[en] A detailed crystal-field analysis, based on the Racah' theory, was carried out for the so-called A, B and G1 isolated charge-compensation centers of Er³⁺ ion doped in CaF₂ crystal. Three sets of crystal-field parameters were obtained by a least-squares fitting of the optical data of Er³⁺ ion diluted in epitaxial Ca_1-xEr_xF_2+x thin film. This theoretical analysis confirms the expected C_4ν site symmetry for the A center and the C_3ν site symmetry for the G1 center. For the B center, however, the site symmetry is not exactly C_3ν in contrast to what is believed. (orig.)

[en] In this paper we have studied the contribution of electrostatic and magnetic turbulence on particles anomalous transport in the tokamak. The diffusion coefficient is evaluated. Comparison between diffusion magnetic field lines and particles is carried out. We also treat the effects of the reversed shear barrier in reducing the particles anomalous transport in the tokamak. (orig.)

[en] N-type lightly doped germanium has been irradiated at room temperature with different particles: swift heavy ions, protons and electrons. Hall effect measurements have been carried out versus either the temperature (at a given fluence) or the fluence (at room temperature). Using the level positions determined by DLTS results previously reported, we extract from the Hall coefficient simulation at low doses the creation kinetics of the irradiation-induced defects. These defects are typically at room temperature the A-centre, the E-centre and the divacancy complexes. At higher doses, in the case of electron irradiation, these simulations are still feasible using only the previous defects mentioned above since the material leads towards a quasi-intrinsic state. But we point out that it is necessary in the case of proton and swift heavy ion irradiations to add an acceptor level in the forbidden band probably associated with a multivacancy defect. Indeed, in these cases, the material becomes p-type. Finally, the experimental introduction rates are compared to the theoretical ones. It appears that the relative damage creation efficiency is not very different from a projectile to another, proving that there is no strong dependence on the electronic energy loss. (orig.)

[en] The phenomena resulting from interaction between ion beam and mammalian cell pose important problems for biological applications. Classic Bethe-Bloch theory utilizing attached V79 mammalian cell has been conducted in order to establish the stopping powers of the mammalian cell for several-MeV single-proton microbeam. Based on the biological structure of the mammalian cell, a physical model is proposed which presumes that the attached cell is a simple MWM model. According to this model and Monte Carlo simulation, we studied the energy deposition and its ratio on the selected attached mammalian cell for MeV proton implantation. We found that the Bragg peak region of several-MeV energetic proton is beyond the thickness of the selected attached mammalian cell

[en] Amorphous thin films of Se_80-xTe₂₀Pb_x (0 < x < 2) have been prepared by thermal evaporation. The effect of 40 MeV ²⁸Si⁵⁺ ion irradiation on the electronic conduction of Se_80-xTe₂₀Pb_x (0 < x < 2) thin films has been investigated. The DC electrical conductivity of the films increases by two to three order of magnitude with increase in irradiation fluence from 10¹² to 5*10¹³ ions/cm². The DC activation energy of conduction also increases with increase in irradiation fluence. Results have been explained on the basis of structural disorders and defects formed due to heavy ion irradiation. (authors)

[en] Microstructural and magnetic properties of ¹⁴N⁺ irradiated Co/Pd multilayers, deposited on ultra-flat large (2.5 in) glass substrates by a special hard disk industrial manufacturing system, are discussed. Upon irradiation with ¹⁴N⁺ ions at different energies (20-30 keV) and doses (10¹⁴ - 10¹⁵ ions/cm²), both the coercive and nucleation fields were found to change with respect to as deposited multilayer. Results indicate that the irradiation process leads to a lowering of the magnetic anisotropy due to the induced disorder and degradation of the interface quality: for an energy of 30 keV; at an irradiation level of 10¹⁵ ions/cm², H_c reduces from H_c ∼ 5.4 kOe for the as deposited multilayer down to 300 Oe, being the easy axis still perpendicular to the multilayer plane; at the highest dose (10¹⁶ ions/cm²), the coercivity vanishes and the perpendicular anisotropy is suppressed. (authors)

[en] This paper reports the first results of an ongoing research work on rapid surface alloying of an AISI 316L stainless steel by low energy, high current pulsed electron beam (LEHCPEB) with the aim of enhancing the corrosion resistance of this material against aggressive halide ions. A Ti powder layer was deposited on the substrate and in-corporate at the top surface by using LEHCPEB. Due to the rapid surface melting, liquid state mixing occurred and a Ti-rich layer formed. The alloyed layer contained a mixture of the α and γ phases because the addition of Ti favors the formation of α. The corrosion resistance of the AISI 316L stainless steel in the simulated body fluid was effectively improved after surface alloying by Ti. (authors)

[en] Solid state nuclear track detectors (SSNTDs), such as Columbia Resin 39 (CR-39), have been used to detect energetic charged particles and neutrons. Of the neutron and charged particle interactions that can occur in CR-39, the one that is the most easily identifiable is the carbon breakup reaction. The observation of a triple track, which appears as three alpha particle tracks breaking away from a center point, is diagnostic of the ¹²C(n, n')3α carbon breakup reaction. Such triple tracks have been observed in CR-39 detectors that have been used in Pd/D co-deposition experiments. In this communication, triple tracks in CR-39 detectors observed in Pd/D co-deposition experiments are compared with those generated upon exposure to a DT neutron source. It was found that both sets of tracks were indistinguishable. Both symmetric and asymmetric tracks were observed. Using linear energy transfer (LET) curves and track modeling, the energy of the neutron that created the triple track can be estimated. (authors)

[en] For many years, nuclearly polarized ³He gas has been used in fundamental research for the generation of polarized neutrons in nuclear physics. The efficiency of the metastability exchange optical pumping (MEOP) performed at elevated ³He gas pressures in high magnetic field was improved by modifying the spatial profile of the pumping laser beam in such a way that it matched the nonuniform distribution of plasma in the optical pumping cell. Comparing to a conventional Gaussian profile, at the ³He gas pressure equal to 267 mbar, both the achieved nuclear polarization (equal to 26%) and the total magnetization in the cell (equal to 1.37 sccfp) are 60% higher when the annular laser beam profile is applied. (authors)

[en] The general method of diagnostics of the transient radiation of ribbon-shaped and axially-symmetric electron beams of small section (0.1 mm) and high-power density (1-100 kW/sm²) is described. Selective analysis of various types of transient radiation detectors of type photo-camera, video-camera and digital photo-camera is carried out at first. Advantages and disadvantages of radiation detectors are pointed out to be taken into account at analysis of the object under investigation. (authors)