arXiv subjects

Siqin Ding

Publications and source records attributed to Siqin Ding.

4 recordsLinked to original sources

arXiv2026

Evolution of Quadrupole Wakefield Driven by Transversely Asymmetric Electron Beams in Hollow Plasma Channels

Plasma wakefield acceleration in hollow plasma channels has emerged as a promising approach for positron acceleration, since an electron beam can drive wakes with a transversely uniform accelerating field and no intrinsic defocusing force for positrons. Recently, it was proposed that a transversely asymmetric electron beam can excite quadrupole-dominated wakefield in a hollow channel, enabling the formation of accelerating and focusing fields suitable for positrons. However, the self-consistent evolution and stability of such asymmetric drivers, which are crucial for sustaining a usable wake over long distances, remain insufficiently understood. In this work, we investigate the evolution modes of wakefield driven by asymmetric electron beams in hollow plasma channels using fully three-dimensional particle-in-cell simulations. We identify two distinct unstable scenarios: a reversal of quadrupole field polarity and continuous penetration of the driver into the plasma wall. By analyzing the transverse dynamics of the driver and the restoring forces provided by the channel ions, we establish simple physical criteria that ensure stable propagation. These results clarify the fundamental constraints governing asymmetric-driver evolution and provide practical guidance for realizing long-lived, quasi-steady wakes in hollow plasma channels.

physics.plasm-ph↗

arXiv2026

Staged Laser Wakefield Acceleration for Saturated Lasing of Bandwidth-Tunable Free-Electron Lasers from EUV to X-ray

Free-electron lasers (FELs) provide a revolutionary tool for capturing the structure and dynamics of matter in real time at the atomic scale. The size and cost of FELs can be substantially reduced by using laser wakefield acceleration (LWFA), which offers acceleration gradients orders of magnitude beyond radiofrequency technology, producing multi-GeV electron beams within tens of centimeters. This compactness opens the possibility of integrating multiple operating modes - from the EUV to X-rays including broadband operation - into one facility. Realizing this vision, however, faces key challenges: current LWFA bunches are too short to sustain sufficient radiation slippage, limiting FEL pulse energy at EUV wavelengths, while the large energy spread and emittance make X-ray lasing even more demanding. Here we present a LWFA-driven FEL scheme that addresses these challenges, enabling multi-mode operation spanning different wavelengths and bandwidths within a single facility. The scheme employs staged acceleration to reach multi-GeV energies while preserving beam quality, combined with a dual-chicane beamline that stretches the bunch to mitigate the radiation slippage for EUV FEL and tailors the energy chirp for diverse FEL bandwidth modes. Simulations demonstrate that the scheme can generate high-quality electron beams with energies up to 7 GeV and tunable energy chirp, enabling both FEL saturation from the EUV to X-ray wavelengths and large bandwidth operation with a bandwidth of up to 11%. This work provides a roadmap for compact, multi-mode FELs based on plasma acceleration, and the high-energy, high-quality beams achieved also point toward compact injectors for next-generation storage-ring light sources.

physics.acc-ph↗

arXiv2025

Energy stability of supercontinuum via femtosecond filamentation in sapphire

The energy stability of supercontinuum (SC) significantly impacts its applications. To achieve the most stable SC, we systematically investigated how input pulse energy, numerical aperture (NA), and crystal thickness affect the energy stability of SC generated by femtosecond filamentation in sapphire. Our findings reveal that the SC energy does not always increase monotonically with input energy for different NA and thicknesses. This phenomenon occurs because, when the input pulse energy just exceeds the filamentation threshold, the pulse splitting structure and spectrum are still rapidly evolving. To generate a more stable SC, the numerical aperture and crystal thickness must be carefully coordinated to prevent this rapid evolution from occurring within the crystal.

physics.optics↗

arXiv2022

Positron beam loading and acceleration in the blowout regime of plasma wakefield accelerator

Plasma wakefield acceleration in the nonlinear blowout regime has been shown to provide high acceleration gradients and high energy transfer efficiency while maintaining great beam quality for electron acceleration. In contrast, research on positron acceleration in this regime is still in a preliminary stage. We find that an on-axis electron filament can be self-consistently formed and maintained by loading an intense positron beam at the back of the electron beam driven blowout cavity. Via an analytic model and fully nonlinear simulations, we show this coaxial electron filament not only can focus the positron beam but changes the loaded longitudinal wakefield in a distinctly different way from electron beam loading in the blowout regime. Using simulations, we demonstrate that a high charge positron beam can be accelerated with tens of percent energy transfer from wake to positrons, percent level induced energy spread and several mm$\cdot$mrad normalized emittance, while significantly depleting the energy of the electron drive beam. This concept can be extended to simultaneous acceleration of electron and positron beams and high transformer ratio positron acceleration as well.

physics.plasm-ph↗