“强光一号”Al丝阵Z箍缩产生K层辐射实验研究

Experimental study on K-shell radiation production of aluminum wire array Z-pinch at Qiangguang-Ⅰ facility

在"强光一号"加速器开展了Al丝阵Z箍缩产生K层辐射的实验研究,固定Al丝线径20μm、丝阵直径12 mm,丝根数为8和12的负载获得K层产额分别为0.9 kJ/cm和1.1 kJ/cm,明显高于16和24根丝负载.辐射功率波形和时间分辨的X射线图像显示,低丝数负载存在拖尾质量引起的多次内爆现象.在60%—80%的内爆时间内,丝阵几乎停留在初始位置;主体内爆在随后的25—30 ns内完成,将部分等离子体留在初始位置,形成质量的拖尾分布;内爆后期驱动电流向外围的拖尾质量迁移,引发二次乃至三次内爆,后续内爆对K层辐射也有相当贡献.拖尾质量的出现与单丝等离子体上形成的轴向调制结构及不均匀性的发展有关.

Experimental study of aluminum wire array Z-pinch was conducted on Qiangguang-I facility （1.5 MA, 80 ns） to produce - 1.7 keV characteristic X-ray radiation. With fixed wire diameter of 20/.tm and annular diameter of 12 mm, K-shell yield up to 0.9 kJ/cm and 1.1 kJ/cm was obtained for wire number N = 8 and N = 12 arrays, respectively, which are much higher than that for N = 16 and N = 24 loads. X-ray power waveforms and time-resolved images showed that several implosions occurred due to the existence of trailing mass. During 60 %-80 % of the whole implosion time, the wire array almost stayed at its initial position rather than running inwards. Main implosion was completed in the next 25-30 ns, with parts of load mass left behind and forming so-called trailing mass. At later time of main implosion, load current was transferred to trailing mass left in outer radii, and caused secondary even tertiary implosion, which also contributed to total K-shell yield. Appearance of trailing mass might be caused by azimuthally correlated axial modulation, consisting of hot spots and gaps on wire plasma column, as well as the development of other inhomogeneities.