Nonlinear plasma wavelength scalings in a laser wakefield accelerator

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• Particle Acceleration

Background:

• Laser wakefield acceleration (LWFA) utilizes intense laser pulses to drive plasma waves.
• Direct experimental study of plasma wave trains in the laser wake has been limited.
• Understanding these waves is key to optimizing LWFA for GeV-scale accelerators.

Purpose of the Study:

• To experimentally quantify plasma waves excited by intense laser pulses.
• To investigate the dependence of nonlinear plasma wavelength on laser parameters.
• To validate and refine analytical models for plasma wave train evolution.

Main Methods:

• Employed few-cycle shadowgraphy and interferometry for plasma wave diagnostics.
• Conducted experiments within the density range relevant to GeV-scale accelerators (a few 10^18 cm^-3).
• Utilized systematic particle-in-cell (PIC) simulations for theoretical validation.

Main Results:

• Demonstrated that analytical models for nonlinear plasma wavelength are accurate only for low driver strengths (a0 ≲ 1).
• Revealed that nonlinear lengthening of plasma wave trains is influenced by both laser peak intensity and focal spot waist.
• Quantified plasma waves in the density regime of advanced accelerators.

Conclusions:

• The study provides direct experimental evidence of plasma wave train dynamics in LWFA.
• Experimental data and simulations show a more complex dependence of plasma wavelength on laser parameters than previously modeled.
• Findings necessitate revised models for accurate prediction of plasma wave behavior in high-intensity laser-plasma interactions.