Studies on collisional pumping of soft X-ray lasers at ILE

X-ray laser research performed at the Institute of Laser Engineering, Osaka University, are reported. The performance of X-ray lasing pumped by a train of 100-ps pulses at the wavelength range between 14 and 4 nm was investigated. The irradiance on the target was up to /spl sim/3/spl times/10/sup 14/ W/spl middot/cm. The double target amplification was successfully demonstrated with two beam irradiation for Ag, Nd, Yb, Hf, and Ta lasing. Moreover double-pass amplification at 7.9 nm has been demonstrated. The higher atomic number X-ray lasing strongly depends upon the transverse distance of the two targets.