1. GridPix Een Detector R & D project voor: Large TPC for ILC
GOSSIP & the ATLAS SCT Upgrade
Harry van der Graaf
NIKHEF, Amsterdam
Electronische Afdeling,
Nikhef April 4, 2007

2. Time Projection Chamber (TPC): 2D/3D Drift Chamber
The Ultimate Wire (drift) Chamber
track of
charged
particle
E-field
(and B-field)
Wire plane
Wire Plane +
Readout Pads
Pad plane

3. Problem With wires: measure charge distribution over cathode pads:
c.o.g. is a good measure for track position;
With GEMs or Micromegas: narrow charge distribution
(only electron movement)
avalanche
GEM
wire
Micromegas
Cathode pads
Solutions: - cover pads with resisitive layer
- ‘Chevron’ pads
- many small pads: pixels!

4. The MediPix2 pixel CMOS chip
256 x 256 pixels
pixel pitch: 55 x 55 μm2
Within each pixel:
preamp + shaper + discr
14-bits counter
discr. thresholds
Developed by MediPix
Consortium, CERN
We apply the ‘naked’ MediPix2 chip
without X-ray convertor!

6. MediPix2 & Micromegas MediPix2 pixel sensor Brass spacer block
55Fe
Cathode (drift) plane
Drift space: 15 mm
Micromegas
Baseplate
MediPix2 pixel sensor
Brass spacer block
Printed circuit board
Aluminum base plate
Very strong E-field above (CMOS) MediPix!

8. He/Isobutane
80/20
Modified MediPix
δ-ray!
Efficiency for
detecting single
electrons:
< 95 %

9. InGrid Integrate GEM/Micromegas and pixel sensor: ‘GEM’ ‘Micromegas’
By ‘wafer post processing’

10. InGrid VS Micromegas Micromegas Electroforming tech. Large areas
Large pillar Ø (250 µm)
Hybrid detector
Manual mounting
InGrid
Micro-electronic tech.
Wafer scale areas
Minimum pillar Ø (30 µm)
Integrated detector
Compact / Mass producible
All geometric parameters accurately controlled
Gap, Holes, Supporting structures

11. Suspended membrane 50 µm above the wafer
Processing InGrids
Strips Litho.
50 µm SU8
UV Exposure
Holes Litho.
0.8 µm Al
Suspended membrane 50 µm above the wafer
Development

12. Prototypes Hex / Pillars Square / Pillars Square / Walls
19 different fields of 15 mm Ø
2 bonding pads / fields
Square / Pillars
Square / Walls
Square / Pillars

13. Experimental Setup 55Fe collimated source Gas sealed chamber
Grid to HV
Cathode to HV
Anode to ground
Connectors to 10 MΩ resistors in series with electrodes

14. Energy resolution in Argon IsoC4H10 80/20
Observation of two lines:
5.9 keV
6.4 keV
FWHM of the Kα distribution
16.7 %
Gain fluctuations
< 5%
Very good energy resolution:
Very precise dimensions d < 0.1 μm

15. Other applications of GridPix:
μ-TPC
Transition Radiation Detectors
GOSSIP: tracker for intense radiation environment

16. The ATLAS Detector

17. ATLAS Semiconductor Tracker (SCT)

18. Lifetime measured from secondary vertex ct ~ 100 micron
Inner Tracker: record all tracks of charged particles For instance: lifetime measurement
Heavy quark mesons….
Lifetime measured from secondary vertex ct ~ 100 micron
Take Lorentz boost into account

19. ALEPH event display

20. Vertexing High spatial resolution low mass low power fast
 Semiconductor pixel detector
Vertex determination
Few points
accuracy O( mm)

21. Semiconductor (pixel, strip) detectors
Depleted Si, 300 μm
Vbias = 150 V
electron-hole
pairs
(pixel) chip with
preamps, shapers,
discriminators

22. ATLAS pixel: basic element
C-C support
sensor
Flex Hybrid
bumps
MCC
Side view
not to scale
Wire-bonding FE’s
Wire-bonding MCC
FE chip
Flex module 2.x

23. The ATLAS Vertex Pixel Detector
~2.0 m2 of sensitive area with 0.8  108 channels
50 m  400 m silicon pixels (50 m  300 m in the B- layer)
Three barrel layers
Three disk layers

24. Barrel SCT unit
EndCap SCT unit

25. barrel SCT
Two of the SCT barrel
support structures

26. Barrel and EndCap SCT

27. Transition Radiation Tracker
X-ray quanta e- π-
Transition Radiation Tracker

28. Si (vertex) track detector GOSSIP
Cluster3
Cathode (drift) plane
Integrated Grid (InGrid)
Cluster2
Cluster1
Slimmed Silicon Readout chip
Input pixel
1mm,
100V
50um,
400V
50um
CMOS chip
Si depletion layer
Vbias
Gas: 1 mm as detection medium
99 % chance to have at least 1 e-
Gas amplification ~ 1000:
Single electron sensitive
All signals arrive within 16 ns
Si strip detectors
Si pixel detectors
MAPs

29. GOSSIP: Gas On Slimmed SIlicon Pixels
MIP
MIP
InGrid
Cathode foil
CMOS pixel array
CMOS chip
‘slimmed’ to 30 μm
Drift gap: 1 mm
Max drift time: 16 ns
GOSSIP: Gas On Slimmed SIlicon Pixels

30. Gas instead of Si Pro: Con:
no radiation damage in sensor: gas is exchanged
modest pixel (analog) input circuitry: low power, little space
no bias current: simple input circuit
CMOS pixel chip main task: data storage & communication (rad hard)
low detector material budget: 0.06 % radiation length/layer
typical: Si foil. New mechanical concepts:
self-supporting pressurized co-centric balloons; ‘laundry line’
low power dissipation : little FE power (2 μW/pixel); no bias dissipation
operates at room temperature (but other temperatures are OK)
less sensitive for neutron and X-ray background
3D track info per layer if drift time is measured
Con:
Gaseous chamber: discharges (sparks): destroy CMOS chip
gas-filled proportional chamber: ‘chamber ageing’
Needs gas flow
Parallax error: 1 ns drift time measurement may be required

31. Discharges
Vonken

32. Silicon Protection: SiProt
CMOS Chip protection against - discharges
- sparks
- HV breakdowns
- too large signals
Silicon Protection: SiProt
Amorph Si (segmented)
Emperical method:
Try RPC technology

33. - ‘Directe’ schade door heet plasma: afwezig
MediPix+SiProt+InGrid
Levensduur: 12 h
He/Isobutane
Met 3 μm SiProt:
- ‘Directe’ schade door heet plasma: afwezig
te groot ladingssignaal voor pixel electronica 
Dikkere SiProt laag (20, 30 , 40, 50 μm ! )
Protectie circuit in pixel
SiProt aan onderkant van InGrid
!!Als dikkere SiProt niet werkt:
MPW test (Gossipo-3)
600 kE nodig voor nieuwe full-scale pixel chip!!

34. A-Si not adequate? Then TwinGrid

35. Irradiation with 8 keV X-rays: No rate effects up to anode current density of 0.2 μA / mm2  very fast track counting possible!
After 0.3 Coulomb/mm2:
 (eq. 3.7 x 1016 MIPs/cm2 !!)
deposit of carbon polymer on anode is clearly visible. Micromegas is clean (!?)
Little deposit on cathode, and……
Chamber still worked!
Ageing

36. Nieuwe Pixel Chips voor GridPix/Gossip

37. GOSSIPO-1: test of preamp-shaper-discriminator for GOSSIP
‘MultiProjectWafer’ in 0.13 μm technology
GOSSIPO chip
Submitted December 2005.
Input pad
Substrate
Cfb=1fF
Ground plane
Output M1 M2 M3 M6 LM
Ground
Very low (parasitic) capacitance
at the input (Cpar → 10 fF) .
Cpar = 10fF…50fF
Parasitic metal-to-metal fringe capacitances.
Coaxial-like layout of the input-feedback interconnection.

38. GOSSIPO (RO-FE) chip design
- match extreme small source capacity: 10 fF
peaking time: 40 ns
noise (expected: 60 e- input eq.)
power: 2 μW/pixel (!)
Triple Well technology: separation of analog and digital ground
100 MHz clock close to analog circuit
Threshold setting (6 x 60 e-) fine!
Effect of digital switching on pixel
analog signal negligible
Vthreshold = 350 e-
discriminator output

39. Maart – Juni 2006: Gossip-DAQ werkgroep

40. GOSSIPO-2 0.13 μm technology test of preamp-shaper-discriminator and
700 MHz TDC per pixel
0.13 μm technology
containing 16 x 16 pixels
Submission Nov 29, 2006
Can be used for GOSSIP demo!
3 x 2 mm2

41. Proposed FE architecture for data communication
pixel
700 MHz
oscillator
avalanche
input pad
start
AmpShaDisc
BX clock
stop
40 MHz
BXcounter
memory 1
BX-ID +Tdrift +Ttime-over-threshold
16 bits
memory 2
BX-ID +Tdrift +Ttime-over-threshold
16 bits
valid BX
DAQ
bus
pixel-ID + Tdrift + TtimeOverthreshold

42. New mechanical concept
(virtual) target: pixel SLHC
Inventarisation of all services to detector units
Integration of services, detectors and support mechanics
services:
cooling
power
data communication
gas

43. New mechanics + cooling concepts for Gossip
As little as possible material
detector consists of foil!
less power required ( less cooling) w.r.t. Si
‘laundry line’
‘balloon’
string: power, chip support, cooling
in 2030….

44. Minimum Material Budget
(% rad length)
Z = 0 mm
Z = +/-600 mm
Gossip detector (50 μm Si)
Cooling (stainless steel tube)
Power (max 0.28 mm aluminium)
Data transfer (max 1.7 mm kapton)
total
angle correction x √ x 2 x √2 3

45. New concepts for optical fiber data transfer
FE chip
laser
Interferometer
rates up to 40 Gb/s
geen materiaal en dissipatie op chip
met 240 Gb/s: ‘all data to shore’: trigger possible

46. Virtual goal: ATLAS pixel vertex
- Ladder strings fixed to end cones
Integration of beam pipe, end cones & pixel vertex detector
5 double layers seems feasible

47. ladder cross section ladder side view ladder top view
data lines (Cu/kapton)
ladder cross section
casted aluminium
Gossip chip + InGrid
drift gap
cathode foil
Stainless steel tube: - string
- power
- CO2 cooling
ladder side view
ladder top view

48. First practical GOSSIP
with
CMS Vertex Pixel FE chip: PSI 46 (+ ATLAS FE pixel chip?)
apply A-Si protection layer
apply InGrid
mount Gossips on pcb: ‘ beam telescope’
Testbeam end 2006
Nijmegen, NIKHEF (,PSI?)

49. Gossip projects at NIKHEF/Univ. Twente/Saclay/CERN
Discharge protection
InGrid/TwinGrid/TripleGrid
Construction of detector: MediPix2 + SiProt + InGrid NewNext-1!
Construction of detector: TimePix + SiProt + InGrid NewNext-1
- Gossipo chip developments
Development of ‘beam telescope’ Gossip demo
Vertex track simulations: signal development, DAQ data streams
- Study of ‘services’ required for Gossip/SLHC:
assume dose rate of 12 tracks/(cm ns)
definition of cooling;
definition of data transfer connection;
definition of power lines
- Ladder prototype: thermal modeling; Design of SS/Alu multifunctional string;
test (mech + thermal) of mechanical model
CO2 cooling: ATLAS/NIKHEF project
Ageing studies