Speaker
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See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.2026.pdf
Some kinds of tailored structured targets were proposed to enhance laser-target coupling and improve the qualities of fast electrons. When an intense propagates in a vacuum capillary, its profile is reshaped due to laser-plasma interaction near the entrance of capillary. Only the relatively low-intensity periphery of the reshaped pulse interacts with the capillary-wall plasma, so that the high-intensity center of the pulse can propagate in the narrow vacuum channel over a distance much larger than the Rayleigh length.
A hollow cone with two opens may be used for attaining extremely high light intensities since it can focus an intense laser to a tiny and highly localized spot. When a thin foil is attached to the tip of the cone, the cone-focused light pulse compresses and accelerates the ions in its path and can punch through the thin target, creating highly localized energetic ion bunches of high density.
A novel copper nanobrush target has been proposed to achieve brighter Ka X ray. Compared to a regular planar target, the simulations show that the laser absorption efficiency by the particular target is remarkably enhanced to near 80%. The depth of laser energy penetration is larger than the skin length and more fast electrons are generated, so the laser coupling efficiency is greatly increased. The physics on the enhancement of Ka photon yield and conversion efficiency from laser to Ka x-ray is studied by combining Monte Carlo simulations and previous particle-in-cell simulation results. Subsequently, the conical nanolayered, cone-nanolayered and tailored cone-nanolayered targets are proposed to enhance coupling efficiency and control the emission angles of fast electrons. They are very promising in designing high brightness X-ray or Ka sources.
Recently, some recent research on laser interactions on solid target with external magnetic fields has been carried out. When the external magnetic field normalized by the laser magnetic field is larger than the relativistic factor, the right-hand (RH-) circularly polarized (CP) lasers will keep on propagating till the laser energy is depleted. Two-dimensional particle-incell simulation results show that in the presence of external longitudinal magnetic field, the energies and yields of fast electrons are greatly enhanced for RH-CP laser. Furthermore, the proton acceleration driven by an RH-CP laser interaction with a pre-magnetized cone target filled with a preformed plasma has also been investigated under the mechanism of target normal sheath acceleration (TNSA). The two-dimensional particle-in-cell simulation results show that with an external longitudinal magnetic field, both the energy and yield of protons accelerated by the sheath electric field at the rear of the target are remarkably increased because of the higher coupling efficiency from RH-CP laser energy to electrons and the more efficient electron acceleration. The maximum cut-off energy of protons with an imposed longitudinal magnetic field can be promoted to be as high as 82MeV.
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- J. C. Zhao, Lihua Cao et al., Phys. Plasmas 25, 033104(2018).
- Jincui Zhao, Jianhua Zheng, Lihua Cao et al., Phys. Plasmas 23,022705(2016).
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