Thin Film Superconducting Devices

Techniques have been developed with which it is possible to fabricate superconducting thin film structures (“bridges”) which show Josephson-like phenomena, with a wide variety of electrical and superconducting parameters. These bridges—based on the proximity effect—are made in layered thin film substrates which have been fabricated from many different, both hard and soft, superconducting materials. The fabrication techniques and the electrical and superconducting characteristics for these proximity effect bridges including a simple low frequency (≤10 GHz) equivalent circuit will be discussed. These bridges have been incorporated into simple thin film circuits for use as galvanometers, magnetometers, gradiometers, detector arrays, etc. Extension of these techniques to more complex superconducting thin film bridge circuits including resistors, capacitors, and inductors will be indicated

Microelectronic fabrication of superconducting devices and circuits

It is expected that thin-film superconductors can be used as detectors or sources of infrared and microwave radiation, as magnetometers, as voltage standards, and for voltage and current measurements, for electronic signal processing, and in digital circuitry

Performance of a superconducting cavity stabilized ruby maser oscillator

We first described an all-cryogenic oscillator system at the 1982 Applied Superconductivity Conference in Knoxville. This oscillator consists of a ruby cavity maser stabilized by a high-Q superconductor-on-sapphire resonator. The maser provides gain with very low noise and small power dissipation, while the sapphire substrate's thermal coefficient of expansion is 100 times smaller than that of superconducting metals. Having tested the major components and proved them satisfactory to the design, we have now assembled the first such oscillator and tested its performance in several preliminary configurations. The results of stability tests in a more advanced configuration will be reported. We shall describe this oscillator and shall report on its performance as a high-stability frequency source

Microwave surface resistance of Nb films

The surface resistance, R_s, of niobium (Nb) films has been experimentally investigated as a function of thickness, preparation technique and substrate material at 8.86 GHz. Nb films were prepared by either sputtering or evaporation in the thickness range Between 0.1 μm and 3.0 μm on either copper (Cu) or sapphire substrate. R_s was determined using a cylindrical TE011mode resonant cavity with one removable end-plate which was utilized as the test substrate. The low field R_s at 4.2 K is lower than that of bulk Nb and shows good agreement with BCS calculation which takes into account the effects of mean free path. The temperature dependence of R_s indicates a normalized film gap parameter, Δ(0)/KTc, nearly equivalent to the bulk value for most of the films. At low temperatures, Rsis dominated by residual resistance (R0) which approaches 1 μΩ. The overall characteristics of Nb on Cu (Nb/Cu) indicate that this composite material is potentially useful in applications requiring high rf field as well as high thermal stability

Magneto-chemical studies with a new ultrasensitive superconducting quantum magnetometer

A magnetometer utilizing quantum superconductivity as the basis for the flux sensor element has been designed and used for biochemical susceptibility measurements in the temperature range from 1.5°K to 300°K. The sensitivity and reproducibility of this instrument have been tested by measurements on small amounts of material of well-known susceptibilities. Using this instrument the temperature dependence of the magnetic susceptibilities of oxy- and metaquohemerythrin have been measured and for the first time their anti-ferromagnetic components have been unambigiously resolved. From this data the exchange coupling constants between the two high-spin iron (III) atoms in each subunit have been determined to be -77 and -134 cm^(-1) respectively

Status of the Stony Brook Superconducting Heavy-Ion Linac

The present status of the Stony Brook Superconducting Heavy-Ion Linear Accelerator is described, with emphasis on recent operational results with a prototype unit of the accelerator. The basic LINAC elements are independently-phased lead-plated copper split-loop resonators operating at 151.7 MHz and optimized for velocities of either ß=v/c= 0.055 or ß=0.10. Resonators are grouped in units of either 4 low-ß or 3 high-ß resonators in compact cryostat modules separated by room-temperature quadrupole-doublet lenses. The LINAC consisting of 4 low-ß and 7 high-ß modules injected with heavy ions of mass A≃16-100 from the Stony Brook EN tandem will produce an additional energy gain of ~18 MeV per unit charge with a total heat dissipation at 4.5K of <300 Watts. In recent tests with low-ß prototype units, individual resonators were operated continuously at accelerating gradients in excess of 3.5 MV/m, and were phase and amplitude stabilized at 3.0 MV/ m using 175 Watts of RF power. Helium-temperature dissipation at 3.0 MV/m is ~8 Watts after helium-gas conditioning. The prototype low-ß module was used to accelerate a 30 Mev ^(16)O^(5+) beam to ~35 MeV

Stock market integration for the transition economies: Time-varying conditional correlation approach

This is the accepted version of the following article: WANG, P. and MOORE, T. (2008), Stock market integration for the transition economies: Time-varying conditional correlation approach. The Manchester School, 76: 116–133. doi: 10.1111/j.1467-9957.2008.01083.x, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/j.1467- 9957.2008.01083.x/abstract.In this paper, we investigate the extent to which the three emerging Central Eastern European stock markets have become integrated with the aggregate eurozone market over the sample period from 1994 to 2006 by utilizing the dynamic conditional correlation. We find a higher level of the stock market correlation during the period after the Asian and Russian crises and also during the post-entry period to the European Union. It is found that financial market integration seems to be a largely self-fuelling process, depending on existing levels of financial sector development for the Czech Republic and Hungary

Real exchange rate in an inter-temporal n-country-model with incomplete markets

We develop an N-country model with stock markets in which closed-form solutions for the real exchange rate is derived. Our model allows for a given number of risky-assets, which form an incomplete market. Risky asset prices and allocations of risky assets among countries are determined endogenously. The risk-free rate is exogenous, so our model is an intermediate step toward a full general equilibrium. To work in such a framework allows an analysis of how fundamental parameters, such as the variance and covariance of the risky assets or demographic variables, affect the real exchange rate. We contrast the predictions of the model to the Balassa-Samuelson effect. We also suggest a new transmission channel of the real exchange rate for parameters such as income on net foreign assets, risk-aversion and risk-hedging opportunities. JEL Classification: F30, F31, F32, F41

Status of the Stony Brook Superconducting Heavy-Ion Linac

We describe the present status of the State University of New York at Stony Brook Superconducting Heavy-Ion LINAC (SUNYLAC). The LINAC will extend at very modest cost the capabilities of the existing FN tandem Van de Graaff into the energy range 5-10 MeV/A for light heavy-ions from oxygen to bromine. The active elements are 43 lead-plated copper superconducting resonators of the split-loop type optimized for either velocity ß=v/c=0.055 or ß=0.10. Phase and amplitude of each resonator is independently set through RF-feedback controllers interfaced to an overall computer control system. Full scale construction work began in July, 1979 following the in-beam demonstration of a prototype LINAC module containing 4 low-ß resonators, and the majority of the installation work on the beam transport and refrigeration systems was completed in the summer of 1980. The project is now well into its final assembly and testing phase, with the completion of assembly scheduled in early 1982. We describe details of the design of key elements of the LINAC and the initial operating experience with the injection beam path, helium refrigerator and first production accelerator module. The progress of a continuing program aimed at optimizing crucial aspects of the LINAC is also reviewed