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The operation of a gamma densitometer (GD) of ID = 100 mm is considered; it is intended for the diagnostics of three-phase oil–water–gas flows using the separationless method, when the composition of components is determined by a spectrometric analysis of gamma irradiation with two different photon energies. The 241Am and 137Cs isotopes, installed in the same housing, are used as gamma sources, while a gamma detector is made on the basis of the BGO crystal of 40 mm in diameter and height. Information about the design, measuring electronics, and main characteristics of the GD is given. The method used for the temperature stabilization of the recorded radiation intensities for both isotopes within a range of ambient temperature from 10 to 35oC is presented.

Credible data on the actual characteristics of thin-film platinum temperature sensors with a nominal value of 1000 Ω in a wide temperature range of 3.8–370 K derived from long-term experimental studies of a large batch of 130 sensors are presented (most likely, for the first time). These characteristics are the temperature dependence of resistance, sensitivity, short-term and long-term stability, response to thermal cycling in the 293–77.3 K range, thermal resistance in liquid nitrogen and helium, measurement accuracy and interpolation polynomials, and gamma-radiation resistance. The calibration data are compared to the DIN EN 60751 standard and equivalent information for a pure platinum sensor. It is demonstrated that the actual parameters of sensors of the studied type are better than the datasheet ones: contrary to literature data, the measurement accuracy at cryogenic temperatures improves as the temperature decreases. Ways to increase the accuracy rating of these sensors are discussed. Data on their practical application in the XFEL superconducting accelerator project (Hamburg) and other projects are also provided.

This paper is a review on implementation of measuring systems for two-phase helium, hydrogen, liquefied natural gas (LNG), and oil-formation/salty water flows. Two types of such systems are presented. The first type is based on two-phase flow-meters combining void fraction radio-frequency (RF) sensors and narrowing devices. They can be applied for superconducting accelerators cooled with two-phase helium, refueling hydrogen system for space ships and some applications in oil production industry. The second one is based on combination of a gamma-densitometer and a narrowing device. These systems can be used to monitor large two-phase LNG and oil-formation water flows. An electronics system based on a modular industrial computer is described as well. The metrological characteristics for different flow-meters are presented and the obtained results are discussed. It is also shown that the experience gained allows separationless flow-meter for three-phase oil-gas-formation water flows to be produced.

The generation mechanism of microwave radiation in the system with azimuthally-periodical current of an electron beam that excites a high-Q quasi-optical dielectric resonator was developed. Eigen parameters of a cylindrical Teflon resonator were determined. Radiation was locked in the investigated system by a detector of 8-mm wave band. Design philosophy of microwave oscillators with high-Q resonators, in which electromagnetic “whispering gallery” modes are excited by electron beam, was developed.

An empirical method is presented to calculate magneto-resistance (MR) and a corresponding temperature shift of the well known TVO temperature sensors in the ranges from 0.1 K to approximately 10 K and up to 8 T. Features of MR, depending on the temperature and magnetic field, are discussed. The maximum positive MR-values, depending on the magnetic field, correspond to the temperature of T ≈ 0.67 K: 12.5% at 8 T. At the fixed magnetic field the zero MR-value is reached both by increasing or decreasing the temperatures with respect to 0.67 K. For example, at the magnetic field of 4 T, the zero MR-value appears at T ≈ 0.2 K and T ≈ 6 K. A constant moderate negative relative MR of 19%, which does not depend on the magnetic field from 2 to 8 T, is revealed at T ≈ 0.1 K. In the ranges from 1.5 to 4.4 K and from 0 to 9 T, in particular, the temperature shift has a linear dependence on B -value and inverse proportionality on the dimensionless sensitivity S . A brief explanation of the behavior of TVO sensors under magnetic fields is presented as well.

Some results of theoretical studies of detonation processes in combustible gaseous mixtures are discussed for a model geometry of large combustion chambers of detonation engines in the case of mixtures of hydrogen and oxygen-enriched air. The effect of geometric characteristics on the operation of pulse detonation engines is analyzed. In particular, the propagation of detonation waves in tubes of small diameter to larger volumes and the evolution of detonation under the action of converging shock waves are considered.

We study the temperature dependences of the frequency characteristics of a capillary-waveguide resonator for strongly absorbing media. The temperature influence on the frequency, Q-factor, and absorption depth in the studied resonance is theoretically revealed and experimentally confirmed.

Parallel with the traditional hypotheses on the predominantly wind (Ekman), gradient, and thermohaline nature of large-scale currents in seas and oceans, there exist hypotheses on the participation of long-period waves in the formation of these currents. As the physical mechanisms of generation of currents by waves, one can mention nonlinear wave transport and the phenomenon of negative viscosity in waves. From the viewpoint of existence of these mechanisms, numerous scientists explain high velocities of jet currents and their stable character. The predominant role of winds and thermohaline processes in the formation of large-scale currents is also accepted. On the basis of the experimental data, we demonstrate additional possibilities for the formation of large-scale currents given by the transport of water masses by long-period waves.

It is found that, when the shape of a dielectric sphere (hemisphere) operating under the whispering gallery mode conditions is perturbed by a surface curvature gradient (ellipticity), the unloaded Q factor of the sphere degrades and its resonance frequencies change. It is shown theoretically and experimentally that an elliptic irregularity removes frequency degeneracy of whispering gallery modes at millimeter waves.

Quasi-TE and quasi-TM oscillations of an anisotropic spherical body immersed in an isotropic medium are studied. An investigation of the set of Maxwell’s equations within the spherical body shows that it reduces to two coupled differential equations, which are analyzed theoretically for small values of the anisotropy parameter. An approximate solution to these differential equations is obtained. A dispersion relation determining the frequencies of the resonant oscillations is derived for the boundary conditions imposed on the surface of the spherical body. The effect of anisotropy on the spectral characteristics of the resonant oscillations is examined.

The anisotropy of parameters is an intrinsic characteristic feature of dielectrics employed in production of high-Q resonators. A theory of azimuthal-homogeneous resonant oscillations in a single-crystal sphere is developed. It is demonstrated that the anisotropy gives rise to TM oscillations of two orders at different frequencies. Oscillations with large polar indices are numerically investigated.

A semicylindrical dielectric resonator with a thin cylindrical inhomogeneity in the region of the field antinode of a whispering gallery eigenmode has been studied. Characteristic equations determining the complex eigenfrequencies of such resonators with axially homogeneous eigenmodes are obtained. It is shown that the presence of a dielectric or conducting inhomogeneity leads to a frequency shift and causes additional energy losses of the eigenmode.

A rigorous theory of the propagation of electromagnetic waves in round anisotropic and semiconductor rods in the presence of an arbitrarily directed anisotropy axis or external magnetic field is developed. New types of independent waves are discovered. Exact dispersion equations are obtained for them, which define the dependence of their spectral characteristics on the parameters of the semiconductor or anisotropic crystal and on the magnitude and direction of the constant external magnetic field. The results of numerical investigations for rods made from a semiconductor or a uniaxial crystal are presented.

This paper reports the investigation of the structure of two-phase helium flows used for cryostatically controlling superconducting magnets in installations such as HERA, NET, UNK and KEK. Flow pattern maps for horizontal round channels and rectangular slot channels are plotted on the basis of experimental data obtained for a wide range of flow parameter variations. Some typical features of the flows (e.g. the absence of a slug pattern) are pointed out and attempts are made to explain these features following a theoretical analysis. Methods for estimating stratification and full mix limits are proposed. The position of the limits on the maps obtained for helium is shown to be quite different from that of other two-phase mixtures.

Results are presented of theoretical and experimental investigations of whispering-gallery oscillations in a shielded isotropic layered spherical dielectric cavity. Oscillations whose Q factor is two orders of magnitude higher than that of the oscillations of an open dielectric sphere are studied. Intermode interaction is observed between various cavity oscillation modes.

Large quantity of cryogenic temperature sensors will be used for operation of the International Linear Collider (ILC). Most of them will be subject to high radiation doses during the accelerator lifetime. Understanding of particle energy spectra, accumulated radiation dose in thermometers and its impact on performance are vital in establishing technical specification of cryogenic thermometry for the ILC. Realistic MARS15 computer simulations were performed to understand the ILC radiation environment. Simulation results were used to establish radiation dose requirements for commercially available cryogenic thermometers. Two types of thermometers, Cernox® and TVO, were calibrated prior to irradiation using different technique. The sensors were subjected then to up to 200 kGy electron beam irradiation with kinetic energy of 5 MeV, a representative of the situation at the ILC operation. A post-irradiation behavior of the sensors was studied. The paper describes the MARS15 model, simulation results, cryogenic ...

Adiabatic invariants of charged particles are constructed that can be utilized to investigate such processes as low-frequency wave propagation in REP, amplification (absorption) of Langmuir waves in a spherically symmetric gravitational field, and particle flux interaction with a nonlinear wave in longitudinal static electrical and magnetic fields. Construction of the adiabatic invariants is executed by reduction of the original problems to a one-dimensional Hamiltonian.

The capability of mechanical frequency tuning of Gunn diode self-oscillator by the both metal and dielectric pin inserted into the partially shielded quasi-optical dielectric resonator is considered. The resonator's eigen frequencies obtained theoretically and experimentally are compared with oscillation frequencies

The influence of defects in spherical forms of semispherical dielectric resonators (DRs) on their oscillation frequency, Q-factor and field distribution has been studied in the present paper. It is shown that even minor deviations (/spl sim/1%) in spherical forms affect the resonator EM characteristics. The frequency splitting and dependence of spectrum parameters on the azimuth angle in semispherical dielectric resonators with small deviation in spherical forms has been observed experimentally.

The resonant modes, which are excited at the shielded dielectric hemisphere, are investigated by the theoretical and experimental methods. The low-Q-factor modes of air cavity and high-Q-factor whispering gallery modes of dielectric structure are existed together in the case of high radial index value. The Q-factor value of the whispering gallery modes of the shielded dielectric sphere with the certain correlation between the sizes of dielectric hemisphere and metal shield can be more great than the Q-factor of the whispering gallery modes of the similar open dielectric resonator.

We have studied the influence of finite dimensions of the end screens on the spectrum of whispering gallery modes in a teflon cylindrical quasioptical resonator. The dependence of the resonance oscillation frequency on the radius of conducting end screens is determined for the first time. Variation of the screen radius leads to transformation of the axial index of HE modes.

A magnetoresistance (MR) of the well known TVO resistor temperature sensors has been studied at ultralow temperatures from approximately 0.8 K down to approximately 0.1 K under strong magnetic fields up to 8 T. A crossover from positive to negative MR with lowering temperature is found at weak magnetic fields. A zero MR-value at the magnetic field of 4 T, for example, is reached at T approximately 0.2 K. At sufficiently strong magnetic field the negative MR is suppressed and MR returns to positive values. A constant negative MR, which does not depend on the magnetic field from 2 to 8 T, is revealed at the lowest temperature T approximately 0.1 K. The observed behavior of the TVO sensor is explained basing on the model of hopping conduction via localized states in the weak localization regime.

Forced oscillations excited by a radial magnetic dipole in a dielectric hemisphere (resonator) placed on a perfectly conducting plane are studied. It is shown that the dipole excites H modes. When the dipole radiation frequency equals the eigenfrequency of the resonator, an amplitude resonance is observed in the spectrum. The excitation efficiency is high when the magnetic dipole is placed at the maximum of the radial field component of the resonator’s eigenmode.

A layered periodic semiconductor-semiconductor or semiconductor-dielectric structure located in a magnetic field oriented parallel to the layer boundaries is considered. Dispersion of oscillations propagating in the plane perpendicular to the magnetic field is studied. The existence of "acoustical" and "optical" magnetoplasmons is predicted. It is shown that consideration of spatial attenuation leads to a significant change in the dispersion of the oscillations. N~erical calculations are presented for an indium antimonide type material.

The conservation of the adiabatic invariant of a charged particle, entrapped by a transverse plane electromagnetic wave, is studied using a well-known method, both for the case when the phase velocity of the wave does not exceed the velocity of light, and for the opposite case. An expression is obtained for the variation of the adiabatic invariant, from which it is seen that the latter is conserved with exponential accuracy in the region of its existence.

Criteria are obtained for the ambiguity of HDC of boiling channels which allow for local inlet and outlet drag. Results of calculations presented for the most commonly used cryogens indicate the possible ambiguity of the HDC.