Quasi-optical multiplexer based on reflecting diffraction grating

The article presents results of theoretical and experimental investigation of quasioptical multiplexer based on reflecting diffraction grating. Diffraction losses caused by reflection into mirror harmonic, and by angle divergence of wave beams are calculated. In an experimental multiplexer, wave beams with the frequencies 70 GHz and 79 GHz were mixed with power losses less than 1%.     

Specular reflection of thermal neutrons from Gd-containing layers and optimization of antireflective underlayers for polarizing coatings

A detailed analysis of specular neutron reflection from an absorbing medium is given. The experimental studies revealed that oxidation and roughness of the surface are the main factors that determine the neutron reflectivity of Gd-containing layers. It is concluded that the empirical approach used at present does not guarantee optimization of underlayer parameters (composition and thickness) and technological regimes. An algorithm of optimization is proposed, in which account is taken of the substrate potential, the dependence of the underlayer potential on the thermal neutron wavelength, the polarizing coating imperfections that enhance reflection of neutrons with the undesired spin. The antireflective TiZrGd underlayer for CoFe/TiZr supermirrors produced at the magnetron facility DIOGEN (PNPI, Gatchina) is optimized.     

High-power free-electron maser with frequency multiplication operating in a shortwave part of the millimeter wave range

The possibility of using frequency multiplication in order to obtain high-power short-wavelength radiation from a free-electron maser (FEM) with a Bragg resonator has been studied. Preliminary experiments with an LIU-3000 (JINR) linear induction accelerator demonstrate the operation of a frequency-multiplying FEM at megawatt power in the 6- and 4-mm wave bands on the second and third harmonic, respectively.     

Increasing the efficiency of combinatorial logical data analysis in recognition and classification problems

Problems of increasing the efficiency of combinatorial logical data analysis in recognition problems are examined. A technique for correct conversion of initial information for reduction of its dimensionality is proposed. Results of testing this technique for problems of real medical prognoses are given. Djukova Elena V. Born 1945. Graduated from Moscow State University in 1967. Candidate’s degree in Physics and Mathematics in 1979. Doctoral degree in Physics and Mathematics in 1997. Dorodnicyn Computing Center, Russian Academy of Sciences, leading researcher. Moscow State University, lecturer. Moscow Pedagogical University, lecturer. Scientific interests: discrete mathematics and mathematical method of pattern recognition. Author of 70 papers. Peskov Nikolai V. Born 1978. Graduated from Moscow State University in 2000. Candidate’s degree in 2004. Dorodnicyn Computing Center, Russian Academy of Sciences, junior researcher. Scientific interests: discrete mathematics and mathematical methods of pattern recognition. Author of ten papers. Inyakin Andrey S. Born 1978. Graduated from Moscow State University in 2000. Dorodnicyn Computing Center, Russian Academy of Sciences, junior researcher. Scientific interests: discrete mathematics and mathematical methods of pattern recognition. Author of ten papers. Sakharov Aleksei A. Born 1980. Graduated from Moscow State University in 2003. Moscow Pedagogical University, graduate student. Scientific interests: discrete mathematics and mathematical method of pattern recognition. Author of three papers.     

Mechanism of free electron maser self-excitation using coupled propagating and trapped modes

A new scheme of feedback in a free-electron maser (FEM), which is based on the mutual scattering of propagating and quasi-cutoff (trapped) modes on a periodic Bragg structure, is considered. The trapped mode makes possible self-excitation of the system, while the energy exchange in a stationary generation regime is almost entirely determined by the interaction with a synchronous propagating wave. Using the proposed method, it is possible to improve mode selectivity with respect to the transverse index and accordingly decrease the working wavelength.     

Optimization of the core composition for a sodium-cooled fast reactor with oxide fuel and fuel-utilization improvement by adopting a closed fuel cycle

The transition to a closed fuel cycle after several years of operation of the BN-800 with oxide uranium fuel in an open fuel cycle is examined. It is shown that there is an advantage to using new fuel assemblies with 91 fuel elements with diameter 8.6 mm in a regime with four refuelings. On the basis of new fuel assemblies with mixed uranium-plutonium oxide fuel, transitional recycling to a closed fuel cycle without separating uranium and plutonium and without external plutonium makeup is examined. It is confirmed that a negative sodium void effect of reactivity is achieved with admissible values of the linear power density of a fuel element. It is shown that a regime with four refuelings can be obtained by adding uranium with enrichment no higher than 15% to replace the poison which is removed. __________ Translated from Atomnaya énergiya, Vol. 104, No. 2, pp. 94–99, February, 2008.