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Status Report on Mk.II Pepperpot

Status Report on Mk.II Pepperpot. Simon Jolly Imperial College 13 th June 2007. Pepperpot Components. Pepperpot head: Tungsten intercepting screen, 50 m m holes on 3mm pitch in 41x41 array. Tungsten sandwiched between 2mm/10mm copper support plates. Quartz scintillator images beamlets.

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Status Report on Mk.II Pepperpot

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  1. Status Report on Mk.II Pepperpot Simon Jolly Imperial College 13th June 2007

  2. Pepperpot Components • Pepperpot head: • Tungsten intercepting screen, 50mm holes on 3mm pitch in 41x41 array. • Tungsten sandwiched between 2mm/10mm copper support plates. • Quartz scintillator images beamlets. • Camera system: • PCO 2000 camera with 2048 x 2048 pixel, 15.3 x 15.6 mm CCD. • Firewire connection to PC. • 105 mm Micro-Nikkor macro lens. • Bellows maintains light tight path from vacuum window to camera. • Main support: • Head and camera mounted at either end of 1100 mm linear shift mechanism, with 700 mm stroke. • All mounted to single 400 mm diameter vacuum flange. Simon Jolly, Imperial College

  3. FETS Pepperpot Design Beam profile head Tungsten mesh Pepperpot head Shutter Bellows Camera Moving rod Vacuum bellows Mounting flange Simon Jolly, Imperial College

  4. Pepperpot Installation Simon Jolly, Imperial College

  5. Pepperpot Location Inside Ion Source “0 mm” position of pepperpot head is 57 mm downstream of cold box exit. 458 mm dynamic range means “300 mm” position is approximately 20 mm upstream of slit-slit scanners. 57 mm 100 mm 458 mm Measurements taken at 100 mm intervals. Simon Jolly, Imperial College

  6. Mk.II Pepperpot Recent Improvements • Completed: • Multiple calibration markings on pepperpot and profile heads. • Sliding camera mount to improve resolution. • Larger, permanent camera-bellows mount (not cardboard!). • To do: • Background light replacement to improve calibration. • Support for new bellows mount. • Clamp to support sliding mount to prevent it toppling forward. • Install new components: Tuesday 16th June? Simon Jolly, Imperial College

  7. Pepperpot Data Image Raw data Calibration image Colour enhanced raw data image, 60 x 60 mm2. Calibration image: use corners of 9 mm x 9 mm square on copper plate to give image scaling, tilt and spot spacing. Simon Jolly, Imperial College

  8. Pepperpot Emittance Extraction Emittance profiles X Y Pepperpot image spots: hole positions (blue) and beam spots (red) Simon Jolly, Imperial College

  9. 13 kV Extract: 0 mm Simon Jolly, Imperial College

  10. 13 kV Extract: 100 mm Simon Jolly, Imperial College

  11. 13 kV Extract: 200 mm Simon Jolly, Imperial College

  12. 13 kV Extract: 300 mm Simon Jolly, Imperial College

  13. Position Variation for 13 kV Extract 0 mm 200 mm ex = 1.36 ey = 1.47 p mm mrad ex = 1.82 ey = 1.96 p mm mrad 100 mm 300 mm ex = 1.65 ey = 1.78 p mm mrad ex = 1.90 ey = 2.04 p mm mrad Simon Jolly, Imperial College

  14. Results of Position Variation • Behaviour as expected: steady expansion in beam size along the beam axis. • Emittances show no obvious nonlinearities; increases may be a result of space charge effects. • Level of space charge compensation needs to be investigated with beam dynamics simulations. • Flat top and bottom of the beam profile are likely due to collimation occurring upstream of the ion source exit. Simon Jolly, Imperial College

  15. 6 kV Extract: 0 mm Simon Jolly, Imperial College

  16. 9 kV Extract: 0 mm Simon Jolly, Imperial College

  17. 13 kV Extract: 0 mm Simon Jolly, Imperial College

  18. 17 kV Extract: 0 mm Simon Jolly, Imperial College

  19. Variation of Extract Voltage at 0 mm 6 kV 13 kV ex = 0.25 ey = 0.77 p mm mrad ex = 1.36 ey = 1.47 p mm mrad 9 kV 17 kV ex = 0.74 ey = 1.14 p mm mrad ex = 2.02 ey = 1.92 p mm mrad Simon Jolly, Imperial College

  20. Results of Extract Variation • Distinct change in beam shape, density distribution and emittance: • 6 kV shows strong asymmetric divergence in both planes. • 9 kV shows mostly vertical expansion. • 13 kV is nearly symmetric and slightly collimated. • 17 kV dominated by collimation. • A number of factors contribute to changes: • Upstream collimation. • Change in extract potential: changes shape of field within extract region, and affects shape of discharge plasma. • Increase in extract potential also requires change in 90° sector magnet current: change focussing effect of fringe fields. • Decrease in post-acceleration voltage means transverse focussing from fringe fields within post-acceleration gap will change. Simon Jolly, Imperial College

  21. Results Summary Simon Jolly, Imperial College

  22. 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 Simon Jolly, Imperial College

  23. Scintillator/Pepperpot Comparison: 6 kV Simon Jolly, Imperial College

  24. Scintillator/Pepperpot Comparison: 9 kV Simon Jolly, Imperial College

  25. Conclusions • First results already promising. • Detailed research program under discussion: start with categorising scintillator. • Clear comparison between scintillator and pepperpot measurements: calibration markings should allow precise correlation between the two. • Quality of results should improve with latest modifications. • Lots of data to take… Simon Jolly, Imperial College

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