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Excess heat capacity in a bolometric detector has the consequence of increasing or leading to multiple device time constants.  The Mo/Au bilayer transition edge sensor (TES) bolometric detectors initially fabricated for the high resolution mid-infrared spectrometer (HIRMES) exhibited two response thermalization scales, one of which is a few times longer than estimates based upon the properties of the bulk materials employed in the design. The relative contribution of this settling time to the overall time response of the detectors is roughly proportional to the pixel area, which ranges between ∼0.3 and 2.6 mm2.  Use of laser ablation to remove sections of the silicon membranes comprising the pixels results in a detector response with a smaller contribution from the secondary time constant.  Additional information about the nature of this excess heat capacity is gleaned from glancing incidence X-ray diffraction, which reveals the presence of molybdenum silicides near the silicon surface which is a consequence of the bi-layer deposition.  Quantitative analysis of the concentration of excess molybdenum, estimated with secondary ion mass spectroscopy, is commensurate to the additional heat capacity needed to explain the anomalous time response of the detectors. [ABSTRACT FROM AUTHOR]

Superconducting titanium thin films are good candidates for transition edge sensors. In this paper, we deposit titanium thin films on cooled silicon-on-insulator substrates by using electron-beam evaporation. The deposition rate dependence of the film stress, resistivity, and superconducting transition temperature are presented and analyzed. The relationship between film electrical properties and thickness is discussed. For investigating the heating influence on thin Ti films, a depth profile of oxygen diffusion in the films is also analyzed by X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Until recently, our work on superconducting thin film phonon sensors for cryogenic detector applications was limited to silicon substrates only. We have now successfully extended low T/sub c/ (/spl les/100 mK) tungsten sensor technology and sensor fabrication capability to include high purity germanium substrates as well. Here, we describe a technique for fabricating low T/sub c/ superconducting tungsten films on germanium, and we present first results from cryogenic characterization experiments with these films. We also summarize our work on the development of a process to independently etch aluminum and tungsten films deposited on the same germanium substrate. The capability to selectively etch aluminum and tungsten films is critical for the fabrication of our silicon and soon also germanium detectors which utilize overlapping thin films of superconducting tungsten and aluminum for the phonon sensors. Due to the nature of their operation, we refer to these sensors as W/Al Quasiparticle trap assisted-Electrothermal feedback-Transition edge (QET) Sensors. [ABSTRACT FROM PUBLISHER]

During the 1980s a SQUID-based superconducting gradiometer prototype utilizing bulk niobium and wire superconducting components cooled by liquid helium was developed by the US Navy. This sensor was successfully utilized in demonstrations for sea mine countermeasures and for the detection of UneXploded Ordnance (UXO). Advances in this sensor technology are being pursued for longer detection ranges and for more versatile operation. An advanced sensor prototype using all thin film niobium circuits and a new liquid helium cooling concept has been built to provide significant increases in sensitivity. In addition, a high Tc sensor concept using liquid nitrogen refrigeration has been developed to reduce package size and to simplify logistic and support requirements for field operation. This paper will review the current status and plans of this program, specifically describing the recent advances in sensor development and results from the demonstration to detect UXO. [ABSTRACT FROM PUBLISHER]