Transverse Emittance Scanning Techniques at ISIS

1. Transverse Emittance Scanning Techniques at ISIS Scott Lawrie

2. Emittance Measurements at ISIS • Transverse emittance only measured at low energy • Slit-slit scanners on ISIS LEBT • Slit-slit & pepperpot on ISDR • Additional laser emittance measurements to be used on FETS

3. Slit-Slit Technique

4. ISIS LEBT Emittance Scanners Installation of RFQ at ISIS, 2004

5. Ion Source Development Rig (ISDR) Emittance Scanners

6. The Slit-Slit Scanners

7. The Slit-Slit Scanners 0.08 x 60 mm slit and Faraday cup 500 V Electron Suppressor 0.25 x 60 mm position sampling slit

8. The Slit-Slit Scanners Vacuum Resistance Springs Main Arm Stepper Motor Data Output Cable Electron Suppressor Voltage Slit and Cup Stepper Motors

9. The Slit-Slit Scanners Main Arm Travel Distance = 18 cm Slit and Cup Travel Distance = 6.4 cm

10. The Slit-Slit Scanners • Maximum position resolution 0.25 mm • Maximum angle resolution 4 mRad • Maximum time sample rate 2 µs • Scan can be split into two • Total position scan range 120 mm • Scanning time 5 mins (0.5 mm res.) or 10 mins (0.25 mm res.) per arm • Soft interlock ensures fully parked before starting scan

11. Example Scan

12. Slit-Slit Scanner Software

13. Slit-Slit Scanner Software • Multiple document interface in C# • Fully multi-threaded throughout • Save and retrieve scans for comparison • Communicate with scanning arms • Hardware independent • Automatic or manual axis scaling • Simple scanning parameter setup

14. Slit-Slit Scanner Software • Suit of data analysis tools • Beam current vs. time plot • Beam integral profile plot • Highlight beam wings and haloes • Background noise drift and bias removal • Repair broken pixels • Thorough emittance calculations • Threshold cut method • SCUBEEx method

15. Pepperpot Technique

16. The ISDR Pepperpot

17. The ISDR Pepperpot 10 µm accuracy digital vernier. Longitudinal movement up to 700 mm Light-tight bellows • PCO 2000 Camera • Temperature controlled CCD • 2048 x 2048 pixel • f / 2.8 shutter • 0.5µs sample rate • FireWire output Beam shutter control

18. The ISDR Pepperpot Window Quartz scintillator glass Moveable stage and camera mount Pepperpot head mount

19. The ISDR Pepperpot • Tungsten mask • 50 µm holes • 3 mm pitch • 41 x 41 array • Copper grid • 2 mm holes • 10 mm drift length • Prevents beamlet crossing • Improves cooling

20. The ISDR Pepperpot • Per spot resolution 3 mm • Per pixel resolution 0.07 mm • Maximum angle resolution 7 mRad • Imaging area 120 x 120 mm² • Calibration image taken for each scintillation image • Match each beam spot with hole it came from to determine divergence • Correct for skew etc

21. Example Images Scintillation Spots Calibration

22. Pepperpot Analysis Software

23. Pepperpot Analysis Software • Image calibration • Skew correction • Display various plots • Spot Image of profile • Quiver plot of profile • Histogram of phase space… etc • Calculate emittance • Export particle positions to GPT

24. Comparison of Results εH = 0.80 norm. π mm mRad εH = 0.82 norm. π mm mRad εV = 0.35 norm. π mm mRad εH = 0.32 norm. π mm mRad

25. Comparison of Results

26. Comparison of Results

27. Photodetachment Technique

28. Future Emittance Measurements • Novel laser wire emittance scanner • Non-destructive • Can use even with high beam power • Laser acts as “slit”, scintillator as “grid” • Profiles taken at various positions • Combine using Maximum Entropy Technique (MENT) to calculate emittance

29. Summary • Transverse emittance well understood for beam from the ISIS ion source • Two highly successful methods • Comprehensive data analysis software • Calculated emittance values agree • Continual improvement and development of new techniques

30. Questions? Scott Lawrie ISIS, Rutherford Appleton Laboratory, STFC, UK scott.lawrie@stfc.ac.uk

31. Additional Slides

32. Slit-Slit Diagnostics Beam profile monitor Beam current monitor

33. Enhance Beam Halo Contrast Contrast off, 0% cut Contrast on, 0% cut 3% cut 7% cut

34. Background Drift Removal Raw data: Data with fixed drift:

35. Fix Broken Pixels/Columns Shifted Pixels Repaired Raw data

36. Pepperpot Plots

37. Scintillator Material • Tested various scintillators for: • Light output intensity • Light decay time • Lifetime of material when exposed to beam • Tried: • P46, P47, P43  good light output, short lives • LYSO, BSCO, PbWO4, CdWO4  poor lifetimes • Ruby, YAG:Ce  Promising, but no big sheets • Settled for pure quartz

38. P46 Phosphor Damage Multi-spot damage (front view) Single spot damage (front view) Spot intensity Single spot damage (side view)

39. Plastic Scintillator Damage Multi-spot damage (front view) Single spot damage (front view) Single spot damage (side view) Spot intensity

40. SCUBEEx Emittance Method Half-axis product = 50 [Ref: Martin Stockli, Rod Keller, Alan Letchford et al, AIP Conference Proceedings, Vol. 639, pp 135-159 (2002)]

41. SCUBEEx Emittance Method Half-axis product = 200

42. SCUBEEx Emittance Method Half-axis product = 500

43. SCUBEEx Emittance Method Half-axis product = 1000

44. SCUBEEx Emittance Method Half-axis product = 5000

45. SCUBEEx Emittance Method Normalised Horizontal emittance = 0.31 ± 0.01 π mm mRad (Re: Emittance calculated using 10% threshold = 0.35 π mm mRad)

46. SCUBEEx Emittance Method

47. SCUBEEx Emittance vs. Time 80 µs 90 µs 150 µs 300 µs