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A Digital Micro-mirror array-based beam halo monitor

A Digital Micro-mirror array-based beam halo monitor. Blaine Lomberg University of Liverpool and The Cockcroft Institute 3 rd OPAC Topical Workshop on Beam Diagnostics. Layout. Aims Basic principles Design and development Halo Monitor operation Software control Masking Algorithm

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A Digital Micro-mirror array-based beam halo monitor

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  1. A Digital Micro-mirror array-based beam halo monitor Blaine Lomberg University of Liverpool and The Cockcroft Institute 3rd OPAC Topical Workshop on Beam Diagnostics B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  2. Layout • Aims • Basic principles • Design and development • Halo Monitor operation • Software control • Masking Algorithm • Preliminary Results • Summary B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  3. Aims To demonstrate the operation of an optimized, programmable light filtering device and use it as a adaptable optical mask that employs a digital micro-mirror array to produce an image of the halo of a beam with an enhanced dynamic range. • “Beam Halo” is associated with many negative effects for high Intensity Beams: • Particle losses lead to nuclear activation, • Increase in secondary emission, space-charge. • Damage of the surrounding vacuum chamber. • Using the monitor to observe the number of particles in the tail region of the beam distribution • and minimise particles at large radii (nσ: n=3-4 ) from beam core. • What makes this monitor so special ? • HDR can be extended easily • Provide knowledge on beam losses which originate in the low-density halo that extend far from the beam core B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  4. Basic Principles • Define Beam Halo: Beam Losses associated with a small fraction of particles surrounding a dense beam core. • Difference between “tail” and “halo” (Beam losses?) • Knowledge about the structure of halo • Depend: beam distribution or halo mechanism • Define it either by “geometrical characteristic” or “nature of mechanism”* • Formation due to specific halo Mechanisms** • Provide understanding and possible control/prevention • *(ICFA Workshop “Halo 03”, Long Island 2003) • **(ICFA Workshop “Halo and Scraping”, Wisconsin 1999) B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  5. 10.8 um Design and Development • 1920 x 1080 array Al micro-mirror [ Discovery 4100] • USB Interface (0.95” Chipset ) • DMD dimensions 14.4x10.8 mm • high-speed port 64-bit @ 400 MHz for data transfer • up to 23.148 full array mirror patterns / sec (48 GBs) B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  6. HALO MONITOR OPERATION 48o Rough Halo 4σ Beam Spot 24o B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  7. Compensations 1. DMD micro-mirrors have three possible states: - all floating, flat state ( no power) - two independent assignable + or - 120 states (power on) 2. Rotation axis along diagonal of each micro-mirror, i.e. at 45 degrees wrt to HD-DMD row or column - rays imaged onto the DMA plane are reflected with different optical path lengths at twice the angle of incidence 3. Diffraction effects: array acts like a 2D grating producing diffraction patterns B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  8. Scheimpflug Angle Lens Path length difference generated by DMD tilted mirror Reflected Beam 24o 12o Target Image on DMD Incident Beam DMD Mirror Pixel B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  9. Software Control B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  10. Calibration/Correction 2 7 • The selection of 8 reference points 8 1 5 4 3 6 B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  11. Masking Algorithm • Integrate the LabView of CCD/DMD with • Improve the effectiveness of the “Masking” on any beam shape • Make a fully automated halo measurement in one simple program Adaptive light filtering for masking any beam shape B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  12. Coordinate Transformations • Information transfer from CCD to DMD • Define area • Set mask limit or size B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  13. Priliminary results • DR with CCD only DR~>10-2 (i.e. ~400) • Extended with HD-DMD B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  14. HD-DMD Filtering Ability Beam on, DMA all off Beam on, DMA all on 1mm CCD exposure time=15ms, gain=1 B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  15. Comparison of Images DMA all on (with Scheimplug compensation) DMA all floating (no compensation) I = 20k counts INormal = 5k counts Texposure=15ms , Gain=1 Texposure=15ms , Gain=1 B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  16. 1.5mm Laser spot image (colour corresponds to pixel value) Masked(Smoothed image ) 1D distributions; Fitted to the equation Masked profile Full profile Vertical (95% confidence bounds) a = 0.2466 (0.239, 0.2542) b = 0.08099 (0.07766, 0.08432) c = 0.1315 (0.1268, 0.1362) Vertical (95% confidence bounds) a = 1.045 (1.037, 1.052) b = 0.09277 (0.09229, 0.09326) c = 0.07938 (0.07869, 0.08007) Goodness of fit: SSE: 0.7308 R-square: 0.7682 Adjusted R-square: 0.7678 RMSE: 0.02436 Goodness of fit: SSE: 0.464 R-square: 0.9867 Adjusted R-square: 0.9867 RMSE: 0.01942 Horizontal (95% confidence bounds) a = 1.041 (1.035, 1..047) b = 0.1314 (0.1311, 0.1317) c = 0.05562 (0.05524, 0.056) Horizontal (95% confidence bounds) a = 0.2366 (0.2298, 0.2433) b = 0.125 (0.1229, 0.1272) c = 0.09309 (0.09003, 0.09616) Goodness of fit: SSE: 0.7007 R-square: 0.7675 Adjusted R-square: 0.7673 RMSE: 0.02079 Goodness of fit: SSE: 0.3539 R-square: 0.9893 Adjusted R-square: 0.9893 RMSE: 0.01478 B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  17. Top Level masking • From a geometrical perspective: • Define the halo as the area that contains all particles outside the Gaussian shaped beam core. • To increase DR, mask needs to be larger and then exposure time extended. B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  18. Overflow (error) • Signs of charge overflow and could allow using the DMD to characterize a whole range of sensors. B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  19. Summary • The method is versatile and adaptable to any accelerator • High or low intensity, energy or any particle species • Preliminary Results • Adaptive mask method developed and use to measure halo of laser • High dynamic range measured (~ 10-4) • Good filtering ~10-4 • Limitations on dynamic range • Beam intensity • Screen property: efficiency, saturation, light filters • Scattered light • Possible solution in accelerator • higher intensity beam (LHC) • More efficient screen, e.g. YAG, or use of OSR, OUR etc. • improve optics (large aperture optics, Lyot stops) B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  20. Future Work • Gas-jet monitor measurements at Cockcroft Institute • Other prospects • Study halo propagation in the BSRT at CERN • Experiments at the ALICE facility at Daresbury Labs B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

  21. Thank you Acknowledgements: This work is supported by the European Union under contract PITN-GA-2011-289485 and by STFC under the Cockcroft Institute Core Grant No. ST/G008248/1. B.Lomberg-3rd OPAC Topical Workshop on Beam Diagnostics: Beam Halo Talk- Vienna, Austria

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