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Modeling of an Extraction Lens System
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  1. Modeling of an Extraction Lens System Thesis Defense Bachelor of Applied Science Karine Le Du Engineering Physics School of Engineering Science, SFU

  2. Overview • Dehnel Consulting Ltd. • Use of Commercial Cyclotrons • Cyclotron Components • Extraction Lens System • Scope of the Study • Computer Simulation Model • Results • Acknowledgements Thesis Defence Karine Le Du

  3. Current Expertise: • Complete Beamline Design • Injection System Design • Beamline Simulator Software • My Project… • Extraction Lens System Design • Future Endeavors • Ion Implantation Thesis Defence Karine Le Du

  4. Use of Commercial Cyclotrons • Radioisotopes for medical use • Detection of soft tissue damage • On-site at hospitals • Short half-lives of radioisotopes • Bombard target with protons • Necessitates beam of H¯ (hydride ions) Photo Courtesy of Ebco Technologies Inc. Thesis Defence Karine Le Du

  5. Injection Line Beamline Cyclotron Components Inflector Cyclotron Extraction Lenses Extraction Probe Ion Source Thesis Defence Karine Le Du

  6. Injection Line Beamline Cyclotron Components Inflector Cyclotron Extraction Lenses Extraction Probe Ion Source Thesis Defence Karine Le Du

  7. vacuum chamber z ~ 405mm beamstop ion source Extraction Lens Assembly Plasma lens Shoulder lens Extraction lens Assembly drawing courtesy of TRIUMF Thesis Defence Karine Le Du

  8. Scope of the Study • Purpose • Identify how changes to system parameters (dimensions and voltage potentials) affect H¯ beam characteristics • Provide data to aid an engineer in optimizing the design of an extraction lens system with regards to beam characteristics Thesis Defence Karine Le Du

  9. Beam Characteristics • Normalized Beam Emittance, εN • Describes size of beam in phase space • Energy normalized • Beam Current, I • Percent of beam transmitted • Low and high beam current applications • Beam Brightness, b Thesis Defence Karine Le Du

  10. Phase Space • Four important coordinates that completely describe an ion’s trajectory are (x, x’, y, y’) • (x, y): transverse position • (x’, y’): divergence from longitudinal axis • z: longitudinal position Thesis Defence Karine Le Du

  11. Beam ellipse x’ x Beam Size • Beam Size: • Area enclosed in beam ellipse • Beam Emittance: • Proportional to beam size Thesis Defence Karine Le Du

  12. Optimal Beam Characteristics • Normalized Beam Emittance, εN • minimize • Small emittance is more efficient • Beam Current, I • Depends on application • Beam Brightness, b • maximize • Achieved by maximizing beam current or minimizing normalized beam emittance Thesis Defence Karine Le Du

  13. Computer Simulation Model • SIMION 3D, Version 7.0, INEEL* • Model consists of 3 electrostatic lenses *Idaho National Engineering and Environmental Laboratory Thesis Defence Karine Le Du

  14. ASSUMPTIONS No plasma meniscus JUSTIFICATIONS Beyond the scope of this study Assumptions Made • No filter magnet • e¯ stripped out early • Ignored space charge repulsion and image forces • Beyond the scope of this study Thesis Defence Karine Le Du

  15. System Parameters • E1: Plasma Electrode • E2: Extraction Electrode • E3: Shoulder Electrode • V1: Voltage Potential of E1 • V2: “ “ of E2 • V3: “ “ of E3 • A1: Aperture of E1 • A2: “ “ E2 • A3: “ “ E3 • D12: Spacing between E1/E2 • D23: “ “ E2/E3 Thesis Defence Karine Le Du

  16. Table of Parameter Values Thesis Defence Karine Le Du

  17. General Trends Thesis Defence Karine Le Du

  18. General Trends Thesis Defence Karine Le Du

  19. b in [(mm·mrad)-2] N in [mm·mrad] Ion Trajectories Thesis Defence Karine Le Du

  20. Limitations/Future Work • Test results limited to ranges of parameter values tested • Test wider ranges of values • Beam loss occurred at downstream aperture of E2 • Downstream aperture had fixed size • May be cause of apparent ineffectiveness in changing A2 and A3 parameter values? • Implement space charge repulsion • Vary plasma meniscus curvature • Implement magnetic filter Thesis Defence Karine Le Du

  21. Acknowledgements • Dr. Morgan Dehnel • Excellent mentoring and guidance • Dr. John F. Cochran and Mr. Steve Whitmore • Invaluable feedback • My family • Support and encouragement • The Caskey Family, and friends • Support and encouragement Thesis Defence Karine Le Du

  22. Crude Beam Current Adjustment Thesis Defence Karine Le Du

  23. x X’ X’ z Beam Optics Thesis Defence Karine Le Du

  24. Normalized Emittance: Beam Size • Beam Emittance: • Ellipse Area: Thesis Defence Karine Le Du