1. 8-10 June 2005 -Institut Henri Poincaré, Paris, France
Conceptual design of a laser wakefield experiment with external bunch injection in front of the laser pulse.
Arsen Khachatryan, Fred van Goor, Mark Luttikhof, Arie Irman, Jeroen Verschuur, Bert Bastiaens, and Klaus Boller.
University of Twente, Enschede, The Netherlands.
International Workshop on High Energy Electron Acceleration Using Plasmas 2005
8-10 June Institut Henri Poincaré, Paris, France

2. Dutch Laser Wakefield Accelerators Program
University of Twente
Laser Physics group
University of Eindhoven
Physics and Applications of Ion Beams
and Accelerators group
FOM-Institute for
Plasma Physics
“Rijnhuizen”
Laser-Plasma XUV Source
and XUV optics group
High Energy Electron Acceleration Using Plasmas 2005

3. High Energy Electron Acceleration Using Plasmas 2005
Support and Topics
Foundation for Fundamental Research on Matter (FOM)
Project duration:
External injection schemes (TUE, UT)
Photo injector (TUE, UT)
Ti-Sapphire laser (UT)
Plasma channel (FOM-Rijnhuizen)
High Energy Electron Acceleration Using Plasmas 2005

4. LWFA The Injection Problem External Injection Internal Injection
(wavebreaking)
Injection
in wakefield
(behind laser)
Injection in
front of laser
Self-modulated regime
All-Optical injection
Bubble regime
High Energy Electron Acceleration Using Plasmas 2005

5. High Energy Electron Acceleration Using Plasmas 2005

6. High Energy Electron Acceleration Using Plasmas 2005
Bunch dynamics
Laser:
a0 = 1.0
gg = 30
Spot radius = 30.5 mm
Pulse duration = 30 fs
Plasma channel:
np = 2x1018 cm-3
lp = 24 mm
Length = 2.3 cm
Injected bunch:
FWHM duration = 300 fs
FWHM width = 82 mm
energy = 1.6 MeV
Accelerated bunch:
Emittance = 8 p-mm-mrad
Length (rms) = 1 mm
Radius (rms) = 1.3 mm
energy = 453 MeV
energy spread = 2.8%
Collection efficiency = 44%
High Energy Electron Acceleration Using Plasmas 2005

7. High Energy Electron Acceleration Using Plasmas 2005
Longitudinal field
Normalized Ez
kpr
kp(z-ct)
High Energy Electron Acceleration Using Plasmas 2005

8. High Energy Electron Acceleration Using Plasmas 2005
Transverse field
Focusing field
kpr
kp(z-ct)
High Energy Electron Acceleration Using Plasmas 2005

9. High Energy Electron Acceleration Using Plasmas 2005
Average Bunch Energy
High Energy Electron Acceleration Using Plasmas 2005

10. High Energy Electron Acceleration Using Plasmas 2005
rms Bunch Radius
High Energy Electron Acceleration Using Plasmas 2005

11. High Energy Electron Acceleration Using Plasmas 2005
rms Bunch Length
High Energy Electron Acceleration Using Plasmas 2005

12. High Energy Electron Acceleration Using Plasmas 2005
rms energy spread
High Energy Electron Acceleration Using Plasmas 2005

13. Normalized rms emittance
High Energy Electron Acceleration Using Plasmas 2005

14. High Energy Electron Acceleration Using Plasmas 2005
Parameters for Proof-of-Principle Experiment with 1J, (30-50) fs Laser Pulse.
Laser pulse:
Wavelength: 0.8 m
Peak intensity at focus: (16)1018 W/cm2
Normalized amplitude, a0: 0.71.7
z: m
r: m
Plasma channel:
On-axis electron concentration, np(0): (0.72) 1018 cm-3
On-axis plasma wavelength, p: (2440) m
Channel length: (25) cm
Injected electron bunch:
Energy mec20: (14) MeV
Bunch duration: (200700) fs
Bunch diameter: (100200) m
Number of electrons: 108109 ((16160) pC)
Accelerated electron bunch:
Energy mec20: (0.24.5) GeV
Bunch duration: (110) fs
Bunch diameter: (210) m
Number of electrons: up to 108 (16 pC)  beam loading limit
High Energy Electron Acceleration Using Plasmas 2005

15. High Energy Electron Acceleration Using Plasmas 2005
The New Scheme +
Plasma channel
Parabolic radial density profile, np ~ cm-3.
Low-energy electron bunch:
Energy (g0) – hundreds keVs to few MeVs
Length (L0) – up to a few hundreds microns
Trapping distance: Ltr ~2 g02L0 =
Ultra-short relativistic electron bunch:
Length – ~ 1 micron (few fs);
Diameter – few microns;
Energy – up to a few GeV’s;
Number of electrons – ~108 (~10 pC, beam-loading limit)
High-intensity laser pulse:
Intensity >1018 W/cm2 +
High Energy Electron Acceleration Using Plasmas 2005

16. High Energy Electron Acceleration Using Plasmas 2005
Experimental Set-Up
e-bunch
Parabolic mirror
Linac
Metal photo cathode
Plasma channel
3rd harmonic
converter
Laser pulse
High Energy Electron Acceleration Using Plasmas 2005

17. Advantages of the LWFA scheme
No ultra-short electron bunch is needed before the acceleration in the laser wakefield;
No femtosecond synchronization is required while injecting the bunch in the wakefield;
No transverse size of a few micron and precise transverse positioning are needed for the injecting e-bunch;
Effective longitudinal and transverse electron-bunch compression;
Good quality of the accelerated bunch;
Scaling to high energies (GeV’s) is possible.
High Energy Electron Acceleration Using Plasmas 2005

18. High Energy Electron Acceleration Using Plasmas 2005
End
High Energy Electron Acceleration Using Plasmas 2005