Guided Mode Evolution and Ionization Injection in Meter-Scale Multi-GeV Laser Wakefield Accelerators

Area of Science:

• Plasma Physics
• Accelerator Physics
• Nonlinear Optics

Background:

• Laser wakefield acceleration (LWFA) is a promising technology for compact electron accelerators.
• Controlling electron beam properties in LWFA remains a challenge.
• Plasma waveguides are used to guide intense laser pulses over long distances.

Purpose of the Study:

• To investigate the nonlinear propagation dynamics of intense laser pulses in meter-scale plasma waveguides.
• To understand the impact of laser-plasma interactions on electron injection and acceleration.
• To characterize the resulting electron beam properties.

Main Methods:

• Experimental investigation of multi-GeV laser wakefield electron accelerators in meter-scale, low-density hydrodynamic plasma waveguides.
• Utilizing continuously and locally doped gas jets for plasma generation.
• Development of a three-stage model for drive laser pulse evolution and ionization injection.

Main Results:

• Discovery of a new nonlinear propagation regime dominated by sustained mode beating in the ponderomotively modified plasma channel.
• Emergent mode beating leads to axially modulated ionization injection.
• Generation of multi-GeV electron energy spectra with multiple quasimonoenergetic peaks or single peaks with <10% energy spread, depending on gas doping.

Conclusions:

• The sustained mode beating in plasma waveguides is a key factor in controlling LWFA performance.
• The developed three-stage model accurately characterizes the observed phenomena and experimental results.
• This work paves the way for enhanced control over electron beam generation in LWFA systems.