Magnetic hysteresis effects in superconducting coplanar microwave resonators

We performed transmission spectroscopy experiments on coplanar half wavelength niobium resonators at a temperature T=4.2 K. We observe not only a strong dependence of the quality factor Q and the resonance frequency f_res on an externally applied magnetic field but also on the magnetic history of our resonators, i.e. on the spatial distribution of trapped Abrikosov vortices in the device. We find these results to be valid for a broad range of frequencies and angles between the resonator plane and the magnetic field direction as well as for resonators with and without antidots near the edges of the center conductor and the ground planes. In a detailed analysis we show, that characteristic features of the experimental data can only be reproduced in calculations, if a highly inhomogeneous rf-current density and a flux density gradient with maxima at the edges of the superconductor is assumed. We furthermore demonstrate, that the hysteretic behaviour of the resonator properties can be used to considerably reduce the vortex induced losses and to fine-tune the resonance frequency by the proper way of cycling to a desired magnetic field

Feuersalamander - Salamandra salamandra

Der Feuersalamander (Salamandra salamandra) ist eine von 18 in Sachsen vorkommenden Amphibienarten. Dieser Schwanzlurch kann etwa 20 cm lang werden und ist mit seiner gelben Flecken- oder Streifenzeichnung auf schwarzem Grund unverwechselbar. Diese signalisiert seinen Feinden, dass er nicht genießbar ist, denn auf seiner Haut befinden sich Drüsen, aus denen er das Gift Samandarin absondert. Deshalb haben erwachsene Feuersalamander auch kaum Feinde. In Gefangenschaft können die Tiere über 50 Jahre alt werden. Jeder Salamander besitzt ein individuelles Fleckenmuster und so kann man die Lurche in freier Wildbahn über lange Zeit beobachten. Bereits bei den mit Büschelkiemen ausgestatteten Larven kann man an jedem Beinansatz einen gelben Fleck erkennen, was sie von den sehr ähnlichen Molchlarven unterscheidet. Zur besseren Abschätzung des Gesamtvorkommens sowie von Rückgangs- bzw. Verlustursachen werden zurzeit alle potenziellen Lebensräume sowie frühere Fundorte auf das aktuelle Vorkommen der Art überprüft. Hierfür brauchen wir Ihre Mithilfe. Wenn Sie Feuersalamander oder deren Larven entdeckt haben, dann schreiben Sie uns Ihre Beobachtung mit Anzahl, Ort, Datum sowie Fundumstände bzw. Verhalten, wenn möglich mit Foto, per Post oder E-Mail an: Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie, Ref. 62 Artenschutz, Stichwort „Feuersalamander“, Pillnitzer Platz 3, 01326 Dresden oder per E-Mail an: [email protected] Redaktionsschluss: 29.08.201

Timing jitter in photon detection by straight superconducting nanowires: Effect of magnetic field and photon flux

We studied the effect of the external magnetic field and photon flux on timing jitter in photon detection by straight superconducting NbN nanowires. At two wavelengths 800 and 1560 nm, statistical distribution in the appearance time of the photon count exhibits Gaussian shape at small times and exponential tail at large times. The characteristic exponential time is larger for photons with smaller energy and increases with external magnetic field while variations in the Gaussian part of the distribution are less pronounced. Increasing photon flux drives the nanowire from quantum detection mode to the bolometric mode that averages out fluctuations of the total number of nonequilibrium electrons created by the photon and drastically reduces jitter. The difference between Gaussian parts of distributions for these two modes provides the measure for the electron-number fluctuations. Corresponding standard deviation increases with the photon energy. We show that the two-dimensional hot-spot detection model explains qualitatively the effect of magnetic field

An inexpensive phantom for evaluating gated blood pool data acquisition/processing systems at heart rates above 400/min

Proceeding of: 1998 IEEE Nuclear Science Symposium and Medical Imaging Conference, Toronto, Ont., 08 - 14 Nov. 1998Equilibrium gated blood pool imaging of the heart is a common diagnostic procedure for visualizing cardiac function in human subjects. Recently, this procedure has been modified to evaluate cardiac function in mice. However, the high heart rates encountered in these animals (often greater than 400 beatdmin) can confound R-wave trigger devices, acquisition systems and image processing software containing default conditions tailored specifically to the lower heart rates of human subjects. In order to determine whether data acquisition and processing components of a commercial or self-generated gated blood pool imaging procedure are performing properly, input of known timing and imaging signals that mimic those generated during high heart rate gated blood pool imaging is required. Here, we describe an inexpensive phantom that is suitable for initial evaluation of an unknown system or for ongoing QC of a previously verified system.Publicad