A COMPLETE MICRO/NANOSYSTEM SOLUTION FOR ALPHA, BETA, GAMMA,

AND NEUTRON DETECTION

Dr. Chester Wilson

Louisiana Tech UniversityPresident, Cybercorps Interactive

Why Is Nuclear Energy a BigPart of The Answer?

• Decades of operational safety exceeding other energy producers.

• Zero greenhouse gas emissions.• Fantastic power densities.• Domestic energy production.

Why Is Nuclear Energy a BigPart of The Answer?

• 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 PlutoniumBecoming 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?

NuclearBomb

Bomb Maker

Terrorist

Lead ?

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

NuclearBomb

Bomb Maker

Terrorist

Plastic ?

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.

Transparency! This scintillator is loaded with 30% gadolinium oxide, but because the nanoparticles are too small to scatter light, it is transparent.

Gadolinium oxide is opaque, but…

Nanoparticle Neutron Detection

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

• 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 Pb3O4 – Gamma/X-ray DetectionGlass – Alpha Detection Gd2O3 – Neutron Detection

Four Channel Device

• Four channels embedded into a sandblasted glass substrate

• Optical cross talk barrier to reduce cross talk between detector channels

DEVICE DESIGN

RESULTSGamma 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

• 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

MULTIPLE LAYERSMORE INFORMATION

Top layer—With a decay constant of 2.3 ns, the created photons produce a ringing pulse.

RESULTSBottom layer—

With a decay constant of 285 ns, the created photons do not produce a ringing pulse.

Power Converter

PRINTED CIRCUIT BOARD

High Voltage

Pulse Shaping

• Design the printed circuit board using Eagle software.

PRINTED CIRCUIT BOARD

• Autoroute function to layout the copper traces after the components are placed.

• Photocathode• Series of Dynodes• Anode

Microscale Photomultiplier Tube

• Photomultiplier tube components

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

• Fully integrated radiation detector• Build smaller and cheaper components

• Integrated Circuits• Miniaturized PM tube

• Goal• Hockey puck style detector• Pager sized• Eventually pen sized

Working Towards Cheap Pen Size Detector

Thanks Funding Sources:

•Entergy Nuclear•Department of Energy•National Science Foundation•Office of the Director of National Intelligence