Plasma electron acceleration driven by a long-wave-infrared laser.

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• Particle Acceleration

Background:

• Laser-driven plasma accelerators typically use 1-micrometer wavelength lasers.
• Longer wavelength lasers offer potential for higher quality electron bunches and lower density plasmas.

Purpose of the Study:

• To investigate a self-injecting plasma accelerator driven by a long-wave-infrared (LWIR) laser.
• To explore the acceleration of electrons in low-density plasmas using CO2 laser pulses.

Main Methods:

• Utilized a chirped-pulse-amplified CO2 laser (approx. 10-micrometer wavelength).
• Employed optical scattering experiments to observe plasma wakes.
• Investigated wakefield generation in hydrogen plasma at densities down to 4x10^17 cm^-3 and 3x10^16 cm^-3.

Main Results:

• Observed plasma wakes driven by 4-picosecond CO2 pulses via self-modulation instability.
• Demonstrated acceleration of plasma electrons to relativistic energies using shorter, more powerful CO2 pulses.
• Identified transition from self-modulation to bubble-regime acceleration.

Conclusions:

• LWIR lasers can drive plasma accelerators in significantly less dense plasmas.
• The observed transition indicates potential for future high-quality accelerators with shorter, more powerful LWIR pulses.