Attosecond γ-ray sources are indispensable for probing ultrafast and high-energy phenomena. However, achieving further pulse compression remains challenging, particularly through target structural modifications. Here, we propose a novel scheme that incorporates a conical-frustum plasma target with a Laguerre–Gaussian laser to generate attosecond γ-ray pulse trains via nonlinear inverse Compton scattering. By tuning the target tilt angle, we control the longitudinal compression of the laser-driven electron sheet and the resulting electron-density distribution. Three-dimensional quantum-electrodynamic-particle-in-cell simulations indicate that, at the optimal tilt angle, the γ-ray pulse duration decreases from 500 as to 200 as, while the orbital angular momentum of the γ-photons is simultaneously enhanced. The emitted γ-photons reach energies up to 410 MeV with a total yield of approximately 1010. A comparative analysis of the original and inverted conical-frustum geometries further elucidates their respective advantages in γ-ray pulse generation. The present work opens new avenues for applications in nuclear-resonance fluorescence, attosecond pump–probe diagnostics and high-resolution imaging.
This paper proposes a novel scheme to generate attosecond γ-ray pulse trains using a conical-frustum plasma target and a Laguerre-Gaussian laser. By tuning the target tilt angle, the researchers control the electron-density distribution, leading to shorter γ-ray pulses (200 as) and enhanced orbital angular momentum of the γ-photons, reaching energies up to 410 MeV.