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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? • 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? • 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
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 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 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 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 Detection Glass – Alpha Detection Gd2O3 – Neutron Detection
DEVICE DESIGN 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 LAYERSMORE INFORMATION 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
Bottom layer— With a decay constant of 285 ns, the created photons do not produce a ringing pulse. RESULTS Top layer— With a decay constant of 2.3 ns, the created photons produce a ringing pulse.
PRINTED CIRCUIT BOARD High Voltage Power Converter Pulse Shaping
PRINTED CIRCUIT BOARD • Autoroute function to layout the copper traces after the components are placed. Design the printed circuit board using Eagle software.
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
Working Towards Cheap Pen Size Detector Fully integrated radiation detector Build smaller and cheaper components Integrated Circuits Miniaturized PM tube Goal 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