摘要:
报道了基于脉冲宽度为16 ns、波长为266 nm、总能量为30 mJ、时间分辨为1.6 ns的紫外激光四分幅阴影成像系统,用于研究Z-pinch产生等离子体与在丝阵负载中心放置塑料泡沫材料相互作用输运规律,研究动态黑腔形成过程的主要物理因素.使用高能高密度激光束透射等离子体,依据等离子体对激光束吸收衰减特性诊断激光束通过等离子体后的空间强度分布,通过理论计算获得等离子体空间密度分布,获得等离子体产生的早期稳定性、箍缩速度等规律.实验研究表明,在X射线峰值前约-25 ns等离子体开始压缩塑料泡沫,在峰值前-5 ns压缩到最小,之后泡沫开始膨胀.在X射线峰值时刻泡沫直径由3 mm压缩到直径约为1 mm,对泡沫的最大压缩比约为9倍.实验测量压缩速度约为3.3×106 cm/s,并给出了不同时刻的磁流体不稳定结构分布.
Abstract:
This paper reports an ultraviolet laser four-framing shadow imaging system based on the laser with a pulse width of 16ns,a wavelength of 266 nm,a total energy of 30 mJ and a temporal resolution of 1.6 ns,which is used to study the transport laws of the interaction of Z-pinch generated plasmas with the plastic foam located at the center of the wire array and the main physical factors affecting the formation of the dynamic hohlraum.The high-energy and high-density laser beam is used to transmit through the plasmas.The spatial density distribution of the plasmas can be obtained by theoretically calculating the spatial intensity distribution of the laser beam after passing through the plasmas,which is diagnosed based on the plasmas absorption and attenuation characteristic to the laser beam.With the spatial density distribution of the plasmas,the laws of the early stability of the generated plasmas,pinch velocity,and so forth can be obtained.Experimental study indicated that plastic foam was compressed by the plasmas starting at about-25 ns before the X ray peak and was compressed to the minimum diameter at-5 ns before the peak.After that,the foam started to expand.At the X ray peak,the foam diameter was compressed from 3 mm to about 1 mm.The maximum compression ratio of the foam is about 9.The compression velocity measured by the experiment was about 3.3 ×106 cm/s,and the unstable structure distribution of the magnetic fluid at different time is given.
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