Laser-Driven Modulation of Electron Beams in a Dielectric Micro-Structure for X-Ray Free-Electron Lasers

Area of Science:

• Physics
• Accelerator Physics
• Laser Physics

Background:

• Free-electron lasers (FELs) require precisely controlled electron beams for generating coherent radiation.
• Generating high-current electron beam spikes is crucial for advanced FEL applications.
• Conventional methods for electron beam modulation often demand substantial laser power.

Purpose of the Study:

• To introduce and evaluate a new method for generating longitudinal electron bunching in FELs.
• To demonstrate the feasibility of using laser-driven modulation within a dielectric micro-structure.
• To assess the efficiency and power requirements of this novel modulation scheme.

Main Methods:

• Utilizing a dielectric micro-structure to modulate the energy of an electron beam with a laser.
• Employing a magnetic chicane to compress the modulated electron beam into high-current spikes.
• Simulating the process for specific parameters, such as those at SwissFEL.

Main Results:

• Achieving longitudinal bunching of the electron beam, resulting in current spikes separated by the laser wavelength.
• Projecting individual spike durations as short as 140 attoseconds (FWHM) for a 30 pC bunch charge.
• Estimating peak currents exceeding 4 kA.
• Predicting a tenfold reduction in required laser power compared to wiggler magnet modulation.

Conclusions:

• The proposed laser-driven modulation in a dielectric micro-structure is an effective method for generating highly bunched electron beams for FELs.
• This technique offers significant advantages in terms of laser power efficiency.
• Strict emittance and charge control are necessary due to the micrometer-scale interaction region.