Hao Zhang University of MarylandUniversity of LiverpoolCockcroft Institute Outline Introduction Motivation to Study Beam Halo Method Adaptive Method Using Digital Micromirror Device Experiment ID: 787543
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Slide1
Beam Halo Monitoring using Optical Diagnostics
Hao
Zhang
University of Maryland/University of Liverpool/Cockcroft Institute
Slide2Outline
Introduction
Motivation to Study Beam Halo
Method
Adaptive Method Using Digital Micro-mirror DeviceExperiment University of Maryland Electron Ring (UMER)JLAB FELInjection of SPEAR3 storage ring
2
Slide3Beam Halo has many
negative
e
ffectsNuclear Activation of The Transport ChannelEmittance GrowthEmission of Secondary Electrons
Increasing Noise in The
Detectors
Halo Picture credit: Kishek, Stratakis
Motivation for Beam Halo Studies
3
Halo can be regarded as small fraction of particles out a well defined beam core.
Slide4Solutions: 1) Passive spatial filtering, e.g. solar
corography
applied to beam imaging
by T.
Mitsuhashi of KEK DR = 106-107 achieved 2) Spectra-Cam CID , DR ~ 106 measured with laser by J. Egberts
, C.
Welsch
, T. Lefevre
and E. Bravin 3) Adaptive Mask based on Digital
Micromirror Array; DR ~ 10
5 measured with laser and 8 bit CCD camera by
Egberts
, Welsch
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.
Imaging Halos
4
Slide5Digital Micro-mirror
arrayDevice
*
Micro-mirror architecture:
12
0
*DLP
TM
Texas
Instruments Inc.
45
0
5
Mirror size: 13.68 um x 13.68 um
Resolution
: 1024 X 768 pixels
Slide6Computer
Mirror
Source
Halo Light
Core Light
DMD
Camera Sensor
L3
L4
L1
L2
Computer
Camera Sensor
L3
Mirror
Source
L1
DMD
L2
L4
Image 2
Image 1
Mask
Adaptive Method for Halo Measurement
6
32mm
Slide7Quadrupole
Screen
Energy (
keV
)
10
Pulse width
(ns)
100
Repetitive rate (Hz)
20-60
Beam current (
mA
)
0.6 ,
6, 21,80
UMER Experiment
7
Slide8Testing filtering ability of DMD
8
Beam on, DMD all on
Beam on, DMD all off
32mm
Average readout of the core region
49616
21
Slide920
275
1000
2000
3000
Integration Frames:
Dynamic Range Test of DMD with intense beam and circular mask*
9
Integration Frames:
32mm
Slide10Circular Mask Data line profile
10
0
1
32mm
Slide1170
280
x
y
(a)
(b)
I
Q
640
660
250
45
45
60
82.9%I
Q
66.3%I
Q
49.7%I
Q
Quadrupole
Current
32mm
Demonstration of Adaptive Masking on UMER
11
Slide12Bending Magnet
Energy
135
MeV
Macro pulse width:
1 ms
Repetitive rate:
60 Hz
Micro-pulse repetition rate :
4.68 MHz
Charge:
60 pc/micro pulse
Halo Experiment with OSR in
JLab
FEL
12
Beam pipe
Slide131
1.2 s
No mask
X
y
4 mm
4 mm
Integration Time
3
5
2
4
6
2.2 s
1.5 s
4 s
80 s
25000
5000
35000
15000
2000
Mask Level
Masking OSR Image of JLAB FEL Beam
13
14 s
Slide14Measurement of Dynamic Range for OSR DMD System
14
10
0
10
-2
10
-4
10
-6
Normalized Counts
pixel
Slide15DMA/DMD Configuration
M=4
M=1
M=0.14
Slide16More Details…
Mechanical Shutter
(5ms)
Diffraction pattern
1000x1000 DMD
Filter wheel
f=+125mm
f=+100mm, 2”
dia
Scheinflug
angle
Slide179.6m
M1=0.138
M2=3.55
DMD
M3=1
M = M1*M2*M3 = 0.4
7.14m
f=+2m
f=+125mm
f=+100mm
Aperture &
Cold finger
24°
PiMax
Filter wheel
OSR
Source
Injector
READOUT
Gate
Injected beam
Stored beam
SPEAR3
D
ata
acquisition
BTS
Slide18PSF measurement of the stored beam
2 ms shutter mode
Increase the mask size by changing the intensity threshold level
ND filter from ND =5 to ND = 0
ND 5
ND 4
ND 3
ND 2
ND 1
ND 0
Mask
18 mm
No Mask
Slide19Injected beam with presence of stored beam with different currents
(a)
(b)
6.11
mA
3.05
mA
1.52
mA
0.42
mA
Current /bunch
Stored beam
Injected
beam
18 mm
Slide20Three matching condition by altering the quads in the BTS
Slide21Evolution of Beam
centroid
and beam size
Slide22Conclusion
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.
Slide23Discussion
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?