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. ShkvarunetsUMD, College Park, Maryland

S. Zhang, S. V. Benson, D. Douglas, F. G. WilsonJLAB, Newport News, Virginia

*Work Funded by US ONR, DOD JTO and DOE Office of HEP1

DITANET Beam Diagnostics Conference November 9-11, 2011, Seville, Spain

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 Plans2

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

3

Challenges to diagnostics of halos

• Need high dynamic range: >~105

• Adaptive to variable beam core

Wire Scanner and Scraper Assembly

Low-Energy Demonstration Accelerator - LANL

DR: 105

T.P.Wangler, et. al., Proc. PAC01

Ionization beam profile monitor

DR: 103

P. Cameron, et al. Proc. of PAC99: 2114-2116, 1999

Previous Experimental Methods

4

High Dynamic Range Camera

Spectra-Cam CID $$

DR >105 measured with laser

C.P. Welsch, et. , Proc. SPIE 6616,9 (2007).

Passive Spatial Filtering

solar coronagraphy applied to beams

DR: 106-107

T. Mitsuhashi, EPAC 2004.

Imaging Techniques

Digital Micro-mirror Device*

120

*DLPTM Texas Instruments Inc.

5

Array dimensions: 14 x 10 mm Pixels: 1024 x 768, Pixel dimension: 14x14 m Switching rate: 9600 fpsIndividual pixel addressable

Used in HD TV & ProjectorsAvailable as development ‘kits’

Optimized to visible, IR, UV

Beam Halo Imaging System using DMD developed at UMD*

Computer

MirrorSource

Halo LightCore Light

DMD

Camera Sensor

L3

L4

L1

L2Computer

Camera Sensor

L3

MirrorSource

L1

DMD

L2

L4

Image 2

Image 1Mask

6

180 Frames

32 m

m

900 Frames

32 m

m*R.Fiorito, H.Zhang, A. Shkvarunets, et. al. Proc. BIW2010

Beam optical radiationPixels near saturation

Pixels near saturation DR >105 Two compensations are needed, DMD rotated 45o & path length

DMD mirror

Target

Image on DMD

12 0

240

Lens

Incident light

reflected light

Scheimpflug compensation

7

Micro-mirrors

θ φ

Image on DMD

Image on CCD

Lensfocus length f

Scheimpflug intersection

vu

arctan(uv

tan)

240

Screen

DMD Imaging Experiments on University of Maryland Electron Ring (UMER)

Energy (keV) 10

Pulse width (ns) 100

Repetitive rate (Hz) 20-60

Beam current (mA) 0.6 , 6, 21,80 9

Screen

Dynamic Range measurement of imaging system

10

Integration Frames:

20

Phosphor screen image of 21 mA beam

275

32m

m

1000

290

pixe

l

2000 3000 5000

11

Dynamic Range Measurement at UMERDynamic Range Measurement at UMER

32mm

Log I/I0

-5

-4

-3

-2

-1

0

32 mm

Spatial Filtering Ability of DMD

100 200 300 400 500

100

200

300

400

500

50

100

150

200

250

100 200 300 400 500

100

200

300

400

500 0

1

2

3

4

5

6

x 104

Beam on, DMD all on Beam on, DMD all off

12

180 180

21 mA beam

32m

m

100 150 200 250 300 350

150

200

250

300

350

400 0

0.2

0.4

0.6

0.8

1

200 250 300 350 400 450

250

300

350

400

450

500 0

0.2

0.4

0.6

0.8

1

DMD all on (with Scheimplug compensation)

Simple Mirror (no compensation)

100 150 200 250 300 350

250

300

350

400

4500

0.2

0.4

0.6

0.8

1

DMD all floating(no compensation)

Comparison of Images obtained with DMD and Mirror

13

Quadrupole

Screen

Quadrupole Induced Halo Experiments on UMER

14

Screen

70

280

xy(a)

(b)

IQ

640 660 250

45 45 60

82.9%IQ 66.3%IQ 49.7%IQ

Demonstration of adaptive threshold masking

Quadrupole Current

32m

m

15

Bending Magnet

Non Interceptive Beam/Halo Imaging at JLAB using Optical Synchrotron Radiation

16

Quadrupoles

500 G 300 G 0G-500 G

-700 G -1000 G

-1700 G

0 G

1

2

3

4

5

6

x 104

-2000 G

-2500 G

-3000 G

4 mm

Quadrupole Scan Using OSR with Tune-up Beam

(E=135 MeV, I= 0.32mA: 2Hz rep-rate, s macro, 4.68MHz micro, 135pC/micro )

Quadstrength

0

1

2

3

4

5

6

x 104

11.6

mm

11.6 mm0.04 s 0.18 s

1.6 s 6.5 s 42 s

OSR Halo Imaging of JLAB CW beam with DMD threshold mask

(I = 0.63 mA, 4.68MHz, 65pc/micropulse, 654nm x 90nm , ND=0.4 )

Measurement of Dynamic Range of imaging system

Measurement of Dynamic Range of 0.6 mA CW Beam

0 2 4 6 8 1010-6

10-5

10-4

10-3

10-2

10-1

100

Position (mm)

Nom

aliz

ed C

ount

(a.u

.)

12345

(1- 10-6 ) Jmax (1 -10-2 ) Jmax

Reconstructed intensity distribution J(x,y) and calculated total radiant energy ETotal

(10-2 -10-6) Jmax

ETotal J(x,y)dxdyS

E ~ 0.99ETotal

E ~ 0.01ETotal

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 1a) Improve background measurements and verify halo is not due to stray

light from upstream internal sources 1b) 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)