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An analytical model is developed for the generation of synchrotron radiation from a laser cluster plasma in the focal waist of an ultra-intense short circularly polarised laser pulse. The rotation of relativistic electrons around the ionised core of the cluster with a radius of rotation smaller than the laser wavelength leads to intense synchrotron radiation in the direction transverse to the laser wave vector. The parameters of the cluster plasma and laser pulse are determined at which, due to the small radius of curvature of the electron trajectory of the cluster shell, the intensity of synchrotron radiation exceeds the intensity of betatron radiation of the electron flux in the longitudinal (along the wave vector) direction.

We propose a focusing mechanism of high-energy ions by an electron cloud produced by a laser interaction with slab plasma. In our 2.5-dimensional (2.5D) particle-in-cell simulations, the laser intensity is 2 × 1020 W/cm2, the laser wavelength λ is 1.053 μm, and the laser spot size is 2.5λ. When the high intensity laser irradiates slab plasma, electrons are accelerated, oscillate around the plasma and produce the electron cloud locally at the sides of the plasma. Because the electrons are localized transversely, a static electric potential is formed to focus ions and at the same time the ions are accelerated longitudinally. Though the longitudinal ion acceleration has been studied well, the ion focusing effect is reported for the first time in this paper. In our calculations, the maximum energy and intensity of the protons are 8.61 MeV and 1.89 × 1017 W/cm2, and the diameter of the proton bunch accelerated are focused to 71.2% of its initial size.

Electron ponderomotive acceleration in a vacuum by a short-pulsed laser of TEM (1, 0) + TEM (0, 1) mode is studied in this paper using a 3-dimensional (3D) particle simulation. It was found that the laser can trap electrons in transverse and accelerate them with the longitudinal ponderomotive force at the same time. Through this electron trapping and acceleration scheme of TEM (1, 0) + TEM (0, 1) mode laser, the electron bunch is confined well in transverse and compressed remarkably in longitudinal. Therefore, a high energy, high density, and low emittances electron bunch is generated. For example, the result shows that for a laser with intensity of a0 = eE0 /mωc = 10, the laser spot size of w0 = 15λ, and the laser pulse length of Lz = 10λ, the maximum energy gain reaches 301 MeV and the average energy 57.7 MeV. The electron bunch transverse radius is about 350λ and the longitudinal size about 20λ. The property of this accelerated bunch is improved compared with that generated by the laser of TEM (0, 0) mode.

Analysis and simulations of fast particles produced by a high-intensity short laser pulse interacting with a foil target are performed. Initially, the plasma density distribution of the foil target has a smooth gradient with the scale length of plasma density varying across it. The absorbed laser energy is transferred to fast electrons, which penetrate in the foil and are partially ejected from the foil rear. These electrons produce an electric field that causes an ion beam to be emitted from the foil. We analyze the mechanism of ion acceleration in the foil plasma and the influence of the density gradient and other laser and plasma parameters on ion acceleration. The angular distributions of the ejected electrons and ions are calculated.

ABSTRACTAn extracellular β-glucosidase (β-D-glucoside glucohydrolase, EC 3.2.1.21) produced by Aspergillus awamori K-1 was purified to electrophoretic homogeneity. The purified enzyme, which had a glycoprotein nature, was a monomer with a relative molecular mass of 116 kDa and pI= 5.8. The β-glucosidase was the most active against aryl-β-glucosides and cellobiose. In addition, the enzyme was able to catalyze the hydrolysis of β-1→2 and β-1 →6-linked diglucosides. The apparent Kmand V values for p-nitrophenyl-β-D-gluco-pyranoside were calculated to be 0.8 mM and 5.29 μmol.min−1respectively. Maximal β- glucosidase activity occurred at 60 °C and pH 5.0. This enzyme was competitively inhibited by β-D-glucose with K1value of 13.15 mM.

This paper considers various channels of electron–positron pair, neutron, and γ-quantum generation via the ultrashort high-power laser pulse interaction with targets made from different materials. The positron yields in materials with different Z are estimated for the positron production by high-speed electrons and γ-photons. It is shown that a picosecond 100-TW laser pulse gives rise to formation of about 1010 positrons, possible channels of the neutron production in light- and heavy-atom materials being studied as well. It is ascertained that the formation of up to 107 laser neutrons per shot is possible when the laser intensity is ~1021 W/cm2 on a heavy-atom target.

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Methods used to generate high-energy ultrashort laser pulses and their applications in various branches of science are reviewed. Special attention is given to the use of ultrastrong laser fields in the initiation of 'fast ignition' thermonuclear reactions.

It is shown that in stimulated Brillouin scattering of picosecond laser pulses the proportion of the energy scattered in a strongly inhomogeneous short dense-plasma layer reaches a fraction of a percent at intensities below 2 ×10¹⁵ W cm^-2 in the absence of a prepulse or less than 2 × 10¹⁴ W cm^-2 if a prepulse is present. This can be used to detect a prepulse and to obtain an experimental estimate of the contrast. In the case of longer (≈10 ps, ≈2 × 10¹⁵ W cm^-2) pulses the proportion of the energy scattered by the stimulated Brillouin process may reach several percent in the absence of a prepulse.

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Some compounds, Sb2Se3, InSe and CuSbSe2have been studied which have relatively low electrical conductivities (< 100 mho/cm) in the liquid state. Experimental results above and below the melting point are reported and discussed for the electrical conductivity, Hall coefficient, thermopower, and the thermal conductivity. We also present the results of a study of the thermal motion of liquid and solid gallium by means of neutron scattering.

Experimental and theoretical investigations were made of the characteristics of the interaction between solid targets and picosecond laser pulses with a complex profile. A prepulse preceding the main picosecond pulse increased the absorption of the s-polarised radiation and reduced the absorption of p-polarised radiation. Moreover, the prepulse made it possible to control the intensity of various components of the x-ray radiation emitted by the laser plasma. A satisfactory agreement between the experimental results and numerical calculations was obtained and a theoretical optimisation of the efficiency of x-ray generation was made.

Numerical simulations were made of the interaction of a relativistically intense laser pulse with a target consisting of nanometre fibres. Fast electrons were shown to execute forced betatron oscillations in the electrostatic fibre field and the laser field. The fibre diameter was determined whereby the amplitude of betatron electron oscillations is resonantly increased. The power of coherent X-ray betatron radiation of the electron bunch was calculated outside of the resonance domain and in the resonance case. We showed that the laser-to-X-ray betatron radiation conversion coefficient in the resonance case amounts to a few percent and the target made up of nanometre fibres may be regarded as an efficient laser-driven source of coherent X- and gamma-ray radiation.

We have investigated the effect of the laser spot shape on the spatial distribution of accelerated ions on the front and back sides of a thin target irradiated by a picosecond laser pulse having the intensity of . Experimental data are compared with numerical calculations. It is shown that the spatial structure of the ion bunch on the front side of the target resembles the laser spot structure rotated by .

The formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2 × 1017W cm−2onto an edge of aluminium foil has been experimentally demonstrated. The electrons had energy distributions peaking in the range from 0.2 to 0.8 MeV and an energy spread less than 20%. The acceleration mechanism related to the generation of a plasma wave as a result of self-modulation instability of the laser pulse in the subcritical plasma formed the prepulse of the laser system (arriving 10 ns before the main pulse) is considered. One-dimensional PIC simulation of the interaction between the laser radiation and plasma with a concentration of 5 × 1019cm−3showed that effective excitation of a plasma wave, as well as the trapping and acceleration of the electron beam with an energy on the order of 1 MeV, may occur in the presence of inhomogeneities in the density at the plasma boundary and in the temporal shape of the beam.

A numerical simulation of the interaction of a laser pulse with ultrathin targets has revealed a possibility of generating thin dense relativistic electron layers. The maximum kinetic energy of the electron mirror can be gained using an optimal combination of the target thickness and the laser pulse intensity and duration. It is proposed to use an additional (second) laser target, located at an optimal distance from the first target to cut off the laser pulse from the electron layer when the latter gains a maximum kinetic energy. This relativistic electron mirror can be used for efficient generation of ‘hard’ coherent radiation via counter reflection of an additional (probe) laser pulse from the mirror.