Effects of pulse chirp on laser-driven proton acceleration

Area of Science:

• Plasma Physics
• Laser-Induced Phenomena
• Particle Acceleration

Background:

• Reproducible proton beam generation from laser-solid interactions demands precise control over laser pulse characteristics and target properties.
• Variations in laser pulse chirp and temporal shape, caused by spectral phase modulations, can affect experimental outcomes.
• Understanding these influences is key to advancing laser-driven particle acceleration.

Purpose of the Study:

• To experimentally investigate the effect of laser pulse chirp on proton acceleration from ultrathin foils.
• To determine how chirp sign influences maximum proton energy.
• To explore the role of relativistic transparency in chirp-dependent acceleration.

Main Methods:

• Experimental study using laser-solid interactions with ultrathin flat foils (10 and 100 nm thickness).
• Controlled variation of laser pulse chirp while minimizing temporal shape asymmetry.
• Measurement of maximum proton energies for different chirp conditions.

Main Results:

• A significant change in maximum proton energy was observed, dependent on the sign of the laser pulse chirp.
• The effect of chirp on proton energy was most pronounced with 10 nm thick target foils.
• Results indicate a dependence of relativistic transparency on the laser pulse chirp.

Conclusions:

• Laser pulse chirp is a critical parameter influencing proton acceleration in laser-solid interactions.
• The observed chirp-dependent relativistic transparency offers insights into optimizing laser-driven proton sources.
• Precise control over laser chirp is essential for reproducible and enhanced proton beam generation.