Alexander Shutov

Disintegration of a charged viscous jet in a high electric field

The paper presents the investigation of excitation conditions of both axisymmetric and nonaxisymmetric perturbations of a charged jet under the action of an electric field. The linearized problem is analyzed in terms of the surface frozen charge approximation. The domination regions of these disintegration types are determined as charge-field variables. Attention is mainly paid to the nonaxisymmetric mode leading to the longitudinal splitting in two of the initial jet. Some versions of the jet instability development are considered when this mode is excited in a high electric field. The experimental data on the longitudinal- and combined longitudinal-axisymmetric disintegrations are presented.

GABRIELA: A new detector array for γ-ray and conversion electron spectroscopy of transfermium elements

With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear Reactions, JINR, Dubna. GABRIELA (Gamma Alpha Beta Recoil Investigations with the ELectromagnetic Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of α- and β-particles, fission fragments, γ- and X-rays and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.

Bioconversion of C19- and C21-steroids with parent and mutant strains of Curvularia lunata

Regio- and stereospecificity of microbial hydroxylation was studied at the transformation of 3-keto-4-ene steroids of androstane and pregnane series by the filamentous fungus of Curvularia lunata VKM F-644. The products of the transformations were isolated by column chromatography and identified using HPLC, massspectrometry (MS) and proton nuclear magnetic resonance (1H NMR) analyses. Androst-4-ene-3,17-dione (AD) and its 1(2)-dehydro- and 9α-hydroxylated (9-OH-AD) derivatives were hydroxylated by the fungus mainly in position 14α, while 6α-, 6β- and 7α-hydroxylated products were revealed in minor amounts. At the transformation of C21-steroids (cortexolone and its acetylated derivatives) the presence of 17-acetyl group was shown to facilitate further selectivity of 11β-hydroxylation. Original procedures for protoplasts obtaining, mutagenesis and mutant strain selection have been developed. A stable mutant (M4) of C. lunata with high 11β-hydroxylase activity towards 21-acetate and 17α,21-diacetate of cortexolone was obtained. Yield of 11β-hydroxylated products reached about 90% at the transformation of 17α, 21-diacetate of cortexolone (1 g/l) using mutant strain M4.

Drop and Bubble Deformation in an Electric Field

A steady problem of drop (bubble) shape in a uniform electric field is considered when the drop and the surrounding medium are immiscible. The electric-charge transport includes both the ohmic current across the interphase boundary and convective transport over the interface. If there is no convective transport, the drop (bubble) may be transformed into either an elongated or a flattened spheroid. Under these conditions, the sign of the deformation remains unchanged for arbitrary values of the problem parameters. Convective charge transport along the surface initiates additional motion in both the drop and the surrounding medium. However, with increase in the convective-transport intensity the deformed drops display different behavior. The compression of a flattened drop slows and, under certain conditions, compression is replaced by extension. However, an elongated spheroid cannot be transformed into a flattened spheroid. The calculations were performed under the assumption that the drop is convex. It was found that, for both an elongated and a flattened drop, the maximum ratio of the major and minor spheroid axes is 2:1. In experiments with oils, the possibility of both a decrease in the drop compression rate and deformation sign reversal was demonstrated.

Proposed High Energy Density Physics Research Using Intense Particle Beams at FAIR: The HEDgeHOB Collaboration

Physics of high energy density (HED) matter is an ever-expanding field of research with very wide applications to basic and applied physics and with great potential for revolutionary technological and industrial applications. Over the past decades, static as well as dynamic configurations have been widely used to research this interesting field of science. Recent technological advances in the development of high-quality well-focused strongly bunched intense particle beams have led to the idea of generating samples of HED matter using isochoric and uniform heating of solid targets by such intense beams. Theoretical work reported in this paper explores the possibility of carrying out novel experiments using the future Facility for Antiprotons and Ion Research at Darmstadt.

Generation of warm dense matter and strongly coupled plasmas using the High Radiation on Materials facility at the CERN Super Proton Synchrotron

A dedicated facility named High Radiation on Materials (HiRadMat) is being constructed at CERN to study the interaction of the 450 GeV protons generated by the Super Proton Synchrotron (SPS) with fixed solid targets of different materials. The main purpose of these future experiments is to study the generation and propagation of thermal shock waves in the target in order to assess the damage caused to the equipment, including collimators and absorbers, in case of an accident involving an uncontrolled release of the entire beam at a given point. Detailed numerical simulations of the beam-target interaction of several cases of interest have been carried out. In this paper we present simulations of the thermodynamic and the hydrodynamic response of a solid tungsten cylindrical target that is facially irradiated with the SPS beam with nominal parameters. These calculations have been carried out in two steps. First, the energy loss of the protons is calculated in the solid target using the FLUKA code [Fasso et...

High-energy-density matter research at GSI Darmstadt using intense heavy ion beams

This paper presents two-dimensional numerical simulations of heating of matter with intense heavy ion beams. It has been shown that it is very advantageous to irradiate the target with two different beams simultaneously, a main high intensity bunched beam of a heavy element like uranium and an unbunched low intensity beam of a lighter element like argon. The main beam is used to heat the target while the second beam is used as a diagnostic tool. Influence of the shape of the focal spot on compression and heating of matter has also been studied using an elliptic focal spot with an ellipticity of 1.5 (semimajor axis is along y-axis and is 1.5 times the semiminor axis which is along x-axis). It has been found that the temporal behavior of the development of density, pressure, and temperature profiles along different directions is quite different, which is not the case with a circular focal spot.

Stability of a surface-charged viscous jet in an electric field

The stability of a surface-charged cylindrical jet in a longitudinal uniform electric field with respect to capillary pertubations is investigated in the linear approximation. The evolution of both axisymmetric and azimuthal-periodic perturbations is analyzed. In the latter case the first two modes among the azimuthal wavenumbers — bending and Bohr — are considered. Axisymmetric and bending instabilities lead to the transverse disintegration of the jet into individual drops and the Bohr mode to the longitudinal separation of the input jet into two parts. It is found that the axisymmetric and bending instabilities, respectively, can be completely suppressed and significantly attenuated by means of an external longitudinal field. In this case the role of the Bohr mode becomes more important leading under certain conditions to longitudinal longwave jet splitting. Events which can be interpreted as manifestations of longitudinal partition of the jet (dumbbell-like cross-section, branching nodes) are observed in experiments with evaporating polymer-solution microjets.

Equilibrium shapes of a drop pendant in an electrostatic field

The stationary shapes of a conducting fluid drop in the gap between the plates of a plane capacitor are studied. The drop is held on the upper plate by the surface tension forces. The self-consistent problem of the determination of the drop shape and the charge distribution over its surface is solved. Estimates are obtained for the maximum volume of the stationary drop at the given fluid parameters and electric field strength.

Annular surface-charged jet in an external electric field

The problem of the shape of an annular charged jet in an external electric field is considered. In the strong-field approximation, the formulation of the problem is reduced to a system of ordinary differential equations. The asymptotics of the solutions at large distances from the point of outflow are investigated. The condition of formation of the jet profile non-increasing along the streamwise coordinate is found.