[en] A previous study of the Ta-H system by the same author revealed certain interesting features of the extra-resistivity Δrho(T) due to the presence of hydrogen, i) a dependence upon the hydrogen concentration, ii) a linear increase when the specimens are cooled from room temperature to the critical temperature Tc corresponding to the hydride formation, iii) a peculiar decrease for T < Tsub(c) owing to the α→α+β phase transformation and iv) again a linear increase for T < 90 K. Anomalies were also found in the behaviour of the thermoelectric power of these alloys in the same temperature ranges. With this in mind, the measurements have been improved in order to obtain further and more precise information. Results are given and discussed. (author)

[en] The phase transformation in the Ta-H system has been studied for different hydrogen concentrations by means of electrical resistivity measurements in hydrogen-doped tantalum wires. (Auth.)

[en] By means of an experimental technique which makes use of the so-called modified Angstrom method, the thermal diffusivity D of some noninsulated tantalum, niobium and copper wires has been measured over a certain range of thermal-oscillation frequency, together with the thermal-loss coefficient which takes into account the heat losses through the lateral surface of the specimen by radiation, conduction and convection. The results give for the thermal diffusivity of the three metals values which are independent of frequency and in good agreement with the literature; on the other hand, the thermal-loss coefficient μ has been found to depend upon frequency. The same measurements led to the evaluation of the characteristic propagation parameters of these thermal waves, such as the phase velocity v, the wave number ß and the attenuation coefficient α. The quantity μ⁰=1/2 αv, which is also related to the thermal losses, was found to depend on the oscillation frequency according to the linear relationship μ⁰=a+bß; the values of the parameter a depend essentially on the physical condition of the surrounding medium, while the parameter b appears as a property of the surface of the specimen itself. For a frequency of 0.01 Hz the phase velocity at room temperature was about 0.22 cm.s^-₁ for tantalum, 0.18 cm.s^-₁ for niobium and 0.40 cm.s^-₁ for copper. The experimental method appears very reliable and suitable for determining the thermal diffusivity and then the thermal conductivity of solids on a wide range of temperature independently of the thermal losses of the specimen; on the other hand, it gives at the same time the values of the surface thermal conductance, which are rather important in connection with the physical properties of the surface of the specimen

[en] The Brillouin light scattering technique has been exploited in situ to study the magnetic properties of ultrathin Fe films, grown on a Cu(1 1 1) single crystal substrate, during the FCC/BCC phase transition. A determination of the magnetic parameters and of the anisotropy constants was achieved

[en] Graphite is a an interesting material for plasma-facing components in fusion experiments, mainly because of its low atomic number and excellent thermal properties. Nevertheless, it contains a large amount of gaseous impurities, which can be released by plasma-surface interactions and affect the purity of the deuterium-tritium plasma. To investigate the outgassing behaviour of graphites, CFC's and doped C composites, a facility was set up to perform outgassing tests on samples, as a function of temperature in the range between 100 and 1600 degrees C. The experimental apparatus, designed to work in UHV conditions, allows outgassing measurements by a quadrupole mass spectrometer (1-200 AMU) using two different methods. The test facility, the quadrupole calibration and preliminary quantitative outgassing measurements on SEP CARB N112 samples are described

[en] The properties of carbon films on metallic surfaces at 77 K, which is approximately the FTU (Frascati Tokamak Upgrade) wall temperature, have been studied for the first time. Very good results up to a maximum film thickness of 3 μm have been obtained. Evidence of blistering on the sample surface appeared only when the current density, during carbonization, exceeded considerably the value of 15 μA/cm². (orig.)

No abstract available

[en] Graphite is a an interesting material for plasma-facing components in fusion experiments, mainly because of its low atomic number and its excellent thermal properties. Nevertheless, it contains a large amount of gaseous impurities, which can be released by plasma-surface interaction and affect the purity of the deuteriumtritium plasma. To investigate the outgassing behaviour of graphites, CFCs and doped C composites, a facility has been set up to perform outgassing tests on samples (dim. 0.02x0.02x0.005 m), as a function of temperature in the range between 373 and 1873 K. The experimental apparatus, designed to work in UHV conditions, allows outgassing measurements by a quadrupole mass spectrometer (1-200 AMU), using two different methods. The test facility, the quadrupole calibration and quantitative outgassing measurements on SEP CARB NU2_and DIINLQP y graphites ase described. (author)

[en] The comprehension of the current re-distribution phenomenon inside multi-filamentary conductors is a crucial point for the design of ITER-relevant coils, as it is by now assessed that current non-uniformity among cable sub-stages may strongly deteriorate Cable-in-Conduit Conductors (CICC) performances. The only feasible way to get information about the current flowing inside CICC sub-stages is an indirect evaluation by self-field measurements in regions very close to conductor surface. A 7m full-size NbTi conductor (Bus-Bar III) has been used as short-circuit during the test of an ITER Toroidal Field Coil HTS current lead at FzK. Its relatively simple shape and the absence of any other magnetic field source (background coils, etc.), made BBIII one of the most desirable candidate for a reliable measurement of the current distribution under controlled conditions. This is why it has been ad hoc instrumented with different arrangements of Hall-probes (rings and arrays), as well as with transverse and longitudinal voltage taps. This paper gives a qualitative interpretation of the current (re-)distribution events inside the conductor as derived from the analysis of the Hall sensors and the voltage taps signals, during Tcs measurements and as a function of different dI/dt. It has been shown that Hall probes represent a very reliable tool to investigate this issue. In fact, re-distribution phenomena have been clearly observed during transition, and even far before reaching Tcs, when voltage transverse signals had not yet showed any appreciable onset

[en] A dedicated facility prepared by ENEA (Italian Agency for Energy and Environment) for the cryogenic testing of by-pass diodes for the protection of the CERN Large Hadron Collider main magnets will be described. This experimental activity is in the frame of a contract awarded to OCEM, an Italian firm active in the field of electronic devices and power supplies, in collaboration with ENEA, for the manufacture and testing of all the diode stacks. In particular, CERN requests the measurement of the reverse and forward voltage diode characteristics at 300 K and 77 K, and endurance test cycles at liquid helium temperature. The experimental set-up at ENEA and data acquisition system developed for the scope will be described and the test results reported