Dense attosecond electron sheets from laser wakefields using an up-ramp density transition

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• Particle Acceleration

Background:

• Laser-driven plasma wakefield acceleration is a promising method for compact particle accelerators.
• Achieving controlled electron injection remains a key challenge for beam quality and reproducibility.
• Standard methods often lead to the bubble regime, which may not be optimal for all applications.

Purpose of the Study:

• To demonstrate controlled, localized electron injection into a laser-driven wakefield.
• To investigate the role of plasma density profiles and laser focusing on injection dynamics.
• To generate a high-quality, ultrathin relativistic electron sheet.

Main Methods:

• Particle-in-cell (PIC) simulations were employed to model the laser-plasma interaction.
• An underdense plasma target with a specific up-ramp density profile followed by a plateau was designed.
• A relatively large laser focus diameter was used to achieve a quasi-one-dimensional (1D) wakefield regime.

Main Results:

• The up-ramp density profile induced sharp one-dimensional wave breaking at the density transition.
• This process generated an ultrathin (nanometer scale, attosecond duration) relativistic electron sheet.
• The simulated electron sheet exhibited a peaked energy spectrum and high charge (near nC).

Conclusions:

• Controlled electron injection and acceleration were achieved using a tailored plasma density profile.
• The quasi-1D wakefield regime, distinct from the bubble regime, facilitates sharp wave breaking and electron sheet formation.
• The generated electron sheet possesses properties suitable for advanced accelerator and light source applications.