Direct observation of the alpha-epsilon transition in shock-compressed iron via nanosecond x-ray diffraction
Physical Review Letters 95 (2005) 075502 4pp
X-ray line transfer in plasmas with large velocity gradients
ASTROPHYS SPACE SCI 298:1-2 (2005) 171-176
Abstract:
An astrophysically relevant experiment is compared to the output of a multidimensional radiation transfer code in which populations and radiation are self-consistently treated. Experimental Al Ly alpha spectra obtained with a very high-resolution spectrometer are presented as quantitative evidence of dot plasma non-planar expansion. Analysis of these spectra using the code is performed, in particular examining the effects of velocity gradients in directions other than that of the primary expansion. These calculations are found to be in good agreement with the experimental results. Usage of the Ly alpha doublet as a planarity diagnostic is discussed.Clocking femtosecond x rays
Physical Review Special Topics - Accelerators and Beams 8 (2005) 1-4
Abstract:
Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms. © 2005 The American Physical Society.Atomic-scale visualization of inertial dynamics
Science 308:5720 (2005) 392-395
Abstract:
The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry
(2005)