Transform-limited X-ray pulse generation from a high-brightness self-amplified spontaneous-emission free-electron laser

A method to achieve high-brightness self-amplified spontaneous emission (HB-SASE) in the free-electron laser (FEL) is described. The method uses repeated nonequal electron beam delays to delocalize the collective FEL interaction and break the radiation coherence length dependence on the FEL cooperation length. The method requires no external seeding or photon optics and so is applicable at any wavelength or repetition rate. It is demonstrated, using linear theory and numerical simulations, that the radiation coherence length can be increased by approximately 2 orders of magnitude over SASE with a corresponding increase in spectral brightness. Examples are shown of HB-SASE generating transform-limited FEL pulses in the soft x-ray and near transform-limited pulses in the hard x-ray. Such pulses may greatly benefit existing applications and may also open up new areas of scientific research

Skin effect with arbitrary specularity in Maxwellian plasma

The problem of skin effect with arbitrary specularity in maxwellian plasma with specular--diffuse boundary conditions is solved. A new analytical method is developed that makes it possible to to obtain a solution up to an arbitrary degree of accuracy. The method is based on the idea of symmetric continuation not only the electric field, but also electron distribution function. The solution is obtained in a form of von Neumann series.Comment: 7 pages, 2 figure

Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet

The linear equations for transverse spin dynamics in a weakly polarized degenerate Fermi liquid with arbitrary relationship between temperature and polarization are derived from Landau-Silin phenomenological kinetic equation with general form of two-particle collision integral. Unlike the previous treatment where Fermi velocity and density of states have been taken as constants independent of polarization here we made derivation free from this assumption. The obtained equations are applicable for description of spin dynamics in paramagnetic Fermi liquid with finite polarization as well in an itinerant ferromagnet. In both cases transverse spin wave frequency is found to be proportional to the square of the wave vector with complex constant of proportionality (diffusion coefficient) such that the damping has a finite value at T=0. The polarization dependence of the diffusion coefficient is found to be different for a polarized Fermi liquid and for an itinerant ferromagnet. These conclusions are confirmed by derivation of transverse spin wave dispersion law in frame of field theoretical methods from the integral equation for the vortex function. It is shown that similar derivation taking into consideration the divergency of static transverse susceptibility also leads to the same attenuating spin wave spectrum.Comment: 7 pages, no figure

Growth and crystallization of molybdenum layers on amorphous silicon

The structure of molybdenum layers deposited by direct current magnetron sputtering onto the amorphous silicon (a-Si) layers as function of nominal layer thickness was studied by methods of transmission electron microscopy. Molybdenum layers with nominal thickness 1.5btMo nomb1.9 nm consist of clusters which should be considered as a transient state between strongly disordered (amorphous) state and crystal one. A transition from clusters to polycrystals takes place within the thickness range of 1.9btMo nomb2.5 nm. Resulting Mo crystallites have an inequiaxial form with dimensions of (3–4)×(15–30)nm2 and consist of blocks. The lateral axis of inequiaxial crystallites is parallel to 110 direction. As the metal layer thickness increases Mocrystallites take the more regular form at the expense of recrystallization