强光一号兆安电流钨丝X箍缩实验研究

为了获得更高亮度的X射线点源,在"强光一号"装置上开展钨丝X箍缩实验研究.基于能量平衡方程,估算了1 MA电流热斑等离子体平衡半径为1—10μm.实验中,测试钨丝直径为25—100μm,丝根数为2—48,负载线质量为0.18—6.9 mg/cm;负载电流峰值为1—1.4 MA,10%—90%前沿为60—70 ns."强光一号"装置上匹配的X箍缩负载为30或32根25μm钨丝X箍缩,这种负载一定概率产生单个脉冲X射线辐射,辐射时刻位于电流峰值附近,典型参数为keV X射线脉宽1 ns,辐射功率35 GW,产额40 J,热斑尺寸～30μm.然而,兆安电流X箍缩通常产生多个热斑及多个脉冲X射线辐射.keV能段首个脉冲X射线辐射时刻与负载线质量正相关,并受到负载丝直径的影响.多个X射线脉冲可能由二次箍缩和局部箍缩产生,多个热斑可能由交叉点处微Z箍缩的长波长扰动和短波长扰动引起.与百千安电流X箍缩相比,兆安电流X箍缩热斑亮度更高,但X射线辐射脉冲的单一稳定性还有待于进一步改善.

Experimental investigations of tungsten X-pinches using the QiangGuang-1 facility

In order to obtain a single brighter point X-ray source, tungsten X-pinch experiments were carried out on the QiangGuang-1 facility. The equilibrium radius of the bright spots was estimated based on the energy balance equation. X-pinch load test covered wire diameters from 25 to 100 μm, wire number from 2 to 48, and the load linear mass from 0.18 to 6.9 mg/cm. The load peak current was 1.0–1.4 MA and the rise time for 10%–90% was 60–70 ns. From the experiments, the matched load for “QiangGuang-1” facility was the 30 or 32 wire-25 μm X pinch with the load linear mass of 2.8–3.0 mg/cm, which can produce a single nanosecond X-ray pulse around current peak with a certain probability. A typical keV X-ray radiation had a pulse width of 1 ns, the radiation power from the bright spot being 35 GW, the radiation yield being 40 J, and the spot size being about 30 μm. Multiple bright spots and multiple X-ray bursts at the crossing were usually observed in the experiments. Multiple X-ray bursts were probably caused by secondary pinches or partial pinches, and multiple bright spots were caused by long wavelength perturbations or localized short wavelength perturbations along the “min Z-pinch” axis. Compared with hundreds of kilo-ampere devices, mega-ampere facilities produced greater X-ray radiation, but further improvements are needed to produce a single X-ray burst steadily.