1. 1

2. 2

3. 3

4. 4

5. History of Electron Accelerators: Livingston Plot
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6. Applications of Accelerators
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7. How to Accelerate Charged Particles
Assume:
an ultrarelativistic particle of charge e
moving along the z axis
accelerated by a plane electromagnetic wave that propagates at an angle ϑ to the z axis k ϑ e- λ
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8. How to Accelerate Charged Particles
Then:
Position of the electron k ϑ e- λ
Electric field
Energy gradient
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9. Lawson Woodward Theorem
Every wave in far field can be written as a superposition of plane waves
The Lawson-Woodward Theorem states:
the total acceleration
of ultrarelativistic particles
by far-field electromagnetic waves
is zero
Need near-field structures
electron
Woodward, J. IEE 93 (1947)
Lawson, IEEE Trans. Nucl. Sci. 26 (1979) Palmer, Part. Accel. 11 (1980)
electromagnetic
wave
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10. RF Acceleration RF Acceleration electrical field Cu
Using a resonant cavity at radio frequencies (RF) (∼GHz)
Electromagnetic field provided by external source (e.g. klystron)
electron
Resonating RF Cavity
Travelling Wave Structure
11.4 GHz 2π/3 Mode Eacc ≥ 50 MV/m
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11. Limits to the Accelerating Field
Normal-conducting accelerators
Breakdown on the surface
Superconducting accelerators
Critical magnetic field
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12. Possibilities for Accelerating Structures
max.
Field (V/m)
Structure
Power Sources
electron beams: klystrons
electron beams: klystrons or integrated structure
Superconducting
5·107
solid state
Metallic
2·108
solid state
Dielectric
109
laser
electron beams
Plasma ≥1011 laser electron beams
Plus: Inverse FEL, disposable structures, excited atoms, muon colliders
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13. > Transformation of far-field into accelerating field
Metallic Structures
> Transformation of far-field into accelerating field
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14. Laser-Based Acceleration
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Laser-Based Acceleration

15. Laser Acceleration (1961)
Koichi Shimoda, Applied Optics 1 (1), 33 (1961)
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16. Laser as a source of electromagnetic fields
1.  Smaller/less expensive than RF. 2.  Energy efficient (near 50%).
3.  High repetition rate (1 to 100 MHz).
4.  Large electric fields (GV/m).
Solid-state laser
RF Klystron
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Bob Byer 16

17. Dielectric Accelerator Structures
> Using much higher frequencies: THz to optical
> Using dielectrics (e.g. SiO2)
> Advantages: higher damage threshold
Higher accelerating fields, up to ~GV/m
> Generate the electromagnetic field
> Cherenkov radiation from an electron beam
> Laser
> Confine the field
> Photonic band gap 8
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18. Planar Structures Elliptical Pillars Rectangular Pillars
Laser
Rectangular Pillars
Laser
Double Slab Grating
Laser e- e- e-
Laser
Laser
Buried Grating
Laser
Asymmetric Grating
Reverse Slab Grating
Laser e- e- e-
Laser
Laser
Laser
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Ken Leedle 18

19. Planar Structures: Measurements
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Joel England 19

20. Circular Structures > Experiment at MIT Franz Kärtner
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Franz Kärtner

21. > Structure geometry:
Circular Structures
> Structure geometry:
electron beam E
metal dielectric d a
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Franz Kärtner

22. Circular Structures: Modeling
> Analytical solution for the electromagnetic fields: 8
>
E J (r r)e
i(kz-!t) ,
r < a
<
>
E = ✓ ◆ z
>
J (r b) :
>
ei(kz-!t),
E J0(r2r) -
0 2
Y0(r2r)
a < r < b 2
Y0(r2b) 8
>
> k
i E
J (r r)e
i(kz-!t) ,
r < a
>
>
< r 1 1 1
Er =
> ✓ ◆
>
> k
J (r b)
>
i E J (r r) - :
0 2
Y (r r) e
i(kz-!t)
, a < r < b r2 2 2
Y0(r2b) 2 8 !
>i
>
E J (r
r)e
i(kz-!t) ,
r < a
>
<
r c 2 1 1 1
B< = ✓ ◆
>
>
> !
J (r b) :
i ✏ E J (r r) -
0 2
Y (r r) e
i(kz-!t)
, a < r < b
r2c2
r 2 2
Y0(r2b) 2
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Max Kellermeier

23. Tool to Calculate Beam Propagation
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Max Kellermeier

24. Circular Structures: Measurements1
Measured Modeled
Measured Modeled
0.8
Counts (Arb.)
0.6
0.4
0.2
Energy (keV)
(a)
45 50
Energy (keV)
(b)
70 75
Figure 4: Measured (black) and modeled (red) energy spec- trum with THz (a) off and (b) on at a gun voltage of 59 kV.
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Nanni et al., Proceedings of IPAC

25. Towards 3-Dimensional Structures: Photonic Crystals
periodic electromagnetic media
1887
1987
1-D
2-D
3-D
periodic in one direction
periodic in two directions
periodic in
three directions
(need a more complex
with photonic band gaps: “optical insulators”
topology)
Steven G. Johnson 9
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26. Photonic Band Gap Structures12
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Chris Sramek 26

27. Installation of a Test Chamber in SwissFEL
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28. Planned Experimental Setup in SwissFEL
> Goal: Acceleration by 1 MeV
Laser
Profile monitor
Quadrupole magnets
Electron beam from SwissFEL
Accelerating structure
Magnetic spectrometer
Paraboloid mirror
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29. Focusing of the Electron Beam90 80 70 60 50 40 30 20 10 x y
β-function (m) 2 4 6 8 10
s [m] 12 14 16 18 2 4 6 8 10 12 14 16 18
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Eduard Prat 29

30. Design of Interaction Chamber
> Design in progress…
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Adriano Zandonella, Goran Kotrle, Eugenio Ferrari 30

31. Plasma Wakefield Acceleration

32. > Linear plasma wake:
Plasma Wakes - Theory
> Unlike electromagnetic waves in vacuum, plasma wakes can have a longitudinal electric field – – + – – + + + – + + + +
+ – + + –
– + – – – + – – + – – + + –
– – – + + + – –
– + – + – +
– – + +
> –
Tajima & Dawson, PRL, 43, 267(1979)
– + – – + +
– – – + – + + + –
– – + – + – + + – +
– + – – +
+ – – + – + + + + + – + – – – + + + – ––
– + + + +
– + – + – – E E E E E E
> Linear plasma wake:
> Limit:
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33. > Above this limit: non-linear wakes, “Blow-out regime”
Plasma Wakes - Theory
> Above this limit: non-linear wakes, “Blow-out regime”
> Fields can be calculated only with numerical methods
> Typical wavelength: 50 µm
> Accelerating fields up to 50 GV/m
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Miaomiao Zhou 33

34. Plasma Wakes - Reality
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35. > Incoming energy: 42 GeV > Peak energy: 85±7 GeV
Energy Doubling
> Plasma length: 85 cm
> Density: 2.7•1023 m−3
> Incoming energy: 42 GeV
> Peak energy: 85±7 GeV
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36. Measurement of Electromagnetic Fields
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37. Measured Electromagnetic Fields
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38. Recent Experiments at PSI
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39. Generation of a Density Ramp
Blade
1.1mm
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40. Charge Measurement
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Andreas Adelmann, Nick Sauerwein, Benedikt Herrmann 40

41. Livingston Plot 44
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42. An Unfair Comparison 44
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43. From Accelerating Fields to Accelerators
There is More to Accelerating Structures than the Accelerating Field
>Power sources
>Beam loading
>Emittance preservation
> Non-linear transverse forces
> Wakefields
There is Much More to an Accelerator than Accelerating Structures
>Particle sources (injectors)
>Bend magnets for storage rings
>Focusing, beam dynamics
>Detectors
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44. Instrumentation and Acceleration Research at PSI
>
Special Thanks to:
Adriano Zandonella Andreas Adelmann Benedikt Herrmann Bob Byer
Chris Sramek Eduard Prat Eugenio Ferrari Franz Kärtner Goran Kotrle Joel England Ken Leedle Malte Kaluza Max Kellermeier Miaomiao Zhou Nick Sauerwein
>
This presentation is available at
© 2017 Paul Scherrer Institut
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