Modeling of an Extraction Lens System

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Modeling of an Extraction Lens System

• Thesis Defense
• Bachelor of Applied Science
• Karine Le Du
• Engineering Physics
• School of Engineering Science, SFU

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Overview

• Dehnel Consulting Ltd.
• Use of Commercial Cyclotrons
• Cyclotron Components
• Extraction Lens System
• Scope of the Study
• Computer Simulation Model
• Results
• Acknowledgements

Karine Le Du
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• Current Expertise
• Complete Beamline Design
• Injection System Design
• Beamline Simulator Software
• My Project
• Extraction Lens System Design
• Future Endeavors
• Ion Implantation

Karine Le Du
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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.
Karine Le Du
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Cyclotron Components
Inflector
Cyclotron
Extraction Lenses
Extraction Probe
Ion Source
Karine Le Du
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Cyclotron Components
Inflector
Cyclotron
Extraction Lenses
Extraction Probe
Ion Source
Karine Le Du
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Extraction Lens Assembly
Plasma lens
Shoulder lens
Extraction lens
Assembly drawing courtesy of TRIUMF
Karine Le Du
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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

Karine Le Du
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Beam Characteristics

• Normalized Beam Emittance, eN
• 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

Karine Le Du
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Phase Space

• Four important coordinates that completely
  describe an ions trajectory are (x, x, y, y)
• (x, y) transverse
• position
• (x, y) divergence
• from longitudinal axis
• z longitudinal
• position

Karine Le Du
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Beam Size

• Beam Size
• Area enclosed in beam ellipse
• Beam Emittance
• Proportional to beam size

Karine Le Du
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Optimal Beam Characteristics

• Normalized Beam Emittance, eN
• 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

Karine Le Du
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Computer Simulation Model

• SIMION 3D, Version 7.0, INEEL
• Model consists of 3 electrostatic lenses
• Idaho National Engineering and Environmental
  Laboratory

Karine Le Du
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Assumptions Made

• ASSUMPTIONS
• No plasma meniscus

• JUSTIFICATIONS
• Beyond the scope of this study

• No filter magnet

• e stripped out early

• Ignored space charge repulsion and image forces

• Beyond the scope of this study

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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

Karine Le Du
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Table of Parameter Values
List of design parameters by name ID tags nominal values Variable parameter test values Variable parameter test values Variable parameter test values
Plasma Electrode E1      
Voltage potential V1 -25 kV      
Aperture diameter A1 13 mm      
Extraction Electrode E2      
Voltage potential V2 -22 kV -23 kV -22.5 kV -21.5 kV
Aperture diameter A2 9.5 mm 10.5mm 11.5mm 12.5mm
Shoulder Electrode E3      
Voltage potential V3 0 V      
Aperture diameter A3 10 mm 9 mm 11 mm  
Separation between electrodes        
E1 E2 D12 4 mm 7 mm 10 mm  
E2 E3 D23 12 mm 8 mm 16 mm  
List of design parameters by name ID tags nominal values Variable parameter test values Variable parameter test values Variable parameter test values
Plasma Electrode E1      
Voltage potential V1 -25 kV      
Aperture diameter A1 13 mm      
Extraction Electrode E2      
Voltage potential V2 -22 kV -23 kV -22.5 kV -21.5 kV
Aperture diameter A2 9.5 mm 10.5mm 11.5mm 12.5mm
Shoulder Electrode E3      
Voltage potential V3 0 V      
Aperture diameter A3 10 mm 9 mm 11 mm  
Separation between electrodes        
E1 E2 D12 4 mm 7 mm 10 mm  
E2 E3 D23 12 mm 8 mm 16 mm  
List of design parameters by name ID tags nominal values Variable parameter test values Variable parameter test values Variable parameter test values
Plasma Electrode E1      
Voltage potential V1 -25 kV      
Aperture diameter A1 13 mm      
Extraction Electrode E2      
Voltage potential V2 -22 kV -23 kV -22.5 kV -21.5 kV
Aperture diameter A2 9.5 mm 10.5mm 11.5mm 12.5mm
Shoulder Electrode E3      
Voltage potential V3 0 V      
Aperture diameter A3 10 mm 9 mm 11 mm  
Separation between electrodes        
E1 E2 D12 4 mm 7 mm 10 mm  
E2 E3 D23 12 mm 8 mm 16 mm  
List of design parameters by name ID tags nominal values Variable parameter test values Variable parameter test values Variable parameter test values
Plasma Electrode E1      
Voltage potential V1 -25 kV      
Aperture diameter A1 13 mm      
Extraction Electrode E2      
Voltage potential V2 -22 kV -23 kV -22.5 kV -21.5 kV
Aperture diameter A2 9.5 mm 10.5mm 11.5mm 12.5mm
Shoulder Electrode E3      
Voltage potential V3 0 V      
Aperture diameter A3 10 mm 9 mm 11 mm  
Separation between electrodes        
E1 E2 D12 4 mm 7 mm 10 mm  
E2 E3 D23 12 mm 8 mm 16 mm  
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General Trends
Karine Le Du
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General Trends
Karine Le Du
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Ion Trajectories

Nominal Configuration, b 0.341, ?N 1.136, I 44 Highest Beam Brightness, b 2.351, ?N 0.508, I 60.7

Lowest Beam Brightness, b 0.127, ?N 1.916, I 46.6 100 Beam Transmission, b 1.731, ?N 0.76, I 100
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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

Karine Le Du
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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

Karine Le Du
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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
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Beam Optics
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Beam Size

• Beam Emittance
• Ellipse Area

Karine Le Du