Analysis of gain generation of the TCE X-ray laser through temporal duration

Ochi, Yoshihiro; Kawachi, Tetsuya; Sasaki, Akira; Nagashima, Keisuke; Hasegawa, Noboru; Tanaka, Momoko; Kishimoto, Maki; Nishikino, Masaharu; Kato, Yoshiaki 

We have measured the temporal duration of the TCE X-ray laser (XRL) with Ni-like silver (Ag; Z = 47), palladium (Pd; Z = 46), and molybdenum (Mo; Z = 42). The pumping pulse was derived from Nd:glass laser system with the chirped pulse amplification at the wavelength of 1053 nm. The duration of the main pulse and prepulse were set to be 4.8 ps and 400 ps respectively. The pulse separation between the pulses was typically 500 ps. A quasi-traveling wave pumping using 6-step mirror was adopted in the focusing system. The X-ray laser outputs were measured by use of an X-ray streak camera coupled with a flat field spectrometer. The observed durations were 9.3 ps, 6.2 ps, and 3.9 ps for Ag, Pd, and Mo XRLs respectively, resulting in the longer duration for the higher atomic number material. We will discuss the gain generation in the plasma medium with the help of numerical simulation and atomic code.