H- Ion Source Development

Dan Faircloth

ISIS Operational Ion SourcePenning H- ion sourceSurface Plasma Source (SPS) 35 mA through 0.610 mm aperture200-250 s, 50 Hz 1% duty cycle

20 ml/min H2 3 g/month Cs 0.17 mm mrad (665 keV, 35 mA, rms)20-30 day average lifetime

Mica

Mounting Flange

Copper Spacer

Ceramic

H- Ion Beam Extract Electrode

Cathode

Anode

Penning Pole Pieces Discharge Region

10mm

Aperture Plate

Source Body

53.7mm

35kV

17kV

Platform Ground

Platform DC Power Supply

Pulsed Extract Power

Supply

Post Extraction

Acceleration Gap

Laboratory Ground

Extraction Electrode,

Coldbox and Analysing Magnet all

Pulsed

35keV H- Beam

+-

+-

18kV

Development Goals

• Increase Pulse Length

• Increase Output Current

• Reduce Emittance

• Maximise Lifetime

35mA to 70mA

200µs to 1.5ms

Thermal Modelling3D Finite Element Model of the Ion Source using ALGOR.

600520440360280200

Steady State Solution

450

500

550

600

650

700

0 0.005 0.01 0.015 0.02 0.025 0.03

Time (seconds)

Te

mp

era

ture

(C

)

012345

0 0.005 0.01 0.015 0.02 0.025 0.03Ins

tan

tan

eo

us

Po

we

r

(kW

) 1000μs duty

Cathode Surface

Anode Surface

ΔT= 73 ºC

ΔT= 39 ºC

Transient Solution

Computational Fluid Dynamic Cooling Calculation

Maximum Discharge Length Obtained1.8ms @ 50Hz

-80

-60

-40

-20

0

20

40

60

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Time (us)

Discharge Current (A)

Beam Current (mA)

Extract Volts (kV)

17 keV normalisedHrms= 0.04 mm mradVrms= 0.16 mm mrad

Existing Extract

17 keV normalisedHrms= 0.03 mm mradVrms= 0.03 mm mrad

Terminated Pierce Extract

Electromagnetic Modelling3D Finite Element Model of the Ion Source using MAFIA.

Potential in Extract Region

0T 0.5T

Magnetic Field in Coldbox

Correctly Terminated Analysing Field

ISDR Infrastructure Changes

Ion SourceAssembly

MagnetAssembly

Top Loading Ion Source

Penning Field

B

Pole tip extensions on the 90°

Analysing Magnet

Separate Penning Field

Ion SourceAssembly

MagnetAssembly

Top Loading Ion Source Separate Penning Field

Penning Field

B

ISDR Infrastructure Changes

Collaboration with IHEP, CAS

Dr. Ouyang and Prof. Zhang

Feb 2007: Dr. He Wei testing ion source components manufactured in China.

78 mA 500 µs 50 Hz

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-100 0 100 200 300 400 500 600 700 800 900 1000

Ext V (kV)

Dis Cur (A)

H- (mA)

Development Goals

• Increase Pulse Length

• Increase Output Current

• Reduce Emittance

• Maximise Lifetime

35mA to 70mA

200µs to 1.5ms

Improved Diagnostics

Retarding Potential Energy Analyzer

Work done in collaboration with Oxford University

0

0.2

0.4

0.6

0.8

1

1.2

-70.00 -20.00 30.00 80.00

Tra

nsm

issi

on

(%)

Bias Voltage (V)

-0.03

-0.02

-0.01

0

0.01

-70.00 -20.00 30.00 80.00

δ(T

rans

mis

sion

) /

δ(−

Vb)

(

%/V

)

Bias Voltage (V)

σ = 17.6 eV +/- 1.5 eV

0

0.2

0.4

0.6

0.8

1

1.2

-70.00 -20.00 30.00 80.00

40A

50A

60A

70A

80A

90A

95A

Bias Voltage (V)

Discharge Current (A)

Tra

nsm

issi

on

(%)

10

15

20

25

30

35

30 50 70 90 110

Discharge Current (A)

Spe

ctru

m w

idth

σ (

eV)

Faraday Cup

IPotential Hill

H- Beam

Current Work

17 kV Extract Potential

-60 -600-30 30

0

50

100

-50

-100

x (mm)

x ‘(m

Ra

ds)

-60 -600-30 30

0

50

100

-50

-100 y (mm)

y ‘(mRads)

0.84 norm πmm mRad 0.92 norm πmm mRad

62 mA Beam Current

10 kV Extract Potential

-60 -600-30 30

0

50

100

-50

-100 x (mm)

x ‘(mRads)

-60 -600-30 30

0

50

100

-50

-100 y (mm)

y ‘(mRads)

0.48 norm πmm mRad 0.55 norm πmm mRad

32 mA Beam Current

6.5 kV Extract Potential

-60 -600-30 30

0

50

100

-50

-100 y (mm)

y ‘(mRads)

-60 -600-30 30

0

50

100

-50

-100 x (mm)

x ‘(mRads)

0.16 norm πmm mRad 0.32 norm πmm mRad

13 mA Beam Current

Scintillator Measurements

5 kV Ext 5.5 kV Ext 6 kV Ext 6.5 kV Ext

7 kV Ext 8 kV Ext 9 kV Ext 11 kV Ext

Ion Source Development Rig

Pepper Pot Emittance Measurement

Support rods

CameraMoving rod

Window

Mounting flange

• To help understand why the emittance is so large

• To allow optimised design of the LEBT for the Front End Test Stand

• To develop diagnostic experience for the FETS collaboration

Scintillator and Pepperpot

Details in the next talk

Future Work

• Scanning Pepperpot and Scintillator studies• Space charge studies with Krypton• Different extraction geometries• Different post acceleration gap• Plasma meniscus modelling• More detailed beam transport modelling• Different materials for extended lifetime studies

Questions?