1. Radiation Hardness of Low-Voltage
Differential Signal Driver
BY TOMMY LAM
August 5, 2016 1
University of Hawaii at Manoa
Summer 2016 SULI Symposium
2. August 5, 2016 2
Background
Super KEKB: Particle accelerator that collides
electrons into positrons at high energies in
Tsukuba, Japan
Belle Experiment: Contributed to awarding of 2008
Nobel Prize in Physics to Kobayashi and Maskawa
Belle II: Next generation experiment with plans to
collect 50 times the data
Introduction
3. August 5, 2016 3
Beam Exorcism for a Stable Belle II (BEAST):
International collaboration commissioned by Belle II to
Measure beam backgrounds
Ensure a safe environment for Belle II detectors
Time Projection Chamber: One of the BEAST
detectors
High speed neutron detector primarily for directional
detection
Data from pixel chip is sent out to readout hardware by
means of a low-voltage differential signal (LVDS) driver
Introduction
BEAST detectors surrounding the interaction point.
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Determine if the driver is radiation hard enough to
survive Phase 2, Phase 3, and beyond
Where: PNNL’s High Exposure Facility for their Co-60
source (35 Gy/Hr at 1m)
What: TPC’s LVDS Driver Electrical Component
TI’s LMH7220 High Speed Comparator with LVDS Output
Evaluation Criteria:
Will the chips work after irradiation?
Any change in performance due to radiation?
SULI Project Goals
5. August 5, 2016 5
Methods for testing
Unpowered chips (17)
Powered Chips: Powered and monitored
through driver-receiver system (3)
Expected to survive irradiation but
unknown if drivers would die immediately
or not after irradiation
Procedure
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Pre-test the unpowered chips with evaluation board
Irradiate Driver/Receiver system for two minutes to ensure survival
(about 30Gy at 20cm)
Irradiate System + 6 unpowered chips for 3 additional minutes and
check for functionality (about 2 Gy at 1m and additional 50 Gy at 20cm,
respectively)
Irradiate all chips for two hours (about 2000Gy at 20cm for powered
+13 unpowered, about 200Gy at 63cm for 4 unpowered)
Procedure
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Driver-Receiver Schematic
LVDS Driver LVDS
Receiver
G V
V Out
HitOr- HitOr+
In
Oscilloscope
Signal Generator
In+ In-
G
9130 Trigger
Output
Programmable DC
Power Supply
9310 Trigger
Output
Programmable DC
Power Supply
MSO-X-3054A Mixed
Signal Oscilloscope
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Evaluation Board
Oscilloscope
Signal Generator
AN-1534 Demo Board LMH7220 High
Speed LVDS Comparator
9310 Trigger
Output
Programmable DC
Power Supply
MSO-X-3054A Mixed Signal Oscilloscope
9. August 5, 2016 9
Irradiation at High Exposure Facility
0cm 20±2cm 63cm
Overall Picture
35 Gy/hr at 1m
Co-60 source
Distance from Source
1m
10. August 5, 2016 10
All the drivers still work!!!!!!!!!!!!!!!!!
No Performance Changes
Current draw remained constant
No change in signal for powered chips monitored during 2hr irradiation
No change in signal for unpowered chips before and after irradiation.
Results
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Overall: LVDS survived
Sufficient radiation hardness for phase 2 and 3
Could survive to full Belle 2 lifetime
Limitations:
Limited to Gamma Radiation due to cost and time constraints
Rate of Gy absorbed and its effect on components
Improvements
Test radiation hardness of drivers for neutron radiation
Increase exposure time to failure rate
Vary exposure times to gamma radiation
Conclusion
14. August 5, 2016 14
THE END
Thank-you very much for your attention!
