Experimental setup for ground-based measurements in preparing cosmic experiments to study nuclear planetology

An experimental laboratory setup combining various gamma spectrometers and neutron generators that is intended for operating at the experimental nuclear-planetology facility deployed at the Joint Institute for Nuclear Research (Dubna, Russia) in order to perform physical calibrations of active gamma and neutron spectrometers is described.     

The LUE-200 accelerator at the IREN facility: Current status and development

The general scheme and current status of an electron linear accelerator with an S-band travelling wave (f = 2856 MHz) accelerating structure—a driver for a pulsed neutron source (the Intense Resonance Neutron source (IREN)) at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research—are presented. The parameters of the accelerating system and the measured parameters of the electron beam—pulse-beam current, duration of the current pulse, repetition rate, electron-energy spectrum, and loading characteristics of the accelerating structure—are given. The beginning of the implementation of the project of the second stage of the IREN facility, which forms the basis for the development of the accelerator aimed at increasing its beam power, is reported. Technical solutions underlying the modernization of the accelerator’s electrophysical systems are discussed: accelerating system, RF power supplies, and modulators.     

Comparison of Sensitivities of Semiconductor (HPGe) and Scintillation (CeBr<Subscript>3</Subscript>) Detectors in the Measurement of Gamma Spectra Induced by Neutrons in the Model of Planetary Soil

The results of neutron-activation measurements performed using the model of planetary soil and detectors based on high-purity germanium (HPGe) and cerium bromide (CeBr₃) are reported. Gamma lines lying in the energy range from 200 keV to 8 MeV are used as indicators to compare these two types of detectors in experiments with the model irradiated by 14-MeV neutrons from a pulse neutron generator. The results will aid the design of scientific instruments for the active neutron and gamma spectroscopy of planet surfaces in future Russian and international lander missions (Luna-Glob, Luna-Resurs, and ExoMars-2020).     

The Gibbs energies of transfer of 2,2′-dipyridyl and pyridine from methanol into methanol-dimethylformamide mixed solvents

The distribution coefficients of 2,2′-dipyridyl and pyridine were determined by the method of distribution between two immiscible phases over the whole range of methanol-dimethylformamide solvent compositions at 298.15 K. The results were used to calculate the Gibbs energies of transfer of 2,2′-dipyridyl and pyridine from methanol into its mixtures with dimethylformamide. Changes in the solvation state of the amines were analyzed using the enthalpy and entropy components of the Gibbs energy of transfer.     

The influence of reagents solvation on enthalpy change of glycine-ion protonation and silver(I) glycine-ion complexation in aqueous-dimethylsulfoxide solutions

The thermal decomposition process and non-isothermal decomposition kinetic of glyphosate were studied by the Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA). The results showed that the thermal decomposition temperature of glyphosate was above 198?°C. And the decomposition process was divided into three stages: The zero stage is the decomposition of impurities, and the mass loss in the first and second stage may be methylene and carbonyl, respectively. The mechanism function and kinetic parameters of non-isothermal decomposition of glyphosate were obtained from the analysis of DTA?CTG curves by the methods of Kissinger, Flynn?CWall?COzawa, Distributed activation energy model, Doyle and ?atava-?esták, respectively. In the first stage, the kinetic equation of glyphosate decomposition obtained showed that the decomposition reaction is a Valensi equation of which is two-dimensional diffusion, 2D. Its activation energy and pre-exponential factor were obtained to be 201.10?kJ?mol^?1 and 1.15?×?10¹⁹?s^?1, respectively. In the second stage, the kinetic equation of glyphosate decomposition obtained showed that the decomposition reaction is a Avrami?CErofeev equation of which is nucleation and growth, and whose reaction order (n) is 4. Its activation energy and pre-exponential factor were obtained to be 251.11?kJ?mol^?1 and 1.48?×?10²¹?s^?1, respectively. Moreover, the results of thermodynamical analysis showed that enthalpy change of ??H ^??, entropy change of ??S ^?? and the change of Gibbs free energy of ??G ^?? were, respectively, 196.80?kJ?mol^?1,107.03?J?mol^?1?K^?1, and 141.77?kJ?mol^?1 in the first stage of the process of thermal decomposition; and 246.26?kJ?mol^?1,146.43?J?mol^?1?K^?1, and 160.82?kJ?mol^?1 in the second stage.     

Dependence of the enthalpies of formation of Ag<Superscript>+</Superscript> complexes with glycinate ion and the protonation of glycinate ion on the content of aqueous ethanol solvent

Enthalpy changes are determined by calorimetry for the reactions of glycinate ion (Gly⁻) proto- nation and its complexation with Ag⁺ ion at a temperature of 298 K and ionic strength 0.1 (NaClO₄) in an aqueous ethanol solvent containing 0.0–0.4 and 0.0–0.3 mole fraction of alcohol, respectively. An abnormal relationship of enthalpy changes is found for the processes of stepwise formation of mono- and bis-glycinates of silver(I) in water. It is shown that varying the ethanol content has virtually no effect on the exothermicity of Ag⁺ complexation reactions with glycinate ions at either coordination step and does not change the relationship of the step enthalpies. An analogy is observed in the relationship of solvation contributions from the reagents to the value of Δ_tr H° for the reactions of glycinate ion protonation and its complexation with silver(I) in aqueous ethanol solvents.     

Complex formation of the Ag<Superscript>+</Superscript> ion with pyridine in a methanol-dimethylformamide binary solvent: Changes in the enthalpy and entropy of the reaction

The heat effects of formation of silver(I) mono- and bicomplexes with pyridine in a methanol-dimethylformamide binary solvent with different compositions at 298.15 K were determined by calorimetry. The changes in the entropy and Gibbs energy of these reactions were calculated, and the effect of the solvent composition on the shift of equilibrium of the complex formation reactions were considered. The contributions of the enthalpy of solvation of the reactants and the change in the heat effects of the reactions were analyzed.     

Thermodynamics of the solvation and phase distributions of 2,2′-dipyridyl in acetonitrile-DMSO-hexane and methanol-DMSO-hexane systems

The Gibbs energies of 2,2′-dipyridyl when transferred from dimethyl sulfoxide to its mixtures with acetonitrile and methanol are determined from the distribution of substance between immiscible phases. It is found that moving from dimethyl sulfoxide to acetonitrile and methanol weakens the solvation of 2,2′-dipyridyl due to a change in the solvation of amino groups and the hydrocarbon substituent, which is reflected in a reduction in the entropy component of the Gibbs energy.     

Thermodynamics of the Solvation and phase distributions of ethylenediamine in acetonitrile-dimethylsulfoxide-hexane systems

The enthalpies of dissolution and solvation of ethylenediamine over the range of compositions of a mixed acetonitrile-dimethylsulfoxide solvent at 298 K are determined calorimetrically. It is found that with an increase in the acetonitrile concentration, the solvation exothermicity of ethylenediamine declines, owing to the resolvation of amino groups. The Gibbs energies of transfer of ethylenediamine from dimethylsulfoxide into its mixtures with acetonitrile are determined from the distribution of a substance between immiscible phases. It is found that increasing the acetonitrile concentration in a binary solvent improves the stability of the ethylenediamine solvatocomplex, owing to a change in the entropy component of the Gibbs energy.