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Adaptive Optical Masking Method and Its Application to Beam Halo Imaging

Adaptive Optical Masking Method and Its Application to Beam Halo Imaging. Ralph Fiorito H. Zhang, A. Shkvarunets, I. Haber, S. Bernal, R. Kishek, P. O’Shea Institute for Research in Electronics and Applied Physics, University of Maryland S. Artikova MPI- Heidelberg C. Welsch

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Adaptive Optical Masking Method and Its Application to Beam Halo Imaging

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  1. Adaptive Optical Masking Method and Its Application to Beam Halo Imaging Ralph Fiorito H. Zhang, A. Shkvarunets, I. Haber, S. Bernal, R. Kishek, P. O’Shea Institute for Research in Electronics and Applied Physics, University of Maryland S. Artikova MPI- Heidelberg C. Welsch Cockcroft Institute, University of Liverpool

  2. Imaging Halos Problems: 1) Need High Dynamic Range ( DR >10(5) - 10(6) ) 2) Core Saturation with conventional CCD’s: blooming, possible damage 3) Diffraction and scattering associated with high core intensity - contaminates halo image Solutions: 1) High Dynamic Range CID Camera (Spectra-Cam), DR ~ 10(6) measured with laser by J. Egberts, et, al. MPI-Heidelberg 2) Spatial filtering a) Fixed mask (solar coronagraphy applied to beams) DR = 10(6) -10(7) beamcore to halo intensity observed by Mitsuhashi (KEK) b)Adaptive Mask based on Digital Micromirror Array; DR ~ 10(5) measured with laser and 8 bit CCD by Egberts, Welsch

  3. 1) High Dynamic Range CID Camera: Thermo Scientific SpectraCAM Features: 1- Non destructive read out 2- DR (advertised): 28 bit; DR > 10(5) measured with laser* 3- CID: greater radiation hardness than CCD 4- High cost > $25K *C.Welsch, E.Bravin and T.Lefevre Proc.SPIE 2007

  4. 2) OSR halo monitor at KEK employing Lyot Coronograph* Lyot Coronograph beam image w/o filter *T. Mitsuhashi, EPAC 2004 and Faraday Cup Award presentation 2004

  5. 120 13.8 um 3) Adaptive Mask using Digital Micromirror Array* *DLPTM TexasInstruments Inc. • 1024 x 768 pixels (XGA) [ Discovery 1100] • USB Interface • high-speed port 64-bit @ 120 MHz for data transfer • up to 9.600 full array mirror patterns / sec (7.6 Gbs) Micro mirror architecture: Segment of DMA:

  6. Basic Idea of the adaptive mask using DMA (4) Integrate and Reimage Halo (1) Image onto DMA (2) Define “core” (3) Generate mask to block “core”

  7. Optics Design Developed at UMD for Beam Imaging with DMA alignment laser 240 lamp target CCD camera magnifying + focusing lenses DMA Image of Circular Target on CCD) Area of DMA 32 mm 450

  8. Mask Generating Algorithm Dx CCD coordinates DMA coordinates 1024 x 768 pixels 512x512 pixels Y’’ y y’ Magnify y0’ Dy y0 Y0” x’ x0’ x0 x X0” X’’ Generate and apply Mask to DMA Re-image beam

  9. Beam Parameters: E = 10 keV I = 1-100 mA Dt = 1- 100 ns www.umer.umd.edu

  10. DMA Imaging Setup at IC1 (first optical cross just after the gun) DMA ICCD mirror lens view port lenses mirror mirror

  11. Optics System and Image process 32 mm 32 mm 900 Frames 180 Frames DMA 13

  12. Dynamic Range Measurement using intense beam and concentric circular masks (23mA beam Bias voltage: 30V Solenoid current: 7.9A) 290 pixel 20 65 140 275 530 820 32mm 1000 1150 1550 2000 2300 2600 5000 3000 3600 4300 5800 7000

  13. Circular Mask Data line profile with smoothing and background subtraction 32mm 1 15 0

  14. Testing the filtering ability of the DMA Beam on, DMA all on Beam on, DMA all off 180 Gates 250 Gain 23mA beam 50V bias voltage 5.5A solenoid current

  15. Comparison of Images with DMA and Mirror DMA all on (with Scheimplug compensation) Mirror (no compensation) DMA all floating (no compensation) INormal = 61k counts INormal = 64k counts INormal = 59k counts 180 Gates 250 Gain 120 Gates 250 Gain 260 gates 250 Gain

  16. Halo Measurement in RC7 32mm 18

  17. Core + Halo Variation by varying Quadruple Focusing at RC7 (23mA) “Matched” 12.4%o 28.8% 32mm 19

  18. Halo measurement (7 mA beam) f0 70 130 280 82.9% f0 20 45 80 360

  19. 66.3% f0 45 85 660 49.7% f0 21 60 250

  20. Future Prospects

  21. OSR-DMA Halo Imaging Experiment at JLAB FEL Site of OTR and OSR diagnostics experiments

  22. Optics for OSR DMA Halo Experiment (Installed at FEL 8/2010 ) 500 mm Gallery optics: side view Gallery optics: top view Vault Optics: side view 24o FEL Vault ceiling Camera 5 m PVC tube 1219 mm DMA OSR Port (2F06) 1000 mm 457 mm

  23. Mitigation of COTR by Fourier Plane Filtering at LCLS COTR Calculations :250 MeV Gaussian beam(σ = 0.2mm > gl/2p) Near Field Intensity Distribution 0.6 0.8 0.4 0.2 0 radius (mm) Far field (Angular) Intensities of COTR and IOTR IOTR COTR 0 0 1/g 2/γ Observation angle

  24. Mitigation of COTR by Fourier Plane Filtering Mask λ=600nm

  25. Optical system for spatial filtering/mitigation of COTR Focal plane of FI (angular Image plane) Splitter with mask Lens1, F1=250mm OTR target 2 F1 2F1 2F2 Sensor focused on target, 1:1 Lens2, F2=125mm 2F2 Sensor focused on splitter, angular image, 1:1

  26. Optical system for Fourier plane filtered Imaging with DMA Source Plane DMA at Focal plane of FI (angular image plane) L1 F1 L2 Sensor focused on Source Plane

  27. Limitations on Dynamic Range of DMA for Halo Imaging 1- Ratio of Beam to Screen size 2- Beam Intensity : Nphotons/cm2 3- Photon Yield of Screen 4- Dynamic Range of Screen itself (saturation, linearity) 5- Light scattering/diffraction in optics 6- Integration time for halo measurement (beam stability issue) Possible solutions: 1- Higher beam intensity + attenuators 2- Higher DR/linearity “screens” e.g. OTR, OSR, OER 3- Improved optics: polarizers, Lyot stops, etc.

  28. Summary • Successful Results • Adaptive mask method developed and use to measure halo of UMER • High dynamic range measured with real beam (~ 105) • Good filtering ~105 • Limitations on dynamic range • Beam intensity • Screen property: efficiency, saturation • Scattered light • Possible solution • higher intensity beam (other accelerators ) • More efficient screen, e.g. YAG, or use of OSR, OUR etc. • improve optics (polarizer, Lyot stops) • Future prospects • Study halo propagation in the first turn in the UMER ring • Experiments at other facilities (JLAB, SLAC/LCLS,SPEAR3) 30

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