Pulsed fast neutron source is critical for the applications of fast neutron resonance radiography and fast neutron absorption spectroscopy. However, due to large transversal source-size (∼ mm) and long pulse duration (∼ ns) of traditional pulsed fast neutron sources, it is difficult to realize high contrast neutron imaging with high spatial resolution, and fine absorption spectrum. Here, we experimentally present a micro-size ultra-short pulsed neutron source by a table-top laser plasma wakefield electron accelerator driving photofission reaction in a thin metal converter. A fast neutron source with sourcesize of ∼500 µm and duration of ∼36 ps has been driven by a tens of MeV, collimated, micro-size electron beam via a hundred TW laser facility. This micro-size ultra-short pulsed neutron source has the potential to improve the energy resolution of fast neutron absorption spectrum dozens of times to e.g. ∼100 eV at 1.65 MeV, which could benefit for high quality fast neutron imaging and deep understanding theoretical model of neutron physics.
The influence of second-order dispersion (SOD) on stimulated Raman scattering (SRS) in the interaction of ultrashort intense laser with plasma was investigated. More significant backward SRS was observed with the increase of the absolute value of SOD (|ψ2|). The integrated intensity of the scattered light is positively correlated to the driver laser pulse duration. Accompanied by the side SRS, filaments with different angles along the laser propagation direction were observed in the transverse shadowgraph. A model incorporating Landau damping and above-threshold ionization was developed to explain the SOD-dependent angular distribution of the filaments.
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