H- Ion Source Development Dan Faircloth

ISIS Operational Ion Source Penning H- ion source Surface Plasma Source (SPS) 35 mA through 0.610 mm aperture 200-250 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

H- Ion Beam Extract Electrode Aperture Plate Penning Pole Pieces Discharge Region Ceramic Anode Source Body Copper Spacer Cathode Mica 10mm Mounting Flange

Platform DC Power Supply Platform Ground 35kV Pulsed Extract Power Supply 17kV - + Laboratory Ground 18kV Extraction Electrode, Coldbox and Analysing Magnet all Pulsed - + 35keV H- Beam 53.7mm Post Extraction Acceleration Gap

Development Goals Increase Pulse Length Increase Output Current Reduce Emittance Maximise Lifetime 200µs to 1.5ms 35mA to 70mA

Thermal Modelling Steady State Solution 600 520 440 360 280 200 Steady State Solution 3D Finite Element Model of the Ion Source using ALGOR. Computational Fluid Dynamic Cooling Calculation 1000μs duty Cathode Surface Anode Surface ΔT= 73 ºC ΔT= 39 ºC Transient Solution

Maximum Discharge Length Obtained 1.8ms @ 50Hz

Electromagnetic Modelling 17 keV normalised Hrms= 0.03  mm mrad Vrms= 0.03  mm mrad Terminated Pierce Extract 3D Finite Element Model of the Ion Source using MAFIA. 17 keV normalised Hrms= 0.04  mm mrad Vrms= 0.16  mm mrad Existing Extract Potential in Extract Region 0T 0.5T Magnetic Field in Coldbox Correctly Terminated Analysing Field

ISDR Infrastructure Changes Top Loading Ion Source Separate Penning Field Ion Source Assembly Magnet Pole tip extensions on the 90° Analysing Magnet Penning Field B

ISDR Infrastructure Changes Top Loading Ion Source Separate Penning Field Ion Source Assembly Penning Field B Magnet Assembly

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

Development Goals Increase Pulse Length Increase Output Current 200µs to 1.5ms Increase Pulse Length Increase Output Current Reduce Emittance Maximise Lifetime 35mA to 70mA

Improved Diagnostics

Retarding Potential Energy Analyzer Transmission (%) Bias Voltage (V) δ(Transmission) / δ(−Vb) (%/V) Bias Voltage (V) σ = 17.6 eV +/- 1.5 eV Bias Voltage (V) Discharge Current (A) Transmission (%) Spectrum width σ (eV) Faraday Cup I H- Beam Potential Hill Work done in collaboration with Oxford University

Current Work

17 kV Extract Potential 62 mA Beam Current 0.84 norm πmm mRad -60 -30 30 50 100 -50 -100 x (mm) x ‘(mRads) 100 50 y ‘(mRads) -50 -100 -60 -30 30 -60 y (mm) 0.84 norm πmm mRad 0.92 norm πmm mRad

10 kV Extract Potential 32 mA Beam Current 0.48 norm πmm mRad 100 100 50 50 x ‘(mRads) y ‘(mRads) -50 -50 -100 -100 -60 -30 30 -60 -60 -30 30 -60 x (mm) y (mm) 0.48 norm πmm mRad 0.55 norm πmm mRad

6.5 kV Extract Potential 13 mA Beam Current 0.16 norm πmm mRad 100 100 50 50 x ‘(mRads) y ‘(mRads) -50 -50 -100 -100 -60 -30 30 -60 -60 -30 30 -60 x (mm) y (mm) 0.16 norm πmm mRad 0.32 norm πmm mRad

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 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 Mounting flange Details in the next talk Window Support rods Moving rod Scintillator and Pepperpot Camera

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?