In order to investigate the modification of the surface structure of FePS3 via Ga+ ion irradiation, we study the effect of thickness and Raman spectrum of multilayer FePS3 irradiated for 0 μs, 30 μs, and 40 μs, respectively. The results demonstrate that the intensity ratio of characteristic Raman peaks are obviously related to the thickness of FePS3. After Ga+ ion irradiation, the FePS3 sample gradually became thinner and the Eu peak and Eg(v11) peak in the Raman spectrum disappeared and the peak intensity ratio of A1g(v2) with respect to A1g(v1) weakened. This trend becomes more apparent while increasing irradiation time. The phenomenon is attributed to the damage of bipyramid structure of [P2S6]4− units and the cleavage of the P-P bands and the P-S bands during Ga+ ion irradiation. The results are of great significance for improving the two-dimensional characteristics of FePS3 by Ga+ ion beam, including structural and optical properties, which pave the way of surface engineering to improve the performance of various two-dimensional layered materials via ion beam irradiation.

One of the common characteristics of the electrothermal breakdown in an underwater discharge acoustic source (UDAS) is the existence of a pre-breakdown-heating phase. In our experiment, two phenomena were observed: (1) the breakdown time that takes on high randomicity and obeys a "double-peak" stochastic distribution; (2) the higher salt concentration that reduces the residual voltage and causes 100% non-breakdown. The mechanism of electrothermal breakdown is analysed. To specify the end of the pre-breakdown-heating phase, a "border boiling" assumption is proposed, in which the breakdown time is assumed to be the time needed to heat the border water around the initial arc to 773 K. Based on this 'border boiling' assumption, the numerical simulation is performed to evaluate the effects of two heating mechanisms: the Joule heating from the ionic current, and the radiation heating from the initial arc. The simulation results verify the theoretical explanations to these two experiment phenomena: (1) the stochastic distribution of the radius of the initial arc results in the randomicity of the breakdown time; (2) the difference in efficiency between the radiation heating and the Joule heating determines that, in the case of higher salt concentration, more energy will be consumed in the pre-breakdown-heating phase.

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A monolayer-graphene-based concentric-double-rings (CDR) structure is reported to achieve broadband plasmon-induced transparency (PIT) on the strength of edge mode in the mid-infrared regime. The theoretical analysis and simulation results reveal that the structure designed here has two plasmonic resonance peaks at 39.1 and 55.4 THz, and a transparency window with high transmission amplitude at the frequency of 44.1 THz. Based on the edge mode coupling between neighbor graphene ribbons, PIT phenomenon is produced through the interference between different (bright and dark) modes. The frequency and bandwidth of the transparency window and slow light time could be effectively adjusted and controlled via changing geometrical parameters of graphene or applying different gate voltages. Additionally, this structure is insensitive to the polarization and incident angle. This work has potential application on the optical switches and slow light modulators.

Radiation uniformity is important for Z-pinch dynamic hohlraum driven fusion. In order to understand the radiation uniformity of Z-pinch dynamic hohlraum, the code MULTI-2D with a new developed magnetic field package is employed to investigate the related physical processes on Julong-I facility with drive current about 7–8 MA. Numerical simulations suggest that Z-pinch dynamic hohlraum with radiation temperature more than 100 eV can be created on Julong-I facility. Although some X-rays can escape out of the hohlraum from Z-pinch plasma and electrodes, the radiation field near the foam center is quite uniform after a transition time. For the load parameters used in this paper, the transition time for the thermal wave transports from r = 1 mm to r = 0 mm is about 2.0 ns. Implosion of a testing pellet driven by cylindrical dynamic hohlraum shows that symmetrical implosion is hard to achieve due to the relatively slow propagation speed of thermal wave and the compression of cylindrical shock in the foam. With the help of quasi-spherical implosion, the hohlraum radiation uniformity and corresponding pellet implosion symmetry can be significantly improved thanks to the shape modulation of thermal wave front and shock wave front.