1. John Power Argonne National Laboratory AAC 2016, August 1, 2016
Demonstration of Longitudinal Bunch Shaping using an EEX beamline at the Argonne Wakefield Accelerator
John Power
Argonne National Laboratory
AAC 2016, August 1, 2016
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2. Longitudinal Bunch Shaping: The Final Frontier
Precise Transverse Bunch Shaping
Straightforward
SIMPLE
COMPLEX
Gaussian
Hollow Cathode
Ring
Pepper Pot
Matrix
Multileaf Collimator
Arbitrary
Profile
Method
Laser Profile
2/27

3. Longitudinal Bunch Shaping: The Final Frontier
What makes longitudinal bunch shaping so difficult?
femtoseconds
800 fs
There is no Fast Gate
Electron bunch has extremely short duration (femtoseconds - picoseconds)
Direct manipulation of the longitudinal bunch shape is difficult
Need indirect methods
3/27

4. Longitudinal Bunch Shaping: The Final Frontier
Limited Longitudinal Bunch Shaping
Difficult, but recent progress
(warning: not a comprehensive list!)
SIMPLE
COMPLEX
Gaussian
Trains
Various (Most Active)
*Laser Comb (SPARC) M. Boscolo 2007
*a-BBO (ANL) M. Conde (PAC12)
*Wakefield + Chicane (Euclid/BNL)
S. Antipov PRL 111, (2013)
*mask+EEX (FNAL/NIU)
Y. –E Sun, PRL 105, (2010)
*R.J. England (UCLA) PRL 100, (2008)
*P. Muggli (UCLA/BNL) PRL 101, (2008)
*L. Emery (NIU) IPAC14
Triangle
Arbitrary
????
a-BBO
Pulse Stacking
Flat
*J.G. Power (ANL) AAC’08
*D. Edstrom (FNAL) IPAC2015
Profile
Method
Laser Profile
4/27

5. Longitudinal Bunch Shaping: The Final Frontier
Precise Longitudinal Bunch Shaping
Emittance Exchange based method
BLACK
BOX
Arbitrary shaping
All transverse shaping methods  longitudinal bunch shaping
M. Cornacchia and P. Emma, Phys. Rev. ST Accel. Beams 5, (2002)
P. Piot et al., Phys.Rev.ST Accel. Beams 14 (2011)
*All schemes have practical limits. We are exploring these limits
5/27

6. APPLICATIONS
& MOTIVATION
6/27

7. Motivation: wakefield acceleration and transformer ratio
Dielectric
Drive bunch
Witness bunch
𝑊 +
𝑊 −
𝐑= 𝑊 + 𝑊 − = Maximum field behind drive bunch Maximum field inside drive bunch
R<2 for symmetric bunches
(Fundamental theorem of Wakefield)
Assume 𝑁=𝑍/𝜆=2 12 6 2 4 9
7/27

8. Other applications… C. Mitchell, PRSTAB 16, 060703 CSR suppression
Y. –E Sun, PRL 105,
Train generation
Zholents, FEL2014 Energy spread control
G. Ha, IPAC2015 Longitudinal diagnostics
[bottom right: resolution limited by correlation] & [bottom left] “beam loading in CWFA”
8/27
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9. Understanding the Eex BEAMLINE
9/27

10. 2 building blocks  dogleg + deflecting cavity
EEX beamline
difficult to understand Exchange process
complex motion of the beam inside the EEX beamline
2 building blocks  dogleg + deflecting cavity
𝑥 1 = 𝑥 0 +𝐿 𝑥 0 ′ +𝜂 𝛿 0
𝑀 𝑑𝑜𝑔𝑙𝑒𝑔 = 1 𝐿 0 h h 1 x
𝑥 1 ′ = 𝑥 0 ′
𝑧 1 =𝜂 𝑥 0 ′ + 𝑧 0 +𝜉 𝛿 0
Dogleg does not affect momentum
𝛿 1 = 𝛿 0
Complementary
blocks
𝑀 𝑇𝐷𝐶 = 𝜅 𝜅 0 0 1
𝑥 1 = 𝑥 0
𝑥 1 ′ = 𝑥 0 ′ +𝜅 𝑧 0
TDC does not affect position
𝑧 1 = 𝑧 0
𝛿 1 = 𝜅 𝑥 0 +𝛿 0
Complementary beamline elements
10/27

11. Emittance exchange with the EEX beamline
Transport Matrix
Position → Momentum
𝑥 𝑓 𝑥 𝑓 ′ 𝑧 𝑓 𝛿 𝑓 = 0 0 𝜅𝐿 𝜂+𝜅𝜉𝐿 0 0 𝜅 𝜅𝜉 𝜅𝜉 𝜂+𝜅𝜉𝐿 0 0 𝜅 𝜅𝐿 𝑥 𝑖 𝑥 𝑖 ′ 𝑧 𝑖 𝛿 𝑖 Ez z x By
Final longitudinal properties are only determined by initial horizontal properties
2 particles (e.g. momentum exchange)
𝛿 0
Δ𝑥=𝜂Δ𝛿
Δ𝛿=Δ𝛿+𝜅𝜂Δ𝛿
Δ𝛿=0
1+𝜅𝜂=0
Momentum → Position
X instead of horizontal is simpler
Double dog-leg emittance exchanger z x By z x z x
11/27
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12. Longitudinal Bunch Shaping with the EEX beamline
AFTER MASK
AFTER EEX
12/27

13. LONGITUDINAL BUNCH SHAPING EXPERIMENT AT THE AWA FACILITY
13/27

14. EEX based Bunch Shaping Experiments at the AWA Facility
*Ph. D. project of Gwanghui Ha (POSTECH and ANL)
Collaboration:
Argonne National Laboratory, HEP: M. Conde, W.Gai, G.Ha, J.G.Power
Argonne National Laboratory, APS: Y. Sun, R.Lindberg, A.Zholents
Northern Illinois University: P.Piot
Los Alamos National Laboratory: D. Shchegolkov, E. Simakov
Euclid Techlabs LLC: C.Jing, A.Kanareykin, P.Schoessow
14/27

15. Double dogleg EEX beam line at AWA
Argonne Wakefield Accelerator
Double dogleg EEX
~68 MeV
Chirp control
Transverse manipulation
Experimental area
~8 MeV
Up to 100 nC
5 nC / 48 MeV
Quadrupole
Dipole
magnet
Transverse
Deflecting cavity
Mask
Beam line parameter
Value
Unit
Bending angle 20
deg
Dipole-to-Dipole
2.0 m
Dipole-to-TDC
0.5
Power to TDC
1.2 MW
15/27

16. Demonstration of property exchange
EXPERIMENT
Pending publication z x
Scan
X instead of horizontal is simpler
16/27
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17. Demonstration of longitudinal bunch shapingz x y
Demonstration of longitudinal bunch shaping
EXPERIMENT
Pending publication
Take initial x-horizontal profile
5 nC / 48 MeV z x y
In preparation for journal
17/27

18. Perturbation on ideal exchange
SIMULATION
𝑧 𝑓 =𝜅𝜉 𝑥 𝑜 + 𝜂+𝜅𝜉 𝐿+ 𝐿 𝐷 + 𝐿 𝑐 𝑥 0 ′
+ 𝑇 𝑛𝑚 𝑋 𝑛 𝑋 𝑚 𝜉Δ𝛿
Second order terms
Collective effects
Linear terms
x-x′
z-δ
Perturbation on the position
Perturbation patterns
EEX
Overlap of position
𝑥 0 ′ 𝑥 0 =− 2 T 11 𝑇 12
Minimize slope
𝑇 11 𝑥 𝑇 12 𝑥 0 𝑥 0 ′ + 𝑇 22 𝑥 0 ′ 2
In preparation for journal
18/27

19. Perturbation control by incoming slope manipulation
EXPERIMENT
X - distribution
Z - distribution
Linac phase control → thick-lens effect and collective effects
-10 deg
-15 deg
-30 deg
-40 deg
Pending publication
Horizontal control → few critical second order terms
0.03
0.17
0.47
0.60
19/27

20. APPLICATIONS AT THE AWA FACILITY
20/27

21. Future Experiment: High Transformer Ratio
SIMULATION
Rectangular Dielectric Wakefield Structure
800 mm
Metal
18 mm
Alumina (130 mm)
3mm (Vacuum gap)
Calculated with Euclid Wake Code and verified with CST microwave studio.
Transverse Profile at Entrance
Take Advantage of the AWA double dog-leg EEX beam’s natural shape
Flat beam profile (horizontal >> vertical)
Bunch Length < 10 mm
Note: A double EEX beamline can easily accommodate a cylindrical wakefield structure

22. Future Experiment: High Transformer Ratio
SIMULATION
Rectangular Dielectric Wakefield Structure
Mask
Beam transport through structure
12 nC
3.9 nC
Beam envelope
Longitudinal Bunch Shape & Transformer ratio
Explain animation
Euclid Techlabs LLC: Q. Gao, C.Jing, A.Kanareykin.
22/27
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23. LONGITUDINAL BUNCH SHAPING
FUTURE DIRECTIONS
IN EEX-BASED
LONGITUDINAL BUNCH SHAPING
23/27

24. Double EEX experiment*
*A.A. Zholents & M.S. Zolotrev (APS LS-327)
New type of bunch compressor
Tunable compression using quad
No chirp requirement. No dechirper
Control all longitudinal property at the same time
Shaping with preserved transverse emittance
2. Transverse manipulation
Already installed
EEX-2
EEX-1
3. Bring the manipulated transverse properties back to longitudinal
1. Bring the longitudinal properties to the transverse space
24/27

25. Double EEX experiment Experimental Area ~1 meter Preliminary Layout
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in[ mm]
in [ mm]
Center of Valve is ZERO
Overall Length in
in[ mm]
in[ mm]
Experimental Area
~1 meter
All Quads Shown 25 cm center/center
Dimensions Unchanged
Trims 15 cm center/center
25/27

26. Preliminary GPT Simulations – shaping capability
longitudinal
phase space
pz (MeV/c)
z (mm)
After EEX-2
Rectangle
EEX-1
After Mask
Horizontal x-profile
EEX-2
Transverse profile
After Mask
After EEX-2
z (mm)
Arbt.
witness
drive
0.6mm
1.5 mm
Longitudinal z-profile
Before EEX-1
Transverse Profile
26/27

27. Summary Longitudinal Bunch Shaping Demonstration Experiment Future:
Method: was done with an EEX beamline
Applications: collinear wakefield acceleration, THz radiation, CSR or energy spread control etc.
Demonstration Experiment
Double dogleg EEX beamline was installed at Argonne Wakefield Accelerator.
Several different longitudinal bunch shapes were successfully generated
Perturbations were controlled with the incoming slope of phase ellipse.
Future:
A high transformer ratio experiment using the EEX beamline is planned
A double-EEX beamline will be installed at the AWA facility.
27/27

28. Acknowledgement G. Ha, M. H. Cho, W. Namkung
(Pohang University of Science and Technology)
E. Wiesniewski, W. Liu, M. Conde, D. S. Doran, C. Whiteford, W. Gai
(Argonne National Laboratory, AWA)
K. –J. Kim, A. Zholents, Y. –E Sun
(Argonne National Laboratory, APS)
C. Jing, S. Antipov
(Euclid TechLabs)
P. Piot
(Northern Illinois University/Fermilab)
Q. Gao
(Tsinghua University)
28/27

29. Thank you for your attention
29/27

30. Backup slides
concepts
30/27

31. Multipole pre-shaping
No sextupole
Sextupole, +5 A
Sextupole, -5 A
31/27

32. A concept of a multi-user FEL facility
Based on:
~50 m
~200 m
SRF: 2.5 GeV
~1 MHz
E-gun
Undulators
~300 m
Spreader
experimental end stations
High repetition rate SRF linac (NGLS-like)
Collinear Wakefield Accelerator (CWA)
Low E spreader
Up to 100 MV/m
CWA imbedded in quadrupole wiggler
Tunable E ~ a few GeV
Tunable Ipk> 1KA
Rep. rate ~50 kHz/FEL
Compact
Inexpensive
Flexible
32/27

33. Motivation: Why do we need collinear DWFA?Cu Q
Dielectric 2a 2b
High gradient
High repetition
Cheap and simple
Why do we need high TR?
400 m Q
4 GeV
𝑊 𝑧 + =200 𝑀𝑉/𝑚/𝑛𝐶
40 m
𝑊 𝑧 − =100 𝑀𝑉/𝑚/𝑛𝐶
8 GeV
1 nC
R=2
100 m Q
1 GeV
𝑊 𝑧 + =50 𝑀𝑉/𝑚/𝑛𝐶
40 m
𝑊 𝑧 − =6.25 𝑀𝑉/𝑚/𝑛𝐶
8 GeV
4 nC
R=8
33/27

34. Backup – AWA EEX beam line
34/27

35. Backup – mask and YAG
35/27

36. High resolution longitudinal diagnostics
Measurement using TDC or spectrometer has clear limit (for the bunch length ~ 10 fs)
Since the limit is originated from correlation, exchange method can overcome this limitation.
36/27

37. Tunable THz or X-ray generation using trans. modulation + EEX
Transverse modulation generated from alternating magnetic field or structure+laser can be converted to longitudinal train with EEX
Tunable train can be used to generate tunable THz or even tunable X-ray y x
3.2 mm -> 0.3 mm
37/27