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Developments of the FETS Ion Source

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

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Developments of the FETS Ion Source

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  1. Developments of theFETS Ion Source Scott Lawrie

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

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

  4. Extraction Mount Extraction Electrode Support Insulators Caesium Shields

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

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

  7. Ion Source Flange Attached to Acceleration Assembly

  8. Ion Source and Controls on HT Platform

  9. High Voltage Cage Inside R8 at RAL

  10. First Beam Achieved April 2009 35 mA 200 µs 50 Hz Presented at PAC’09

  11. Movable Diagnostics Vessel

  12. 2 kV Accelerating jacket Faraday cup Slit-Slit Emittance Scanners Differential Pumping and Laser-Profile Vessel 400 Ls-1 turbo pump Electron Analysing Dipole Accelerating Electrode Assembly Light bellows Gated CCD Camera Ion Source Vacuum bellows Beam shutter Toroid 2 Isolating Column Toroid1 Pepperpot or profile scintillator head Movable Diagnostics Vessel Laser Beam Strips Electrons 4 × 800 Ls-1 + 1 x 400 Ls-1 turbo pumps

  13. 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

  14. Toroid Currents RMS Normalised Emittance / π mm mRad Twiss Parameters

  15. 2mm Jaw Separation Deep E-field Penetration Voltage scale: -1000V to 0V 60mA Space Charge Tracking scale: 0 eV to 17 keV

  16. 1mm Jaw Separation Less E-field Penetration Voltage scale: -1000V to 0V 60mA Space Charge Tracking scale: 0 eV to 17 keV

  17. Pierce-type Electrodes Voltage Scale: -17000V to 0V Initial Focus Counteracts Defocusing Lens of Extraction Jaws Tracking scale: 0 eV to 17 keV

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

  19. Emittance Scanner Improvement Mechanical Resolution of Scanners

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

  21. 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

  22. 14kV Extract 38kV Platform 55A Discharge 27.3 mA 30.5 mA ISIS Standard 0.8 mm Wide Aperture Slit 31.5 mA 37.0 mA Pierce & Sharp Jaws 1 mm Jaw Separation

  23. Standard ISIS Extract

  24. 1 mm Extract Jaw Separation

  25. H2 gas pulse ~ 200 μs Timing Arc discharge pulse 800 µs. Want to extend to ~ 2.5 ms. ~ 600 μs Extraction volts pulse 300 µs. Want to extend to 2 ms. ~ 250 μs H- Beam pulse length same as extraction volts. Want 2 ms. Source Runs at 50 Hz Rep Rate

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

  27. Low Rep-Rate Long Pulse Beam 1 mm Separated Extract Jaws 18kV extract, 42kV platform, 55A Discharge 3.125Hz Rep. Rate, 40-30 mA beam

  28. 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

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

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