An atomic inner-shell laser pumped with an x-ray free-electron laser

Abstract

Focusing an x-ray free electron laser (XFEL) pulse into a gas target, a plasma of transiently core-excited ions can be created within a few femtoseconds, building a pathway to an inner-shell keV atomic x-ray laser. Varying the XFEL parameters, a wide variety of pulse structures can be created with comparable peak-intensities to XFELs: isolated pulses of sub-femtosecond duration, trains of pulses with increased temporal coherence, and trains of femtosecond pulses of different wavelengths. We present self-consistent gain and amplification calculations, tailored to predict first experiments on lasing on neon pumped by the Linac Coherent Light Source at Stanford.