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
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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 - PowerPoint PPT Presentation
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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
Imaging Halos
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
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
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
2) OSR halo monitor at KEK employing Lyot Coronograph*
*T. Mitsuhashi, EPAC 2004 and Faraday Cup Award presentation 2004
Lyot Coronograph
beam image w/o filter
3) Adaptive Mask using Digital Micromirror Array*
Segment of DMA:Micro mirror architecture:
13.8 um
120
*DLPTM Texas Instruments 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)
Mitigation of COTR by Fourier Plane Filtering at LCLS
250 MeV, Far field Intensities
Angle [1/]
0 2 4 6 8 10
Inte
nsity
[arb
. uni
ts]
1e-6
1e-5
1e-4
1e-3
1e-2
1e-1
1e+0
COTRIOTR
Mitigation of COTR by Fourier Plane Filtering
λ=600nm
Mask
Optical system for spatial filtering/mitigation of COTR
OTR target Lens1, F1=250mm
Lens2, F2=125mm
Splitter with mask
Sensor focused on target, 1:1
Sensor focused on splitter, angular image, 1:1
2 F1
Focal plane of FI(angularImage plane)
2F2
2F2 2F1
Optical system for Fourier plane filtered Imaging with DMA
SourcePlane
L2
Sensor focused on Source Plane
DMA at Focal plane of FI (angular image plane)
L1
F1
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.
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)