Calculation of the ion transverse velocity distribution function under ion cyclotron resonance heating

The ion transverse velocity distribution functions and the fraction η of ions heated above a certain energy W ₁ are calculated as applied to the ion cyclotron resonance heating method of isotope separation. It is assumed that the longitudinal ion velocity distribution in a plasma source is nonequilibrium. Under high heating temperatures, the averaged ion transverse velocity distribution becomes essentially nonequilibrium and exhibits two maxima. The ion heating efficiency η is calculated for W ₁=40 eV and various values of the parameter p=λ/L, where λ is the wavelength of the electric field of an antenna and L is the heating zone extension. The relative contributions of the time-of-flight and Doppler broadenings are evaluated.     

A review of furfural derivatives as promising octane boosters

Prospects for using furfural derivatives as octane boosters for gasoline are discussed on the basis of analysis of their physicochemical and operation properties. Knock resistance data, toxicity parameters, and results of motor bench tests are considered for furan compounds, furfural ethers, furfurylamine, and other furfural derivatives.     

Heating of gadolinium plasma ions by the ion cyclotron resonance method

Resonance rf heating of gadolinium plasma ions is calculated in the configuration when an electric field travels along a permanent magnetic field and simultaneously rotates in the direction normal to the latter. Two model functions are taken as initial ion distribution functions over longitudinal velocities: one is a linear function of the velocity in the low velocity range and the other is a shifted semi-Maxwellian function. The ion transverse velocity distribution function is calculated under the assumption that the initial “transverse” distribution function is Maxwellian with a temperature of 5 eV. Ion fluxes toward collector plates are calculated by integrating the total distribution function over the allowed ranges of longitudinal and transverse velocities and transverse coordinates of the guiding center of the ions before the collector. The calculation is performed as applied to the ¹⁵⁷Gd target isotope and its two nearest neighbors. The effect of the longitudinal temperature on the width of the heating efficiency resonance line and of the longitudinal magnetic field on the ion heating selectivity is studied. Also, the influence of the longitudinal wavenumber of the warming traveling electric field on the selectivity of an ion cyclotron resonance reactor is investigated. The heating efficiency is estimated from the frequency dependence of the fraction of ions heated to an energy above a given value.     

Characteristics of a hot ion collector placed in a weak ion cyclotron resonance magnetic field

The separation characteristics of a planar collector system placed in the weak magnetic field region of a facility that separates isotopes of stable metals by the ion-cyclotron-resonance method are calculated. An increase in the gyroradius of the accelerated ions in the weak field allows the designer to increase the collector plate spacing and decrease undesired screen losses. It is theoretically shown that placing the collector in the week field increases the degree of separation. Also, the transverse-to-longitudinal ion energy conversion makes it possible to extend the product deposition area on the collector plates and, thus, to reduce the thermal load on the collector and facilitate the long-term production of the target material in large amounts.     

Circulation Plasma Centrifuge with Product Flow

We have analyzed the isotope separation in a high-frequency plasma circulating centrifuge operating with a product flow. The rotation of a weakly ionized plasma is ensured by a rotating magnetic field, while the countercurrent flow (circulation) is produced by a traveling magnetic field. We have calculated the dependences of the enrichment factor and the separative power of the centrifuge on a product flow. The optimal characteristics of the separation unit have been determined.     

5-fluorouracyl. Molecular structure in the gas phase

By means of gas electronography studies combined with nonempirical calculations (BLYP/6-31G*) data on the structure of 5-fluorouracyl corresponding to the theoretical calculations were obtained. Some propeties of 5-fluorouracyl as compared to its isomer, 6-fluorouracyl, were studied. Main geometrical parameters of 5-fluorouracyl molecule are as follows: interatomic distances (r _α, Å) N¹-C¹ 1.396(1), N³-C⁴ 1.412(1), C⁴-C⁵ 1.452(1), C³=C⁶ 1.452, C⁶-C¹ 1.349, C-F 1.337(2); bond angles, deg: N¹C²N³ 113.6(2), C²N³C⁴ 128.9(5), N³C⁴C⁵ 113.0(2), C⁴C⁵C⁶ 120.2(3), C⁵C⁶N¹ 121.1(4), C⁶N¹C² 123.3(4), FC⁵C⁶ 120.3. Pyrimidine cycle was regarded as planar according to the quantum chemical calculations. Comparative analysis of difference in 5- and 6-fluorouracyl + H₂O systems was carried out.     

Three-dimensional gas flow in a rotating cylinder with a retarding cover

The study of rotating flows is of interest due to both the development of the centrifugal method of separation of gas and isotope mixtures and the possibility of astrophysical applications. An analytical nonlinear model for calculating the hydrodynamic characteristics of the viscous incompressible fluid flow in a rotating cylinder in the presence of a retarding cover is presented. The cases of stationary and rotating covers are considered. The analysis is performed on the basis of the system of hydrodynamic Navier-Stokes equations. The flow domain is divided up into the main flow and end boundary layers at the cylinder bottom and at the rotating cover. In its turn, the main flow is divided up into an inviscid quasi-rigid core and a lateral layer within which almost the entire upward circulatory flow is concentrated. The equations of the boundary layers at the end surfaces are analyzed by the approximate Slezkin-Targ method. The solutions in the boundary and lateral layers are “stitched” together with the velocity distribution in the main flow core. The unknown angular velocity ω ₁ and radial boundary R ₁ of the core are determined from the balance of the moments of the friction forces acting on the main rotating flow and the continuity condition for the circulatory flow. The experimental and calculated data are compared.     

Three-dimensional rotational MHD flows in bounded volumes

Three-dimensional laminar flows of a viscous conducting gas in the neighborhood of a rotating disk are considered. The simultaneous impact of an external magnetic field, suction from the disk surface, and the axial temperature gradient as well as the action of the external axial magnetic field on three-dimensional flows in the neighborhood of rigid permeable surfaces are first studied. An exact analytic solution of the system of the boundary layer equations is obtained. It is found that the direction of the radial flow initiated in the boundary layer can be varied by changing the temperature ratio in the external flow and on the disk for various Prandtl numbers Pr. An approximate solution of the problem of flow in the rotating cylinder in the presence of a retarding cover is constructed on the basis of the approach developed for extended disks.     

Estimates of the electron density in an ECR source of calcium plasma

A technique is proposed for estimating parameters of the plasma produced by a source based on the electron cyclotron resonance. The analysis is made for the ion cyclotron resonance (ICR) facility designed for separating calcium isotopes. It is assumed that the resonance condition for an extraordinary wave is fulfilled for electrons moving towards the wave. The plasma optical thickness, the transverse energy of resonance electrons, and its dependence on the longitudinal velocity are determined. The charged particle density in the plasma flow is estimated in terms of the balance of the electrons generated as a result of vapor ionization in the discharge zone and the electron losses due to longitudinal ambipolar diffusion.