smurf research at texas a&m dr. tye w. botting texas a&m university
TRANSCRIPT
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SMURF Research at Texas A&MSMURF Research at Texas A&M
Dr. Tye W. Botting
Texas A&M University
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Special
Microbeam
Utilization
Research
Facility
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OverviewOverview
IntroductionBrief BackgroundCurrent ResearchFuture InterestsClosing Comments
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BackgroundBackground
Synthetic Organic Chemistry• natural product precursor development
Environmental Testing• analytical equipment troubleshooting
Nuclear Chemistry• fission dynamics
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Fission DynamicsFission Dynamics
Neutron calorimetry• The TAMU Neutron Ball
Timescale of nuclear fission• compare two conflicting methods• 4 reactions analyzed in detail• statistical model analysis of data
FOR MORE INFO...
TAMU Cyclotron Institute (http://cyclotron.tamu.edu)
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Rate of Nuclear FissionRate of Nuclear Fission
Two “clocks” that did not seem to agree• Neutron evaporation clock• Giant Dipole Resonance (GDR) -ray clock
Required 150+ detectors• ~500 parameters per event• Required statistics produced 80+ GB of data
Statistical model calculations• Monte Carlo methods• Comparison with experiment yielded timescales
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So, how fast So, how fast isis nuclear fission? nuclear fission?
Very fast!
~110-20 seconds
for medium-energy reactions
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Current ResearchCurrent Research
Accelerator Development• Improvements and additions
Physics / Engineering• Krypton gas neutron detector• Hot water energy reclamation
Health Physics• Microdosimetry
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Accelerator DevelopmentAccelerator Development
Ion source stabilityBeam developmentSoftware development
• Accelerator control• Microbeam targeting
Additions
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Physics / EngineeringPhysics / Engineering
Improve understanding of the interaction of neutrons with matter
Develop new detector technologies Energy conservation / reclamation
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Health PhysicsHealth Physics
Our main objective is to achieve a better understanding of risk to human health from everyday exposure to low doses of ionizing radiation.
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Health Physics…Health Physics…
Evalaution of risk at low radiation doses has been based on linear extrapolation of observed effects of very high doses.
There are problems with this approach…
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Health PhysicsHealth Physics
High-dose radiation exposure results in individual cells receiving multiple hits
Low-dose radiation exposure consists of sparsely distributed single hits
No reason to expect that a low-dose linear extrapolation model should work
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Our ApproachOur Approach
Investigate both high- and low- linear energy transfer (LET) radiations
• positive ions (high LET)• electrons and X Rays (low LET)
Irradiate specific cells in vitro• use low doses directly• a line of cells on a dish, on individual cells• look for microscopic effects
– mutations
– cell-cell communication
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ToolsTools
• Positive ion accelerator• 2MV Tandem Van de Graaff
• Electron accelerator• 100keV electrostatic accelerator
• X-ray apparatus• 1 Gray/min at Emax=250keV
• Hot water reflux apparatus• trial run in progress
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2MV Tandem Van de Graaff2MV Tandem Van de Graaff
Alphatross Ion SourceBending and Focusing ElementsCharging System
• Tandem = “double ended”• Produces 4 MeV protons, 6 MeV alphas
Experimental Beam Lines• Neutron “beam”• Positive-Ion Microbeam
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Ion Source
Accelerator Tank
Magnet
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Accelerator Tank Magnet
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Pelletron Charging SystemPelletron Charging System
Illustration courtesy of...
National Electrostatics Corp. (http://www.pelletron.com)
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Experimental BeamlinesExperimental Beamlines
Neutron “beam”• Protons incident on LiF target
Positive-Ion Microbeam• 5m beam thickness• Targeting
– Individual cell nuclei– Line traces
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Microscope Assembly direct and camera
Detectors (3 photomultipliers) special petri dishes go below
Fine collimators 2 sets of x and y axes
Beam Stop
Coarse collimators 1 set, only y axis
Microbeam
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Cell culture dishesCell culture dishes
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Electron AcceleratorElectron Accelerator
Only 4 feet high
Different type of collimator assembly
Accelerator tube has up to 100,000 Volts to produce up to 100keV electrons
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ResultsResults
Accelerator Development• Improved ion-source stability• Added positive-ion microbeam assembly
– Made its endstation software functional
• Developed usable proton and neutron beams• Added neutron production beam line and facility• Always a work in progress!
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Results…Results…
Physics / Engineering• Krypton gas neutron detector experiments run
– Data still being analyzed to determine next step(s)
• Hot water energy conservation / reclamation– Designed apparatus
– Construction nearing completion
– Should begin trial runs within the month
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Results…Results…
Health Physics• X-ray irradiations (adapt and challenge)
– Appears low doses good for cell survival upon later higher-dose exposure
• Positive-ion irradiations– Mixed low-dose results (cell-line effect?)
• Electron irradiations– Appears that low fluence low-LET radiation is not
as damaging as predicted by the linear extrapolation model
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Results NotesResults Notes
An interesting observation has arisen that irradiation of petri dishes prior to cell culturing seems to contribute to in vitro cell death.
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Future DirectionsFuture Directions
At TAMU:• Continued accelerator development• Continued microbeam work
– Perhaps non-biological applications
• Further refinement of the Kr n-detectors• Hot water energy reclamation trial runs• Acquiring PIXE/RBS capability
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Wider Future Directions…Wider Future Directions…
• Using PIXE/RBS to characterize surface pollution and degradation• Further investigation of irradiation pre-
treatment as a bio-inhibitory• Application of nuclear science methods in
materials science in general
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Thank you all very much for your time and for the opportunity to visit both NCPTT and NSULA.