SMURF Research at Texas A&MSMURF Research at Texas A&M

Dr. Tye W. Botting

Texas A&M University

Special

Microbeam

Utilization

Research

Facility

OverviewOverview

IntroductionBrief BackgroundCurrent ResearchFuture InterestsClosing Comments

BackgroundBackground

Synthetic Organic Chemistry• natural product precursor development

Environmental Testing• analytical equipment troubleshooting

Nuclear Chemistry• fission dynamics

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)

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

So, how fast So, how fast isis nuclear fission? nuclear fission?

Very fast!

~110-20 seconds

for medium-energy reactions

Current ResearchCurrent Research

Accelerator Development• Improvements and additions

Physics / Engineering• Krypton gas neutron detector• Hot water energy reclamation

Health Physics• Microdosimetry

Accelerator DevelopmentAccelerator Development

Ion source stabilityBeam developmentSoftware development

• Accelerator control• Microbeam targeting

Additions

Physics / EngineeringPhysics / Engineering

Improve understanding of the interaction of neutrons with matter

Develop new detector technologies Energy conservation / reclamation

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.

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…

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

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

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

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

Ion Source

Accelerator Tank

Magnet

Accelerator Tank Magnet

Pelletron Charging SystemPelletron Charging System

Illustration courtesy of...

National Electrostatics Corp. (http://www.pelletron.com)

Experimental BeamlinesExperimental Beamlines

Neutron “beam”• Protons incident on LiF target

Positive-Ion Microbeam• 5m beam thickness• Targeting

– Individual cell nuclei– Line traces

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

Cell culture dishesCell culture dishes

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

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!

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

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

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.

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

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

Thank you all very much for your time and for the opportunity to visit both NCPTT and NSULA.