Hypres, Inc.

Wisconsin Alumni Research Foundation

The United States of America As Represented by the United States

Sandia Corporation

Gert K Hohenwarter

Jon S Martens

Vincent Mark Hietala

James B Beyer

James E Nordman

Sadeg Mustafa Faris

David Samuel Ginley

Gregory A Vawter

Thomas E Zipperian

Chris P Tigges

Thomas A Plut

Stephen R Whiteley

John A Grange

A process for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO.sub.3 crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O.sub.3, followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry.

High temperature superconductor step-edge Josephson junctions using

A HTS switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time.

Reflective HTS switch

Apparatus and method for determining and imaging superconductor surface resistance. The apparatus comprises modified Gaussian confocal resonator structure with the sample remote from the radiating mirror. Surface resistance is determined by analyzing and imaging reflected microwaves; imaging reveals anomalies due to surface impurities, non-stoichiometry, and the like, in the surface of the superconductor.

Apparatus and method for measuring and imaging surface resistance

A superconducting active device has dual control inputs and is constructed such that the output of the device is effectively a linear mix of the two input signals. The device is formed of a film of superconducting material on a substrate and has two main conduction channels, each of which includes a weak link region. A first control line extends adjacent to the weak link region in the first channel and a second control line extends adjacent to the weak link region in the second channel. The current flowing from the first channel flows through an internal control line which is also adjacent to the weak link region of the second channel. The weak link regions comprise small links of superconductor, separated by voids, through which the current flows in each channel. Current passed through the control lines causes magnetic flux vortices which propagate across the weak link regions and control the resistance of these regions. The output of the device taken across the input to the main channels and the output of the second main channel and the internal control line will constitute essentially a linear mix of the two input signals imposed on the two control lines. The device is especially suited to microwave applications since it has very low input capacitance, and is well suited to being formed of high temperature superconducting materials since all of the structures may be formed coplanar with one another on a substrate.

Dual control active superconductive devices

Active superconducting devices are formed of thin films of superconductor which include a main conduction channel which has an active weak link region. The weak link region is composed of an array of links of thin film superconductor spaced from one another by voids and selected in size and thickness such that magnetic flux can propagate across the weak link region when it is superconducting. Magnetic flux applied to the weak link region will propagate across the array of links causing localized loss of superconductivity in the links and changing the effective resistance across the links. The magnetic flux can be applied from a control line formed of a superconducting film deposited coplanar with the main conduction channel and weak link region on a substrate. The devices can be formed of any type to superconductor but are particularly well suited to the high temperature superconductors since the devices can be entirely formed from coplanar films with no overlying regions. The devices can be utilized for a variety of electrical components, including switching circuits, amplifiers, oscillators and modulators, and are well suited to microwave frequency applications.

Active superconducting devices formed of thin films

A system for delivering a cryogenic fluid to cool devices, such as electronic devices, in an open-cycle environment. The system comprises a dewar which stores a cold fluid, a cryogenic module for holding a device to be cooled and a cold fluid transfer line which delivers the cold fluid from the dewar to the device within the cryogenic module. The system further comprises an interlock mechanism to hold the transfer line and the dewar securely together and a coupling mechanism to allow the transfer line to securely engage the cryogenic module. The system also comprises a control subsystem which monitors and controls the flow of cold fluid from the dewar and through the transfer line.

Cryogenic fluid delivery system

A monolithic chip is described which is suited for a superconductive device. The chip includes a substrate with high and low temperature region, a superconductive device formed on the low temperature region and various lines for transmitting signals between the device and the high temperature region. Various configurations are described for optional separation of the high and low temperature region as well as high and low bandwidth signal lines. Chips with various geometric substrates are also described.

Low temperature monolithic chip

Apparatus and a method are disclosed for cooling a low temperature circuit substrate without the need for a vacuum chamber or total immersion, involving subjecting the circuit to a stream of cold fluid, such as liquid helium, and allowing the fluid thereafter to dissipate into the surrounding environment. The apparatus may include an enclosure for holding the circuit, and means for guiding the fluid onto another portion of the substrate after it strikes the circuit. The exit path for the fluid may fold back past the circuit so as to help convect out heat which enters the vicinity radially from the outside. The circuit may also be cooled indirectly by directing the stream of cold fluid through a thermally conductive block, the block having a small surface thermally connectable to the circuit. Additionally, radiation shields may be placed at desired locations in the apparatus and can be cooled by the waste fluid after it cools the circuit.

Growing community of inventors

Madison, WI, United States of America

Gert K Hohenwarter