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Beam Halo Monitoring using Optical Diagnostics. Hao Zhang University of Maryland/University of Liverpool/Cockcroft Institute. Outline. Introduction Motivation to Study Beam Halo Method Adaptive Method Using Digital Micro-mirror Device Experiment

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Beam halo monitoring using optical diagnostics

Beam Halo Monitoring using Optical Diagnostics

Hao Zhang

University of Maryland/University of Liverpool/Cockcroft Institute


Outline
Outline

  • Introduction

    • Motivation to Study Beam Halo

  • Method

    • Adaptive Method Using Digital Micro-mirror Device

  • Experiment

    • University of Maryland Electron Ring (UMER)

    • JLAB FEL

    • Injection of SPEAR3 storage ring


Motivation for beam halo studies
Motivation for Beam Halo Studies

Halo can be regarded as small fraction of particles out a well defined beam core.

  • Beam Halo has many negative effects

    • Nuclear Activation of The Transport Channel

    • Emittance Growth

    • Emission of Secondary Electrons

    • Increasing Noise in The Detectors

Halo Picture credit: Kishek, Stratakis


Imaging halos
Imaging Halos

Problems: 1) Need High Dynamic Range ( DR >105 - 106)

2) Core Saturation with conventional CCD’s: blooming, possible damage

3) Diffraction and scattering associated with high core intensity

contaminate halo

4) Adaptability when the beam core shape change.

Solutions: 1) Passive spatial filtering, e.g. solar corography applied to beam imaging

by T. Mitsuhashi of KEK DR = 106-107achieved

2) Spectra-Cam CID , DR ~ 106measured with laser

by J. Egberts, C. Welsch, T. Lefevre and E. Bravin

3) Adaptive Mask based on Digital Micromirror Array; DR ~ 105 measured with laser and 8 bit CCD camera by Egberts, Welsch


Digital micro mirror arraydevice

120

Digital Micro-mirror arrayDevice*

*DLPTM TexasInstruments Inc.

Micro-mirror architecture:

  • Mirror size: 13.68 um x 13.68 um

  • Resolution: 1024 X 768 pixels

450


Adaptive method for halo measurement
Adaptive Method for Halo Measurement

Source

Source

Mirror

Mirror

L1

L1

Computer

Computer

L2

L2

L3

L3

L4

L4

Halo Light

Core Light

Image 2

Camera Sensor

Camera Sensor

32mm

Mask

Image 1

DMD

DMD


Umer experiment

Quadrupole

Screen

UMER Experiment


Testing filtering ability of dmd
Testing filtering ability of DMD

Beam on, DMD all on

Beam on, DMD all off

32mm

Average readout of the core region

49616

21


Dynamic range test of dmd with intense beam and circular mask
Dynamic Range Test of DMD with intense beam and circular mask*

32mm

Integration Frames:

20

275

1000

Integration Frames:

2000

3000



Demonstration of adaptive masking on umer
Demonstration of Adaptive Masking on UMER mask*

Quadrupole Current

IQ

82.9%IQ

66.3%IQ

49.7%IQ

32mm

(a)

y

x

70

45

45

60

(b)

280

640

660

250


Halo experiment with osr in jlab fel
Halo Experiment with OSR in mask* JLab FEL

Bending Magnet

Beam pipe


Masking osr image of jlab fel beam
Masking OSR Image of JLAB FEL Beam mask*

y

1

3

2

4 mm

X

4 mm

1.2 s

No mask

Integration Time

Mask Level

2.2 s

25000

35000

1.5 s

6

5

4

14 s

4 s

15000

80 s

2000

5000


Measurement of dynamic range for osr dmd system
Measurement of Dynamic Range for OSR DMD System mask*

100

Normalized Counts

10-2

10-4

10-6

pixel


DMA/DMD Configuration mask*

M=0.14

M=4

M=1


More Details… mask*

Mechanical Shutter

(5ms)

Filter wheel

f=+125mm

f=+100mm, 2” dia

1000x1000 DMD

Scheinflug angle

Diffraction pattern


D ata acquisition
D mask* ata acquisition

Injector

Gate

Injected beam

READOUT

BTS

M3=1

f=+100mm

PiMax

24°

DMD

Stored beam

SPEAR3

f=+125mm

Filter wheel

M2=3.55

M = M1*M2*M3 = 0.4

Aperture &

Cold finger

OSR

Source

M1=0.138

9.6m

7.14m

f=+2m


Psf measurement of the stored beam
PSF measurement of the stored beam mask*

  • 2 ms shutter mode

  • Increase the mask size by changing the intensity threshold level

  • ND filter from ND =5 to ND = 0

No Mask

18 mm

ND 3

ND 4

ND 5

Mask

ND 0

ND 1

ND 2


Injected beam with presence of stored beam with different currents

Injected mask*

18 mm

Stored beam

beam

Current /bunch

0.42

mA

1.52

mA

3.05

mA

6.11

mA

Injected beam with presence of stored beam with different currents

(a)

(b)



Evolution of beam centroid and beam size
Evolution of Beam mask* centroid and beam size


Conclusion
Conclusion mask*

  • Applied a adaptive optics to detect small image signals from either beam halo or Injected beam compared with beam core or stored beam.

  • Achieve a high dynamic range with this method.


Discussion
Discussion mask*

  • How can we apply this method to other existing machines?

  • What is the limitation of dynamic range?

  • For Proton machine, since the beam is destructive, are there any usable screens?


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