XLO-II, a high-repetition rate X-ray laser oscillator

Recently we proposed to build an X-ray laser oscillator (XLO) in the 6-10 keV range providing intense, stable, transform-limited x-ray pulses in the 6-10 keV range, based on an x-ray pulse train operated at 100 Hz repetition rate. Here, we provide an analysis of recent experimental results and theoretical/numerical simulations showing that it is possible to build and operate a second generation x-ray laser oscillator, XLO-II, operating at up to 125 kHz and pumped by 6-10 keV x-ray SASE pulses generated by the new LCLS-II-HE x-ray free-electron laser (XFEL) now under construction at SLAC National Accelerator Laboratory. XLO-II will generate transform limited, coherent x-ray pulses, with an average power in the tens of mW range. It will open new experimental capabilities, for instance in fields like imaging, interferometry and quantum x-ray optics. We discuss the recent results leading to this conclusion and present the main characteristics of XLO-II and of its main components, like the optical cavity

Characterization of SiGe thin films using a laboratory X-ray instrument

The technique of reciprocal space mapping using X-rays is a recognized tool for the nondestructive characterization of epitaxial films. X-ray scattering from epitaxial Si0.4Ge0.6 films on Si(100) substrates using a laboratory X-ray source was investigated. It is shown that a laboratory source with a rotating anode makes it possible to investigate the material parameters of the super-thin 2–6 nm layers. For another set of partially relaxed layers, 50–200 nm thick, it is shown that from a high-resolution reciprocal space map, conditioned from diffuse scattering on dislocations, it is possible to determine quantitatively from the shape of a diffraction peak (possessing no thickness fringes) additional parameters such as misfit dislocation density and layer thickness as well as concentration and relaxation

Bunches of misfit dislocations on the onset of relaxation of Si0.4_{0.4}Ge0.6_{0.6}/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

The experimental x-ray diffraction patterns of a Si$_{0.4}$Ge$_{0.6}$/Si(001) epitaxial film with a low density of misfit dislocations are modeled by the Monte Carlo method. It is shown that an inhomogeneous distribution of 60$^\circ$ dislocations with dislocations arranged in bunches is needed to explain the experiment correctly. As a result of the dislocation bunching, the positions of the x-ray diffraction peaks do not correspond to the average dislocation density but reveal less than a half of the actual relaxation

Generation of Intense Phase-Stable Femtosecond Hard X-ray Pulse Pairs

Coherent nonlinear spectroscopies and imaging in the X-ray domain provide direct insight into the coupled motions of electrons and nuclei with resolution on the electronic length and time scale. The experimental realization of such techniques will strongly benefit from access to intense, coherent pairs of femtosecond X-ray pulses. We have observed phase-stable X-ray pulse pairs containing more thank 3 x 10e7 photons at 5.9 keV (2.1 Angstrom) with about 1 fs duration and 2-5 fs separation. The highly directional pulse pairs are manifested by interference fringes in the superfluorescent and seeded stimulated manganese K-alpha emission induced by an X-ray free-electron laser. The fringes constitute the time-frequency X-ray analogue of the Young double-slit interference allowing for frequency-domain X-ray measurements with attosecond time resolution.Comment: 39 pages, 13 figures, to be publishe

Theoretical concepts of X-ray nanoscale analysis: theory and applications

This book provides a concise survey of modern theoretical concepts of X-ray materials analysis. The principle features of the book are: basics of X-ray scattering, interaction between X-rays and matter and new theoretical concepts of X-ray scattering. The various X-ray techniques are considered in detail: high-resolution X-ray diffraction, X-ray reflectivity, grazing-incidence small-angle X-ray scattering and X-ray residual stress analysis. All the theoretical methods presented use the unified physical approach. This makes the book especially useful for readers learning and performing data an

XLO-II, a high-repetition rate X-ray laser oscillator

Recently we proposed to build an X-ray laser oscillator (XLO) in the 6-10 keV range providing intense, stable, transform-limited x-ray pulses in the 6-10 keV range, based on an x-ray pulse train operated at 100 Hz repetition rate. Here, we provide an analysis of recent experimental results and theoretical/numerical simulations showing that it is possible to build and operate a second generation x-ray laser oscillator, XLO-II, operating at up to 125 kHz and pumped by 6-10 keV x-ray SASE pulses generated by the new LCLS-II-HE x-ray free-electron laser (XFEL) now under construction at SLAC National Accelerator Laboratory. XLO-II will generate transform limited, coherent x-ray pulses, with an average power in the tens of mW range. It will open new experimental capabilities, for instance in fields like imaging, interferometry and quantum x-ray optics. We discuss the recent results leading to this conclusion and present the main characteristics of XLO-II and of its main components, like the optical cavity

Stochastic modeling of superfluorescence in compact systems

We propose an approach based on stochastic differential equations to describe superfluorescence in compact ensembles of multi-level emitters in the presence of various incoherent processes. This approach has a numerical complexity that does not depend on the number of emitters. The stochastic differential equations are derived directly from the quantum master equation. In this study, we present a series of numerical examples, comparing our solution to exact calculations and discussing the limits of applicability. For many relevant cases, the proposed stochastic differential equations provide accurate results and correctly capture quantum many-body correlation effects