Impact of measurement approach on the quality of gamma scanning density profile in a tray type lab-scale column

This article presents a study for investigating impact of the measurement approach on the quality of gamma scanning density profile in tray type columns using experimental and computational evaluations. Experimental density profiles from the total and the photopeak count measurements, as two approaches in gamma ray column scanning technique, has been compared with the computational density profile from Monte Carlo simulation results. We used a laboratory distillation column of 51 cm diameter as an illustrative example for this investigation. ¹³⁷Cs was used as a gamma ray source with the activity of 296 MBq (8 mCi), with a NaI(Tl) detector. MCNP4C Monte Carlo code has been used for simulations. The quality of the density profile in the photopeak count approach is relatively within 155–204% better than that of the total count approach for experimental results. The same comparison for simulation results leads to a relative difference within 100–135% for the density profile.     

Diurnal variations in cosmic ray intensity caused by high latitude magnetospheric-ionospheric current systems

Cosmic ray intensity measurements obtained with the neutron monitors at Thule (geomagnetic latitude, 84.8°) and McMurdo (geomagnetic latitude, −79.9°) in 2007–2009 were used to test the effect of the magnetic field generated by magnetospheric currents flowing along geomagnetic field lines in the high latitude region on cosmic ray intensity. The existence of such a relation in a region where the geomagnetic field lines are virtually radial should revise our concept of the unimpeded access that cosmic ray particles have to the Earth’s atmosphere.     

Weakly divergent ray and diffraction beams in oceanic waveguides

Conditions that should be satisfied by the sound velocity profile of an oceanic waveguide for the dependence of the ray cycle length on the ray phase velocity to contain smooth extrema are formulated. The extrema correspond to weakly divergent ray beams forming “caustic” beams. It is found that diffraction effects cause a considerable smoothing of the sharp extrema that occur in the dependence of the interference period of neighboring modes on their phase velocity. As a result, in addition to the weakly divergent ray beams, weakly divergent diffraction beams and the corresponding “diffraction” caustics can be formed.     

Specially profiled reflector for spherical front beams focusing

Focusing the power emitted from a source with spherical wave front by a specially profiled reflecting surface has been attempted using the simple ray tracing method. The reflector (mirror) surface profile that achieves such power redistribution is obtained from solving an ordinary first order differential equation using common numerical techniques. Furthermore, the proposed methodology can be useful to design complex reflectors for the electomagnatic and the acoustic systems, which finds broad engineering, industrial and biomedical applications.     

Structure of a collisionless shock front with relativistically accelerated particles

A nonlinear self-consistent analytic theory is developed to describe the front structure of a strong magnetohydrodynamic (MHD) collisionless shock wave that generates accelerated particles (including ultrarelativistic particles). The theory is used to predict the degree of compression of matter at the plane front of such a wave, which can greatly exceed compression at an ordinary gas-dynamic front, and also the velocity, density, and pressure profiles. The energy spectrum of the accelerated particles, which is produced by the complex velocity profile at the shock transition, is determined self-consistently. New nonlinear effects are predicted that have not been discussed previously in the literature: a strong dependence of the particle acceleration regimes on the rate of injection; the existence of several regimes within a certain range of injected powers with differing spectra of accelerated particles, shapes of the shock transition profile, and magnitudes of compression of the medium; and the possibility of spontaneous jumps between different states of the shock transition. The question of stability of these states is discussed. For the values of the system parameters used here, the nonlinear regimes correspond to extremely low injection rates, of order 10⁻²–10⁻¹⁰ of the plasma flux density advancing into the front, and to exponents of the power-law spectra of accelerated particles between 5 and 3. Zh. éksp. Teor. Fiz. 112, 1584–1602 (November 1997)     

Wave front transformation of optical vortices with multiwave interactions in resonant media

The transformation of singular light beams is analyzed theoretically for multiwave interactions on amplitude and phase dynamic holograms in media with a resonant nonlinearity. The possibility of multiplying topological charge using different diffraction orders is demonstrated and optimal conditions for parametric energy exchange are determined which ensure retention of the structure of the wave front of optical vortices. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 395–402, May–June, 2009.     

PIXE in the studies of stable cesium sorption from water solutions

The possibility of cesium content evaluation by the particle induced X‐ray emission method from X‐ray emission L‐shell at sorption from water solutions has been investigated. Consideration has been given to the processes of dynamic cesium sorption by zeolites from water solutions. The technique has been developed for preparing targets analyzable in the proton beam of energy up to 2.0 MeV. The relationship has been determined between the cesium content and the intensity of X‐ray emission L‐shell. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamics of the Earth’s outer radiation belt in November 2009 based on the experimental data from the CORONAS-Photon and Meteor-M No. 1 satellites

The dynamics of the Earth’s outer radiation belt were traced at altitudes of 500–830 km during weak geomagnetic disturbances based on the data of simultaneous experiments carried out in November 2009 onboard the CORONAS-Photon solar observatory and the Meteor-M No. 1 artificial satellite. The average statistical profile of external boundary of the outer radiation belt that is characteristic for a quiet magnetosphere has been found from the analysis of variations in the position of the polar boundary of the capture region in the Earth’s magnetosphere.     

Local anisotropy of cosmic rays with <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 10<Superscript>17</Superscript> eV from Yakutsk EAS array data

The arrival directions of primary cosmic ray particles with energies E ₀ ≥ 10¹⁷ eV and zenith angles θ ≤ 60° recorded on the Yakutsk array over the period 1974–2009 are analyzed. These events are shown to have different anisotropies in different energy ranges.     

Peculiarities of the anisotropy of cosmic rays with E0 ≥ 1019 eV from Yakutsk EAS array data

The arrival directions of primary cosmic ray particles with energies E ₀ ≥ 10¹⁹ eV and zenith angles θ ≤ 60° recorded on the Yakutsk array over the period 1974–2009 are analyzed. These events separated by different time intervals are shown to have different global anisotropies.     

Investigation of the Energy Loss of Muon Bundles in the Cherenkov Water Calorimeter

Investigations of the energy loss of muon bundles are being conducted at the Experimental complex NEVOD. Such investigations are directed to detailed study of “muon puzzle” (the excess of multi-muon events observed in several cosmic ray experiments at ultra-high energies). Results of measurements of the muon bundle energy deposit during a long period of observations in primary cosmic ray energy range 10–1000 PeV have been obtained and have been compared with simulations performed on the basis of the CORSIKA code.     

Nonadiabatic corrections to the velocity of a Brownian motor with a complex potential profile

A number of laws have been established that govern the motion of a Brownian particle in a periodic potential profile for the adiabatically fast (with the time τ₀) and adiabatically slow variations in its shape. The average velocity of a particle has been calculated including a nonadiabatic contribution depending on τ₀ and the characteristic times of the system, which are determined by the characteristic features of the potential profile. It has been shown that the nonadiabatic correction to the velocity is proportional to τ₀² for a smooth potential profile and to τ₀ for a hopping movement in a potential containing barriers and wells, and this correction limits the large values of the rectification factor of motion for a high-performance motor operation mode.     

On the possibility of controlling transonic profile flow with energy deposition by means of a plasma-sheet nanosecond discharge

A way of effectively affecting the gasdynamic structures of a transonic flow over a surface by means of instantaneous local directed energy deposition into a near-surface layer is proposed. Experimental investigations into the influence of a pulsed high-current nanosecond surface discharge of the “plasma sheet” type on gas fast flow with a shock wave near the surface are carried out. The self-localization of energy deposition into a low-pressure region in front of the shock wave is described. Based on this effect, a facility for automated energy deposition into a dynamic region bounded by the moving shock front can be designed. The limiting value of the specific energy deposition on the surface in front of the shock wave is found. With the help of the direct-shadow method, an unsteady quasi-two-dimensional discontinuous flow arising when a plasma sheet is initiated on the wall in a flow with a plane shock wave is studied. By numerically solving the two-dimensional nonstationary equations of gas dynamics, the influence of the energy of a pulsed nanosecond discharge, which is applied in the frequency regime, on the aerodynamic characteristics of a high-lift profile is investigated. It is ascertained that the energy delivered to the gas before the closing shock wave in a local supersonic region that is located in the neighborhood of the profile contour in zones extended along the profile considerably decreases the wave drag of the profile.     

Influence of the benthic front on the mode structure of acoustic field in the ocean

The characteristic features of the mode structure of low-frequency sound field in the ocean are investigated for the ocean regions containing the benthic front, which represents the boundary between the Antarctic bottom water and the deep water. The hydrographic characteristics of the benthic front are described with the use of the data of the international WOCE experiment. On the basis of mathematical simulation, the changes introduced by the benthic front into the phase and group velocities and the vertical structure of modes are estimated for a frequency range of 5–20 Hz. Possible ways of reconstructing the hydrographic characteristics of the benthic front by the mode tomography methods are considered.     

On the properties of “short” granular magnets with disordered chains of grains: A field between grains

The values and functional exponential form of the demagnetizing factor of “short” cylindrical samples of the polyspherical medium and samples (elements) of this medium, i.e., chains of spheres, have been established. The tortuosity factor of chains formed by spheres (as effective elementary conductors of the magnetic flux in a magnetized granular medium) has been analyzed. It has been demonstrated that the tortuosity factor for chains in a filling medium is insignificant. The strength of the field between spheres in the chain, like the magnetic permeability of the effective magnetization channel, has an extremum (bell-shaped) profile. It has been revealed (by using magnetophoresis of finely dispersed ferroparticles) that the gradient of this strength exhibits a two-extremum profile.     

Short-pulse Calorimetric Load for High Power Millimeter-wave Beams

A spherical compact matched load, for high vacuum operation suited for short pulses (2 MW, 0.1 s) precise measurement has been designed to test high power gyrotrons Bruschi, Gandini, Muzzini, Spinicchia, Cirant, Gittini, Granucci, Mellera, Nardone, Simonetto, and Sozzi (Fusion Eng. Des. 56–57:649–654, 2001); Bruschi, Cirant, Gandini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, and Spinicchia (Nucl. Fusion 43:1513–1519, 2003); Bruschi, Cirant, Gandini, Gittini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, Spinicchia, Angella, and Signorelli (Development of CW and short-pulse calorimetric loads for high power millimeter-wave Beams, 23rd Symposium on Fusion Technology, September 20–24, 2004, Venice, Italy). In order to enhance the power handling capability of the load and to reduce the operation problems that may arise from an excessive reflection from the load, a ray tracing code has been written to model the power distribution on the inner surface and the pattern of the reflected radiation. The outcome of this code has been used to select a more convenient profile for the spreading mirror of the load and to optimize a pre-load specially conceived to minimize the power reflected fraction.     

A study of the evaporative deposition process: Pipes and truncated transport dynamics

We consider contact line deposition of an evaporating thin drop. Following Dupont’s proposal (unpublished), we focus on transport dynamics truncated by a maximal concentration as the single deposition mechanism. The truncated transport process, formalized as the “pipe model”, admits a characteristic shock front that has a robust functional form and depends only on local hydrodynamic properties. By applying the pipe model, we solve the density profile in different asymptotic regimes. In particular, we find that near the contact line the density profile follows a scaling law that is proportional to the square root of the concentration ratio defined as the initial solute volume concentration divided by the maximal concentration. The maximal deposit density occurs at about 2/3 of the total drying time for uniform evaporation and 1/2 for diffusion-controlled evaporation. Away from the contact line, areal density decays exponentially with the radial distance to the power of -3 for the uniform evaporation and -7 for the diffusion-controlled evaporation.     

Observation of slowly decreasing molecular oscillations in ultrathin liquid films using X-ray reflectivity

We studied ~0.5 μm and 30–80 ? thick films of a normal dielectric liquid, tetrakis(2-ethylhexoxy)silane (TEHOS), at temperature range 228–286 K, deposited onto silicon (111) substrate with native oxide using X-ray reflectivity. TEHOS is spherical with size ~10 ?, non-polar, non-reactive, and non-entangling; TEHOS has been reported to show interfacial layering at room temperature and surface layering at 0.23 T_c (T_c≈ 950 K). For films m thick, the reflectivity data did not change significantly as a function of temperature; for films 30–80 ? thick, the reflectivity data did change. The data could be fitted with an electron density model composed of a minimum necessary number of Gaussians and a uniform density layer with error-function broadened interfaces. When the film thickness is 60–80 ? below 246 K, we found that the interface and the surface layering coexist but do not overlap. When the film thickness is 30–40 ? below 277 K, they overlap and the electron density profile shows slowly decreasing molecular oscillations at the air-liquid interface.     

Optimization of the wave front of high order harmonics

We present a full optimization of the high harmonics wave front owing to the use of a soft X-ray Hartmann sensor. The sensor was calibrated using a high harmonic source with an accuracy of λ/50 root-mean-square (rms) with λ around 30 nm. We observed a high harmonic wave front of λ/7 rms, which is two times the diffraction-limit, astigmatism being the dominant aberration for every condition of generation. By clipping slightly the unfocused high harmonic beam, it is possible to produce a diffraction-limited beam containing approximately 90% of the incident energy.     

High‐resolution x‐ray analysis with multilayer gratings

Periodic multilayers are nowadays widely used to perform x‐ray analysis in the soft x‐ray range (photon energy lower than 1 keV). However, they do not permit to obtain high‐resolution spectra such as natural or synthetic crystals. Thus, multilayers cannot resolve interferences between close x‐ray lines. It has been shown and demonstrated experimentally that patterning a grating profile within a multilayer structure leads to a diffractive optics with improved resolving power. We illustrate the use of an Mo/B₄C multilayer grating in the Fe L and C K spectral ranges, around 700 and 280 eV, respectively. First, in the Fe L range, the improved spectral resolution enables us to distinguish the Fe Lα and Lβ emissions (separated by 13 eV). In addition, using a sample made of a mix of LiF and an iron ore, we show that it is possible to easily resolve the F K and Fe L emissions. These examples demonstrate that an improved x‐ray analysis can be obtained with multilayer gratings when there is the need to study samples having elements giving rise to close emission lines. Second, in the C K range, by comparing C Kα spectra from B₄C and cellulose, we show that the shape of the emission band is sensitive to the chemical state of the carbon atom. Copyright © 2009 John Wiley & Sons, Ltd.