P326 Gigatracker Pixel Detector

baconossifiedMechanics

Oct 29, 2013 (3 years and 8 months ago)

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04/10/06

G. Stefanini/LC WG/P326/GTK

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

P326 Proposal



10
-
11

branching ratio



high intensity K beam



high background rejection




≈ 5.10
12

K decays/year



≈ 100 events by 2011

04/10/06

G. Stefanini/LC WG/P326/GTK

3

P326 Beam


modified NA48 K12 beam line


3.10
12

protons on target (400GeV) ==> 60% pions, 20% protons, 14% electrons,
6% kaons


overall particle rate ≈ 0.8GHz ==> “Gigatracker”


beam cross
-
section ≈ 12cm
2
at GTK

Tracking, momentum, time stamp

04/10/06

G. Stefanini/LC WG/P326/GTK

4

GTK Si Pixels


P. Riedler

04/10/06

5

Required Gigatracker time resolution

P(>1hit in
D
t) =1
-
exp(
-
D
t*rate)


D
t (
±
2
s
) @0.8GHZ @1GHZ

400 27% 33%

500 33% 39%

600 38% 45%

Dependence of the signal to

background
(from
K
+


p
+
p
0

)

as a function of the gigatracker

time resolution


K
+


p
+
p
0


04/10/06

G. Stefanini/LC WG/P326/GTK

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%X
o

per plane

04/10/06

G. Stefanini/LC WG/P326/GTK

7

Radiation Levels in Gigatracker (GTK)


Calculated fluence

≈ 2. 10
14

(1 MeV n
eq

cm
-
2
)

100 days



For comparison:


ATLAS SCT/CMS TK

≈ 1.5 10
14

(1 MeV n
eq

cm
-
2
)

10 years



Safety factors in estimates



04/10/06

G. Stefanini/LC WG/P326/GTK

8

GTK Hybrid Pixel Design Parameters
(Preliminary)


Pixel cell size

300
m
m x 300
m
m


Sensor thickness

200
m
m


charge collection time vs signal amplitude


Pixel chip thickness

≤ 100
m
m


Bump bonding

Pb
-
Sn


Material budget


≈ 0.4% X
0
(each station)


Operating temp.

T ≤ 5
°
C (in vacuum)


Cooling

≈ 120
m
m CF radiator/support with


peripheral cooling

hybrid pixels

04/10/06

G. Stefanini/LC WG/P326/GTK

9

Si Sensors


Radiation effects


type inversion (higher V
b

required)


leakage current increase


D
I
vol
=
a f
ne
(
a

≈ 5 x

10
-
17

A/cm)


Remedies


M
-
CZ material (to be studied)


operation at low(er) temp (in vacuum...)


I


exp(
-
E
g
/2kT)



(up to ≈ 200
m
A/cm
2

@ 25
°
C )


D
I reduction ≈ 16x @ 0
°
C


periodic replacement of station


04/10/06

G. Stefanini/LC WG/P326/GTK

10

GTK Pixel ASIC


Technology: CMOS8 (0.13
m
m)



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
(CMOS6 0.25
m
m)

8,192 pixel cells

04/10/06

G. Stefanini/LC WG/P326/GTK

11

Bump Bonding


Bump bonding of 150
m
m pixel chips to
200
m
m sensors: in volume production
(ALICE SPD 10
7

pixels)


Pb
-
Sn (VTT/Finland)


Thinning of pixel wafers (D=200mm) is
done after bump deposition


Thinning/bb to 100
m
m (or less)
requires prototyping


Preliminary test under way with ALICE
pixel dummy wafers


Key issue: flatness of sensors


©VTT

Pb
-
Sn

~20
-
25
µ
m

04/10/06

G. Stefanini/LC WG/P326/GTK

12

Readout Wafer Thinning


200mm Si wafer thinned to 150
m
m


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

04/10/064 July, 2006

A. Kluge

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

24 mm

12 mm

6 mm

04/10/06

G. Stefanini/LC WG/P326/GTK

17

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%)


04/10/064 July, 2006

A. Kluge

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 mm
2


Pixel size 300 um x 300 um


=> 40 x 40 pixels = 1600 pixels



Avg Rate of center column: ~ 96 MHz/cm
2


=> 86 kHz/pixel


=> 138 MHz/chip


=> 138 MHz/chip * ~ 32 bit = ~4.4 Gbit/s

04/10/06

G. Stefanini/LC WG/P326/GTK

19

Cooling


Power dissipation (pixel plane) ≈ 20W


Operating temperature < 5
°
C (==> sensor leakage current)


CF radiator fins coupled to cooling circuit


Adhesive/filler (≈ 50
m
m) thermal conductivity ≈ 1 W/(m K)


Cooling system options


fluid coolant


evaporative cooling


C
4
F
10


C
4
F
8


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


(Si @ T=300K)



Density (g/cm
3

)


≈ 1.9/2.2



X
0

(g/cm
2
)


≈ 42



(≈ 21 cm)









(≈ 9.36cm for Si)


2
-
ply radiator thickness

≈ 120
m
m

04/10/06

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 i
deal contact between materials

Case


A


B1


B2


B3


B4

04/10/06

23

Temperature gradient of the Silicon Pi
xel detector
in dependence of the
thermal conducti
vity of the
cooling

plane

04/10/06

24

Results with
thermal resistance between
materials

04/10/06

25

Influe
nce 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

Δ
T, hand calculation

72.0

54.0

46.3

25.9

22.3

Δ
T, CFD
-
Simulation

80.0

59.6

49.5

26.6

23.7

Δ
T with thermal contact
resistance

R
t,c
= 0.2 x 10
-
4
m
2
K/W

--

--

--

33.9

28.4

Δ
T with thermal contact
resistance

R
t,c
= 0.9 x 10
-
4
m
2
K/W

--

--

--

37.5

31.6

04/10/06

G. Stefanini/LC WG/P326/GTK

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