Metal frame as local protection of superconducting films from thermomagnetic avalanches

Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them. The level of screening depends on the ratio of the sheet conductance of the metal and the superconductor in the resistive state, and for ratios much larger than unity the screening is very efficient

Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films

Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical imaging and voltage measurements allowed the pulses to be associated with individual flux branches penetrating the superconductor below the metal coating. From detailed characteristics of pulse and flux branches, the electrical field in the superconductor is found to be in the range of 5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close to 5 km/s. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing

Recepční pulty

The theoretical part deals with the reception desks in terms of their history, typology and functional possibilities. The market research part is devoted to the description of lighting, colours, dimensions and materials used in reception desks. The design of reception desk is the subject of the practical part and is based on the results of the theoretical part