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

Karine Le Du
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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
Karine Le Du
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General Trends
Karine Le Du
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General Trends
Karine Le Du
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Ion Trajectories
Karine Le Du
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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
Karine Le Du
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Beam Optics
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Beam Size

• Beam Emittance
• Ellipse Area

Karine Le Du