以“阳”加速器(1 MA,80 ns)驱动的Z箍缩等离子体为X射线源研究X射线加载下金属表面出现的电荷分离现象,Z箍缩负载为16根直径5 μm的钨丝组成的丝阵,丝阵半径3 mm。强度107 W/cm2、半高宽30 ns的软X射线脉冲通过直径5 mm的限光孔辐照半径30 mm、厚3 mm的铜盘中心,在金属表面产生了脉宽相近,幅值kV的电势。测量了该电势沿金属表面的分布,观测到微弱的调制现象。电势的极性表明电子主要沿金属表面运动而不是垂直表面运动,这表明热电效应是造成电荷分离的主要机制。入射X射线强度较弱时,电子的个体行为--光电效应、康普顿效应占主导;当入射强度较大时,弱关联的集体行为--热效应占主导;进一步增大入射X射线强度将出现强关联的集体行为--电荷密度调制状态。

The measurement of charge separation potentials of metal targets irradiated by 107 W/cm2,30 ns X-ray pulses produced by Z pinch on “Yang” accelerator (1 MA,80 ns) shows kilovolt target potentials existing for 40 ns. The pinch load was tungsten wire array (3 mm in radius) consisting of 16 wires with a radius of 5 μm. The measurement also gives the distribution of potentials on the targets. The polarity of the potential indicates that the electrons move along target surfaces,not along the normal direction. The experimental results show that thermoelectric effect is the main mechanism causing this charge separation. The conclusions reveal that,electrons’ individual behavior including photoelectric effect and Compton effect dominates when targets are irradiated by weak X-ray;for intense X-ray incidence weak correlation collective behavior (thermoelectric effect) dominates;for ultra-intense X-ray incidence strong correlation collective behavior (charge density modulation state) appears.