Modelling the energy gap in transition metal/aluminium bilayers"

We present an application of the generalised proximity effect theory.Comment: 15 pages, 11 figures, presented at workshop on low temperature superconducting electronics at the University of Twente, The Netherland

Optical Characterisation of a Camera module Developed for Ultra-low NEP TES Detector Arrays at FIR Wavelengths

Here we report on the optical design and on the spectral-spatial characterisation of a small 16 pixel camera. The prototype uses TES detectors with NEPs ~10-16 W/Hz0.5 which have been fabricated with near identical optical coupling structures to mimic their much lower NEP counterparts (~10-19 W/Hz0.5). This modification, which is achieved through changing only the pixel thermal conductance, G, has allowed us to perform spectral/spatial cryogenic testing using a 100mK ADR to view room temperature thermal sources. The measurements show a flat spectral response across the waveband and minimal side lobe structure in the antenna patterns down to 30dB

Optical requirements and modelling of coupling devices for the SAFARI instrument on SPICA

The next generation of space missions targeting far-infrared bands will require large-format arrays of extremely low-noise detectors. The development of Transition Edge Sensors (TES) array technology seems to be a viable solution for future mm-wave to Far-Infrared (FIR) space applications where low noise and high sensitivity is required. In this paper we concentrate on a key element for a high sensitivity TES detector array, that of the optical coupling between the incoming electromagnetic field and the phonon system of the suspended membrane. An intermediate solution between free space coupling and a single moded horn is where over-moded light pipes are used to concentrate energy onto multi-moded absorbers. We present a comparison of modelling techniques to analyse the optical efficiency of such light pipes and their interaction with the front end optics and detector cavity

Quasiparticle and phonon transport in superconducting indium and quasiparticle trapping

The dynamics of the excess quasiparticles and phonons created in single crystal superconducting indium by pulsed laser irradiation have been investigated at temperatures below 1 K using superconducting tunnel junction detectors. The changes in the time evolution of these excitations have been investigated when quasiparticle trapping occurs from the single crystal into a film of smaller gap superconductor, or of a normal metal where an energy gap is induced by the proximity effect. The experiments deduce a value for the characteristic quasiparticle time in the normal metal film. The phenomenon of trapping has also been investigated for thin film geometries. These experiments identify the mechanisms of the trapping effect and indicate the occurrence of current gain. The characteristic quasiparticle time for the trap material is deduced and is consistent with previous measurements in clean films. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:D203950 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Readout-power heating and hysteretic switching between thermal quasiparticle states in kinetic inductance detectors

A model is presented for readout-power heating in kinetic inductance detectors. It is shown that the power dissipated by the readout signal can cause the temperature of the quasiparticle system in the superconducting resonator to switch between well-defined states. At low readout powers, only a single solution to the heat balance equation exists, and the resonance curve merely distorts as the readout power is increased. At high readout powers, three states exist, two of which are stable, and the resonance curve shows hysteretic switching. The power threshold for switching depends on the geometry and material used but is typically around ?70 dBm for Aluminum resonators. A comprehensive set of simulations is reported, and a detailed account of the switching process is given. Experimental results are also shown, which are in strong qualitative agreement with the simulations. The general features of the model are independent of the precise cooling function, and are even applicable for resonators on suspended, thermally isolated, dielectric membranes, where an increase in quasiparticle lifetime is expected. We discuss various extensions to the technique, including the possibility of recovering the cooling function from large-signal measurements of the resonance curve.QN/Quantum NanoscienceApplied Science

Cryopreservation, hepatocyte monolayers and DMSO shock

Cryopreservation of primary hepatocyte monolayers may provide a means of long-term storage of the cells for in vitro studies of xenobiotic metabolism and toxicity. This talk focuses on cryopreservation, hepatocyte monolayers and DMSO shock

Cryopreservation of viable hepatocyte monolayers in cryoprotectant media with high serum content: metabolism of testosterone and kaempherol post-cryopreservation

Little work in the literature focuses on the cryopreservation of primary hepatocytes as monolayer cultures, yet this technique offers many distinct advantages over other cryopreservation systems, including high recovery, high post-thaw nutrient penetration, and low numbers of trapped dead cells. This article investigates the cryopreservation of primary rat hepatocytes at −78 °C attached as monolayers to collagen coated culture dishes, and describes efforts to increase post-thaw viability and function through manipulation of the freeze/thaw protocol. Different concentrations of foetal calf serum (FCS) with 10% (v/v) dimethyl sulphoxide (ME2SO) were tested as cryopreservation media, and high cryoprotectant serum levels were found to be important in maintaining membrane integrity and function in the cryopreserved rat hepatocyte monolayer cultures. Cultures cryopreserved with 90% (v/v) FCS plus 10% (v/v) ME2SO maintain 79.7 ± 6.5% of the monolayer area as viable cells with normal morphology (by image analysis), 112.7 ± 14.2% protein concentration, 55.4 ± 4.2% carboxyfluorescein diacetate de-acetylation, 27.2 ± 7.5% kaempherol glucuronidation (a measure of UDP-glucuronosyl transferase activity), and 39.3 ± 7.3% testosterone hydroxylation (a measure of cytochrome P-450 activity) compared with non-cryopreserved controls. This method of cryopreservation may provide a simple, convenient means of long-term storage of hepatocytes for in vitro metabolism studies