Radiation-Hard/High-Speed Data
Transmission Using Optical Links
Richard Kass
The Ohio State University
W. Fernando, K.K. Gan, A. Law, H.P. Kagan, R.D. Kass, J. Moore, D. S. Smith
The Ohio State University
OUTLINE
Introduction-ATLAS/Pixel Detector/SuperLHC
System Architecture-issues
0.13 μm opto-chip prototype
Summary
R. Kass
IEEE08/NSS
N64-4 1
The Current ATLAS Pixel Detector
ATLAS is a detector at CERN designed to study 14 TeV pp collisions
Detector upgrade planned for Super-LHC in 2016
Pixel Detector:
ATLAS’s Inner most charged particle tracker
Measures (x,y,z) to ~30 mm
Pixel detector is based on silicon
Pixel size 50mm by 400 mm ~80 million pixels
Radiation hardness is an issue
must last ~ 10 years
A pixel module contains:
1 sensor (2x6cm) ~40000 pixels
16 front end (FE) chips 2x8 array
Flex-hybrid
1 module control chip (MCC)
There are ~1744 modules
~1.85m
R. Kass
IEEE08/NSS
N64-4 2
Present Pixel Opto-link Architecture
Current optical link of pixel detector transmits signals at 80 Mb/s
Opto-link separated from FE modules by ~1m
transmit control & data signals (LVDS) to/from modules on micro twisted pairs
Use PIN/VCSEL arrays
Use 8 m of rad-hard/low-bandwidth SIMM fiber fusion
spliced to 70 m rad-tolerant/medium-bandwidth GRIN fiber
a Simplify opto-board and FE module production
a Sensitive optical components see lower radiation level than modules
a PIN/VCSEL arrays allow use of robust ribbon fiber
~80m
~1m
optoboard
VCSEL:
VDC:
PIN:
DORIC:
R. Kass
Vertical Cavity Surface Emitting Laser diode
VCSEL Driver Circuit
PiN diode
Digital Optical Receiver Integrated Circuit
IEEE08/NSS
optoboard holds VCSELs, VDCs, PINS
N64-4 3
SLHC Pixel Opto-link Architecture
published in: NIM A 555 (2005)
VDC
VCSEL
Housing
DORIC Pin array
2cm
Opto-pack
Present
Proposed
R. Kass
IEEE08/NSS
N64-4 4
R&D Issues for Super-LHC
Radiation hardness of all components
PIN array
VCSEL arrays
Opto-board ASICs: VDC, Receiver (replace DORIC)
SI (PIN) @ SLHC (3000fb-1)
1.5 x 1015 1-MeV neq/cm2
2.6 x 1015 p/cm2 or “69 Mrad” for 24 GeV protons
GaAs (VCSEL) @ SLHC (3000fb-1)
8.2 x 1015 1-MeV neq/cm2
1.6 x 1015 p/cm2 or “34 Mrad” for 24 GeV protons
Increased speed of components
Receiver: 160Mb/s or 320Mb/s
VDC: 3.2Gb/s
Clock multiplier: generates fast clock for 3.2Gb/s serializer
R. Kass
IEEE08/NSS
N64-4 5
Opto-Chip Prototype
Designed with 0.13μm process
640 Mb/s VCSEL Driver
3.2 Gb/s VCSEL Driver
640 MHz clock multipliers
(4 x 160 and 16 x 40 MHz)
PIN receiver/decoder
(40, 160, 320 MHz)
1.5 mm x 2.6 mm
R. Kass
IEEE08/NSS
N64-4 6
Testing the 0.13um Opto-Chips
Chips were tested in our lab at OSU
Chips were irradiated to SLHC dose at CERN
Use CERN’sT-7 beamline, 24 GeV protons to test:
8 VDCs 4 “Slow” & 4 “Fast”
4 Clock Multipliers
4 Purely Electrical Receivers
4 Receivers + 4 Si PIN (Taiwan)
Due to limitations in the cabling could only operate DORIC/VDC at 40Mb/s
Designed special card to allow testing of PLL at 640MHz
R. Kass
IEEE08/NSS
N64-4 7
VDC: VCSEL Driver Chip
Slow VDC 640 Mb/s
Fast VDC 1 Gb/s
Fast VDC 3.2 Gb/s
2.5Gb/s VCSEL+macro-package
not optimal
Both blocks (fast/slow) work in preliminary study
BER < 10-13 at 3.2 GB/s driving Optowell VCSEL
LVDS-like receiver works at high speed (3.2Gb/s)
Need detailed study with smaller/no package
PLCC
package
R. Kass
IEEE08/NSS
N64-4 8
VDC
Irradiation results
VDC driving 25Ω with constant Iset and 40MHz input signal
power supply
Fast VDC
Slow VDC
bright
dim
Decrease in drive current can be compensated by increase in Iset
R. Kass
IEEE08/NSS
N64-4 9
Receiver
PIN Receiver/Decoder Chip
Properly decodes 40, 80, & 160 Mb/s BPM signals
recovered clock jitter < 250/100/50 ps for 40/80/160 MHz (<1%)
LVDS-like output has good amplitude and baseline
Amplitude 475mV, baseline=0.625V
rise/fall time 125 ps
No significant degradation after irradiation to SLHC dose
40 Mb/s BER threshold for 1 bit error/s
supply current @1.5V
Peak to Peak thresholds
BER Threshold
R. Kass
IEEE08/NSS
N64-4 10
Clock Multiplier
Need to multiply recovered clock 160MHz/40MHz
up to 640MHz for serialization.
Both 4x and 16x clock multipliers work
Low Clock jitter < 8 ps (0.5%)
No change in current consumption after irradiation
BUT: Two of the four chips lost lock during irradiation & needed power cycling
to resume operation at 640 MHz
Could not reproduce this behavior at OSU on test bench
R. Kass
IEEE08/NSS
N64-4 11
Summary
J First 0.13μm chip submission mostly successful
J Full characterization of pre/post irradiation
in progress
Waiting for the chips to “cool off” so they can be shipped
from CERN to OSU
J Aim for next chip submission in winter 2009
Will irradiate the chips at CERN, summer 2009
R. Kass
IEEE08/NSS
N64-4 12
extra slides
R. Kass
IEEE08/NSS
N64-4 13
Setup for Irradiation in Shuttle at CERN
25 meter optical fiber
Opto-boards
Rad hard
optical
fibers
CERN T7
Remotely moves
in/out of beam
R. Kass
IEEE08/NSS
CERN T7
N64-4 14
Radiation-Hardness of PIN
Gb/s
GaAs
ULM
AOC
Optowell
Hamamatsu G8921
Si
Taiwan
Hamamatsu S5973
Hamamatsu S9055
R. Kass
4.25
2.5
3.125
2.5
1.0
1.0
1.5/2.0
IEEE08/NSS
Responsivity (A/W)
Pre
Post
0.50
0.13
0.60
0.19
0.60
0.25
0.50
0.32
0.55
0.47
0.25
0.33
0.37
0.21
N64-4 15
Real Time Monitoring in T7 Beam Test
Real time testing of opto-board system using loop-back setup
Compare transmitted and decoded data
measure minimum PIN current for no bit errors
Signal routed back to
Measure optical power
opto-baord via test board
25m optical
attached to 80-pin
connector & test board
Opto-board
fiber cable
bi-phase marked
optical signal
clock
PIN
DORIC
data
decoded data
VCSEL
VDC
decoded clock
VCSEL
VDC
In control room
Opto-Chip setup
In beam
Bit error test setup
at CERN’sT-7 beamline
24 GeV protons
Two VCSEL arrays
from same vendor
per opto-board
R. Kass
IEEE08/NSS
N64-4 16