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
Extraction
Lenses
Inflector
Cyclotron
Extraction
Probe
Ion
Source
March 2003
Injection
Line
Thesis Defence
Beamline
Karine Le Du
Cyclotron Components
Extraction
Lenses
Inflector
Cyclotron
Extraction
Probe
Ion
Source
March 2003
Injection
Line
Thesis Defence
Beamline
Karine Le Du
Extraction Lens Assembly
vacuum
chamber
Plasma
lens
Shoulder
lens
ion
source
Extraction
lens
beamstop
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, 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
b
I
 
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
ellipse
x’
x
March 2003
Thesis Defence
Karine Le Du
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
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


No filter magnet


Ignored space
charge repulsion and
image forces
March 2003
Thesis Defence

Beyond the scope of
this study
e¯ stripped out early
Beyond the scope of
this study
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
parameters by name
ID tags &
nominal
values
Plasma Electrode
E1
Voltage potential
V1 = -25 kV
Aperture diameter
A1 = 13 mm
Extraction Electrode
Variable parameter test
values
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
E1 & E2
D12 = 4 mm
7 mm
10 mm
E2 & E3
D23 = 12 mm
8 mm
16 mm
Separation between
electrodes
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.
beam brightness (mm.mrad)
-2
50% to 59.9% trans.
60% to 69.9% trans.
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
beam brightness (mm.mrad)-2
2.5
2.25
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)
March 2003
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
Thesis Defence
Karine Le Du
Ion Trajectories
b in [(mm·mrad)-2]
N in [mm·mrad]
Nominal Configuration,
Highest Beam Brightness,
b = 0.341, N =1.136, I = 44%
b = 2.351, N =0.508, I = 60.7%
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’
March 2003
Thesis Defence
z
Karine Le Du
Beam Size



  xm aximum  x'i ntercept
Ellipse Area:
A  
Normalized Emittance:  N    
Beam Emittance:
March 2003
Thesis Defence
Karine Le Du