ease matching of optimized chip layout
without degradation of beam quality
04/10/06
G. Stefanini/LC WG/P326/GTK

14. Configuration I Highest rate Pads for power supplies and clock
(additional material budget)
04/10/064 July, 2006
A. Kluge

15. Configuration II Max rate on one chip, but chip smaller
04/10/064 July, 2006
A. Kluge

16. Configuration IV
60 mm
6 mm
12 mm
24 mm
04/10/064 July, 2006
A. Kluge

17. G. Stefanini/LC WG/P326/GTK
Time Stamp
Fast discriminator with time walk compensation is key element
TDC bin size 100ps
TDC options
one TDC per pixel cell (linear discharge)
cell area, power dissipation, dead time
group multiplexed TDC
efficiency loss (must be limited to <2%)
04/10/06
G. Stefanini/LC WG/P326/GTK

18. Chip size/data rate With a beam of 24 x 60 mm -> 2 x 5 chips
Assume chip matrix of 40 rows x 40 columns: 12 mm x 12 mm = 144 mm2
Pixel size 300 um x 300 um
=> 40 x 40 pixels = 1600 pixels
Avg Rate of center column: ~ 96 MHz/cm2
=> 86 kHz/pixel
=> 138 MHz/chip
=> 138 MHz/chip * ~ 32 bit = ~4.4 Gbit/s
04/10/064 July, 2006
A. Kluge

19. G. Stefanini/LC WG/P326/GTK
Cooling
Power dissipation (pixel plane) ≈ 20W
Operating temperature < 5 °C (==> sensor leakage current)
CF radiator fins coupled to cooling circuit
Adhesive/filler (≈ 50mm) thermal conductivity ≈ 1 W/(m K)
Cooling system options
fluid coolant
evaporative cooling
C4F10
C4F8
Peltier cell ?
04/10/06
G. Stefanini/LC WG/P326/GTK

20. Carbon Fibre (CF) Composites
CTE (ppm/K) ≈ -1.5/+12
Th. conductivity (W/m K) ≈ 150 (M55J)
≈ 1,000 (K-1,100)
≈ 390 (Cu)
≈ 145 T=300K)
Density (g/cm3 ) ≈ 1.9/2.2
X0 (g/cm2) ≈ 42 (≈ 21 cm)
(≈ 9.36cm for Si)
2-ply radiator thickness ≈ 120 mm
04/10/06
G. Stefanini/LC WG/P326/GTK

21. Initial Situation Case A: without cooling plane
Case B: with cooling plane and with different thermal contact resistances between the solids
Total Heat Load of 2 W/cm²
Case
Cooling plane
Thermal conductivity
k [W/(cm K)] B1
Toray M55J
1.5 B2
Carbon-Carbon
2.5 B3
Thornel 8000X panels
8.0 B4
Thornel K-1100
10.0
04/10/06

22. Results with ideal contact between materials
Case A B1 B2 B3 B4
04/10/06

23. Temperature gradient of the Silicon Pixel detector in dependence of the thermal conductivity of the cooling plane
04/10/06

24. Results with thermal resistance between materials
04/10/06

25. Influence of the thermal resistance
It is quite difficult to calculate the real thermal resistance of the contact surfaces between the materials.
Differences between hand calculation and CFD-Simulation, show the influence of the bumps.
Case A B1 B2 B3 B4
ΔT, hand calculation
72.0
54.0
46.3
25.9
22.3
ΔT, CFD-Simulation
80.0
59.6
49.5
26.6
23.7
ΔT with thermal contact resistance
Rt,c= 0.2 x 10-4 m2K/W --
33.9
28.4
Rt,c= 0.9 x 10-4 m2K/W
37.5
31.6
04/10/06

26. Detector Development Team (Very preliminary)
Sensors CERN 1 Phys Staff, 1 Fellow INFN Ferrara 1 PostDoc (tbc)
Analog electronics CERN 1 Eng, 1 Fellow (but...) INFN Torino 2 Eng
Electronic system & integration CERN 1 Eng INFN Ferrara (tbd) INFN Torino (tbd)
CERN staff (sensors and system) for the time being fully committed to LHC activities (ALICE SPD)
==> 2 FELL/DOCT student required (1 already available)
Mechanics & cooling CERN), Ferrara
04/10/06
G. Stefanini/LC WG/P326/GTK

27. Planning (Preliminary)
System architecture def. & simulation H1 YR1
Small scale prototype submission ≈ Q3 YR1
Engineering run 1 submission ≈ Q2 YR2
Engineering run 2 submission ≈ Q2 YR3
Production of final chip ≈ Q1 YR4
Detector assembly ≈ Q3 YR4
YR1 start of PH support & funding
04/10/06
G. Stefanini/LC WG/P326/GTK