Laser-accelerated, low divergence 15 MeV quasi-monoenergetic electron bunches at 1 kHz

Abstract

We demonstrate laser wakefield acceleration of quasi-monoenergetic electron bunches up to 15 MeV at 1 kHz repetition rate with 2.5 pC charge per bunch and a core with < 7 mrad beam divergence. Acceleration is driven by 5 fs, < 2.7 mJ laser pulses incident on a thin, near-critical density hydrogen gas jet. Low beam divergence is attributed to reduced sensitivity to laser carrier envelope phase slip, achieved in two ways using laser polarization and gas jet control: (1) electron injection into the wake on the gas jet's plasma density downramp, and (2) use of circularly polarized drive pulses. Under conditions of mild wavebreaking in the downramp, electron beam profiles have a 2D Lorentzian shape consistent with a kappa electron energy distribution. Such distributions had previously been observed only in space or dusty plasmas. We attribute this shape to the strongly correlated collisionless bunch confined by the quadratic wakefield bubble potential, where transverse velocity space diffusion is imparted to the bunch by the red-shifted laser field in the bubble.

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Cited by in corpus (6)

• 2022 Review of Data-Driven Plasma Science
• Carrier-envelope phase effects in Laser Wakefield Acceleration with near-single-cycle pulses
• Sub-femtosecond wakefield injector and accelerator based on an undulating plasma bubble controlled by a laser phase
• Carrier-envelope phase controlled dynamics of relativistic electron beams in a laser-wakefield accelerator
• Impact of Electron Transport Models on Capillary Discharge Plasmas
• Polarization control of electron injection and acceleration in the plasma by a self steepening laser pulse