A Search for Gain on 2p-2s Transitions in a Collisionally Excited Ge Plasma

Soft x-ray amplification in collisionally excited Ne-like Ge plasmas has been extensively studied. Gains in excess of 4 cm-1 have been reported for the 3p-3s transitions. Significant gains have been observed over a wide range of irradiance conditions. The present experiments make use of a novel focusing arrangement[1] that employs a segmented wedge array (SWA) to overlap several line foci to produce a highly uniform linear plasma. The reproducibility of the XUV spectra was improved allowing gain to be inferred on a core-excited 2s2p63d-2s2p63p J=2-1 transition[2]. The 3d-2s quadrupole (E2) emission from the upper state of this transition was also identified in the L-shell emission spectrum. These measurements have now been extended into the 60-80 Å region where gain on 2s2p63s-2s2p53s and 2s2p63d-2s22p63d transitions is expected. Observation of gain on these Ne-like transitions would be significant as it would allow Ne-like lasers to scale to shorter wavelengths, into the "water window".