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Ultrafast Laser -Driven Wakefield Accelerators Oleg Korovyanko 01/12/2009 SLAC AARD seminar. Outline. Part 1: Wakefield accelerators: techniques to generate short e bunches Part 2: Production of quality electron beams, characterization and applications Part 3: Relevant laser techniques

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Ultrafast Laser

-Driven Wakefield Accelerators

Oleg Korovyanko 01/12/2009SLAC AARD seminar


Outline
Outline

Part 1: Wakefield accelerators: techniques to generate short

e bunches

Part 2: Production of quality electron beams, characterization and applications

Part 3: Relevant laser techniques

Part 4: Conclusion and perspectives


Rf vs plasma

100 mm

Plasma cavity

RF vs Plasma

E-field max~ 10 MeV /m

E-field max~ 10 GeV/m

Courtesy of V. Malka

1 m

RF cavity

DWA

Diel. surface field breaks down @~ 10 GeV/m



> 1.6 W @ 400 nm

SHG2

SHG1

FS

D3-4

IR4

D1

D2

IR1

WP

SHGxtal

THGxtal

> 900 mW @ 266nm

IR2-3

Prepared by DSF2059, 031307, RLS


Anl awa 1 3 ghz tsa 50
ANL AWA1.3 GHz, TSA 50

  • Built as DWA: witness, drive bunches

  • Two 248nm pulses go to photocathode of RF gun, one or several drive bunches

    inter-pulse separation controlled w/ mechanical delay stage 23 cm, ~770ps, or 10.5Lo, Lo=22mm

  • A new UV stretcher utilizes thick BBO crystals in series

  • Laser mode at photocathode: adjustable iris at 1 m from photocathode




Monoenergetic beams from literature
Monoenergetic Beams from Literature

Intensity

tL/Tp

Energy

dE/E

Charge

Ne

[pC]

Article

Name

Lab

3

/cm

x10

W/cm

]

18

2

x1018

[MeV]

[%]

Mangles

Nature (04)

RAL

73

6

22

20

2,5

1,6

Geddes

Nature (04)

L'OASIS

86

2

320

19

11

2,2

Faure

Nature (04)

LOA

170

25

500

6

3

0,7

Hidding

PRL (2006)

JETI

47

9

0,32

40

50

4,6

Hsieh

PRL (2006)

IAMS

55

336

40

2,6

Hosokai

PRE (2006)

U. Tokyo

11,5

10

10

80

22

3,0

Miura

APL (2005)

AIST

7

20

432E-6

130

5

5,1

Hafz

PRE (2006)

KERI

4,3

93

200

28

1

33,4

Mori

ArXiv (06)

JAERI

20

24

0,8

50

0,9

4,5

Mangles

PRL (2006)

Lund LC

150

20

20

5

1,4

State-of-art gradient

27 GeV/m, SLAC, 27 GeV drive, Nature’2007


Towards longer interaction length
Towards longer interaction length

Diffraction length L~pr2/l0Rayleigh

Dephasing length ~ a0 lp3/ l02

Pump depletion length a0 >>1

  • Expanding Bubble Injection regime

    Degrades emittance due to high transverse field – control trapping

Pre-formed channel injection : plasma “fiber”

Optical injection by colliding pulse

Capillary discharge channel


250 mJ, 30 fs ffwhm=30 µm

I ~ 4×1017 W/cm2

a1=0.4

700 mJ, 30 fs, ffwhm=16 µm

I ~ 3×1018 W/cm2

a0=1.2

LOA

Experimental set-up

electron spectrometer

to shadowgraphy

diagnostic

Probe

beam

LANEX

Gas

jet

B Field

Pump beam

Injection beam



-

=

×

18

3

n

1

.

5

10

cm

m

l

=

m

0

.

8

=

m

m

p

w

20

0

t

=

30

fs

f(E) (a.u.)

=

P

200

TW

After 5 Zr / 7.5 mm

=

a

4

0

2.5

2

1.5

1

0.5

0

800

1200

1600

2000

Energy (MeV)

Laser plasma injector :

GeV electron beams

Courtesy of UCLA& Golp groups


Monoenergetic bunch comes from

colliding pulses: polarization test

Parallel

polarization

Crossed

polarization



Cubic dispersion (gratings etc.)

No significance

Quadratic dispersion (glass etc.)

Spectral Phase


Water radiolysis

D.A. Oulianov et al JAPS’ (2007).


  • How to control injection?

    -inject electron beam from LINAC (SLAC, Nature’07)

    ANL LINAC Chuck Jonah, 1988

    21 MeV; 7 ps; 4nC; plasma density 4-7x1010 cm-3

    -use laser-based ionization

    DWA : “chirped” bunches, break down due to CCR multiphoton ionization

  • *control of laser PW, wavelength

  • How to control acceleration?

    -plasma density

    -channel guiding (LBNL)

    -colliding pulse (LOA)


Acousto-optic shaping

Dazzler - from Fastlite

No need for zero dispersion stretcher

Controls different dispersion orders



Injection assisted by laser ionization
Injection assisted by laser ionization

  • Laser-assisted ionization of atoms or ions

  • Two types: multiphoton and Frank-Keldysh tunneling

  • 13.6 eV vs 1.5 eV

  • DFG: Reducing laser frequency increases ponderomotive potential ~w-2

  • HE TOPAS ~100 mJ @ l~9 mm


Laser techniques
Laser techniques

  • Multi-bunch generation w/ DWA

  • Pulse shaping

  • DFG due to detuned from 800 synchronized Regen pulses

  • Atto-second science: CEP


Applications conclusions and perspectives
Applications,Conclusions and Perspectives

DW should be 7.2 GeV with laser parameters (100TW, a0 ~3, Li~3.8cm)

  • THz source CCR

  • Hard X-ray fs source

  • X-ray free electron lasers

  • Radiology, biophysics around water window

  • Early stage of proton acceleration

  • 1TeV is a goal for HE physics is too far

    32 kJ of laser energy (100 lasers of 300J)

  • Optical Parametric CPA




Background. Parametric interaction

wp = ws + wi

phase matching conditions in a uniaxial x-stal such as BBO

kp = ks + ki

Non-collinear

Each photon in idler beam generated together with a photon in signal beam

S P

I II P


PW

Spectral Phase

Cubic dispersion (gratings etc.)

No significance

Quadratic dispersion (glass etc.)


Frogs
FROGs

  • Frequency Resolved Optical Gating (Kane and Trebino’ Opt Lett’ 1993)

  • Suitable for single-shot detection

  • Not an interferometric technique, just 2D spectrogram of cross-correlation function

  • Not easy to reconstruct E(w,t): iterative algorithm, t-direction ambiguity

  • Slight modification (Masalov et al, JOSA 2001) makes use of spatial interferometry

wavelength

slit

2nd harmonic

Doubling x-stal

t



Spider
SPIDER

c2

2p/t

  • Spectral phase interferometry for direct electric-field reconstruction (Iaconis and Walmsley, Opt Lett. ‘ 1998)

  • Spectral interferogram of two frequency-shifted up-converted pulses; no reference needed

  • Non-iterative reconstruction algorithm; 1D data set

t~2 ps

t

w






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