Holographic study of chain length in photopolymerizable compositions

We describe a study of the free-radical homopolymerization kinetics for a system based on acrylamide, triethanolamine and methylene blue by analyzing temporal variations of the diffraction efficiency. The modulation index is related to the component’s parameters, giving as a result a method that can be used to determine the chain length of the polymer and the kinetic rate constants. By using this method we have studied the effect of intensity on the kinetic parameters of the photopolymerization process. Received: 20 August 2001 / Published online: 7 February 2002     

Holographic recording of laser-induced plasma

We report on a holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail. Plasma is generated by focusing a femtosecond pulse in air. We also demonstrate the capability of the holographic technique of capturing the time evolution of the plasma-generation process.     

Dynamics of a lasing atom in hot plasma

We study theoretically the dynamics of lasing atoms in a very hot plasma capillary, which produce coherent X-ray radiation. The atoms which participate in the lasing action are treated as a dilute gas, embedded in the plasma, whose electrons play the dominant role in inducing relaxations and decoherences. The active atom interacting with the electron reservoir in thermal equilibrium is described by a general Hamiltonian. In analogy with a radiation reservoir, by eliminating the degrees of freedom of the electron reservoir, the evolution rates of the Master Equation, i.e. the transition rates for the populations and dephasing rates for coherences, are calculated. It is demonstrated, by going beyond the dipole approximation, that the contribution of the adiabatic dephasing rate is significant compared to that of the non-adiabatic rate, in contrast to the case of a radiation reservoir. We also study other dephasing mechanisms, e.g. the motion of the lasing atoms center of mass, and the role of other atomic levels.Received: 13 May 2004, Published online: 24 August 2004PACS: 52.20.Hv Atomic, molecular, ion, and heavy-particle collisions - 32.70.Jz Line shapes, widths, and shifts     

Axion emission from a hot plasma

We give the technics for the calculation of production and energy loss rates for axion-like particles (scalar or pseudo-scalar coupling to the gauge boson) from a hot QED (or QCD) heat bath. We compute the contribution coming from, the decay mode of a transverse to a longitudinal photon (or gluon). The energy loss rate for this process behaves asT ⁷. Considering the supernova SN1987A event, this behaviour could improve the upper bound on the coupling constant between asions and photons.     

Radiation transport in a spherically symmetric hot plasma

An analytical solution is obtained for the problem of radiation transport in a spherically symmetric plasma. The ions are assumed to be in a complete steady state with constant ion density and electron temperature. The radiation density is assumed to be small so that the rate of the radiative processes in the plasma is small relative to that of the collisional processes, but not negligible. The effect of the plasma on the radiation density, as well as the influence of the radiation on the population probabilities, are properly accounted for. Under these conditions explicit expressions are given, valid to the first order in the plasma dimensions, for the radiation density and the population probability of the ionic states.     

Flow-shear instability of a potential hump in hot plasma

Low-frequency instability arising in hot magnetized plasma with a hump-shaped transverse profile of the potential has been observed experimentally. As a result of the instability, the plasma in the region of the maximum of the potential decomposes into an array of dense plasmoids and deep rarefactions. The instability is due to nonuniform E×B drift and is apparently a Rayleigh instability which reaches a strongly nonlinear stage. In the process, strong transverse transport arises, resulting in plasma losses. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 134–139 (10 August 1996)     

Magnetic trap for confining a hot plasma

The magnetic field of a two-helix Tornado trap has all the properties needed to efficiently confine a hot plasma. However, its practical utilization has been restricted because of the ponderomotive interaction between the turns of the helices, which disrupts the structure of the magnetic field. A modification of a Tornado trap, which permits significant reduction of the ponderomotive interaction is considered, and arguments in favor of using a magnetic field to maintain the properties of the field in an unmodified trap are presented. Zh. Tekh. Fiz. 67, 25–28 (September 1997)     

Luminescence in hot semiconductor plasma

We report measurement of the luminescence spectra of highly photoexcited semiconductor samples of GaAs, CdTe and InP. The experiments were performed under similar conditions as those imposed on the systems in previous work devoted to the observation of inelastic (Doppler - Raman) scattering of light. We show that our results are fully consistent with the interpretation of the macroscopic thermodynamic state of the system in terms of a hot excitation model.     

Anti-de sitter/conformal-field-theory calculation of screening in a hot wind

One of the challenges in relating experimental measurements of the suppression in the number of J/psi mesons produced in heavy ion collisions to lattice QCD calculations is that whereas the lattice calculations treat J/psi mesons at rest, in a heavy ion collision a cc[over ] pair can have a significant velocity with respect to the hot fluid produced in the collision. The putative J/psi finds itself in a hot wind. We present the first rigorous nonperturbative calculation of the consequences of a wind velocity v on the screening length L(s) for a heavy quark-antiquark pair in hot N=4 supersymmetric QCD. We find L(s)(v,T)=f(v)[1-v(2)](1/4)/piT with f(v) only mildly dependent on v and the wind direction. This L(s)(v,T) approximately L(s)(0,T)/sqrt[gamma] velocity scaling, if realized in QCD, provides a significant additional source of J/psi suppression at transverse momenta which are high but within experimental reach.     

Delayed hot spots in a low energy plasma focus

In a low energy Mather-type plasma focus device, hot spots having temperature in the range of few KeV have been observed even 1 μs after the pinch disintegration and in regions away from the pinch area. These hot spots are perhaps created by the thermal runway due to temperature fluctuations in the background gas.     

Holographic diagnostics of the plasma: A review

A review of works concerning holographic diagnostics of the plasma that have been conducted in the laboratory of plasma optics at the Ioffe Physico-Technical Institute since 1966 is presented. The potential and features of holographic diagnostics as applied to different plasma objects are discussed. The results of investigations into the laser-induced spark in gases and current sheets forming in 2D and 3D magnetic fields with X lines are reported.     

Ultrarelativistic excitation of beat waves in a hot magnetized plasma

Summary A theoretical investigation is made on the nonlinear relativistic excitation of an electrostatic electron plasma wave at the beat frequency of two high-power colinear laser beams in a hot, homogeneous and magnetized plasma. The relativistic Vlasov equation expressed in gyrokinetic variables has been employed to find the nonlinear response of the magnetized plasma electrons. It is noted that the power density associated with the excited beat wave is much higher for the relativistic consideration than that for the nonrelativistic consideration. The authors of this paper have agreed to not receive the proofs for correction.     

Localization of intense electromagnetic waves in a relativistically hot plasma

We consider nonlinear interactions between intense short electromagnetic waves (EMWs) and a relativistically hot electron plasma that supports relativistic electron holes (REHs). It is shown that such EMW-REH interactions are governed by a coupled nonlinear system of equations composed of a nonlinear Schro dinger equation describing the dynamics of the EMWs and the Poisson-relativistic Vlasov system describing the dynamics of driven REHs. The present nonlinear system of equations admits both a linearly trapped discrete number of eigenmodes of the EMWs in a quasistationary REH and a modification of the REH by large-amplitude trapped EMWs. Computer simulations of the relativistic Vlasov and Maxwell-Poisson system of equations show complex interactions between REHs loaded with localized EMWs.     

Compton散射下等离子体球太赫兹散射特性

为了研究Compton散射对等离子体球太赫兹(THz)散射特性的影响,将多光子非线性Compton散射模型引入到该研究中,提出了将Compton散射作为影响等离子体球太赫兹散射的重要因素,给出了各向异性等离子体球散射场修正方程及介电常数张量、观测方位、极化状态等因素对THz波散射的影响,并进行了仿真实验。结果表明:微分散射截面随THz波频率变化近乎呈准谐振规律变化,较散射前增大了0.001;微分散射截面随观测方位和极化状态的变化较散射前增大了0.002。     

Compton transport cross section for a hot plasma

The equation for diffusion transport of photons in a hot, Compton-scattering-dominated plasma is derived and a transport cross section is identified. Using a reasonable assumption for the frequency dependence of the flux, this relativistically—correct cross section is numerically evaluated for a set of photon energies and electron temperatures. A simple but accurate fit to the calculation is also presented.