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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. [ABSTRACT FROM AUTHOR]

We realized a \ery fast and large Superconducting Strip Line Detector based on a parallel configuration of nanowires. The detector with size 200×200 μm2 recorded a sub-nanosecond pulse width of 700 ps in FWHM (400 ps rise time and 530 ps relaxation time) for lysozyme monomers/multimers molecules accelerated at 175 keV in a Time of Flight Mass Spectrometer. This record is the best in the class of superconducting detectors and comparable with the fastest NbN superconducting single photon detector of 10×10 μm2. We succeeded in acquiring mass spectra as the first step for a scale-up to ∼mm pixel size for high throughput MS analysis, while keeping a fast response. [ABSTRACT FROM AUTHOR]

In order to realize fast readout and no-cross talk among one hundred wiring cables for a superconducting tunnel junction detector array, coaxial cables with low-thermal conduction were investigated. Through a steady-state heat-flow method, heat into a cryogen-free cryostat 3He pot was confirmed to be 5.7 μW when one hundred 70–30 CuNi-based assembled coaxial cable are wired between its 0.3 K and 3 K stages, which is less than 10 % of the heat caused by the support structure of 3He pot. The coaxial cables were actually installed to the cryostat and the detector stage could be kept at 0.3 K for an enough long time to perform time-of-flight mass spectrometry experiments. To our knowledge, this is the first time that such large number of the coaxial cables has been installed at 0.3 K successfully. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We suggest two methods for the enlargement of the sensitive area of NIS tunnel junction detectors: (1) segmented absorbers connected in parallel and (2) segmented absorbers connected to a common sensor through heat switches which can control a heat flow and can confine the volume of temperature rise. The energy resolutions are evaluated for each method. The method (2) is found promising. [ABSTRACT FROM AUTHOR]

We report an anomalous x-ray detection property in a superconducting tunnel junction with quasiparticle trapping layers at high bias voltage. Being different from the conventional quasiparticle diffusion and edge loss model, the important characteristic parameters, such as a height and decay time of current pulse signals, are totally dependent on the incident position of photons and the applied bias voltage. This can be explained by the non-equilibrium state in a superconducting electrode induced by excess quasiparticle injection. We suppose that the property at high bias voltage should be advantageous for phonon detection and high count rate photon detection. [ABSTRACT FROM AUTHOR]

We developed a high count rate x-ray detector using a superconducting tunnel junction (STJ) having a structure of Nb/Al/AlO[sub x]/Al/Nb with a fast current readout system. The STJ has a current rise time of 100 ns, a current decay time of 160 ns and resistance of 20 ω at 0.4 K. High count rate capability of the x-ray detector has been measured by synchrotron radiation. The energy resolution is ∼230 eV at 100 cps and ∼265eV at 100k cps for 4keV x-rays. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 SiN[sub x] 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 SiN[sub x] 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 5x 5 pixel structure had dimensions of 6 x 10 mm². Each pixel consisted of a Ti/Au bilayer with a size of 0.5 x 0.7 mm² on a 1 µm-thick SiN[sub x] membrane of 0.7 x 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 fabricating mushroom-shaped absorbers. [ABSTRACT FROM AUTHOR]

We are developing a tungsten transition edge sensor (W-TES) for x-ray imaging spectroscopy applications. The conventional readout scheme for TES array has a great difficulty in reading out multi-channel x-ray signals. Therefore we have considered a new readout scheme for a W-TES array. This scheme is based on a cooling time measurement in a saturation mode. In this scheme, we only need time information, therefore we can expect to simplify a readout system. Although the currently achieved energy resolution of our W-TES (0.5mm x 0.5mm) using the cooling time measurement is 55eV (FWHM) at 5.9keV, much higher energy resolution is expected by making smaller devices. [ABSTRACT FROM AUTHOR]