Effective erosion coefficient and plasma velocity limitation in the channel of an electromagnetic rail accelerator

The concept of an effective erosion coefficient, which takes into account the capture and entrainment in motion (by accelerated plasma) of only part of the erosion mass lost by rail accelerator electrodes, is introduced to describe the plasma acceleration dynamics in the channel of an electromagnetic rail accelerator. This parameter is determined from a comparison of the experimental and calculated plasma velocities at the stage of velocity saturation. The plasma velocity is calculated using a model that takes into account the pressure force of a shock-compressed gas and the deceleration force that appears during the capture of the erosion mass by a plasma piston. The ratio of the captured mass to the mass lost by the electrodes is found to depend on the current; for copper, this ratio is 1/4–2/3. The effective erosion coefficient is 0.6–0.7 mg/C at a current of ～40 kA.     

Photophysical and Photocatalytic Parameters of Sulfo and Tetrabromosulfo Derivatives of Fluorescein

Acid-base, absorption, and luminescence properties of Fluorescein and Eosin analogs containing a sulfo group have been examined. Using the flash photolysis technique, triplet-triplet absorption and formation of radical anions and radical cations have been detected. The dyes under study form hydrophobic complexes with cationic surfactants at a ratio of 1 : 2. Photocatalytic activity of the dyes in generation of hydrogen from water has also been studied.     

Formation of compression shocks in a nonequilibrium plasma flow in a magnetic field

Plasma flow in a linearly widening, ideally sectioned, short-circuited magnetohydrodynamic (MHD) channel is studied. MHD flows are classified into two types: continuous flows and flows with a compressional MHD shock in plasmas that are stable and unstable against the onset of ionization instability. Specific features in the evolution of a stationary compression MHD shock are investigated, and its position as a function of the Stewart number is determined. It is found that, in a plasma flow in which ionization instability develops, a compression MHD shock arises at lower values of the MHD interaction parameter than in a stable plasma flow. An unidentified type of instability of MHD discontinuities is revealed.     

Parameters of an erosion carbon plasma in the channel of a railgun

The working current dependences of the thermodynamic and electrophysical parameters of a free plasma piston moving with a near-maximal velocity in the channel of an electromagnetic rail launcher with graphite electrodes are obtained. The composition and weight of the plasma depend on the degree of electrode erosion due to discharge current passage (i = 40–80 kA). It is shown that the mean temperature of the plasma piston only slightly depends on the plasma mean pressure and plasma piston weight and increases with current by a near-power law. The measured values of the maximal velocity of the plasma piston front are compared with the calculated value of the sound velocity inside the piston. With the working current and cross-sectional area of the channel fixed, the initial gas density in the channel is found to influence the ratio of the piston maximal velocity to the sound velocity in the plasma. If the initial gas density is low (lower than some critical value), the maximal velocity of the plasma piston front exceeds the sound velocity in the plasma.     

A Source for Fuel Supply to a Fusion Reactor Core

We present the results of studies of the plasma source based on the coaxial accelerator with the slothole channel geometry for plasma acceleration and working gas inlet into the accelerator via the electrodynamic valve. The plasma parameters at the output of the accelerator are measured. The slot-hole channel of the accelerator created higher jet pressure, as compared to the coaxial channel, especially at large distances from the source. The jet pressure reached 10⁶ N/m² at a distance of 0.7 m. The source created moderately pure plasma for a current below 80 kA. The density was (2.5–5) × 10²² m^–3, which was higher than the density obtained with the coaxial gun.     

Photochromism of 2-(2,4-dinitrobenzyl)benzimidazole in solution

Spectral and kinetic parameters of photochromic 2-(2,4-dinitrobenzyl)benzimidazole in various solvents were studied by flash photolysis. The absorption band of the photoinduced colored form of 2-(2,4-dinitrobenzyl)benzimidazole shifts red with rise in the relative dielectric constant of the solvent. The rate of bleaching of the photoinduced species in ethanol, propan-2-ol, acetone, acetonitrile, and dimethyl sulfoxide is lower by 2–3 orders of magnitude than in benzene, toluene, and hexane due to formation of intermolecular hydrogen bond with the solvent.     

Synthesis of 2-Naphthylselenoacetic Acid Dialkylamides from 4-(2-Naphthyl)-1,2,3-selenadiazole

Russian Journal of General Chemistry - Under the action of potassium hydroxide, 4-(2-naphthyl)-1,2,3-selenadiazole readily decomposes with the evolution of nitrogen and the formation of potassium...     

Syntheses and structural studies of the nickel(II) octahedral complexes Ni(N∩N)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>L<Subscript>2</Subscript> with nitrogen-containing and carboxylate ligands

A series of new mononuclear octahedral nickel(II) complexes with the Ni(N∩N) _x L₂ framework (x = 2 or 3, N∩N = Рhen (1,10-phenanthroline), AMPy (2-(aminomethyl)pyridine), L is H₂O, anions of carboxylic acids (CF₃CO₂?, CCl₃CO₂?, HCO₂?), chloride ion, and water) is synthesized and described by IR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction analysis: [Ni(Рhen)₂(OH₂)Cl]Cl · 2H₂O (I), [Ni(Рhen)₂(OH₂)(O₂CCF₃)](O₂CCF₃) (II, IIa), [Ni(Рhen)₂(HCOO)_1.618(H₂O)_0.382](HCOO)_0.382 · 4.618H₂O (III), ([Ni(Рhen)₂(OH₂)₂](O₂CCCl₃)₂ · 6.2H₂O (IV), [Ni(AMPy)₂(OH₂)₂](HCO₂)₂ · 6H₂O (V), and [Ni(Рhen)₃](CCl₃COO)₂ · 7H₂O (VI). The subunit containing two formate ligands in the inner sphere of the [Ni(Рhen)₂(HCO₂)₂] complex prevails in the crystal structure of complex III, which is not characteristic of the nickel carboxylate complexes of this type. In aqueous solutions complex IV undergoes decarboxylation to form [Ni(Рhen)₂(CO₃)] · 7H₂O. A change in the nature of the N-donor ligands in Ni(N∩N)₂L₂ leads to the change (cis or trans) in the configuration of the whole complex (СIF files CCDC no. 880414 (I), 842336 (II), 1430414 (IIa), 1478111 (III), 1430430 (IV), 1443133 (V), and 1430415 (VI)).     

Formation of Oligo-Nuclear Carboxylate Nickel(II) Complexes with Nitrogen-Containing Ligands. Quantum-Chemical Simulation

Using the DFT method PBE0/6-31G(d, p) and taking into account the solvent, the formation of bi- and pentahedral Ni(II) complexes with carboxylate and N-containing ligands in the gas phase was studied, and ΔG° of their formation from simple compounds was estimated. The functional role of bridging groups and hydrogen bonds in the formation of polynuclear structures was revealed. A model of self-organization of penta-nuclear coordination compounds [Ni^II₅(O₂CR)₈L_2n(μ-OH)₂]⁰ from binuclear complex [Ni^II₂(O₂CR)₄L_n(μ-H₂O)]⁰ was proposed, into the structure of which mononuclear Ni^II cations are embedding and promote proton transfer from bridging aqua ligands.

     

Influence of electric and magnetic fields on the shock wave configuration at the diffuser inlet

The possibility is investigated of influencing the shock wave configuration in a xenon plasma flow at the inlet of a supersonic diffuser by applying electric and magnetic fields. Flow patterns resulting from interaction of the plasma with external fields in the entire diffusor volume and its different sections are compared. The patterns are obtained by the Schlieren method using two recording regimes: individual frames or a succession of frames. The study focuses on the normal shock wave formation process under strong MHD interaction over the whole diffuser volume. Basic factors affecting the plasma flow velocity in the diffuser under externally applied fields are compared, namely, the ponderomotive force and the Joule heating of the gas by the electric field, which decelerate the supersonic flow, and the heat removal to the external electric circuit producing the opposite effect. It has been shown that the external fields are most effective if applied to the inlet part of the diffuser, while the flow in the diffuser section, where there is a large density of dissipative structures, is not readily responsive to external factors. It is suggested that the measure of response can be estimated by the energy that goes to the shock wave formation as a result of the flow interaction with the diffuser walls.