High Dynamic Range Beam Imaging with a Digital

High Dynamic Range Beam Imaging with a Digital Optical Mask* Presented by Tim Koeth (UMD) on behalf of R. B. Fiorito, H. D. Zhang, A. Shkvarunets UMD, College Park, Maryland S. Zhang, S. V. Benson, D. Douglas, F. G. Wilson JLAB, Newport News, Virginia DITANET Beam Diagnostics Conference November 9 -11, 2011, Seville, Spain *Work Funded by US ONR, DOD JTO and DOE Office of HEP 1

Outline • Introduction • Motivation and Challenges of Halo Measurements • Current diagnostic techniques • New Adaptive Halo Imaging Technique using Digital Micromirror Device (DMD) • Experimental Results • University of Maryland Electron Ring (UMER) • JLAB FEL • Future Plans 2

Motivation and Challenges Negative effects of Beam Halo • Beam Loss • Activation of Beam line components • Emittance Growth • Emission of Secondary Electrons • Increased Noise in Detectors Challenges to diagnostics of halos • Need high dynamic range: >~105 • Adaptive to variable beam core 3

Previous Experimental Methods Wire Scanner and Scraper Assembly Ionization beam profile monitor Low-Energy Demonstration Accelerator - LANL DR: 103 DR: 105 P. Cameron, et al. Proc. of PAC 99: 2114 -2116, 1999 T. P. Wangler, et. al. , Proc. PAC 01 Imaging Techniques High Dynamic Range Camera Passive Spatial Filtering Spectra-Cam CID $$ solar coronagraphy applied to beams DR >105 measured with laser DR: 106 -107 C. P. Welsch, et. , Proc. SPIE 6616, 9 (2007). T. Mitsuhashi, EPAC 2004. 4

Digital Micro-mirror Device* *DLPTM Texas Instruments Inc. 120 Optimized to visible, Used in HD TV & Pro Available as developm Array dimensions: 14 Pixels: 1024 x 768, Pixel dimension: 14 x 1 Switching rate: 9600 Individual pixel addre 5

Beam Halo Imaging System using DMD developed at UMD* *R. Fiorito, H. Zhang, A. Shkvarunets, et. al. Proc. BIW 2010 Pixels near saturation 32 mm Beam optical radiation Source Mirror L 1 180 Frames Computer L 2 L 3 L 4 Halo Light Core Light 32 mm Image 2 Camera Sensor Mask Image 1 900 Frames Pixels near saturation DR >105 DMD Two compensations are needed, DMD rotated 45 o & path length 6

Scheimpflug compensation Lens Target reflected light 240 Incident light 120 Image on DMD mirror Scheimpflug intersection θ Micro-mirrors φ u Image on DMD Lens focus length f v Image on CCD 7

DMD Imaging Experiments on University of Maryland Electron Ring (UMER) Screen Energy (ke. V) 10 Pulse width (ns) 100 Repetitive rate (Hz) 20 -60 Beam current (m. A) 0. 6 , 6, 21, 80 9

Dynamic Range measurement of imaging system 32 mm Phosphor screen image of 21 m. A beam 20 275 1000 290 pixel Integration Frames: 2000 3000 5000 10

Dynamic Range Measurement at UMER 0 32 mm -1 Log I/I 0 -2 -3 -4 -5 32 mm 11

Spatial Filtering Ability of DMD Beam on, DMD all off 32 mm Beam on, DMD all on 180 21 m. A beam 12

Comparison of Images obtained with DMD and Mirror DMD all on (with Scheimplug compensation) DMD all floating (no compensation) Simple Mirror (no compensation) 13

Quadrupole Induced Halo Experiments on UMER Quadrupole Screen 14

Demonstration of adaptive threshold masking Quadrupole Current (a) y 70 82. 9%I Q 66. 3%I Q 49. 7%I Q 32 mm IQ x 45 45 60 640 660 250 (b) 280 15

Non Interceptive Beam/Halo Imaging at JLAB using Optical Synchrotron Radiation Bending Magnet Quadrupoles 16

Quadrupole Scan Using OSR with Tune-up Beam (E=135 Me. V, I= 0. 32 m. A: 2 Hz rep-rate, 250 ms macro, 4. 68 MHz micro, 135 p. C/micro ) Quad strength 4 mm 500 G 0 GG 300 -500 G 0 G -700 G -1000 G -1700 G -2000 G -2500 G -3000 G

OSR Halo Imaging of JLAB CW beam with DMD threshold mask 11. 6 mm (I = 0. 63 m. A, 4. 68 MHz, 65 pc/micropulse, l= 654 nm x 90 nm , ND=0. 4 ) 0. 04 s 0. 18 s 11. 6 mm 1. 6 s 6. 5 s 42 s

Measurement of Dynamic Range of imaging system

Measurement of Dynamic Range of 0. 6 m. A CW Beam

Reconstructed intensity distribution J(x, y) and calculated total radiant energy ETotal (1 - 10 -6 ) Jmax (1 -10 -2 ) Jmax (10 -2 -10 -6) Jmax

Summary • Results • • • Developed and tested high-dynamic range ( DR ~105 ) halo diagnostic imaging system using a phosphor screen + DMD at UMER Developed a non interceptive OSR DMD imaging system to observe beam halo at JLAB FEL under CW operating conditions; with measured DR > 106. Performed quad scan of JLAB tune-up beam using OSR • Future plans UMER: Do time-resolved halo imaging and multi-turn halo evolution studies at UMER using DMD to study/mitigate factors effecting halo • JLAB: Short terms: Verify and possibly improve DR >~10(5) of present system 1 a) Improve background measurements and verify halo is not due to stray light from upstream internal sources 1 b) decrease optical magnification onto DMD and /or increase current density via current, focusing/tune; Long term: Extend DR of halo measurement to limit: 1) add Lyot and/or apodizing stops to decrease effect of diffraction 2) improve optical transport with enclosures and antireflection coating on optics port to further reduce any external stray light • Compare emittance measurements using OTR and OSR quad scans • Explore possibility of using DMD to measure halo/core emittances and to do optical phase space mapping (optical analogy of pepper pot technique) •