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内容記述 |
A relativistically intense femtosecond laser pulse passing through subcritical gas jet plows away all electrons in its path and creates multi-stream flows in the electron distribution. These flows exhibit folds and cusp singularities that were proposed as nano-scale sources of x-ray radiation. Recently, PIC simulations in a simplified 2D setting indicated that the ensuing Coulomb explosion of the trailing ions also produces multi-stream flows with ring-shaped cusps and associated long-lived spikes in the ion distribution. This has now been confirmed using self-consistent 3D PIC simulations. Extensive parameter scans (w.r.t. density, ion mass, temperature, laser intensity, Rayleigh length, pulse shape) were performed to clarify the conditions for the formation of such long-lived structures in the ion distribution. While a Gaussian laser pulse produces off-axis density spikes that are diluted via radial expansion in 3D, a donut-shaped Gauss-Laguerre pulse is shown to produce on-axis density spikes that are enhanced by an order of magnitude. Applications for this fundamental research are currently being sought. |
