ACTIVATION OF SINGLE-BUBBLE SONOLUMINESCENCE AND RADIOLUMINESCENCE OF GD3+ AND DY3+ IONS BY ELECTRON ACCEPTORS IN AQUEOUS SOLUTIONS AS CONSEQUENCE OF THE HYDRATED ELECTRON GENERATION DURING WATER SONOLYSIS AND RADIOLYSIS

Discovered the activation of moving single-bubble sonoluminescence and radioluminescence for Gd3+ and Dy3+ ions in aqueous solutions of GdCl3 and DyCl3 by the acceptor of a hydrated electron (eaq-): H+, Cd2+, etc. This activation is similar to the previously found activation by acceptors of eaq- radioluminescence and single-bubble sonoluminescence for the Tb3+ ion. Electron acceptors do not affect the quantum yield of the said lantha-nide ions photoluminescence. They also do not affect the yield of their multibubble sonoluminescence in aqueous solutions, since eaqdoes not appear in significant amounts during multibubble sonolysis. The found luminescence activation effects of lanthanide ions are interpreted as a consequence of the suppression of the quenching (reduction) reactions of these electronically excited ions eaq: *Ln3+ + eaq- → Ln2+ by acceptors. The feasibility of these reactions was predicted for all Ln3+ ions based on a theoretical estimate of their free energy. The discovery of the described effects of activation of the luminescence of Ln3+ ions is a consequence and serves as confirmation of not only the known generation of eaq- during radiolysis, but also its previously unknown generation during moving single-bubble sonolysis of water.

Theoretical Estimate of Cooling Time of a Liquid Hydrogen Tank during Structural Tests

Russian enterprises continue developing rocket and space vehicles based on cryogenic propellants, i.e. liquid hydrogen, oxygen, and methane. Hence, the issues of fuel tanks’ thermal strength are increasingly important. During structural tests, the operating temperatures of the test object should be simulated, since the temperature condition affects the strength and rigidity of the structure. Consequently, during ground-based experimental tests, hydrogen tanks must be cooled down to 20 K, the boiling point of hydrogen. JSC TsNIIMash is developing a helium system capable of cooling large-sized structures to a temperature of 20 K. Helium can be used in a gaseous state to cool down the structure, since the boiling point of helium, 4 K, is lower than the boiling point of hydrogen. Until now, the tanks were cooled only by filling with liquid nitrogen, therefore the temperature state of the tanks during the tests was simulated only for this case. In order to determine the applicability of the method developed, the cooling time of large-sized containers was estimated by cooling a hydrogen tank, which by its dimensions is typical for an advanced medium-class second stage launcher, to 20 K by gaseous helium.

Solid-State Heating Using the Multicaloric Effect in Multiferroics

The multicaloric effect is defined as the adiabatic reversible temperature change in multiferroic materials induced by the application of an external electric or magnetic field, and it was first theoretically proposed in 2012. The multicaloric effects in multiferroics, as well as other similar caloric effects in single ferroics, such as magnetocaloric, elastocaloric, barocaloric, and electrocaloric, have been the focus of much research due to their potential commercialization in solid-state refrigeration. In this short communication article, we examine the thermodynamics of the multicaloric effect for solid-state heating applications. A possible thermodynamic multicaloric heating cycle is proposed and then implemented to estimate the solid-state heating effect for a known electrocaloric system. This work offers a path to implementing caloric and multicaloric effects to efficient heating systems, and we offer a theoretical estimate of the upper limit of the temperature change achievable in a multicaloric cooling or heating effect.

Evaporation of a liquid, initiated by condensation of vapor on its surface

The paper considers mechanisms of initiation of liquid evaporation by contact with hot vapor (with temperature greater and much greater than the temperature of liquid). Two fundamentally different mechanisms of such initiation are distinguished - equilibrium and non-equilibrium. The process of non-equilibrium initiation of evaporation by hot vapor was studied using the method of molecular dynamics; the results agree with the theoretical estimate given in the work for determining the temperature of the beginning of the non-equilibrium mechanism of evaporation initiation.

Effect of inductance on the parameters of the plasma focus in a pulsed coaxial accelerator

Based on the physical analysis of the processes occurring in pulsed plasma accelerators, the pos­sibility of their use for the creation and study of a plasma focus is justified. In particular, the influence of inductance on the parameters of the plasma focus in kilojoule­range «Plasma focus» (PF) installations created on the basis of a pulsed coaxial accelerator is studied. An equivalent installation scheme is proposed and justified, based on the analysis of which the influence of the inductance of the circuit and the capacitance of the capacitor bank on the value of the maximum current and neutron output is analyzed, without taking into account the parameters of the spark gap and the conducting wires. Based on the theoretical estimate of the inductance of the installation, its most probable value is calculated. . It turned out that in the installations of the considered energy range, the inductance is approximately 7.5•10­7 Gn and depends on the capacitance of the capacitor bank. On the contrary, in installations with megajoule energy, the inductance does not depend on the number and capacity of capacitors, so that an increase in the latter does not affect the increase in current strength. Experimental and theoretical dependences of the discharge current on the applied voltage at different capacitances of the capacitor bank are obtained. A comparative analysis of theoretical and experimental current waveforms is pre­sented. The greatest coincidence of theoretical and experimental results was found for the duration of the discharge pulse T = 30 microseconds.

Specific Heat on Single-crystalline YVO3

The specific heat of single-crystalline YVO3 was measured from 2 K up to 250 K at zero field. The results reveal three transitions, at around 75, 115, and 200 K. The transitions at around 115 K and 200 K show that the phase transition is of the second-order type, whereas at around 75 K, unusual features of the specific heat are found. These unusual features are attributed to the effect of a large change in the volume. The specific heat data were analyzed in terms of a lattice contribution, a Schottky contribution and an excess magnetic contribution at high temperature. The magnetic contribution well above the magnetic ordering temperature is ascribed to short-range interactions due to the presence of strong magnetocrystalline anisotropy. The magnetic entropy considered by using this approach is 9.13 J/mole K which is close to the theoretical estimate for the S = 1 system.

Theoretical Estimate of the Glass Transition Line of Yukawa One-Component Plasmas

The mode coupling theory of supercooled liquids is combined with advanced closures to the integral equation theory of liquids in order to estimate the glass transition line of Yukawa one-component plasmas from the unscreened Coulomb limit up to the strong screening regime. The present predictions constitute a major improvement over the current literature predictions. The calculations confirm the validity of an existing analytical parameterization of the glass transition line. It is verified that the glass transition line is an approximate isomorphic curve and the value of the corresponding reduced excess entropy is estimated. Capitalizing on the isomorphic nature of the glass transition line, two structural vitrification indicators are identified that allow a rough estimate of the glass transition point only through simple curve metrics of the static properties of supercooled liquids. The vitrification indicators are demonstrated to be quasi-universal by an investigation of hard sphere and inverse power law supercooled liquids. The straightforward extension of the present results to bi-Yukawa systems is also discussed.

Electric Mode Excitation in the Atmosphere by Magnetospheric Impulses and ULF Waves

Variations of vertical atmospheric electric field Ez have been attributed mainly to meteorological processes. On the other hand, the theory of electromagnetic waves in the atmosphere, between the bottom ionosphere and earth’s surface, predicts two modes, magnetic H (TE) and electric E (TH) modes, where the E-mode has a vertical electric field component, Ez. Past attempts to find signatures of ULF (periods from fractions to tens of minutes) disturbances in Ez gave contradictory results. Recently, study of ULF disturbances of atmospheric electric field became feasible thanks to project GLOCAEM, which united stations with 1 sec measurements of potential gradient. These data enable us to address the long-standing problem of the coupling between atmospheric electricity and space weather disturbances at ULF time scales. Also, we have reexamined results of earlier balloon-born electric field and ground magnetic field measurements in Antarctica. Transmission of storm sudden commencement (SSC) impulses to lower latitudes was often interpreted as excitation of the electric TH0 mode, instantly propagating along the ionosphere–ground waveguide. According to this theoretical estimate, even a weak magnetic signature of the E-mode ∼1 nT must be accompanied by a burst of Ez well exceeding the atmospheric potential gradient. We have examined simultaneous records of magnetometers and electric field-mills during >50 SSC events in 2007–2019 in search for signatures of E-mode. However, the observed Ez disturbance never exceeded background fluctuations ∼10 V/m, much less than expected for the TH0 mode. We constructed a model of the electromagnetic ULF response to an oscillating magnetospheric field-aligned current incident onto the realistic ionosphere and atmosphere. The model is based on numerical solution of the full-wave equations in the atmospheric-ionospheric collisional plasma, using parameters that were reconstructed using the IRI model. We have calculated the vertical and horizontal distributions of magnetic and electric fields of both H- and E-modes excited by magnetospheric field-aligned currents. The model predicts that the excitation rate of the E-mode by magnetospheric disturbances is low, so only a weak Ez response with a magnitude of ∼several V/m will be produced by ∼100 nT geomagnetic disturbance. However, at balloon heights (∼30 km), electric field of the E-mode becomes dominating. Predicted amplitudes of horizontal electric field in the atmosphere induced by Pc5 pulsations and travelling convection vortices, about tens of mV/m, are in good agreement with balloon electric field and ground magnetometer observations.