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Development of an Electron Microbeam for Cell Culture Studies

Development of an Electron Microbeam for Cell Culture Studies. T. W. Botting, L. A. Braby, and J. R. Ford Texas A&M University. Overview. Background Construction Operation Current Experiments Future. Objective.

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Development of an Electron Microbeam for Cell Culture Studies

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  1. Development of an Electron Microbeam for Cell Culture Studies T. W. Botting, L. A. Braby, and J. R. Ford Texas A&M University

  2. Overview • Background • Construction • Operation • Current Experiments • Future

  3. Objective Our main objective is to achieve a better understanding of the risk to human health due to everyday exposure to low doses of ionizing radiation.

  4. Most occupational and public radiation exposures are due to x and g rays so concern is about the effects of small numbers of moderate energy electrons (10 to 1000 keV)

  5. How do we study this directly? • Need source for low-to-moderate energy electrons • Need method to deliver them exactly where desired • We have used an electron microbeam to try to quantify bystander effects produced by moderate energy electrons

  6. mbeam delivery of electron dose • Targeting • irradiation paths • discrete locations • Dose • duration • intensity • Energy

  7. Electron Beam Production • Electron source • low-power tungsten filament • low voltage power supply • isolation transformer • Accelerator Tube • custom-made 3-section ceramic • equipotential rings • high voltage power supply

  8. Beam Delivery • Collimator Assembly • capillary tube • swivel mounts for alignment • Cell dish stage • x-y motion control • Microscope and camera • targeting

  9. Electron Microbeam Apparatus Less than 4 feet high Capillary-style collimator Accelerator tube up to 100,000 Volts to produce up to 100keV electrons

  10. Source and Accelerator \ Faraday Cup control Turbo pump - Equipotential rings / - Accelerator tube Voltage dividers - - Source

  11. 3D Schematic

  12. Collimator Stand and Microscope CCD camera - Light Source / - Stage X-Y motion control | \ Capillary Collimator

  13. Cell culture dishes

  14. Final Construction Details • Voltage dividers • 30 MW per tube section for smooth gradient • Exit collimation • 5mm and 300mm exit aperatures • Exit window • 2mm thick mylar (same as cell dishes)

  15. Operation • Electron source • provides electron beam up to 1 nanoamp on the Faraday cup • Stable at up to 85 kV so far • beams at up to 90kV • Software control of targeting • line traces • discrete spots

  16. Desired Improvements • Beam stability • Beam current • Beam transmission

  17. Bystander Effect Experiments • Irradiate nearly confluent cells • CDKN1A and PCNA versus distance • AG 1522 human fibroblasts • Clone 9 rat liver line • RIE mouse intestine line • HBEC human primary bronchial cells • Micronuclei assay • AG 1522 human fibroblasts

  18. Some Future Directions… • Further micronuclei assays • Clone 9 rat liver line • RIE mouse intestine line • HBEC human primary bronchial cells • NTEC Rat primary tracheal cells • All three methods (CDKN1A, PCNA, micronuclei) • Complete comparison matrix with our positive ion mbeam results as a control

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