Solveig Anders

Sub-micrometer-sized, cross-type Nb―AlOx―Nb tunnel junctions with low parasitic capacitance

We report on a technology for the fabrication of sub-micrometer sized cross-type Josephson tunnel junctions in niobium technology. We present the fabrication scheme and properties of cross-type junctions with linear dimensions from 10 down to 0.6??m. Sidewall passivation of the junctions is achieved by anodization as well as by planarizing the junctions with SiO in a self-aligned deposition step. The measured ratio of the sub-gap resistance to the normal resistance is about 35. Because of their low sub-gap current and low parasitic capacitance such junctions are well suited for applications like high resolution SQUIDs.

Toward high-sensitivity and high-resolution submillimeter-wave video imaging

Against a background of newly emerged security threats, the well-established idea of utilizing submillimeter-wave radiation for personal security screening applications has recently evolved into a promising technology. Possible application scenarios demand sensitive, fast, flexible and high-quality imaging techniques. At present, best results are obtained by passive imaging using cryogenic microbolometers as radiation detectors. Building upon the concept of a passive submillimeter-wave stand-off video camera introduced previously, we present the evolution of this concept into a practical application-ready imaging device. This has been achieved using a variety of measures such as optimizing the detector parameters, improving the scanning mechanism, increasing the sampling speed, and enhancing the image generation software. The camera concept is based on a Cassegrain-type mirror optics, an optomechanical scanner, an array of 20 superconducting transition-edge sensors operated at a temperature of 450 to 650 mK, and a closed-cycle cryogen-free cooling system. The main figures of the system include: a frequency band of 350±40 GHz, an object distance of 7 to 10 m, a circular field of view of 1.05 m diameter, and a spatial resolution in the image center of 2 cm at 8.5 m distance, a noise equivalent temperature difference of 0.1 to 0.4 K, and a maximum frame rate of 10 Hz.

Investigation of all niobium nano-SQUIDs based on sub-micrometer cross-type Josephson junctions

We report on the development of highly sensitive SQUIDs featuring sub-micrometer loop dimensions. The integration of high quality and low capacitance SIS Nb/AlOx/Nb cross-type Josephson tunnel junctions results in white flux noise levels as low as 66 n

First Direct Comparison of a Cryocooler-Based Josephson Voltage Standard System at 10 V

\Phi_0

SQUIDs based on submicrometer-sized Josephson tunnel junctions fabricated in a cross-type technology

/Hz

SQUID-based setup for the absolute measurement of the Earth?s magnetic field

^{ 1/2}

Development of passive submillimeter-wave video imaging systems for security applications

, well below state-of-the-art values of their Nb-based counterparts based on constriction type junctions. Estimation of the spin sensitivity of the best SQUIDs yield

Progress report on Safe VISITOR: approaching a practical instrument for terahertz security screening

S_\mu^{ 1/2} < 7 \mu_B

Design, realization, and characteristics of a transition edge bolometer for sub-millimeter wave astronomy

/Hz

On-chip integrated SQUID readout for Superconducting bolometers

^{ 1/2}