Soft X-ray recombination laser research at the Institute of Laser Engineering

Soft X-ray laser experiments recently carried out using the Gekko MII glass laser facility at the Institute of Laser Engineering, Osaka University, are described. Hydrogenic and lithiumlike lasing schemes in recombining plasmas were investigated using foil targets exploded with line-focused 532 nm laser radiation of approximately 100 J energy. In a preliminary study, time-integrated emissions of Balmer-α transitions in C⁸⁺ and O⁷⁺ and 5-3 transitions in Al¹⁰⁺ were found to increase nonlinearly with increasing target length, yielding gain coefficients of G=0.9 to 2.3 cm ^-1. In a subsequent, more refined study, which included time-resolved measurements, the authors obtained a gain of G=2 cm^-1 and a gain-length product GL=3 for the Balmer-α transition in F⁸⁺ at 80.9 Å