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A plug-in wire system is designed for a 200-pixel superconducting tunnel junction (STJ) X-ray detector array for a helium-3 cryostat. The STJ array and the room-temperature electronics are electrically connected by wire modules that have connectors at both ends. Two types of wire module are used to balance the electric conductance and thermal conductance under various temperature conditions. One type uses a copper-based miniature coaxial cable harness, and is utilized to electrically connect the room-temperature electronics to the 3 K stage. The other type uses woven wire looms of twisted-pairs of NbTi wire, and is used to electrically connect the 3 K stage to the helium-3 stage. With the installation of all wire modules, the temperature of the cold stage is less than 310 mK, and the holding time is more than 80 hours. The plug-in wire system is suitable for large-scale STJ X-ray detector arrays.

One of the most important factor of the superconducting tunnel junction for a particle and radiation detection is the sub-gap leakage current. An anodization of a junction edge is an effective method to reduce the sub-gap leakage current. In a new fabrication process of a Nb/Al-AlO/sub x/-Al/Nb junction, the sputtered Al/sub 2/O/sub 3/ layers with 10 nm thickness are used as not only the protection layer for the upper surface of both the base and counter electrodes in the anodization process, but also the etching stop layer for the formation of the contact hole by reactive ion etching process.

Mass spectrometry (MS) is a method of analyzing ions based on their mass/charge (m/z) ratios. The m/z peak identification requires speculation on the ionic unit-charge states. This problem can be solved by using superconducting junction devices to measure the kinetic energies of single molecules. However, the kinetic energy measurement is followed by the dead time of 1-20 µs, which is fatally slow for modern high-resolution time-of-flight (TOF) analyzers. In this paper, we demonstrate that a superconducting nano-stripline detector (SSLD) composed of a 10-nm-thick and 800-nm-wide NbN strip realizes the charge-state derivation, and furthermore satisfies the ideal MS detector specifications such as a nano-second response, a short recovery time, a wide mass range, and no noise.

We proposed a model of fault and slip formation to explain the excessive increase of the leak current of Nb/Al superconducting tunnel junction detectors and the nano‐structural deformation. Observations of the cross‐sections at pinpoint places in the array detectors with transmission electron microscopy (TEM) support our model. The nano‐scale tectonism due to the relaxation of the residual stress in the sputtered films, which corresponds to a wafer bend motion at a few tens nm at 10 mm‐apart two points, generates the vertical fault in the Nb/Al film and the slip plane in the 1 nm‐thick AlOx tunneling layer. The slip in the AlOx layer can cause the leak current increase.

Superconducting-tunnel-junction (STJ) array detectors have exhibited excellent characteristics for fluorescence-yield x-ray absorption fine structure (XAFS) for trace light elements in structural and functional materials. For XAFS, we have developed new fabrication processes for close-packed STJ pixels by using a three-dimensional structure (3D-STJ), in which the layers of STJ pixels are formed after caldera planarization of the base SiO2 layer deposited on the patterned wiring leads. The 3D-STJ has an operation yield of 88% and a mean energy resolution of 23.8 +/−1.9 eV for the C-Kα x-ray.

Future cosmic microwave background experiments for high-resolution anisotropy mapping and polarisation detection require large arrays of bolometers at low temperature. We have developed a process to build arrays of antenna-coupled bolometers for that purpose. With adjustment of the Nb x Si 1 - x alloy composition, the array can be made of high impedance or superconductive (TES) sensors.

Superconducting tunnel junction photon detectors, which exhibit high performance in a range between infrared and soft x-rays, are sensitive to magnetic flux quanta, so called vortices, trapped in the superconducting thin films. The vortex trapping easily occurs when a residual magnetic field is present. We have investigated the details of the dependence of vortex trapping patterns on the strength of magnetic fields perpendicular to the junction surface by using a scanning SQUID microscope in niobium-based tunnel junctions. It has been found that the vortices are not trapped near junction edges, which can be the cause of spatial inhomogeneity of signal heights, and that there is a threshold field for vortex trapping. The present results offer a guideline for magnetic shield designs in practical applications.

Spatial uniformity in the response of superconducting tunnel junction detectors (STJ) to photons is a main concern in the development of these devices. Low Temperature Scanning Synchrotron Microscopy (LTSSM) has been used to directly image spatial profiles of the response of Nb-based STJ to X-ray photons. Scanning an X-ray microbeam with a diameter of 5–10 μm enables visualization of the spectroscopic properties of STJ X-ray detectors at an actual working temperature of about 0.4 K. We have found that the inhomogeneity of the junction response strongly depends on the junction size, the bias points, and the strength of applied magnetic field parallel to the insulation barrier. It is proposed that some resonance phenomena in the junction may influence signal creation processes.

The present stage of cryogenic detector development is focused on fabrication of arrays. Arrays of superconducting-transition-edge-sensor (TES) microcalorimeters have generally been fabricated on SiNX membranes. In conventional membrane structures fabricated by backside etching, it is difficult to realize arrays having both mechanical toughness and a large filling factor. It is possible to overcome these difficulties by using a bridge-type membrane structure, in which SiNX membranes are raised above the Si substrate with a gap of 10–50 μm. In order to carry out etching and other processes, we have fabricated a small scale array with a bridge-type membrane structure. A preliminary version of a TES microcalorimeter array with a 5×5 pixel structure had dimensions of 6×10 mm2. Each pixel consisted of a Ti/Au bilayer with a size of 0.5×0.7 mm2 on a 1 μm-thick SiNX membrane of 0.7×2 mm2. Although the current array exhibited a small filling factor of about 0.1, it is possible to obtain a high filling factor by f...

This paper provides detailed response characteristics of a Nb/Al-AlOx/Al/Nb superconducting tunnel junction for X-ray of 5keV to 15keV investigated by using synchrotron radiation.