STREAK CAMERA 101 − Visualizing charged-particle beam dynamics Bingxin Yang ASD/DIAG, Advanced...
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Transcript of STREAK CAMERA 101 − Visualizing charged-particle beam dynamics Bingxin Yang ASD/DIAG, Advanced...
STREAK CAMERA 101 − Visualizing charged-particle beam dynamics
Bingxin Yang
ASD/DIAG, Advanced Photon Source, Argonne National Laboratory
Beam Instrumentation Workshop – May 3, 2006
2Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Outline and references
Outline of this talk Dual-sweep streak camera basics Visualizing longitudinal (phase) motion Visualizing transverse motion Viewing the bunch closely: projection at an angle Final remarks and summary
Past Papers / Reviews Alex Lumpkin, “Advanced, time-resolved imaging techniques for electron-
beam characterizations,” BIW 1990. Ed Rossa, “Real time single shot three-dimensional measurement of
picosecond photon bunches,” BIW 1994. K.Scheidt, “Review of streak cameras for accelerators: features, applications
and results,” EPAC 2000.
3Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Streak camera basics: under the hoodCathode Ray Tube: Z-axis Oscilloscope
A device displaying a long sequential signal in a 2D space, folded
A fast time axis and a slow time axis
Visualize the length and phase of a quasi-periodic pulse train
Streak camera basics: under the hoodCathode Ray Tube: Television
4Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Streak camera basics: under the hoodPrinciple of dual sweep streak camera
Use streak camera to visualize quasi-periodic light pulse train Low optical magnification: the spot size has no consequences Decide on two natural time scale of the dynamics being studied. Set
scale of fast time axis (vertical) to match the shorter one, and that of the slow time axis (horizontal) to match the longer one
For very short time scales, use synchroscan: direct sine-wave drive
5Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing longitudinal motion Streak Image for Different APS Storage Ring Fill Patterns
24-singlets Hybrid: 1+8*7 324-singlets
Bunch length (rms)
40 psSinglet (8 mA): 50 ps
Septuplet: 32 ps25 ps
T1 (5 µs range)
24-singlets
T1 (5 µs range)
1+8*7
T1 (5 µs range)
324-singlets
T2
(1
ns r
ange
)
T2
(1
ns r
ange
)
T2
(1
ns r
ange
)
A.H. Lumpkin, F. Sakamoto, and B.X. Yang, Dual-sweep streak camera measurements of the APS user beams, PAC05.
* Synchroscan streak camera was critical for reliable phase information
6Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
A high order harmonic of RF cavity drives the longitudinal instability Each bunch oscillates at synchrotron frequency Relative phase of the bunches are given by the 2fHOM·nbucket·RF
1 ms
1 ns
Visualizing longitudinal motion Longitudinal Instability at 200 mA Driven by an HOM
7Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing longitudinal motion ALS study of longitudinal beam dynamics at injection
J. M. Byrd and S. De Santis, “Longitudinal injection transients in an electron storage ring,” Phys. Rev. ST AB 4, 024401(2001)
8Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing longitudinal motion APS Particle Accumulator Ring bunch compression
Left panel from C.Y. Yao, Harmonic Beam Capture Observation and Its Application to Harmonic RF Phase Control
9Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing longitudinal motion Storage Ring bunch compression via RF phase modulation
RF phase modulation induced beam shortening (Glenn Decker)
– Every bunch for several micro-seconds
– Low-cost approach to obtain compression ratio of 2
Glenn Decker et al. Transient Bunch Compression using Pulsed Phase Modulation in High-Energy Electron Storage Rings
10Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing Longitudinal Dynamics: Summary
Summary Used as a very long-trace oscilloscope . The smaller the light spot size, the better. Match the fast and slow time scales to those of beam dynamics of
interest.
Other techniques: Some measurements can be made by fast digital oscilloscopes as they become ever faster every year.
11Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing transverse dynamicsA film strip of the front view
Fact: bunch length << bunch spacing in most accelerators Increase optical magnification so we can see particle
distribution Slow down the fast scan speed so images of head and tail
of the bunch overlap
Photo and copyright by Professor Andrew Davidhazy, Rochester Institute of Technology. Use with permission
12Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing transverse dynamicsFilm Strips of a Single Bunch / Multipass
Kicker induced beam motion in the APS Storage Ring Vertical scale chosen to image betatron motion, horizontal and vertical Horizontal scale chosen to visualize decoherence and emittance
damping
13Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing transverse dynamicsTransverse Multi-bunch Instabilities: short train
(A) =0 (B) =0-3.0
(C) =0 -4.8 (B) =0-5.2
100 ns
50 s
14Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing transverse dynamicsTransverse Multi-bunch Instabilities: 324 Uniform Pattern
Bursting mode instability Centroid oscillation in bursts. Not periodic. Streak camera captures beam centroid motion and size changes
Work in progress
15Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing Transverse Dynamics: Summary
Summary for Framing Camera Mode Need to select optical magnification so beam size or centroid motion can
be measured. (Optical synchrotron radiation limited in spatial resolution!) Match the fast and slow time scales to those of beam dynamics of
interest.
Other techniques: Slower measurements, such as single-bunch single-turn imaging for a large accelerator, can be made by fast CMOS cameras.
Optical Magnification
Low High
Scan SpeedSlow
(1) Longitudinal motion(2) Transverse motion
Fast (3) Bunch side/top views
16Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveGeometric Interpretation of Streak Images
Projection Tangent vs Aspect Ratio Front-view: tan y << y/z Top-view: tan y >> y/z Side-view: tan x >> x/z
y/zAspect Ratio
z = ct
y
z = cty
y
tan y = y/z = yFS/ctFS
Projection Tangent
ELECTRON BUNCH TV SCREEN
17Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveTop View Streak Image: Head-Tail Instability
High bunch current head-tail instabilities High bunch current and low chromaticity Synchrotron and betatron coupled excitation
18Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveSynchro-betatron coupled motion - 1
Excited Head-Tail Oscillation Synchro-betatron coupled motion excited by a transverse kicker The motion has major contribution to decoherence of betatron
motion Proposal by Weiming Guo to generate ps x-ray pulse. To date, we
have produced 6 ps photon bunch from 25 ps electron bunches.
Turn 30Turn 0
HEADTAIL
Turn 120Turn 60 Turn 80
Turn 195
19Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveSynchro-betatron coupled motion - 2
At high bunch current, the vertical size increases faster after the kick. Decoherence is current dependent.
Is the claw-shaped bunch related to horizontal coupling? Three dimensional imaging should reveal the answer. (3D imaging, Edward Rossa, 1994)
Kicker Off
Z (MM)
-40 -30 -20 -10 0 10 20 30 40
Y (
MM
)
0
2
4
6
8
10
12
14
16
18
Turn 125 (123 - 127)
Z (MM)
-40 -30 -20 -10 0 10 20 30 40
Y (
MM
)
0
2
4
6
8
10
12
14
16
18 HEADTAILTURN #123
Turn 110 (108 -112)
Z (MM)
-40 -30 -20 -10 0 10 20 30 40
Y (
MM
)
0
2
4
6
8
10
12
14
16
18
TURN #112
Turn 155 (153 - 157)
Z (MM)
-40 -30 -20 -10 0 10 20 30 40
Y (
MM
)
0
2
4
6
8
10
12
14
16
18 HEADTAILTURN #153
20Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveImaging in the longitudinal phase space
J. Rönsch, et al, “Longitudinal phase space studies at PITZ,” FEL’05, p 552.
On streak camera monitor, the location of an electron’s image point is given by
x x
streaky y v t
At a highly dispersive section, using a fast sweep, the energy and time terms dominate in the expressions, and we have an approximate longitudinal phase space map.
In linac, such map can be obtained at the spectrometer.
21Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Visualizing longitudinal motion ALS study of longitudinal beam dynamics at injection
J. M. Byrd and S. De Santis, “Longitudinal injection transients in an electron storage ring,” Phys. Rev. ST AB 4, 024401(2001)
22Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspectiveImaging in the longitudinal phase space: ring
Off-phase injection of APS Booster (50 s horizontal FS)
Off-phase injection of APS Booster (50 ms horizontal FS)
23Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Streak images: Longitudinal phase space damping
Off-phase injection of APS Booster showing phase space (50 s horizontal FS)
24Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Viewing the bunches in perspective: Summary
Summary Need to set optical magnification so the beam size can be measured. Fast time scale always matches the bunch length. Only slow time scales is adjustable for beam dynamics of interest. It
sets a limit of several images per picture. At locations of high dispersion, direct longitudinal phase space map
can be taken.
Other techniques: More powerful (expensive) “streak cameras,” and only on linacs– Transverse deflection cavity + high-res OTR screens– Energy chirp using 0-phasing RF cavity + spectrometer
25Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Final remark on optics design issuesDispersion and bunch lengthening
Converters Optical synchrotron radiation: fast, limited spatial resolution Optical transition radiation screens: fast, high spatial resolution Cherenkov radiators: fast, high spatial resolution Scintillators: fluorescence lifetime too long, good only for front view movies when
bunch spacing is large.
Optics transport Ideally all mirror optics transport. Dispersion of glass lengthens the light pulse.
Narrow bandpass filter is necessary for ps-resolution. Good spatial resolution requires large numerical aperture (optics acceptance
angle). With large field of view, the optical transport has a minimum phase space requirement. It often determines a minimum diameter of the long transport pipe.
26Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Streak camera 101: Summary
Summary Streak camera has become standard imaging tools in the past
two decades. It is a flexible tool for visualizing beam dynamics in different
time and spatial scales. Your need to – vary optical magnification to match the scale of the motion. – vary fast and slow time scales to match characteristic time
of the dynamic phenomena. Watching some of the pictures are entertaining.
Homework Will you find a way to put it into everyone’s lab?
27Streak camera 101: Visualizing charged-particle beam dynamicsBeam Instrumentation Workshop, May 3, 2006
Bingxin [email protected]
Acknowledgment
AcknowledgmentSUPPORT AND ENCOURAGEMENT
John Galayda, Glenn Decker, Om Singh
STUDIES
Alex Lumpkin, Louis Emery, Michael Borland,
Kathy Harkay, Weiming Guo, Yong-Chul Chae, C. Y. Yao
TECHNICAL SUPPORT
Frank Lenkszus, Bob Laird, Ned Arnold, Elbio Rotela,
Sushil Sharma, Joe Gagliano, George Goeppner
SPECIAL THANKS
Alex Lumpkin