Laser-Plasma Based Seeded Free Electron Laser in the High-Gain Regime

Area of Science:

• Physics
• Accelerator Science
• Quantum Optics

Background:

• Compact laser-plasma accelerator (LPA) driven free electron lasers (FELs) have been pursued for two decades.
• Previous efforts were hindered by electron beam quality and stability issues, limiting FEL lasing.
• LPA-based FELs were previously demonstrated in self-amplified spontaneous emission and low-gain seeded modes.

Purpose of the Study:

• To report the observation of the high-gain regime in a seeded LPA-driven FEL.
• To demonstrate the potential for FEL saturation using LPA technology.
• To investigate the impact of seed pulse duration on FEL performance.

Main Methods:

• Experimental demonstration of a seeded LPA-driven FEL operating in the high-gain regime.
• Characterization of exponential FEL signal growth via spectral charge density measurements.
• Systematic variation of seed pulse duration (via chirping) to study its effects on FEL output.

Main Results:

• Observation of exponential FEL signal growth with a measured gain length of 0.55 m.
• Achievement of 45 nJ FEL pulse energies at approximately 272 nm wavelength within a 2 m undulator.
• Quantitative agreement between experimental results and numerical simulations.
• Detailed study of seed pulse duration effects, analogous to radio-frequency accelerator FELs.

Conclusions:

• The high-gain seeded regime in LPA-driven FELs has been successfully achieved.
• This opens a pathway towards FEL saturation and the development of compact FELs.
• The findings encourage future scaling of LPA-driven FELs to shorter wavelengths.