Search

Your search keyword '"Maasilta, I. J."' showing total 213 results
Start Over Author "Maasilta, I. J."
213 results on '"Maasilta, I. J."'

52. Energy of dendritic avalanches in thin-film superconductors

Author

Qureishy, T, Vestgarden, J I, Qviller, A J, Fjellvag, A S, Meckbach, J M, Torgovkin, A, Johansen, Tom H, Ilin, K, Siegel, M, Maasilta, I J, Mikheenko, Pavlo, Qureishy, T, Vestgarden, J I, Qviller, A J, Fjellvag, A S, Meckbach, J M, Torgovkin, A, Johansen, Tom H, Ilin, K, Siegel, M, Maasilta, I J, and Mikheenko, Pavlo

Abstract

A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great advantage, because of their unpredictable and non-reproducible nature. The relative losses in energy are much higher than the relative losses in moment.

Published
2018

53. Thermoelectric radiation detector based on superconductor-ferromagnet systems

Author

Academy of Finland, European Commission, Ministerio de Economía, Industria y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Heikkilä, T. T., Ojajärvi, Risto, Maasilta, I. J., Strambini, Elia, Giazotto, Francesco, Bergeret, F. S., Academy of Finland, European Commission, Ministerio de Economía, Industria y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Heikkilä, T. T., Ojajärvi, Risto, Maasilta, I. J., Strambini, Elia, Giazotto, Francesco, and Bergeret, F. S.

Abstract

We suggest an ultrasensitive detector of electromagnetic fields exploiting the giant thermoelectric effect recently found in superconductor-ferromagnet hybrid structures. Compared with other types of superconducting detectors where the detected signal is based on variations of the detector impedance, the thermoelectric detector has the advantage of requiring no external driving fields. This is especially relevant in multipixel detectors, where the number of bias lines and the heating induced by them are an issue. We propose different material combinations to implement the detector and provide a detailed analysis of its sensitivity and speed. In particular, we perform a proper noise analysis that includes the cross correlation between heat and charge current noise and thereby describes also thermoelectric detectors with a large thermoelectric figure of merit.

Published
2018

59. Metal frame as local protection of superconducting films from thermomagnetic avalanches

Author

Mikheenko, Pavlo, Vestgarden, J I, Chaudhuri, Supratim, Maasilta, I J, Galperin, Y, Johansen, Tom H, Mikheenko, Pavlo, Vestgarden, J I, Chaudhuri, Supratim, Maasilta, I J, Galperin, Y, and Johansen, Tom H

Abstract

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.

Published
2016

61. Broadband Ultrahigh-Resolution Spectroscopy of Particle-Induced X Rays: Extending the Limits of Nondestructive Analysis

Author

Palosaari, M. R. J., primary, Käyhkö, M., additional, Kinnunen, K. M., additional, Laitinen, M., additional, Julin, J., additional, Malm, J., additional, Sajavaara, T., additional, Doriese, W. B., additional, Fowler, J., additional, Reintsema, C., additional, Swetz, D., additional, Schmidt, D., additional, Ullom, J. N., additional, and Maasilta, I. J., additional

Published
2016
Full Text
View/download PDF

66. Stability, sub-gap current, 1/f-noise, and elemental depth profiling of annealed Al:Mn-AlOx-Al normal metal-insulator-superconducting tunnel junctions.

Author

Julin, J. K., Chaudhuri, S., Laitinen, M., Sajavaara, T., and Maasilta, I. J.

Subjects
ANNEALING of metals, TUNNEL junctions (Materials science), SUPERCONDUCTORS
Abstract

In this paper we report a study of the effect of vacuum annealing at 400°C on the properties of normal metal-insulator-superconductor (NIS) tunnel junctions, with manganese doped aluminium (Al:Mn) as the normal metal, aluminum as the superconductor and amorphous aluminum oxide as the tunneling barrier (Al:Mn-AlOx-Al). The annealing treatment improves the stability of the junctions, increases their tunneling resistance and does not have a negative impact on the low-temperature current-voltage characteristics. The measured 1 / f resistance noise of the junctions also changes after annealing, in the best case decreasing by over an order of magnitude. All these observations show that annealing is a viable route to improve NIS junction devices after the sample has been fabricated. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

69. Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films

Author

Mikheenko, P, Qviller, A J, Vestgarden, J I, Chaudhuri, S, Maasilta, I J, Galperin, Y M, Johansen, Tom H, Mikheenko, P, Qviller, A J, Vestgarden, J I, Chaudhuri, S, Maasilta, I J, Galperin, Y M, and Johansen, Tom H

Abstract

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.

Published
2013

70. Transition-Edge Sensors for Particle Induced X-ray Emission Measurements

Author

Palosaari, M. R. J., primary, Kinnunen, K. M., additional, Julin, J., additional, Laitinen, M., additional, Napari, M., additional, Sajavaara, T., additional, Doriese, W. B., additional, Fowler, J., additional, Reintsema, C., additional, Swetz, D., additional, Schmidt, D., additional, Ullom, J., additional, and Maasilta, I. J., additional

Published
2013
Full Text
View/download PDF

72. Table-Top Ultrafast X-Ray Microcalorimeter Spectrometry for Molecular Structure

Author

Uhlig, J., primary, Fullagar, W., additional, Ullom, J. N., additional, Doriese, W. B., additional, Fowler, J. W., additional, Swetz, D. S., additional, Gador, N., additional, Canton, S. E., additional, Kinnunen, K., additional, Maasilta, I. J., additional, Reintsema, C. D., additional, Bennett, D. A., additional, Vale, L. R., additional, Hilton, G. C., additional, Irwin, K. D., additional, Schmidt, D. R., additional, and Sundström, V., additional

Published
2013
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results