Developments of the FETS Ion Source Scott Lawrie

Main Components: The FETS project is a collaboration between ISIS and: 65 keV, 60 mA, 2 ms, 50 Hz, H - Ion Source 3 Solenoid Magnetic LEBT 324 MHz, 3 MeV, 4 Vane RFQ MEBT and Beam Chopper Beam Diagnostics and Beam Dump Laser Profile Measurement

Cathode Hydrogen Feed Heated Caesium Transport Line Air Cooling Source Body Hollow Anode Discharge Power Feed Thermocouples

Extraction Electrode Support Insulators Caesium Shields Extraction Mount

Ion Source Flange Rear-Loading Ion Source Housing Analysing Sector Magnet Cold Box Exit Hole

Pumping Holes HT Column Mounting Flange Magnetic Shielding Protection, Suppression & Ground Electrodes H - Beam Beam Leaving Cold Box Accelerated to 70 keV

Ion Source Flange Attached to Acceleration Assembly

Ion Source and Controls on HT Platform

High Voltage Cage Inside R8 at RAL

First Beam Achieved April mA 200 µs 50 Hz Presented at PAC’09

Movable Diagnostics Vessel

Differential Pumping and Laser-Profile Vessel 4 × 800 Ls x 400 Ls -1 turbo pumps Toroid1 Vacuum bellows Gated CCD Camera Light bellows Slit-Slit Emittance Scanners Pepperpot or profile scintillator head 400 Ls -1 turbo pump Toroid 2 Beam shutter Isolating Column Accelerating Electrode Assembly Ion Source 2 kV Accelerating jacket Faraday cup Electron Analysing Dipole Laser Beam Strips Electrons

Experiments Performed Transmission through laser vessel Properties of the beam to enter LEBT Attempt to increase beam current Attempt to reduce emittance Try to understand discharge & extraction Long pulse operation

RMS Normalised Emittance / π mm mRad Toroid Currents Twiss Parameters

60mA Space Charge 2mm Jaw Separation Deep E-field Penetration Voltage scale: -1000V to 0V Tracking scale: 0 eV to 17 keV

Voltage scale: -1000V to 0V 1mm Jaw Separation Less E-field Penetration 60mA Space Charge Tracking scale: 0 eV to 17 keV

Voltage Scale: V to 0V Tracking scale: 0 eV to 17 keV Pierce-type Electrodes Initial Focus Counteracts Defocusing Lens of Extraction Jaws

Beam within ±20 mRad: 74.0% Norm. Emittance: 0.16 π mm mRad Beam within ±20 mRad: 56.0% Norm. Emittance: 0.13 π mm mRad Beam within ±20 mRad: 43.3% Norm. Emittance: 0.32 π mm mRad Convex Meniscus Beam Current: 80 mA Extraction Potential: 25 kV Concave Meniscus Flat Meniscus 5° 22.5° (Pierce Angle) 30°

Emittance Scanner Improvement Mechanical Resolution of Scanners

Emittance Scanner Improvement 4 x Oversampled Image Deconvoluted using Lucy-Richardson Algorithm

Extraction Electrodes Tested ISIS standard extraction electrode with either 0.6mm or 0.8mm wide aperture slit Extraction electrode with smaller, 1 mm jaw separation Aperture plate with Pierce 22.5° inclination angle and 1.5mm separated, sharp jaw extraction electrode

14kV Extract 38kV Platform 55A Discharge ISIS Standard 0.8 mm Wide Aperture Slit 1 mm Jaw Separation Pierce & Sharp Jaws 27.3 mA 30.5 mA 37.0 mA 31.5 mA

Standard ISIS Extract

1 mm Extract Jaw Separation

Timing H 2 gas pulse ~ 200 μs Extraction volts pulse 300 µs. Want to extend to 2 ms. ~ 250 μs Source Runs at 50 Hz Rep Rate Arc discharge pulse 800 µs. Want to extend to ~ 2.5 ms. ~ 600 μs H - Beam pulse length same as extraction volts. Want 2 ms.

Standard 50Hz Short Pulse Beam 0.8mm Wide Aperture Slit 18kV extract, 42kV platform, 55A Discharge 50 Hz Rep. Rate, 65 mA beam

Low Rep-Rate Long Pulse Beam 1 mm Separated Extract Jaws 18kV extract, 42kV platform, 55A Discharge 3.125Hz Rep. Rate, mA beam

Next Steps Long-term running of FETS ion source Finish LEBT installation & commission Test LEBT mid-vessel diagnostics Achieve first beam through LEBT Assess properties of transported beam Try to achieve beam required for RFQ

Low Energy Beam Transport Installed Downstream of High Voltage Cage … to be continued!