Activity study of graphite from the chernobyl NPP reactor

The content of the isotopes ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁶⁰Co, ⁹⁰Sr, ^93m Nb, ¹⁰⁸Ag, ¹³³Ba, ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu, and ¹⁵⁵Eu in the GRP-2-125 graphite from the reactor of Power Unit 2 at the Chernobyl Nuclear Power Plant was measured. The results were compared with the calculations and literature data. Some regularities and correlations were revealed in the content of various radionuclides in graphite. Graphite porosity and desorption of radionuclides from graphite were studied. Original Russian Text ? M.D. Bondar’kov, D.M. Bondar’kov, A.M. Maksimenko, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, V.V. Petrov, A.I. Savin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 274–278.     

Measurement of the e+e? → π+π? cross section with the CMD-2 detector in the 370–520-MeV energy range

The results of the experiment on the measurement of the e ⁺ e ⁻ → π⁺π⁻ cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the vector dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The cross section for the production of a muon pair is measured in the energy range of the experiment. Original Russian Text ? V.M. Aul’chenko, R.R. Akhmetshin, V.Sh. Banzarov, L.M. Barkov, N.S. Bashtovoĭ, D.V. Bondarev, A.E. Bondar’, A.V. Bragin, N.I. Gabyshev, D.A. Gorbachev, A.A. Grebenyuk, D.N. Grigor’ev, S.K. Dhawan, D.A. Epifanov, A.S. Zaĭtsev, S.G. Zverev, F.V. Ignatov, V.F. Kazanin, S.V. Karpov, I.A. Koop, P.P. Krokovny, A.S. Kuz’min, I.B. Logashenko, P.A. Lukin, A.P. Lysenko, A.I. Mil’shteĭn, K.Yu. Mikhaĭlov, I.N. Nesterenko, M.A. Nikulin, A.V. Otboev, V.S. Okhapkin, E.A. Perevedentsev, A.S. Popov, S.I. Redin, B.L. Roberts, N.I. Root, A.A. Ruban, N.M. Ryskulov, A.L. Sibidanov, V.A. Sidorov, A.N. Skrinsky, V.P. Smakhtin, I.G. Snopkov, E.P. Solodov, J.A. Thompson, G.V. Fedotovich, B.I. Khazin, V.W. Hughes, A.G. Shamov, Yu.M. Shatunov, B.A. Shvarts, S.I. éĭdel’man, Yu.V. Yudin, 2006, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2006, Vol. 84, No. 8, pp. 491–495.     

Observation of spontaneous spin reorientation in Nd1 ? xDyxFe3(BO3)4 ferroborates with a competitive R-Fe exchange

The magnetic, magnetoelectric, and magnetoelastic properties of DyFe₃(BO₃)₄ single crystals and the Nd_0.75Dy_0.25Fe₃(BO₃)₄ substituted compound with the competitive Nd-Fe and Dy-Fe exchange interactions have been investigated in magnetic fields up to 210 kOe. It has been shown that the antiferromagnetic state in Nd_0.75Dy_0.25Fe₃(BO₃)₄ below the Néel temperature is easy-plane and a spontaneous spin-reorientation transition to a uniaxial state occurs near 25 K. Anomalies are observed in various physical characteristics in a spin-flop transition induced by the magnetic field along the trigonal axis. The H-T phase diagrams are constructed; they are in good agreement with a simple model taking into account the anisotropy of the exchange splitting and g factors of the ground doublets of the Dy³⁺ and Nd³⁺ ions. The features of the magnetoelectric effect in various magnetic phases have been studied. Spontaneous electric polarization has been revealed in the region of the existence of an easy-plane antiferromagnetic state in the substituted compound. A qualitative theoretical justification of the possibility of the appearance of the spontaneous spin-reorientation transition in the Nd_0.75Dy_0.25Fe₃(BO₃)₄ substituted compound is given. Original Russian Text ? Yu.F. Popov, A.M. Kadomtseva, G.P. Vorob’ev, A.A. Mukhin, V.Yu. Ivanov, A.M. Kuz’menko, A.S. Prokhorov, L.N. Bezmaternykh, V.L. Temerov, 2009, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 89, No. 7, pp. 405–411.     

Baikal neutrino telescope: Status, results, and prospects of development

The main physical results obtained with the Baikal neutrino telescope NT200 during the period 1998–2003 are reviewed: the limits for the diffuse flux of high-energy neutrinos, high-energy muons, and magnetic monopoles and the results of search for neutrinos from the center of the Earth due to annihilation of weakly interacting massive particles and from local neutrino sources. In April, 2005, the neutrino telescope NT200 was extended by introduction of three new strings, located at a distance of 100 m from the NT200 center. The new deep-water complex NT200+ has an effective volume for detecting cascades from high-energy neutrinos larger than that of NT200 by a factor of 4. At a cascade energy of 10 PeV, the effective volume of the new complex is 10⁷ m³. Further development of the Baikal neutrino experiment is related to the design and fabrication of a detector with a volume of about 1 km³. Original Russian Text ? K.V.Antipin, V.M. Ainutdinov, V.A. Balkanov, I.A. Belolaptikov, D.A. Borshchev, N.M. Budnev, R.V. Vasil’ev, R. Vishnevskii, I.A. Danil’chenko, G.V. Domogatskii, A.A. Doroshenko, A.P. D’yachok, Zh.-A.M. Dzhilkibaev, O.N. Gaponenko, K.V. Golubkov, O.A. Gress, T.I. Gress, O.I. Grishin, V.A. Zhukov, A.M. Klabukov, A.I. Klimov, A.A. Kochanov, K.V. Konishchev, A.P. Koshechkin, L.A. Kuz’michev, V.F. Kulepov, E. Middel, T. Mikokaiskii, M.B. Milenin, R.R. Mirgazov, S.P. Mikheev, E.A. Osipova, G.L. Pan’kov, L.V. Pan’kov, A.I. Panfilov, D.P. Petukhov, E.N. Pliskovskii, P.G. Pokhil, V.A. Poleshchuk, E.G. Popova, V.V. Prosin, M.I. Rozanov, V.Yu. Rubtsov, Yu.A. Semenei, B.A. Tarashchanskii, S.V. Fialkovskii, B.K. Shaibonov, A.A. Sheifler, A.V. Shirokov, K. Spiring, I.V. Yashin, 2007, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2007, Vol. 71, No. 4, pp. 597–601.     

Use of photophysically active units of ionic polypseudorotaxanes for analysis of the supramolecular structure of the polymer necklace

The structure and supramolecular ordering of polymer complexes formed as the result of a combination of ionic and hydrophobic-hydrophilic interactions are determined. The efficiency of the combined use of the X-ray diffraction analysis, the second-harmonic generation technique, and luminescence spectroscopy in solids for determining the structure and supramolecular ordering is demonstrated using ionic polypseudorotaxane, which is based on poly(2-acrylamido-2-methyl-propanesulfonic acid), N,N-dimethyl-N′-(4-nitrophenyl)-decane-1,10-diamine, and α-cyclodextrin and contains photophysically active groups in side chains. Original Russian Text ? A.V. Ten’kovtsev, T.E. Sukhanova, M.E. Kompan, V.A. Lukoshkin, A.é. Bursian, M.P. Perminova, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 584–589.     

Magnetic anisotropy and magnetoelectric properties of Tb1 ? xErxFe3(BO3)4 ferroborates

Magnetic and magnetoelectric properties of ferroborate single crystals with complex composition (Tb_{1 − x} Er _x Fe₃(BO₃)₄, x = 0, 0.75) and with competing exchange Tb-Fe and Er-Fe interactions are investigated. Jumps in electric polarization, magnetostriction, and magnetization are observed as a result of spin-flop transitions, as well as a considerable decrease in the critical field upon an increase in the Er concentration, in a field H _c parallel to the c axis. The observed behavior of phase-transition fields is analyzed and explained using a simple model taking into account anisotropy in g factors and exchange splitting of funda-mental doublets of the easy-axis Tb³⁺ ion and easy-plane Er³⁺ ion. It is established that magnetoelectric and magnetostriction anomalies under spin-flop transitions are mainly controlled by the Tb subsystem. The Tb subsystem makes a nonmonotonic contribution ΔP _a (H _a , T) to polarization along the a axis: the value of ΔP _a reverses its sign and increases with temperature due to the contribution from the excited states of the Tb³⁺ ion. Original Russian Text ? A.K. Zvezdin, A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P. Pyatakov, V.Yu. Ivanov, A.M. Kuz’menko, A.A. Mukhin, L.N. Bezmaternykh, I.A. Gudim, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 136, No. 1, pp. 80–86.     

Proton and light-ion acceleration to relativistic GeV energies by the superstrong laser radiation interacting with a structured plasma target

A new scheme is proposed for proton and light-ion acceleration to relativistic energies by superstrong laser radiation interacting with a structured plasma target. The proposal consists in the use of two-component targets consisting of heavy and light ions, where an ambipolar field is formed under the action of the ponderomotive force of incident radiation, and, in contrast to the traditional schemes, acceleration starts from the front boundary of the layer. It is shown that, for the optimized target parameters, monoenergetic GeV ion beams can be produced for radiation pulse intensities on the order of 10²¹−10²² W/cm². Original Russian Text ? A.V. Korzhimanov, A.A. Gonoskov, A.V. Kim, A.M. Sergeev, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 662–669.     

Enhancement of hard X-ray yield under the interaction of Cr: Forsterite femtosecond laser radiation with Xe clusters

Experiments on the interaction of femtosecond laser radiation (1240 nm, 140 fs,10¹⁶W/cm²) with a Xe cluster beam in a Xe-Ne binary mixture are carried out. The formation of Xe clusters in the presence of light carrier gas (Ne) is found to narrow the Xe cluster beam and enhance the x-ray yield (at about 4 keV). X-ray generation efficiency is about 10⁻⁸. Original Russian Text ? A.P. Golubev, V.M. Gordienko, M.S. Dzhidzhoev, I.A. Makarov, D.N. Trubnikov, 2009, published in Vestnik Moskovskogo Universiteta. Fizika, 2009, No. 2, pp. 112–114.     

Investigation of the 13C(d,α)11B reaction mechanism at Ed = 15.3 MeV

The differential cross section of the ¹³C(d, α)¹¹B reaction at E _d = 15.3 MeV with the formation of ¹¹B nucleus in the ground and three low-lying excited states have been measured. The experimental data are compared with the results of calculations under the assumption of different reaction mechanisms: deuteron pick-up, ⁹Be-cluster exchange, two-step consecutive cluster transfer, and compound nucleus formation. Original Russian Text ? L.I. Galanina, N.S. Zelenskaya, I.A. Konyukhova, V.M. Lebedev, N.V. Orlova, A.V. Spassky, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 853–856.     

Imperfection of the nanostructure, phase transitions, 55Mn NMR, and magnetoresistive properties of La 0.73+ Ca 0.3 ? x2+ Sr x2+ MnO3 ± δ ceramics

Magnetoresistive ceramic samples La_0.7Ca_{0.3 − x} Sr _x MnO_{3 ± δ} sintered at temperatures of 1150 and 1350°C are investigated using X-ray diffraction, microscopic, resistance, and magnetic (χ, ⁵⁵Mn NMR) measurements. The specific features of the influence of the composition on the type and parameters of the perovskite structure, its imperfection, the porous crystallite structure, the metal-semiconductor and ferromagnetic-paramagnetic phase transitions, the ⁵⁵Mn NMR spectra, and the magnetoresistance effect are established. The magnetic phase diagram is constructed. The conclusions are drawn regarding the nonuniformity of the distribution of ions and vacancies around manganese involved in the high-frequency electron-hole exchange (Mn³⁺ ai Mn⁴⁺) and the nanostructured separation of the perovskite structure containing anion and cation vacancies, with the concentrations and magnetoresistance effect decreasing and the lattice parameters and phase transition temperatures increasing as calcium is replaced by strontium. Original Russian Text ? A.V. Pashchenko, A.A. Shemyakov, V.P. Pashchenko, V.A. Turchenko, V.K. Prokopenko, Yu.F. Revenko, Yu.V. Medvedev, B.M. éfros, G.G. Levchenko, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 6, pp. 1127–1136.     

Investigation of the influence of gradual substitution K ? Rb on the structure and phase transition in K x Rb1 ? x Pb2Br5 solid solutions

Single crystals of K _x Rb_{1 − x} Pb₂Br₅ solid solutions have been grown and investigated using X-ray diffraction and polarized light microscopy in the temperature range 270–640 K. The regions of existence of the tetragonal (I4/mcm) and monoclinic (P2₁/c) phases have been determined. It has been demonstrated that the partial introduction of rubidium into KPb₂Br₅ leads to an increase in the temperature of the ferroelastic phase transition (P2₁/c↔mmm), so that it approaches the melting temperature. In the solid solutions with x ≈ 0.4−0.5, the temperature region of existence of the orthorhombic phase is narrowed to ≈ 1−2 K. It has been revealed that an increase in the potassium content in the material results in a considerable increase in the incorporation coefficient of Er³⁺ ions. Original Russian Text ? L.I. Isaenko, S.V. Mel’nikova, A.A. Merkulov, V.M. Pashkov, A.Yu. Tarasova, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 554–557.     

Calculations of 8He + p elastic scattering cross sections using the microscopic optical potential

The optical potential of ⁸He+p scattering is calculated using the folding model for its real part and the high-energy approximation for the imaginary part. On this basis, the experimental differential elastic scattering cross sections are analyzed at energies below 100 MeV/nucleon. Conclusions are drawn on the applicability of the optical potential model and on the selection of an adequate model of the ⁸He nucleus structure. Original Russian Text ? V.K. Lukyanov, E.V. Zemlyanaya, K.V. Lukyanov, D.N. Kadrev, A.N. Antonov, M.K. Gaidarov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 887–891.     

Optically active Er3+ centers in Si/Si1 ? x Ge x structures under optical pumping

The Si/Si_{1 − x} Ge _x :Er/Si heterostructures, which are of interest for laser applications, have been investigated. The types of optically active Er³⁺ centers making a dominant contribution to the photoluminescence response of the structures studied are analyzed and their relationship with the parameters of the Si_{1 − x} Ge _x :Er heterolayer and the post-growth annealing conditions is shown. On the basis of the PL kinetic analysis of the structures with an isolated type of optically active Er³⁺ centers, it is concluded that population inversion of Er³⁺ ion states can be obtained under optical pumping and the effect of nonradiative recombination channels in Si_{1 − x} Ge _x :Er heterolayers on the excitation efficiency of Er centers and the conditions for population inversion is shown. Original Russian Text ? L.V. Krasilnikova, N.A. Baidakova, M.V. Stepikhova, Z.F. Krasilnik, V.Yu. Chalkov, V.G. Shengurov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 1, pp. 103–108.     

球床高温气冷堆燃料颗粒中放射性核素的累积释放份额研究

本文利用Fick扩散定律,给出经典方法和改进的两种累积释放份额的严格数学表达式,并分析与之相关的穿透时间的物理内涵,并分别用以上两种方法计算137Cs,90Sr,110mAg三种重要放射性核素通过SiC层扩散的累积释放份额.研究表明,传统的"穿透时间"概念并非放射性核素释放到SiC层外的时间,本文提出的改进方法可以更准确的描述放射性核素在燃料元件中的输运和扩散行为.     

Accelerator mass spectrometry of the heaviest long-lived radionuclides with a 3-MV tandem accelerator

A 3-MV pelletron tandem accelerator is the heart of the Vienna environmental research accelerator (VERA). The original design of the beam transport components allows the transport of ions of all elements, from the lightest to the heaviest. For light ions the suppression of neighboring masses was sufficient to measure isotopic ratios of ¹⁴C/¹²C and ²⁶Al/²⁷Al as low as 10⁻¹⁵ and ¹⁰Be/⁹Be down to 10⁻¹³. To suppress neighboring masses for the heaviest radionuclides in the energy range of 10–20 MeV, the resolution of VERA was increased both by improving the ion optics of existing elements at the injection side and by installing a new high-resolution electrostatic separator at the high-energy side. Interfering ions which pass all beam filters are identified with a Bragg-type ionization detector and a high-resolution time-of-flight system. Two ultra-thin diamond-like carbon (DLC) foils are used in the start and stop detector, which substantially reduces losses due to beam straggling. This improved set up enables us to measure even the heaviest long-lived radionuclides, where stable isobaric interferences are absent (e.g. ²³⁶U and ²⁴⁴Pu), down to environmental levels. Moreover, the advantage of a ‘small’ and well manageable machine like VERA lies in its higher stability and reliability which allows to measure these heavy radionuclides more accurately, and also a large number of samples.     

Reflective interferometer for investigation of the amplitude-phase characteristics of semiconductor nanostructures

It is proposed to apply a reflective interferometer in measurements of the spectral dependence of the phase of reflection of mirrors based on multilayer semiconductor nanostructures. The interferometer has been tested on the semiconductor mirror initiating the self-locking mode of a Nd³⁺: KGd(WO₄)₂ laser. The technique proposed can be applied in a wide wavelength range and has a higher sensitivity for measuring the phase characteristics in comparison with the conventional two-beam interferometers. Original Russian Text ? A.A. Kovalev, V.V. Preobrazhenskii, M.A. Putyato, O.P. Pchelyakov, N.N. Rubtsova, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 290–291.     

Photofission induced by linearly polarized photons

The asymmetry coefficients of fragments’ angular distribution (FAD) for fission of ^{234, 236, 238}U and ^{238, 240, 242}Pu isotopes, induced by linearly polarized photons, have been calculated. The optimal energies for observing the polarization parts in this asymmetry are found. Based on the experimental data on FAD for ²³²Th photofission induced by linearly polarized photons with the maximum energy E _γ = 10 MeV (with neglect of the contribution of absorption of electric quadruple photons), it is shown that the theoretical and experimental FAD asymmetry coefficients coincide within standard deviations. Original Russian Text ? S.G. Kadmensky, L.V. Titova, O.S. Khmelevskaya, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 878–881.     

The production and isolation of Cu-64 and Cu-67 from zinc target material and other radionuclides

A two-stage method is described for the purification of Cu radionuclides from up to 5 g of ^natZn and other radionuclides. After proton bombardment, co-produced ^66,67Ga is removed by passing the dissolved zinc in 7 M HCl through a 2.5 ml column of AmberChrom CG-71, a methacrylate-based polymeric resin. This first column eluate, which contains ⁶⁵Zn, ^64,67Cu, and ^56,57,58Co, is taken to incipient dryness and reconstituted in 300 ml 0.05 M HCl. This solution is then pumped through a novel 10 ml column of dithizone impregnated AmberChrom CG-71, where Cu radionuclides are efficiently retained with no breakthrough. Zinc and Co radionuclides elute smoothly during washing with no tailing. More than 97% Cu is eluted by washing with 40 ml 5 M HNO₃ warmed to 50 °C. No dithizone is detected in this eluate.     

Investigation of the dynamic susceptibility of antiferromagnetic MnCO3 near the NMR of Mn55

The real part χ″ of the dynamic magnetic susceptibility of antiferromagnetic MnCO₃ is measured near the NMR of Mn⁵⁵. Two new phenomena are discovered: χ″ vanishes at the unshifted NMR frequency in the region of large dynamic frequency shift (DFS) of NMR, and the NMR line is broadened as the shift varies from large to small values. The results obtained are described satisfactorily by the concept of the DFS of NMR developed in the works of E. A. Turov, M. I. Kurkin, and V. I. Tsifrinovich. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 9, 636–640 (10 November 1996)     

Dynamical analysis of the induced fission time obtained by the crystal blocking technique for the 235U + α reaction

The crystal blocking technique has been used to measure the total time of the induced fission process for the ²³⁵U + α reaction in the energy rage of bombarding α-particles from 25.9 to 31.2 MeV. The experimental fission lifetimes observed in this reaction vary from 10⁻¹⁷ to 10⁻¹⁶ s, depending on the projectile energy. The experimental data (along with the corresponding data on the angular anisotropy and fissionability of Pu isotopes produced in the investigated reaction) have been analyzed within the dynamic-statistical approach with allowance for the nuclear dissipation phenomenon and the double-humped fission barrier model. It is demonstrated that the time of induced fission reaction at low excitation energies is sensitive to the nuclear viscosity. Original Russian Text ? A.A. Dermenev, V.A. Drozdov, D.O. Eremenko, F. Malaguti, P. Olivo, S.Yu. Platonov, V. Togo, A. Uguzzoni, O.V. Fotina, O.A. Yuminov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 882–886.