The introduction of artificial pinning sites in YBa2 Cu3O7−d (YBCO) epitaxial thin films has been\ud
obtained by pulsed laser deposition ͑PLD͒ technique from YBCO-BaZrO3 ͑BZO͒ composite targets\ud
with BZO concentration ranging from 2.5 to 7 mol %. The typical critical temperature, Tc , drop\ud
observed in YBCO-secondary phase films grown by PLD has been successfully recovered by\ud
increasing the deposition temperature. Transport properties analyses revealed improved pinning\ud
force values for YBCO-BZO films for BZO concentration above 5 mol %. These films exhibited an\ud
anomalous dual peak structure which has been ascribed to the presence of two pinning\ud
contributions. The crossover field, Bm , separating these two pinning regimes has been observed to\ud
be temperature independent suggesting the occurrence of the matching field effect. The measured\ud
value of Bm agreed with the matching field value, B⌽ = Knd⌽0 , as evaluated from transmission\ud
electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making\ud
YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below Bm in all\ud
the temperature range inspected. On the contrary, in the high magnetic field range ͑above Bm͒, the\ud
effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting\ud
that at low temperatures the dominant pinning contribution arises from isotropic pinning centers
The structural and chemical evolution of propionate based low fluorine
YBa2Cu3O7 − δ
(YBCO) precursor during the conversion thermal treatment to obtain
superconducting film has been investigated by both x-ray photoelectron
and diffraction techniques in a set of partially converted films on
SrTiO3
single crystals. The pyrolysis temperature within the range 400–480 °C
mainly affects the copper valence state with an increase of the
Cu2 +
fraction with temperature with respect to the
Cu1 +
oxidation state. During the subsequent thermal treatment up to
700 °C, the reduction of fluorine content is mainly ascribed to the hydrolysis of
YF3. At higher temperatures,
Ba hydrolysis, Y2Cu2O5
and YBCO phase formation (nucleation at
700 °C and
725 °C,
respectively) have been observed. The temperature dependences of the formation and decomposition of
YBCO, Y2Cu2O5
and Ba-oxyfluoride were evaluated by x-ray diffraction measurements. The reaction path
emerging from these analyses agrees with the one observed for YBCO films obtained
with the standard MOD method based on metal tri-fluoroacetate precursors.
The DEMO reactor is expected to be the first application of fusion for electricity generation in the near future. To this aim conceptual design activities are progressing in Europe (EU) under the lead of the EUROfusion Consortium in order to drive on the development of the major tokamak systems. In 2014 the activities carried out by the magnet system project team were focused on the Toroidal Field (TF) magnet system design and demonstrated major achievements in terms of concept proposals and of consolidated evaluations against design criteria. Several magnet system R&D activities were conducted in parallel, together with broad investigations on High Temperature Superconductor (HTS) technologies. In this paper we present the outcomes of the work conducted in two areas in the 2014 magnet work program: (1) the EU inductive reactor (called DEMO1) 2014 configuration (power plant operating under inductive regime) was the basis of conceptual design activities, including further optimizations; and (2) the HTS R&D activities building upon the consolidated knowledge acquired over the past years
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