Modeling of an Extraction Lens System Thesis Defense Bachelor of Applied Science Karine Le Du Engineering Physics School of Engineering Science, SFU
Overview Dehnel Consulting Ltd. Use of Commercial Cyclotrons Cyclotron Components Extraction Lens System Scope of the Study Computer Simulation Model Results Acknowledgements March 2003 Thesis Defence Karine Le Du
Current Expertise: Complete Beamline Design Injection System Design Beamline Simulator Software My Project… Extraction Lens System Design Future Endeavors Ion Implantation March 2003 Thesis Defence Karine Le Du
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. March 2003 Thesis Defence Karine Le Du
Cyclotron Components Inflector Cyclotron Extraction Lenses Extraction Probe Ion Source Injection Beamline Line March 2003 Thesis Defence Karine Le Du
Cyclotron Components Inflector Cyclotron Extraction Lenses Extraction Probe Ion Source Injection Beamline Line March 2003 Thesis Defence Karine Le Du
Extraction Lens Assembly vacuum Plasma chamber Shoulder lens lens ion beamstop source Extraction lens z ~ 405mm Assembly drawing courtesy of TRIUMF March 2003 Thesis Defence Karine Le Du
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 March 2003 Thesis Defence Karine Le Du
Beam Characteristics Normalized Beam Emittance, ε N 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 I b 2 N March 2003 Thesis Defence Karine Le Du
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 March 2003 Thesis Defence Karine Le Du
Beam Size Beam Size: Area enclosed in beam ellipse Beam Emittance: Proportional to beam size Beam x’ ellipse x March 2003 Thesis Defence Karine Le Du
Optimal Beam Characteristics Normalized Beam Emittance, ε N 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 March 2003 Thesis Defence Karine Le Du
Computer Simulation Model SIMION 3D, Version 7.0, INEEL* Model consists of 3 electrostatic lenses *Idaho National Engineering and Environmental Laboratory March 2003 Thesis Defence Karine Le Du
Assumptions Made ASSUMPTIONS JUSTIFICATIONS No plasma meniscus Beyond the scope of this study No filter magnet e¯ stripped out early Ignored space Beyond the scope of charge repulsion and this study image forces March 2003 Thesis Defence Karine Le Du
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 March 2003 Thesis Defence Karine Le Du
Table of Parameter Values List of design List of design List of design List of design ID tags & ID tags & ID tags & ID tags & Variable parameter test Variable parameter test Variable parameter test Variable parameter test parameters by name parameters by name parameters by name parameters by name nominal nominal nominal nominal values values values values values values values values Plasma Electrode Plasma Electrode Plasma Electrode Plasma Electrode E1 E1 E1 E1 Voltage potential Voltage potential Voltage potential Voltage potential V1 = -25 kV V1 = -25 kV V1 = -25 kV V1 = -25 kV Aperture diameter Aperture diameter Aperture diameter Aperture diameter A1 = 13 mm A1 = 13 mm A1 = 13 mm A1 = 13 mm Extraction Electrode Extraction Electrode Extraction Electrode Extraction Electrode E2 E2 E2 E2 Voltage potential Voltage potential Voltage potential Voltage potential V2 = -22 kV V2 = -22 kV V2 = -22 kV V2 = -22 kV -23 kV -23 kV -23 kV -23 kV -22.5 kV -22.5 kV -22.5 kV -22.5 kV -21.5 kV -21.5 kV -21.5 kV -21.5 kV Aperture diameter Aperture diameter Aperture diameter Aperture diameter A2 = 9.5 mm A2 = 9.5 mm A2 = 9.5 mm A2 = 9.5 mm 10.5mm 10.5mm 10.5mm 10.5mm 11.5mm 11.5mm 11.5mm 11.5mm 12.5mm 12.5mm 12.5mm 12.5mm Shoulder Electrode Shoulder Electrode Shoulder Electrode Shoulder Electrode E3 E3 E3 E3 Voltage potential Voltage potential Voltage potential Voltage potential V3 = 0 V V3 = 0 V V3 = 0 V V3 = 0 V Aperture diameter Aperture diameter Aperture diameter Aperture diameter A3 = 10 mm A3 = 10 mm A3 = 10 mm A3 = 10 mm 9 mm 9 mm 9 mm 9 mm 11 mm 11 mm 11 mm 11 mm Separation between Separation between Separation between Separation between electrodes electrodes electrodes electrodes E1 & E2 E1 & E2 E1 & E2 E1 & E2 D12 = 4 mm D12 = 4 mm D12 = 4 mm D12 = 4 mm 7 mm 7 mm 7 mm 7 mm 10 mm 10 mm 10 mm 10 mm E2 & E3 E2 & E3 E2 & E3 E2 & E3 D23 = 12 mm D23 = 12 mm D23 = 12 mm D23 = 12 mm 8 mm 8 mm 8 mm 8 mm 16 mm 16 mm 16 mm 16 mm March 2003 Thesis Defence Karine Le Du
General Trends 2.5 D12 = 4 mm D12 = 7 mm D12 = 10 mm less than 39.9% trans. 2 40% to 49.9% trans. 50% to 59.9% trans. -2 60% to 69.9% trans. beam brightness (mm.mrad) 70% to 79.9% trans. 80% to 89.9% trans. 1.5 90% to 99.9% trans. 100% transmission V2 = -23 kV V2 = -22.5 kV 1 V2 = -22 kV V2 = -21.5 kV 0.5 0 0.5 0.75 1 1.25 1.5 1.75 2 normalized beam emittance (mm.mrad) March 2003 Thesis Defence Karine Le Du
General Trends 2.5 -2 2.25 beam brightness (mm.mrad) 2 1.75 1.5 1.25 1 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 normalized beam emittance (mm.mrad) D12 = 10mm 50% to 59.98% trans. 60% to 69.98% trans. 70% to 79.98% trans. 80% to 89.98% trans. 90% to 99.98% trans. 100% transmission V2 = -23 kV V2 = -22.5 kV V2 = -22 kV V2 = -21.5 kV March 2003 Thesis Defence Karine Le Du
Ion Trajectories b in [(mm·mrad) -2 ] N in [mm·mrad] Nominal Configuration, Highest Beam Brightness, b = 2.351, N =0.508, I = 60.7% b = 0.341, N =1.136, I = 44% Lowest Beam Brightness, 100% Beam Transmission, b = 0.127, N =1.916, I = 46.6% b = 1.731, N =0.76, I = 100% March 2003 Thesis Defence Karine Le Du
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 March 2003 Thesis Defence Karine Le Du
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 March 2003 Thesis Defence Karine Le Du
Crude Beam Current Adjustment Parameter Suggested value D12 10 mm D23 16 mm A2 9.5 mm (same) A3 10 mm (same) V2 Vary to achieve desired beam current make more positive for higher beam current March 2003 Thesis Defence Karine Le Du
Beam Optics x X’ X’ z March 2003 Thesis Defence Karine Le Du
Beam Size Beam Emittance: x x ' m aximum i ntercept Ellipse Area: A Normalized Emittance: N March 2003 Thesis Defence Karine Le Du
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