X-ray laser experiments in recombining plasma with double-target configuration pumped by pulse-train laser

Abstract
We have been developing a tabletop x-ray laser based on the recombination plasma scheme. An advanced experiment has been started to improve x-ray laser output substantially. Two 11-mm-long laser produced plasmas were produced so that their axis aligned into a line, the double-target configuration. X-ray intensity of the 15.47 nm transition line of the Li-like Al ion has been enhanced in the double-target configuration. Half-cavity experiments in the double-target configuration were also performed, the enhancement of x-ray was also observed. The results in the half-cavity experiment were consistent with a simple estimation, where the two plasmas having positive gain-length products contribute to amplify x-rays passing through each plasma.