Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb at 4 K and seems to have much less power dependence than high-Tc materials such as YBCO. However, it was also found that it will depend on the way you dep...

Niobium is a dosimeter used to characterize fast-neutron reaction rates monitor nuclear reactor vessels. Its characterization based on the activity of 93m Nb resulting from 93 Nb(n,n’) activation reaction. The decay results mainly in emission niobium K X-rays which are determine Nb. Direct measurement using X-ray spectrometry does not require any sample preparation, but fluorescence effects, du...

In this work, TT niobia-phase nanocrystals with controlled morphology were obtained by the hydrothermal treatment of a niobium peroxo complex precursor at very low temperatures. The materials obtained by this route presented a very high surface area (ranging from 79 to 327 m(2)/g), disordered NbO(6), NbO(7), and NbO(8) polyhedra, Nb-O superficial sites, and a superficial OH group, which must ha...

We discuss the microwave energy losses in superconductors in the critical state. The field-induced variations of the surface resistance are determined, in the framework of the Coffey and Clem model, by taking into account the distribution of the vortex magnetic field inside the sample. It is shown that the effects of the critical state cannot generally be disregarded to account for the experime...

Recent results at 1 THz using normal-metal tuning circuits have shown that SIS mixers can work well up to twice the gap frequency of the junction material (niobium). However, the performance at 1 THz is limited by the substantial loss in the normal metal films. For better performance superconducting films with a higher gap frequency than niobium and with low RF loss are needed. Niobium nitride ...

The growth of niobium carbide in austenite involves the diffusion of both niobium and carbon. These elements diffuse at very different rates. A model is presented for the overall transformation kinetics of niobium carbide precipitation in austenite that takes into account the multicomponent nature of the diffusion process while at the same time allows for the curvature of the transformation fro...

For a TeV energy particle physics, R&D of electron/positron linear colliders has been conducted very hard at many laboratories. Development of high field gradient cavities is one of key issues to realize such a machine. Field emission loading is a dominant phenomenon limiting high field. Particulate contamination on the inner surface is a main source of field emission. In this paper, we report ...

We characterize low-loss electron-beam evaporated niobium thin films deposited under ultra-high vacuum conditions. Slow deposition yields with a high superconducting transition temperature ( 9.20±0.06 K) as well residual resistivity ratio of 4.8. fabricate the into coplanar waveguide resonators to extract intrinsic loss due presence two-level-system fluctuators using microwave measurements. For...

Ceramic samples of polycomponent solid solution (Y0.96Eu0.01Sm0.01Tb0.01Er0.01)Nb0.7Ta0.3O4 have been prepared by sol–gel synthesis from fine powders obtained using nitrate solutions rare earth elements REE and coprecipitated hydroxides niobium tantalum. The structural state the initial powders’ crystal lattice has investigated. morphological features microstructure ceramics studied in dependen...