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FETS H - Ion Source Experiments and Installation

FETS H - Ion Source Experiments and Installation. Scott Lawrie, Dan Faircloth , Alan Letchford, Christoph Gabor, Phil Wise, Mark Whitehead, Trevor Wood, Mike Perkins, Mick Bates, Pete Savage, David Lee, Juergen Pozimski, Rafael Enparantza. Front End Test Stand (FETS). Main Modifications.

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FETS H - Ion Source Experiments and Installation

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  1. FETS H- Ion Source Experiments and Installation Scott Lawrie, Dan Faircloth, Alan Letchford, Christoph Gabor, Phil Wise, Mark Whitehead, Trevor Wood, Mike Perkins, Mick Bates, Pete Savage, David Lee, Juergen Pozimski, Rafael Enparantza

  2. Front End Test Stand (FETS)

  3. Main Modifications • Post extraction acceleration gap • Analysing dipole magnet • Extraction electrodes • Power supplies

  4. Platform DC Power Supply Platform Ground -35 kV 250µs Pulsed Extraction Power Supply 17kV Extraction system - + Laboratory Ground 90° Analysing Magnet 35 keV H- Beam 18 kV - + 55 mm Post Extraction Acceleration Gap ISIS Ion Source

  5. Platform DC Power Supply Platform Ground -65 kV 2ms Pulsed Extraction Power Supply 25kV Extraction system - + Laboratory Ground 90° Analysing Magnet 65 keV H- Beam 40 kV - + 9mm Post Extraction Acceleration Gap Proton Suppressor FETS Ion Source

  6. Post ExtractionAcceleration Gap

  7. ISIS LEBT Line Post Extraction Acceleration Diagnostics Sol. 3 Ion source Solenoid 1 Solenoid 2

  8. FETS LEBT Line Post Extraction Acceleration PLUS Diagnostics Diagnostics Sol. 3 Ion source Solenoid 1 Solenoid 2

  9. Ion source, analysing dipole magnet and cold box Steel mounting and pumping flange Laser diagnostics dipole apparatus Electrode and mu-metal shielding assembly

  10. Electrode Spacer Assembly

  11. Analysing Sector Magnet

  12. Reasons For Use of Dipole • Analyse out co-extracted electrons • Allow caesium to collect in cold box • Modify beam from slit to round shape • Weakly focus beam to LEBT entrance • Convenient 90° loading geometry

  13. Field Stronger Field Stronger n > 1 n = 1 n < 1 Field Weaker Axial Beam Size Radial Beam Size Angle Around Dipole Angle Around Dipole 0° 90° 0° 90° Field Weaker Magnetic Field Index:

  14. Predicted beam profiles n < 1 n = 1 n > 1 Measured beam profiles

  15. Extraction Electrode Setup

  16. Beam Parameters Determined by Extraction System: • Ion species (H-) • Current needed for application (70 mA) • High current density at plasma aperture • High extraction voltage: • Low divergence angle (ε < 0.5 π mm mRad) • Concave plasma meniscus • Focussing electrostatic lens geometry • Space charge compensation • Low ion temperature

  17. Standard ISIS Extraction Geometry

  18. Pierce-Style Extraction Geometry

  19. Alternative Pierce-Style Geometry

  20. Overview of Experimental Work

  21. Norm. εh = 0.82 π mm mRad Norm. εv = 0.75 π mm mRad 46.6 mA ISIS Ion Source

  22. Norm. εh > 0.69 π mm mRad Norm. εv > 0.45 π mm mRad 56.0 mA Reduced Post-Extraction Acceleration Gap ISIS Ion Source +

  23. Norm. εh = 0.68π mm mRad Norm. εv = 0.42π mm mRad 49.6 mA Reduced Post-Extraction Acceleration Gap Improved Sector Magnet Good Field Region ISIS Ion Source + +

  24. Norm. εh = 0.57π mm mRad Norm. εh = 0.39π mm mRad 42.6 mA Reduced Post-Extraction Acceleration Gap Improved Sector Magnet Good Field Region Pierce-Style Extraction Geometry ISIS Ion Source + + +

  25. FETS Ion SourceInstallation Progress

  26. Questions? • Ion Source Latest Status: • Commissioning timing signals • Mains operable on platform • Platform 70 kV imminent • Extract power ready • Beam due very soon!

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