Modeling of an Extraction Lens System

Thesis Defense Bachelor of Applied Science

Karine Le Du Engineering Physics

School of Engineering Science, SFU

March 2003 Thesis Defence

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

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

Use of Commercial Cyclotrons

Photo Courtesy of Ebco Technologies Inc.

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)

Karine Le Du

March 2003 Thesis Defence

Cyclotron Components

Karine Le Du

Ion Source

Extraction Lenses

Injection Line

Inflector Cyclotron

Extraction Probe

Beamline

March 2003 Thesis Defence

Cyclotron Components

Karine Le Du

Ion Source

Extraction Lenses

Injection Line

Inflector Cyclotron

Extraction Probe

Beamline

March 2003 Thesis Defence

Extraction Lens Assembly

Karine Le Du

Assembly drawing courtesy of TRIUMF

vacuum

chamber

beamstop ion

source

z ~ 405mm

Plasma lens

Extraction lens

Shoulder lens

March 2003 Thesis Defence

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

March 2003 Thesis Defence

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

Karine Le Du

2N

Ib

March 2003 Thesis Defence

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

Karine Le Du

March 2003 Thesis Defence

Beam Size

Beam Size: Area enclosed in beam ellipse

Beam Emittance: Proportional to beam size

Karine Le Du

x

x’ Beam ellipse

March 2003 Thesis Defence

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

Karine Le Du

March 2003 Thesis Defence

Computer Simulation Model

SIMION 3D, Version 7.0, INEEL*

Model consists of 3 electrostatic lenses

*Idaho National Engineering and Environmental Laboratory

Karine Le Du

March 2003 Thesis Defence

Assumptions Made

ASSUMPTIONS

No plasma meniscus

JUSTIFICATIONS

Beyond the scope of this study

Karine Le Du

No filter magnet

Ignored space charge repulsion and image forces

e¯ stripped out early

Beyond the scope of this study

March 2003 Thesis Defence

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

March 2003 Thesis Defence

Table of Parameter Values List of design parameters by name

ID tags & nominal 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

Karine Le Du

List of design parameters by name

ID tags & nominal 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

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

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

March 2003 Thesis Defence

General Trends

0

0.5

1

1.5

2

2.5

0.5 0.75 1 1.25 1.5 1.75 2

normalized beam emittance (mm.mrad)

be

am

bri

gh

tne

ss

(m

m.m

rad

)-2

D12 = 4 mm

D12 = 7 mm

D12 = 10 mm

less than 39.9% trans.

40% to 49.9% trans.

50% to 59.9% trans.

60% to 69.9% trans.

70% to 79.9% trans.

80% to 89.9% trans.

90% to 99.9% trans.

100% transmission

V2 = -23 kV

V2 = -22.5 kV

V2 = -22 kV

V2 = -21.5 kV

Karine Le Du

March 2003 Thesis Defence

General Trends

Karine Le Du

1

1.25

1.5

1.75

2

2.25

2.5

0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9

normalized beam emittance (mm.mrad)

beam

bri

gh

tness (

mm

.mra

d)-2

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

Ion Trajectories

Karine Le Du

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%

b in [(mm·mrad)-2]

N in [mm·mrad]

March 2003 Thesis Defence

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

March 2003 Thesis Defence

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

March 2003 Thesis Defence

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

Karine Le Du

March 2003 Thesis Defence

Beam Optics

Karine Le Du

z

x

X’

X’

March 2003 Thesis Defence

Beam Size

Beam Emittance:

Ellipse Area:

Karine Le Du

nterceptiaximumm xx '

A

N

Normalized Emittance: