Fully coherent, soft X-ray attosecond pulses are now available through high-order harmonic generation (HHG); however, the output energy is insufficient for various applications, such as attosecond-scale soft X-ray nonlinear experiments, the seeding of soft X-ray free-electron lasers, attosecond-pump-attosecond-probe spectroscopies, and single-shot imaging. In this paper, we combine a newly developed TW class mid-infrared femtosecond laser and a loose focusing geometry for HHG. A soft X-ray harmonic beam up to the water window region is demonstrated, which is more than 100 times intense compared to previous works. We achieve a high conversion efficiency, low beam divergence and a significantly reduced medium gas pressure. As the first application, we demonstrate near edge X-ray absorption fine structure experiments with clear fine absorption spectra near the K- and L-edges observed. The robust energy scaling method on HHG opens the door for demonstrating single-shot absorption spectrum and live-cell imaging with a femtosecond time resolution.

现在可以通过高次谐波产生（HHG）获得完全相干的软X射线阿秒脉冲；但是，输出能量不足以用于各种应用，例如亚秒级软X射线非线性实验，软X射线自由电子激光的播种，阿秒泵-阿秒探针光谱学和单次成像。在本文中，我们结合了新开发的TW类中红外飞秒激光器和用于HHG的宽松聚焦几何形状。展示了直至水窗区域的软X射线谐波光束，其强度是以前作品的100倍以上。我们实现了高转换效率，低束发散度和显着降低的中等气压。作为第一个应用程序，我们展示了近边缘X射线吸收精细结构实验，在观察到的K和L边缘附近具有清晰的精细吸收光谱。HHG上强大的能量缩放方法为展示单次吸收光谱和飞秒时间分辨率的活细胞成像打开了大门。