By means of a novel experimental design called double-massive-target coupling, significant amplification of five lasing lines was observed with wavelengths (λ) of 19.6, 23.2, 23.6, 24.7, and 28.6 nm from 3p–3s transitions in Ne-like Ge ions at an irradiance of 1.2 × 10<sup>13</sup> W/cm<sup>2</sup> on the axis of an elongated plasma column. The maximum gain–length product (GL) values achieved were greater than 14 for 2 of the 5 lasing lines at 23.2 and 23.6 nm. Temporally resolved measurements of x-ray laser spectra indicate that the duration of the gain was ˜0.8 ns, which is comparable with the Gaussian driving laser pulse width of 1 ns (FWHM) in our experiments. The measured divergence and refraction angles of the x-ray laser beam at 23.6 nm are presented. The dimension and position of the gain region are estimated.
© 1992 Optical Society of America
Shiji Wang, Yuan Gu, Guanlin Zhou, Songyu Yu, Sizu Fu, Yuanlong Ni, Jiang Wu, Zhengliang Zhou, Guoqiang Han, Zucong Tao, Zunqi Lin, Shusen Wang, Wannian Chen, Dianyuan Fan, Guoping Zhang, Jiatian Sheng, Huimin Peng, Tanxin Zhang, and Yunfeng Shao, "Experimental investigation of high-gain Ne-like Ge soft-x-ray laser by double-massive-target coupling," J. Opt. Soc. Am. B 9, 360-368 (1992)