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[en] An extremely large magnetoresistance of PtSn4 has been recently observed and discussed from a viewpoint of de Haas-van Alphen (dHvA) oscillations and theoretical small Fermi surfaces. We have studied precisely the Fermi surfaces by measuring angular dependences of dHvA frequencies and have also carried out the full potential LAPW band calculation. Furthermore, small Fermi surfaces have been detected in another Pt-based compound of Pt3In7 with the cubic structure.
[en] CeTiGe_3 is one of the few Kondo-lattice compounds which order ferromagnetically (T_C ∼ 14 K); LaTiGe_3 may be used as its nonmagnetic reference, since both compounds crystallize in the same hexagonal perovskite structure. We report on angular-resolved de Haas-van Alphen oscillations in single crystals of CeTiGe_3, LaTiGe_3, and Ce_0_._1La_0_._9TiGe_3 grown from Ge flux, measured in magnetic fields up to 13 T in a cantilever-type torque magnetometer. We found several dHvA frequencies, ranging in CeTiGe_3 from 100 to 530 T and with effective masses around 0.7 m_0, featuring a comparably weak angular dependence. Further, we give an interpretation of our results on the basis of DFT calculations of the electronic band structure of CeTiGe_3 and LaTiGe_3.
[en] The interdiffusion coefficients are estimated either following the Wagner's method expressed with respect to the composition (mol or atomic fraction) normalized variable after considering the molar volume variation or the den Broeder's method expressed with respect to the concentration (composition divided by the molar volume) normalized variable. On the other hand, the relations for estimation of the intrinsic diffusion coefficients of components as established by van Loo and integrated diffusion coefficients in a phase with narrow homogeneity range as established by Wagner are currently available with respect to the composition normalized variable only. In this study, we have first derived the relation proposed by den Broeder following the line of treatment proposed by Wagner. Further, the relations for estimation of the intrinsic diffusion coefficients of the components and integrated interdiffusion coefficient are established with respect to the concentration normalized variable, which were not available earlier. The veracity of these methods is examined based on the estimation of data in Ni–Pd, Ni–Al and Cu–Sn systems. Our analysis indicates that both the approaches are logically correct and there is small difference in the estimated data in these systems although a higher difference could be found in other systems. The integrated interdiffusion coefficients with respect to the concentration (or concentration normalized variable) can only be estimated considering the ideal molar volume variation. This might be drawback in certain practical systems.
[en] The reconstruction of the Radiological Research Accelerator Facility (RARAF) at the Nevis Laboratory of Columbia University is nearing completion. In a previous report the early part of the construction of the RARAF building within the Nevis cyclotron building was described. This year we describe the completion of the building, the RARAF staff, assembly of the 4 MV Van de Graaff accelerator, and the first phase of its operation. 2 references
[en] Principle and description of the 9 MV tandem, 1 MV Van de Graaff and connected physics installations at Saclay are given
[fr]Les principes elementaires des machines electrostatiques du type Van de Graaff et tandem sont rappeles. Le tandem 9 MV de Saclay, le Van de Graaff 1 MV et quelques installations de physique sont presentes
[en] The characteristics and performance of accelerator tubes required by the new generation of large tandem accelerators and by the upgrading of existing machines are summarized. Recent experiments on surface flashover of insulators in vacuum and on the control of surface charging are briefly reviewed current theories of the microdischarge process are examined and their relevance to the operation of UHV and conventional tubes is discussed. The role of microparticles, the evidence for their existence and their influence on breakdown is reported in the light of recent experiments using laser scattering and electron microscopy. Finally, current practice and achievements are compared with the data presented by Cranberg in 1952 and some conclusions are drawn about future progress and developments
[en] The up-grading transformation of the Saclay FN-Tandem asked for the replacement of the aluminum electrode accelerating tube by a new one with stainless steel electrodes, and the old (yellow) resistors of the column by a set of new (blue) resistors. The first problem to be faced with was the behavior of the vacuum conditions as a function of time. A second one was due to the instability that appeared at voltages higher than 6.5 volts. This instability problem was overcome by replacing the whole set of resistors by the set of old ones