Self-Photopumped X-Ray Lasers from Elements in the Ne-like and Ni-like Ionization State

Abstract

Self-photopumped x-ray lasers in laser-produced plasma have been previously proposed as an alternative scheme to electron collisional excitation. While, in general, self-photopumped lasers suffer from somewhat lower gain, their higher saturation intensity could in principle lead to higher peak irradiace. We have performed experiments on the 3d $^1$P$_1$ $\rightarrow$ 3p $^1$P$_1$ and 4f $^1$P$_1$ $\rightarrow$ 4d $^1$P$_1$ transitions for Ne-like and Ni-like ions, respectively. Lasing on the self-photopumped laser line has been observed for the first time for several elements including Ne-like V, Cr, Fe, and Co as well as Ni-like Ru, Pd, and Ag. We have investigated the lasing process by varying the prepulse delay, which shows a shift of the optimum main pulse to second prepulse delays towards lower values with higher atomic number Z. Experiments have been performed with the Bern Advanced Glass Laser (BeAGLE) laser using three pulses with total energy up to 15 J at a wavelength of 1054 nm.