[en] A voltage calibrator with self-calibrating components for operation at liquid nitrogen temperature is to be developed on the basis of high-temperature superconductors (HTSL). As the production technology of HTSL-Josephson contacts is still deficient, the voltage calibrator is to be simplified as compared to the quantum voltmeter. Parallel to the development of the quantum voltmeter on the basis of classic superconductors in the context of the other part-projects, serial circuits of shunted HTSL contacts will be enlarged, optimized by microwave technology, and used for step-by-step optimisation of the voltage calibrator so as to make it work with sufficient accuracy. The feasibility for commercial use at a later stage will be demonstrated by a laboratory-scale unit. (orig.)

[en] In this report we present results of a systematical study of relevant properties of superconducting Nb thin films of thickness from 8 to 200 nm deposited on Si. We have found that a reduction of thickness d below 50 nm leads to a significant decrease of the critical temperature T_C and a strong increasing of the residual resistivity in normal state ρ₀ and a strong increase of the Ginzburg-Landau magnetic penetration depth λ_GL(0). Taking into account the dependencies of T_C and ρ₀ on the thickness of the film, we have obtained good agreement between experimental dependencies of λ_GL(0) on d and theoretical estimations in dirty limit for films thinner than 100 nm

[en] As device dimensions shrink for VLSI circuitry, the demands for increased electromigration resistance, better step coverage and lower contact resistance require the development of new interconnection processes. Chemical vapor deposition (CVD) of tungsten with characteristically low deposition temperature, low contact resistance, high electromigration resistance and conformal step coverage, even at aspect ratios greater than one, has shown great promise as an advanced interconnect metallurgy. Magnetron-enhanced reactive ion etching with an MRC Aries has been used to fabricate tungsten contact plugs in micron and sub-micron vias, using a photoresist/tungsten planarization etch process that results in maximum filling of the tungsten plug. This paper describes the characteristics of low-pressure magnetically enhanced reactive ion etching which gives it unique ability to meet the process requirements for tungsten contact plug fabrication. Specifically, the process characteristics and advantages of magnetically enhanced etching for this application are discussed

[en] The recent results for a superconducting single-photon counter are presented. The detection mechanism of the photon counter is based on the combined action of the hot-spot formation after photon absorption and the subsequent current-assisted formation of a normal domain in a thin and narrow superconducting strip. Dark count rates caused by fluctuations of the superconducting order parameter as a function of the applied current are discussed

[en] We present a new numerical method for calculating an evolving 2D Hele-Shaw interface when surface tension effects are neglected. In the case where the flow is directed from the less viscous fluid into the more viscous fluid, the motion of the interface is ill-posed; small deviations in the initial condition will produce significant changes in the ensuing motion. The situation is disastrous for numerical computation, as small roundoff errors can quickly lead to large inaccuracies in the computed solution. Our method of computation is most easily formulated using a conformal map from the fluid domain into a unit disk. The method relies on analytically continuing the initial data and equations of motion into the region exterior to the disk, where the evolution problem becomes well-posed. The equations are then numerically solved in the extended domain. The presence of singularities in the conformal map outside of the disk introduces specific structures along the fluid interface. Our method can explicitly track the location of isolated pole and branch point singularities, allowing us to draw connections between the development of interfacial patterns and the motion of singularities as they approach the unit disk. In particular, we are able to relate physical features such as finger shape, side-branch formation, and competition between fingers to the nature and location of the singularities. The usefulness of this method in studying the formation of topological singularities (self-intersections of the interface) is also pointed out. 47 refs., 10 figs., 1 tab

[en] Eleven children in whom a retropertioneal neuroblastoma was suspected on the basis of plain radiographic or urographic findings underwent computed tomography (CT). CT identified and localized a neurogenic tumor in eight patients. Calcifications were demonstrated by CT in six lesions, but by urography in only four. One neuroblastoma detected by CT was not seen on the urogram; in five patients greater extent of the tumor was defined by CT than by conventional radiologic procedures. In three patients CT excluded a neuroblastoma, but diagnosed other disorders (hepatic tumor, pancreatitis, and retrocaval ureter). Our results confirm that CT is a simple and accurate method for diagnosis, delineation of extent, or exclusion of neuroblastoma

[en] The EPA Standard for geologic disposal of high level waste requires demonstration that the cumulative discharge of individual radioisotopes over a 10,000 year period at points 5 kilometers from the engineered barrier system will not exceed the limits prescribed in 40 CFR Part 191. The roles of the waste package, engineered facility, hydrogeology and geochemical processes in limiting radionuclide releases all must be considered in calculations designed to assess compliance of candidate repositories with the EPA Standard. In this talk, they will discuss the geochemical requirements of calculations used in these compliance assessments. In addition, they will describe the complementary roles of (1) simple models designed to bound the radionuclide discharge over the widest reasonable range of geochemical conditions and scenarios and (2) detailed geochemical models which can provide insights into the actual behavior of the radionuclides in the ground water. Finally, they will discuss development of sensitivity/uncertainty techniques designed to identify important site-specific geochemical parameters and processes using data from a basalt formation

[en] We are studying flux qubits based on Nb/Al/Al₂O₃/Nb tunnel junctions. The qubit consists of three Josephson tunnel junctions connected in series in a superconducting loop and is read out by an inductively coupled SQUID. In order to obtain a nondestructive readout, the SQUID is part of an LC circuit, whose resonant frequency depends on the inductance of the SQUID and hence on the qubit state. We have carried out numerical simulations in order to obtain values for the minimum energy level splitting Δ and the persistent current I_p. Suitable design parameters were found and the influence of possible parameter deviations due to fabrication tolerances was studied. Furthermore, we investigated methods to reduce the stray inductance of the readout LC circuit and hence increase the readout resolution. (orig.)

[en] Published in summary form only

[en] Published in summary form only