1. Silicon Pixel Detector for the PHENIX experiment at the BNL RHIC
R. Ichimiya (RIKEN)
for the PHENIX/VTX Collaboration
R. Ichimiya PIXEL2008

2. Outline Introduction Silicon pixel Detector Summary PHENIX experiment
Requirements from the physics
Silicon pixel Detector
Silicon pixel detector system
Key components
High signal density signal bus
High throughput front-end ASIC
Summary
R. Ichimiya PIXEL2008

3. The PHENIX experiment at RHIC
The RHIC Collider
Located at BNL
The first collider of heavy ion
Top Energy:
√sNN = 200 GeV for Au-Au
10 times the energy previously available!
√total s = 40 TeV for Au+Au
Luminosity
Au-Au: 2 x 1026 cm-2 s-1
p-p : 2 x 1031 cm-2 s-1 (polarized)
The PHENIX experiment
Located at 8 O’clock on the RHIC
Experiments for
Heavy ion collision (QGP)
Polarized proton collision (spin physics)
R. Ichimiya PIXEL2008

4. The PHENIX experiment The PHENIX detector consists of
Two central arms to measure electron, photon, and hadrons
Three Global detectors for trigger and event characterization
Two forward muon spectrometers
They measure lepton, photon and hadron with
High rate and good Particle ID capability
Limited solid angle
Building Vertex detector gives
4p solid angle near the collision point
Precise vertex information especially for the heavy particles (bottom, charm).
Vertex detector
vertex
R. Ichimiya PIXEL2008

5. Pixel detector for vertex detector
Vertex measurement for heavy quarks (b, c) near the collision point:
Adds Silicon detectors near the collision point.
Forms cylindrical 4 layers at barrel region.
Inner 2 layers are pixel detectors. <= This talk.
We used the pixel detector which originally developed for Alice/LHBb experiment at LHC.
Modification and Optimization for this detector is the topic of this talk.
Outer 2 layers are strip (stripixel) detectors.
Rachid will give a talk at this afternoon.
Strip
decay point
Pixel
Heavy quark
Heavy ion
Vertex point
Heavy ion
Silicon vertex tracker
R. Ichimiya PIXEL2008

6. Pixel detector for vertex detector
Vertex measurement for heavy quarks (b, c) near the collision point:
　 Requirements for the Pixel detector
Collision Rate ~ 10MHz
-> Timing Resolution < 100nsec
Trigger Rate Max. ~20kHz
Occupancy < 1% for pixel detector
Tracking Resolution 50micron for displacement
Material Budget ~ 1% of radiation length
-> To prevent multiple scattering of charged particles and pair-creation of e+e- with g-ray.
This requires
High trigger rate
Thin
R. Ichimiya PIXEL2008

7. Pixel detector for vertex detector
Strip detector
VTX
Layer R1 R2 R3 R4
Geometrical dimensions
R (cm)
2.5 5 10 14
Dz (cm)
21.8
31.8
38.2
Area (cm2)
280
560
1960
3400
Channel count
Sensor size
R  z (cm2)
1.28  1.36
(256 × 32 pixels)
3.43 × 6.36
(384 × 2 strips)
Channel size
50  425 mm2
80 mm  3 cm
(effective 80  1000 mm2)
Sensors/ladder
4  4 6
Ladders 20 18 26
Sensors
160
320 90
156
Readout chips
1080
1872
Readout channels
1,310,720
2,621,440
138,240
239,616
Radiation length
(X/X0)
Sensor
0.22%
0.67 %
Readout
0.16%
0.64 %
Bus
0.28%
Ladder & cooling
0.78%
0.78 %
Total
1.44%
2.1 %
Total channel: 4Mch
Radiation length (X/X0): 1.44%
R. Ichimiya PIXEL2008

8. Pixel detector for vertex detector
Specification of the Pixel detector
p-in-n silicon pixel sensor
Width 200mm (MIP:15000e-)
32 x 256 (x4) pixel
Pixel size
50 x 425mm2
Sensitive area 12.8 x 13.6mm2
Depletion Voltage 〜8V
5cm wafer
50mm
425mm
1pixel of the pixel detector
R. Ichimiya PIXEL2008

9. Pixel detector system Pixel bus (half stave) Bus extender
Readout board
Four Signal layers
Wire bonding
Power Layers
Pixel sensor module
Bending point
Readout chip
Support & Cooling
PHENIX pixel bus
bump
20 mm
100um gluing with Araldite
R. Ichimiya PIXEL2008

10. Pixel bus Pixel bus (half stave) Bus extender SPIRO
250 mm
13.9mm
SPIRO
500 m
120 m
Width 30mm, spacing 30mm
Low material flexible PC board
Ultra high-density like IC substrate
& large scale (250mm).
R. Ichimiya PIXEL2008

11. High throughput front-end ASIC
ALICE readout board (MCM)
(near detector)
ALICE readout 1 2 3 4 5 6 7 8 9 10
32 bit
256 bit
Serial
Readout time:
256 x 10 x 106ns = 271ms
Trigger rate
3.6kHz
PHENIX readout
(far detector)
PHENIX readout
Data
128 bit 2 1
32 bit
Parallel
32 bit
Readout time:
256 x 2 x 106ns = 54.3ms
Trigger rate
18.2kHz
R. Ichimiya PIXEL2008

12. High throughput front-end ASIC
PHENIX readout
Data
128 bit
Parallel 2 1
32 bit 2 1
32 bit 2 1
32 bit 2 1
32 bit
To achieve fast trigger rate (~20kHz),
Readout board locates far detector to get space margin.
Introduce 4 parallel readout for the detector.
Developed double input width (64bit) front-end ASIC (Digital Pilot ASIC).
Expanded input and output data width.
~300 chips fabricated with same radiation tolerant process of IBM.
R. Ichimiya PIXEL2008

13. Summary
The PHENIX detector is being upgraded with Silicon detectors to get vertex information of heavy quarks by 2010.
Silicon Pixel detector is for inner 2 layers, it has
Low material budget (X/X0 =1.44%),
Fast trigger rate (~20kHz).
To achieve these requirement, we developed
Thin and high-density readout bus,
High throughput front-end ASIC (Digital Pilot ASIC).
Almost items has been developed and moving to production phase.
R. Ichimiya PIXEL2008