Transcript NANOPARTICLE LOADED RADIATION DETECTORS

A COMPLETE MICRO/NANOSYSTEM
SOLUTION FOR ALPHA, BETA, GAMMA,
AND NEUTRON DETECTION
Dr. Chester Wilson
Louisiana Tech University
President, Cybercorps Interactive
Why Is Nuclear Energy a Big
Part of The Answer?
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Decades of operational safety exceeding other
energy producers.
Zero greenhouse gas emissions.
Fantastic power densities.
Domestic energy production.
Why Is Nuclear Energy a Big
Part of The Answer?
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Decades of operational safety exceeding other
energy producers.
Zero greenhouse gas emissions.
Fantastic power densities.
Domestic energy production.
Around 40% of plant fuel comes from
reprocessed ex-soviet nuclear weapons.
Weapons Grade Plutonium
Becoming Energy
Other Guys Want it Too
Traditional Radiation
Detectors
Traditional Method of
Detection is Geiger
Counter.
Problem: Most detect Alphas,
Betas, Gammas, but not
Neutrons.
He3 and BF3 tubes detect
neutrons, but are toxic and
expensive.
Traditional Radiation
Detectors
Traditional Method of
Detection is Geiger
Counter.
Problem: Most detect Alphas,
Betas, Gammas, but not
Neutrons.
He3 and BF3 tubes detect
neutrons, but are toxic and
expensive.
Important because weapons grade
plutonium emits neutrons, not much
else does
How do you shield
neutrons?
Terrorist
Nuclear
Bomb
Lead ?
Bomb Maker
Neutrons vs. Lead
Neutron interacting with Pb
• Since the mass of the
neutron is much smaller
than the larger Pb atoms,
the neutron recoils without
losing much energy. The
neutrons continuously
bounce around able to exit
the lead shielding.
NEED FOR DETECTORS
Terrorist
Nuclear
Bomb
Plastic ?
Bomb Maker
NEED FOR DETECTORS
Neutron interacting with H
• Since the mass of the
neutron is approximately
equal to the H atoms, the
neutron can transfer up to
its full energy. The recoil H
nuclei has a small range
losing energy quickly.
Nanoparticle Neutron Detection
Gadolinium oxide is
opaque, but…
Transparency! This scintillator is loaded with
30% gadolinium oxide, but because the
nanoparticles are too small to scatter light, it is
transparent.
And this allows a patternable film to make imaging
Arrays with better spatial resolution and gamma
selectivity.
Nanoparticle Neutron Detection
Neutron detection is enabled through
gadolinium nanoparticles, 255,000 barn
absorption: 1000X smaller than anything else.
Measurements taken at Entergy Nuclear’s Grand Gulf Facility
Four Channel Device
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Problem: limited to the types of radiation detected
Solution: dope with charge conversion nanoparticles
Radiation impinging on tailored nanoparticles create
electrons, which scintillates a background matrix.
WO3 – Beta Detection
Glass – Alpha Detection
Pb3O4 – Gamma/X-ray Detection
Gd2O3 – Neutron Detection
DEVICE DESIGN
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Four channels embedded into a sandblasted glass
substrate
Optical cross talk barrier to reduce cross talk
between detector channels
RESULTS
Gamma detection—
60Co
emits both gammas and
betas so lead sheets are used
to block betas in order to
detect only gammas and
demonstrate the difficulty in
shielding gammas.
Pulse height spectroscopy—
Tailored resins use different
conversion mechanisms producing
varying PM tube outputs
MULTIPLE LAYERS
MORE INFORMATION
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Varying thicknesses for top layer scintillator allows
for different count rates
Energy spectroscopy capability by determining
where the energy deposition took place as a
function of top layer thickness
RESULTS
Top layer—
With a decay constant of
2.3 ns, the created photons
produce a ringing pulse.
Bottom layer—
With a decay constant of
285 ns, the created photons do
not produce a ringing pulse.
PRINTED CIRCUIT BOARD
Power
Converter
High Voltage
Pulse
Shaping
PRINTED CIRCUIT BOARD
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Design the printed circuit board using Eagle
software.
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Autoroute function
to layout the copper
traces after the
components are
placed.
Microscale
Photomultiplier Tube
• Photomultiplier tube components
• Photocathode
• Series of Dynodes
• Anode
Beating the State of the Art
• The count rates increase from non-doped scintillator
to heavier doped scintillator.
• Neutron sensitivity around 11% vs. around 0.2% on
tube
0%
1%
5%
10%
BF3 tube
Counts per Minute
1400000
1200000
1000000
800000
600000
400000
200000
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0
0.5
1
1.5
2
Thickness (mm)
2.5
3
Working Towards Cheap
Pen Size Detector
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Fully integrated radiation detector
Build smaller and cheaper components
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Integrated Circuits
Miniaturized PM tube
Goal
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Hockey puck style detector
Pager sized
Eventually pen sized
Thanks
Funding Sources:
•Entergy Nuclear
•Department of Energy
•National Science
Foundation
•Office of the Director of
National Intelligence