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 2005 -Institut Henri Poincaré, Paris, France

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

High Energy Electron Acceleration Using Plasmas 2005 Support and Topics Foundation for Fundamental Research on Matter (FOM) Project duration: 2002 - 2008 External injection schemes (TUE, UT) Photo injector (TUE, UT) Ti-Sapphire laser (UT) Plasma channel (FOM-Rijnhuizen) High Energy Electron Acceleration Using Plasmas 2005

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

High Energy Electron Acceleration Using Plasmas 2005

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

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

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

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

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

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

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

Normalized rms emittance High Energy Electron Acceleration Using Plasmas 2005

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: 7.65-12.75 m r: 20-50 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

High Energy Electron Acceleration Using Plasmas 2005 The New Scheme + Plasma channel Parabolic radial density profile, np ~1017-1018 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

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

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

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