Soft x-ray amplification in aluminium recombining plasma produced from a thin coated fibre

Thin carbon fibres, coated with aluminium, are irradiated with approximately=120 ps, 0.53 mu m laser pulses yielding a specific absorbed energy of approximately=4 J cm^-1 and time-resolved gain measurements on the n=4-3 and n=5-3 transitions of lithium-like Al XI ions in the recombining plasma are made. In particular, gain on the 4f-3d line at 15.4 nm is measured with alpha _max approximately=2-3 cm^-1 using both single-shot and multi-shot techniques. Gain measurements from multi-shot data on the 5f-3d line at 10.6 nm indicate alpha _max approximately=1.5 cm^-1. Observations are compared with theoretical calculations, discrepancies are noted and the need for reproducible plasma conditions in low gain-length product data sets is discussed.