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Laser-based Beam Diagnostics for the RAL Front End Test Stand

Laser-based Beam Diagnostics for the RAL Front End Test Stand. David Lee david.a.lee@imperial.ac.uk 28.01.2009. Outline. The Front End Test Stand (FETS) Beam diagnostics Beam profile measurements Non-intrusive beam diagnostics Laser-based H − diagnostics FETS laser profile monitor

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Laser-based Beam Diagnostics for the RAL Front End Test Stand

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  1. Laser-based Beam Diagnostics for the RAL Front End Test Stand David Lee david.a.lee@imperial.ac.uk 28.01.2009

  2. Outline • The Front End Test Stand (FETS) • Beam diagnostics • Beam profile measurements • Non-intrusive beam diagnostics • Laser-based H− diagnostics • FETS laser profile monitor • Conclusion Laser-based Beam Diagnostics for the RAL Front End Test Stand • 1

  3. The Front End Test Stand Laser-based Beam Diagnostics for the RAL Front End Test Stand • 2 David Lee • 28/01/2009

  4. The Front End Test Stand Beam dump and laser emittance measurementupstream (not shown) MEBT and chopper RFQ Magnetic LEBT H− ion source Laser profile monitor Laser-based Beam Diagnostics for the RAL Front End Test Stand • 3

  5. Neutrino Factory Laser-based Beam Diagnostics for the RAL Front End Test Stand • 4

  6. Neutrino Factory Laser-based Beam Diagnostics for the RAL Front End Test Stand • 4

  7. Status Laser-based Beam Diagnostics for the RAL Front End Test Stand • 5

  8. Status Laser-based Beam Diagnostics for the RAL Front End Test Stand • 5

  9. Status Laser-based Beam Diagnostics for the RAL Front End Test Stand • 5

  10. Status Laser-based Beam Diagnostics for the RAL Front End Test Stand • 5

  11. Beam Diagnostics Laser-based Beam Diagnostics for the RAL Front End Test Stand • 6 David Lee • 28/01/2009

  12. Beam Profile Measurements • Why are beam profile measurements of interest? • First half of the beam emittance • Gives information about the charge density • And so the beam’s self field / space charge • Will the beam fit through the beam pipe? • What is the beam halo like? • … • How are they typically done? • Scintillator • Wire scanner • … Laser-based Beam Diagnostics for the RAL Front End Test Stand • 7

  13. Non-intrusive diagnostics • Allows for online monitoring of the beam • Keeps users happy Laser-based Beam Diagnostics for the RAL Front End Test Stand • 8

  14. Non-intrusive diagnostics • Allows for online monitoring of the beam • Keeps users happy • Beam dynamics not affected by the instrument • Keeps accelerator group happy Residual gas ion energy analyser RGIE spectrum (beam potential distribution) depending on position of emittance scanner Ion source dl’ / dW [μA / (eV m)] 200V 0V Allison scanner in / out Beam dump 0V 0.406T 0.365T W / eV Laser-based Beam Diagnostics for the RAL Front End Test Stand • 8

  15. P46 Plastic Ruby Non-intrusive diagnostics • Allows for online monitoring of the beam • Keeps users happy • Beam dynamics not affected by the instrument • Prevents the beam from damaging the instrument • Keeps accelerator group happy Laser-based Beam Diagnostics for the RAL Front End Test Stand • 8

  16. Ionisation Cross Section Laser-based Beam Diagnostics for the RAL Front End Test Stand • 9

  17. Ionisation Cross Section Laser-based Beam Diagnostics for the RAL Front End Test Stand • 9

  18. To measure Beam profiles Longitudinal emittances use photo-detached electrons Laser-based H− diagnostics Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  19. To measure Beam profiles Longitudinal emittances use photo-detached electrons Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  20. Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  21. Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  22. Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  23. Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  24. Laser-based H− diagnostics Collect the detached electrons − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Photo-ionise someof the H- ions Separate species usinga dipole magnet Laser-based Beam Diagnostics for the RAL Front End Test Stand • 10

  25. To measure Transverse emittances use photo-ionised neutrals Laser-based H− diagnostics Laser-based Beam Diagnostics for the RAL Front End Test Stand • 11

  26. To measure Transverse emittances use photo-ionised neutrals − − − − − − − − − − − − − − − − Laser-based H− diagnostics Use a dipole to separate out the particles neutralised by residual gas interactions Laser-based Beam Diagnostics for the RAL Front End Test Stand • 11

  27. To measure Transverse emittances use photo-ionised neutrals − − − − − − − − Laser-based H− diagnostics − − − − − Photo-ionised neutrals Photo-ionise some of the H- ions in the dipole Residual gasneutrals Laser-based Beam Diagnostics for the RAL Front End Test Stand • 11

  28. To measure Transverse emittances use photo-ionised neutrals CCD − − − − − − − − Laser-based H− diagnostics − Image with scintillator and CCD − − − − Photo-ionised neutrals Photo-ionise some of the H- ions in the dipole Residual gasneutrals Laser-based Beam Diagnostics for the RAL Front End Test Stand • 11

  29. CCD − − − − − − − − Laser-based H− diagnostics − Image with scintillator and CCD − − − − Photo-ionised neutrals Photo-ionise some of the H- ions in the dipole Residual gasneutrals Laser-based Beam Diagnostics for the RAL Front End Test Stand • 11

  30. The Front End Test StandLaser Profile Monitor Laser-based Beam Diagnostics for the RAL Front End Test Stand • 12 David Lee • 28/01/2009

  31. The Benefit of Multiple (>2) Projections Laser-based Beam Diagnostics for the RAL Front End Test Stand • 13 David Lee • 28/01/2009

  32. The Benefit of Multiple (>2) Projections Laser-based Beam Diagnostics for the RAL Front End Test Stand • 13

  33. The Benefit of Multiple (>2) Projections Laser-based Beam Diagnostics for the RAL Front End Test Stand • 13

  34. The Benefit of Multiple (>2) Projections Laser-based Beam Diagnostics for the RAL Front End Test Stand • 13

  35. Laser-scanning setup • To get multiple projections, need to be able to pass laser through beam at variety of angles • To do this, use movable mirrors mounted in vacuum vessel Laser-based Beam Diagnostics for the RAL Front End Test Stand • 14

  36. Laser-scanning setup Laser-based Beam Diagnostics for the RAL Front End Test Stand • 15

  37. Laser-scanning setup Laser-based Beam Diagnostics for the RAL Front End Test Stand • 15

  38. Optics A simple, one lens setup will be used to begin with Laser-based Beam Diagnostics for the RAL Front End Test Stand • 16

  39. Optics Laser-based Beam Diagnostics for the RAL Front End Test Stand • 17

  40. The Detector Faraday Cup Electrons Magnet H−, H0 Copperacceleratingsheath Laser-based Beam Diagnostics for the RAL Front End Test Stand • 18

  41. The Detector • Constructed here in the workshop • Compact; the whole assembly is~80x100x250 mm Beamdirection Laser-based Beam Diagnostics for the RAL Front End Test Stand • 19

  42. Simulations • Detector’s E and B fields simulated using a electromagnetic finite element program • CST EM Studio • Particle tracking was performed by the General Particle Tracer package • Input distribution from a pepperpot correlated emittance measurement of the ion source Laser-based Beam Diagnostics for the RAL Front End Test Stand • 20

  43. Simulations Faraday Cup Magnet yoke Copperacceleratingsheath Laser-based Beam Diagnostics for the RAL Front End Test Stand • 21

  44. Dipole Field Map • To confirm the simulation results the dipole had its field (bending component; By) mapped Laser-based Beam Diagnostics for the RAL Front End Test Stand • 22

  45. Dipole Field Map Laser-based Beam Diagnostics for the RAL Front End Test Stand • 23

  46. Dipole Field Map Laser-based Beam Diagnostics for the RAL Front End Test Stand • 24

  47. Longitudinal Acceptance • Electrons from residual gas interactions form a background to our measurement • Problem made worse by proximity to ion source • 20 ml per minute of hydrogen gas • To reduce this background, the longitudinal acceptance of the detector can be reduced byintroducing an additional electrode Laser-based Beam Diagnostics for the RAL Front End Test Stand • 25

  48. Longitudinal Acceptance Laser-based Beam Diagnostics for the RAL Front End Test Stand • 26

  49. Longitudinal Acceptance Laser-based Beam Diagnostics for the RAL Front End Test Stand • 26

  50. Longitudinal Acceptance Laser-based Beam Diagnostics for the RAL Front End Test Stand • 26

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