Soft x-ray free-electron laser imaging by LiF crystal and film detectors over a wide range of fluences.

LiF crystal and film detectors were used to measure the far-field fluence profile of a self-amplified spontaneous-emission free-electron laser beam and diffraction imaging with high spatial resolution. In these measurements the photoluminescence (PL) response of LiF crystal and film was compared over a wide range of soft x-ray fluences. It was found that the soft x-ray fluence dependences of LiF crystal and film differ.

Generation of hard x rays by femtosecond laser pulse interaction with solid targets in atmosphere.

X ray radiation as high as 50 keV, including K(α) of Ba and Mo, have been observed from a solid target during the interaction of low energy ~0.65 mJ, 1 kHz 40 femtosecond laser pulses focused in air at atmospheric pressure. Energetic electrons generating such x rays are possibly produced when the field strength in laser pulse wake exceeds the runaway threshold in air.

Propagation-based phase-contrast enhancement of nanostructure images using a debris-free femtosecond-laser-driven cluster-based plasma soft x-ray source and an LiF crystal detector.

We demonstrate in-line phase-contrast imaging of nanothickness foils by using a relatively large, polychromatic, debris-free femtosecond-laser-driven cluster-based plasma soft x-ray source, and a high-resolution, large dynamic range LiF crystal detector. The spatial coherence length of radiation in our setup reached a value of 5 microm on the sample plane, which is enough to observe phase-contrast enhancement in the images registered by the detector placed only a few hundred micrometers behind the object. We have developed a tabletop soft x-ray emission source, which emits radiation within a 4pi sr solid angle, and which allows one to obtain contact and propagation-based phase-contrast imaging of nanostructures with 700 nm spatial resolutions.

Modeling energy dependence of the inner-shell x-ray emission produced by femtosecond-pulse laser irradiation of xenon clusters.

We employ the Los Alamos suite of atomic physics codes to model the inner-shell x-ray emission spectrum of xenon and compare results with those obtained via high-resolution x-ray spectroscopy of xenon clusters irradiated by 30fs Ti:Sapphire laser pulses. We find that the commonly employed configuration-average approximation breaks down and significant spin-orbit splitting necessitates a detailed level accounting. We reproduce an interesting spectral trend for a series of experimental spectra taken with varying pulse energy for fixed pulse duration.