Susceptibilities and correlation functions of the anisotropic spherical model

The static transverse and longitudinal correlation functions (CF) of a 3-dimensional ferromagnet are calculated for the exactly solvable anisotropic spherical model (ASM) determined as the limit D → ∞ of the classical D- component vector model. The results are nonequivalent to those for the standard spherical model of Berlin and Kac even in the isotropic case. Whereas the transverse CF has the usual Ornstein-Zernike form for small wave vectors, the longitudinal CF shows a nontrivial behavior in the ordered region caused by spin-wave fluctuations. In particular, in the isotropic case below T _c one has S _zz(k) ∝ 1/k (the result of the spin-wave theory) for k ? κ_m ∝ T _c - T.     

High-power lasers at the Russian Federal Nuclear Center (VNIIEF)

The development of laser plants with different purposes, which originally began in the mid-1960s, are being successfully carried out at the Laser Physics Research Institute (LPRI). Investigations of the physical fundamentals of the laser operation, nonlinear optics, and the properties of high-temperature dense plasma that is formed under the action of the intensive laser emission on matter are realized at these plants.     

Analysis of lasing threshold of a nuclear-pumped gas laser depending on the lasing medium residence time in the laser module case

It is shown experimentally that an increase in the lasing mixture residence time in the case of a laser module over 60–120 min prior to an experiment elevates the lasing threshold and deteriorates the energy parameter of the laser. The worsening of the energy parameters of the laser may be due to accumulation of impurity gases. It is shown that the presence of impurities affects the working characteristics of the laser media under investigation to various extents.     

Narrow-directed fast-ion flow generation from targets irradiated by a picosecond laser pulse

The proton and deuteron yields from thin targets irradiated by a picosecond laser pulse with an average radiation intensity of ≤4×10¹⁸ W/cm² at the target were measured in the megaelectron-volt energy range. A ring structure was observed for the outgoing ions, and the angular ion-beam divergence was found to be extremely small (0.5°). The fast-ion generation mechanism allowing for the appearance of ring structure is discussed, and the characteristic energies and spatioangular ion-beam distribution are estimated.     

The MAGO system (magnetic compression)

Results of experimental and theoretical investigations are presented in the frame of magnetohydrodynamic implosion conception MAGnitnoye Obzhatiye or magnetic compression (MAGO). This approach suggests magnetized deuterium-tritium (DT)-plasma preliminary heating and its subsequent adiabatic compression by liner imploded by a magnetic field. DT-plasma preliminary heating is performed using a special plasma chamber MAGO where magnetized plasma is accelerated in an annular nozzle up to velocities ~100 cm/μs and heated in arising collisionless shock waves. Subsequent plasma compression and bringing of its characteristics to the ignition can be realized using explosive magnetic generators with energy 100-500 MJ. This paper discusses the plasma chamber MAGO, physical effects essential for its operation, their relation with other plasma physics areas, as well as problems arising in the MAGO system. Due to its cylindrical symmetry with sole toroidal magnetic field component and essential role of magnetohydrodynamics, the MAGO system and its problems are similar to these in related systems, such as Z-pinches, plasma accelerators, and liner systems     

Hydrogen migration in metals under the combined action of acoustic and ionizing radiation

The hydrogen migration in metals under the action of ionizing and acoustic radiation is considered. The joint action of ionizing and acoustic radiation is found to enhance the hydrogen migration in metals (“interference” effect). The hydrogen transport mechanism is determined by the interaction of ionizing radiation with the hydrogen subsystem of a metal and a vibrodiffusion effect.     

Applying the stochastic parallel gradient algorithm in the auto alignment problem for the amplifier channel of the UFL-2M facility

The procedure of automatic alignment of the four-pass amplifier channel of a UFL-2M facility has been simulated numerically in the presence of aberrations in the optical path. The alignment procedure is based on the “marker” or “reference” method. The control elements are directed by the stochastic parallel gradient algorithm. The order of executing the automatic alignment is determined. The numerical simulation shows the possibility of positioning the beam at the exit from the channel with an accuracy of 1% of the pinhole size in the far field and of 0.1% of the beam aperture size in the near field. It was established that the centering accuracy of the alignment beam in inner pinholes in the presence of optical inhomogeneities in the amplifier channel can be worse than at the exit of the channel. The possibility of symmetrizing the picture of far-field markers has been considered in the case where the position of the optical axis of the channel is unknown.