I. V. Makarenko

On the synthesis and thermal conductivity of nanocomposites with multiwalled carbon nanotubes

A method for growing arrays of vertically aligned carbon nanotubes and synthesizing a polymer composite based on vertically aligned, horizontally aligned, and unaligned carbon nanotubes is described. The thermal conductivity of polymer composites is studied by the laser-flash method. It is found that filling of the polymer with vertically aligned carbon nanotubes leads to an increase in the thermal conductivity coefficient of the epoxy resin by a factor of 10 and more.

Strength Analysis and Process Simulation of Subway Contact Rail Support Bracket of Composite Materials

An application of composites for construction of subway brackets is a very effective approach to extend their lifetime. However, this approach involves the necessity to prevent process-induced distortions of the bracket due to thermal deformation and chemical shrinkage. At present study, a process simulation has been carried out to support the design of the production tooling. The simulation was based on the application of viscoelastic model for the resin. Simulation results were verified by comparison with results of manufacturing experiments. To optimize the bracket structure the strength analysis was carried out as well.

Multineutron photodisintegration of the 197Au nucleus behind the giant dipole resonance

An experiment in which the gold isotope 197Au was irradiated with a beam of bremsstrahlung photons having an endpoint energy of Eγm = 67.7 MeV and originating from the RTM-70 racetrack microtron of the Institute of Nuclear Physics at Moscow State University was performed. The gammaray spectra of the residual beta activity of an irradiated sample were measured. Multinucleon photonuclear reactions on 197Au nuclei were observed in the experiment. Photonuclear reactions on a 197Au nucleus that involve the emission of up to seven neutrons were recorded for the first time. The experimental results in question suggest the important role of the quasideuteron photodisintegration mechanism in the energy region behind the giant dipole resonance.

The RTM-70 accelerator as a pulsed source of neutrons and photons

The possibility of using the RTM-70 race-track microtron for pulsed production of photons and neutrons is analyzed. Optimum parameters of such sources are obtained through a computer simulation.

Cross sections of multiparticle photonuclear reactions with 203, 205Tl isotopes

An experiment on the irradiation of the natural mixture of 203,205Tl isotopes by the bremsstrahlung beam of pulsed racetrack microtron RTM-70 (Skobeltsyn Institute of Nuclear Physics, Moscow State University) at an electron energy of 67.7 MeV was performed. The yields and integral cross sections of multiparticle photonuclear reactions with 203,205Tl isotopes were measured.

Yields of multiparticle photoneutron reactions on the 209Bi isotope

The relative yields of multiparticle photoneutron reactions on the 209Be isotope with emission of two to seven neutrons from the nucleus are measured. The experiment was carried out with the bremsstrahlung beam from the RTM-70 pulsed race-track microtron (INP, MSU) with a maximum photon energy Eγm = 67.7 MeV.

Isospin symmetry and giant resonance in nuclei of mass number A = 14

An analysis of the cross sections for photon absorption by isobar nuclei 14C and 14N in the giant-dipole-resonance region demonstrates a high degree of isospin symmetry for this type of collective excitations in the above nuclei. Giant resonances in A = 14 isobar nuclei are related by a simple rescaling procedure that is based on the fact that, for these nuclei, the isospin remains a good quantum number in the process of dipole excitations of energy up to about 40 MeV. The features of the isospin splitting of the giant resonance in the 14C nucleus are refined. The shape of the cross section for photoabsorption in the 14C nucleus—in particular, a large width of the giant resonance in this nucleus—is exhaustively explained.

Multineutron photonuclear reactions on the 197Au isotope

An experiment on irradiation of the 197Au isotope by a beam of bremsstrahlung γ-rays of maximum energy Eγm = 70 MeV has been carried out at the RTM-70 race-track microtron of the INP MSU. Residual activity spectra of the irradiated sample were measured. Multiparticle photonuclear reactions on the 197Au nucleus are observed. Photonuclear reactions with emission of as many as six neutrons are observed for the first time.

Multiparticle photonuclear reactions in 203Tl nuclei

The thallium isotopes 203Tl and 205Tl were irradiated using a beam of bremsstrahlung gamma quanta with the maximum energy Eγm = 50 MeV from an RTM-70 electron racetrack microtron installed at the Scobeltsyn Nuclear Physics Research Institute (Lomonosov Moscow State University, Russia). The gamma spectra of the residual activity were measured for an irradiated sample. Photonuclear reactions in the 203Tl nuclei with emission from one to four neutrons were observed experimentally. The relative yields of the reactions 203Tl(γ,n)202Tl, 203Tl(γ,2n)201Tl, 203Tl(γ,3n)200Tl, and 203Tl(γ,4n)199Tl were determined for the first time.