MASH stands for Macros for the Automation of SHadow". It allows to run a set of ray-tracing simulations,
for a range of photon energies for example, fully automatically. Undulator gaps, crystal angles etc. are tuned automatically. Important output parameters, such as photon flux, photon irradiance, focal spot size, bandwidth, etc. are then directly provided as function of photon energy. A photon energy scan is probably the most commonly requested one, but any parameter or set of parameters can be scanned through as well.
Heat load calculations with finite element analysis providing temperatures, stress and deformations (Comsol) are fully integrated. The deformations can be fed back into the ray-tracing process simply by activating a switch.
MASH tries to hide program internals such as le names, calls to pre-processors etc., so that the user (nearly) only needs to provide the optical setup.
It comes with a web interface, which allows to run it remotely on a central computation server. Hence, no local installation or licenses are required, just a web browser and access to the local network.
Numerous tools are provided to look at the ray-tracing results in the web-browser. The results can be also downloaded for local analysis. All files are human readable text files that can be easily imported into third-party programs for further processing.
All set parameters are stored in a single human-readable file in XML format.
Zone folded coherent acoustic phonons were generated in a multilayered GaSb/InAs epitaxial heterostructure via rapid heating by femtosecond laser pulses. These phonons were probed by means of ultrafast x-ray diffraction. Phonons both from the fundamental acoustic branch and the first back-folded branch were detected. This represents the first clear evidence for phonon branch folding based directly on the atomic motion to which x-ray diffraction is sensitive. From a comparison of the measured phonon-modulated x-ray reflectivity with simulations, evidence was found for a reduction of the laser penetration depth. This reduction can be explained by the self-modulation of the absorption index due to photogenerated free carriers.
The analysis of the fine structure observed in spectra of hydro genic aluminum emitted from a constrained-flow plasma indicates the presence of the laser-induced satellites. The measured profiles of the Al Lyman line (beta) exhibit peaks in the wings consistent with theoretical predications of the spectral line modification by strong single-frequency electric fields. The experimental identification of laser satellites opens up significant applications in the diagnosis of transient plasmas submitted to external oscillating fields.
Although the realisation of femtosecond X-ray free electron laser (FEL) X-ray pulses is still some time away, X-ray diffraction experiments within the sub-picosecond domain are already being performed using both synchrotron and laser- plasma based X-ray sources. Within this paper we summarise the current status of some of these experiments which, to date, have mainly concentrated on observing non-thermal melt and coherent phonons in laser-irradiated semiconductors. Furthermore, with the advent of FEL sources, X-ray pulse lengths may soon be sufficiently short that the finite response time of monochromators may themselves place fundamental limits on achievable temporal resolution. A brief review of time-dependent X-ray diffraction relevant to such effects is presented.
The collision of laser-produced plasmas has been diagnosed by x-ray spectroscopy and imaging. The two colliding plasmas are produced on Al thin foils at a distance of 200 to 900 micrometers irradiated at (lambda) equals 0.53 micrometers with laser intensities of 3 X 1013 to 6 X 1013 W/cm2. Interpretation of the plasmas was visualized by replacing one of the foils material by magnesium. The main diagnostics were x-ray crystal optics based on flat, cylindrical, and toroidal crystals viewing the inter-target space. A multifluid eulerian monodimensional hydrodynamic code coupled with a radiative-atomic package provided simulations of the experiments. Hydrodynamic 2D simulations calculating the lateral expansion of the plasma enabled a reliable treatment of reabsorption along the line of sight of the spectrographs. The size and the time duration of the collision, the plasma parameters in the collision region (Te, Ti, and ne) and interpenetration were measured. The hydrocode simulations give a good understanding of the behavior of the collision in function of intertarget distance and laser intensity.
Conference Committee Involvement (2)
Advances in Computational Methods for X-Ray Optics IV
9 August 2017 | San Diego, California, United States
Advances in Computational Methods for X-Ray Optics III
19 August 2014 | San Diego, California, United States