Results 1 - 10 of 565
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[en] This study is devoted to the angular and spatial distribution of protons channeling through a bent and radially deformed single-wall boron-nitride nanotubes (SWBNNTs). These nanotubes are more thermal and chemical stable then carbon nanotubes, and they are good candidates for future channeling experiments. This investigation is continuation of our previous study [1, 2] and now we investigate channeling properties of SWBNNTs as a function of the very realistic effects: bending angle of nanotube and its radial deformation. For the first time we presented here investigation of these effects with boron-nitride nanotubes and combination of both effect. The angular and spatial distributions of channeled protons were generated using the Molière’s expression for the continuum potential of the SWBNNT’s atoms and computer simulation method. We also calculate the total yield of protons channeled in the nanotubes as a function of the bending angle. We demonstrate that varying bending angle and taking into account radial deformation we can get a significant rearrangement of the propagating protons within the boron-nitride nanotube. This investigation may be very useful to give us detailed information on the relevant interaction potentials inside SWBNNTs and for creating nanosized proton beams to be used in different applications in medicine and materials science. © 2019, Editura Academiei Romane. All rights reserved.
[en] This work aims to investigate the effect of TiO2 nanoparticles addition on the fluorescence emission of solutions of Rhodamine 6G excited in micro-volumetric droplets. In this paper are presented the similarities and the differences of the emission spectra by modifying parameters such as TiO2 concentration, solutions pH and laser fluence. The pumping laser source used was the second harmonic beam emitted by a pulsed ns Nd:YAG laser at 532 nm. Lasing emission is observed and it is favorised by the solution acidity and laser beam intensity. © 2018, Editura Academiei Romane. All rights reserved.
[en] The working program of the Experimental Particle Physics Group (EPPG) will be presented. The group's program contains the experimental testing of the Standard Model for the elementary particle interactions. The participation of the EPPG in different collaborations is discussed. It began with the contributions to the L3 collaboration on the tracker construction as well as to the MC simulation of different reactions in the electron-positron interactions at LEP with CMS energy of 190-209 GeV. The participation in the strange particle electroproduction experiment in electron-nucleus interactions at Thomas Jefferson Laboratory Accelerator in interactions of an electron beam with nuclei will be mentioned. The group activities in the construction of the CMS detector at CERN LHC (p-p 14 TeV interaction) machine, by manufacturing in Romania a series of dummy detectors for different tests as well as the contributions to the radiation hardness studies of the silicon detector are mentioned. Finally, the participation in the AMS 1-2 cosmic is presented. The results obtained in the prototype AMS 1 flight are discussed from the physical as well as technical point of view. As a principal physical result, an upper limit of 1.1 x 10-6 of the ratio Antihelium/Helium in cosmic rays was found. Technically, a series of improvements in comparison with the flown prototype were considered. The change from a permanent magnet to a superconducting one was decided and the change and modification of the detection systems was proposed. Finally, some considerations are made about the construction and schedule of the AMS 2 detector complex to be installed on the ISS space station in 2005. (authors)
[en] In order to perform an efficiency calibration for different measurement geometries a good knowledge of the detector characteristics is required. The Monte Carlo simulation program GESPECOR is used. The detector characterization required for Monte Carlo simulation is achieved by a trial and error procedure using the efficiency values measured with point sources placed in several positions. (authors)
[en] The quantum field theory in curved space-time has been a matter of great interest in recent years because of its applications to cosmology and astrophysics. The evidence of the existence of strong gravitational fields in our Universe led to study of the quantum effects of material fields in external classical gravitational field. Within the framework of Bianchi type-I (BI) space-time we studied the Bel-Robinson tensor and its impact on the evolution of the Universe. We use different definitions of the Bel-Robinson tensor existing in the literature and compare the results. (authors)
[en] The results on electron temperature of a copper vapors plasma obtained through the spectral intensities ratios method in a particular type discharge i. e. thermionic vacuum arc are presented. For an arc current Iarc = 705 mA an arc voltage Uarc = 500 V, an electronic temperature of plasma Te 5875 ±455 K was obtained. (authors)
[en] An important tool for the development of devices (detectors, solar cells , electronic circuit components) for high energy accelerator facilities or for space utilization, where new missions and experiments will be operated, is to find new materials with harder radiation properties. The radiation fields in these environments are extremely complex and the tests of the behaviour of different materials and devices for concrete situations are difficult to be realised and very expensive. Thus, scaling of degradation effects would represent a useful tool and it is the main aim of the present contribution. Some analytical expressions for NIEL that suggest possible scaling formula are given. (authors)
[en] The aim of this paper is to estimate the collision time integral of the kinetic equation describing a stochastic mechanism of acceleration. This mechanism, namely the chaotic gun effect, might be an efficient mechanism of injection. The efficiency of the mechanism can be expressed using the collision integral of the charged particles moving in a turbulent electromagnetic field. (author)
[en] Nucleon spectroscopy studies the nucleon and its resonances. In photoproduction of mesons below a beam energy of 2 GeV, the main process is the excitation of nucleon resonances. This can be used to complement the study of these resonances, usually carried out with pion-nucleon scattering. A basic presentation of the lightest mesons and the resonances is done. The formalism of the pseudoscalar meson photoproduction is given. The data bases are described. Detailed developments in η and ω meson photoproduction on the proton are reported. (author)
[en] Existence of two kinds of scission configurations associated with symmetric and asymmetric fission modes is pointed out in the fission of actinides: elongated and compact configurations. Each scission property is discussed in terms of shape elongation evaluated from fragment total kinetic energy (TKE). Fragment deformation at scission is also discussed based on neutron multiplicity measurements. From the systematic study of the scission properties in a wide range of actinides, the bimodal fission observed in the spontaneous fission (SF) of the heavy actinides would be interpreted as the result of the presence of the two fission paths; the ordinary asymmetric fission path is still exiting while the symmetric one is bifurcated by strongly shell-influenced effects. (authors)