122 research outputs found
Effect of a thin AlO_x layer on transition-edge sensor properties
We have studied the physics of transition-edge sensor (TES) devices with an
insulating AlOx layer on top of the device to allow implementation of more
complex detector geometries. By comparing devices with and without the
insulating film, we have observed significant additional noise apparently
caused by the insulator layer. In addition, AlOx was found to be a relatively
good thermal conductor. This adds an unforeseen internal thermal feature to the
system.Comment: 6 pages, 5 figures, Low Temperature Detectors 14 conferenc
IXO/XMS Detector Trade-Off Study
This document presents the outcome of the detector trade-off for the XMS instrument on IXO. This trade-off is part of the Cryogenic instrument Phase-A study as proposed to ESA in the Declaration of Interest SRONXMS-PL-2009-003 dated June 6, 2009. The detector consists of two components: a core array for the highest spectral resolution and an outer array to increase the field of view substantially with modest increase in the number of read-out channels. Degraded resolution of the outer array in comparison with the core array is accepted in order to make this scheme possible. The two detector components may be a single unit or separate units. These arrays comprise pixels and the components that allow them to be arrayed. Each pixel comprises a thermometer, an absorber, and the thermal links between them and to the rest of the array. These links may be interfaces or distinct components. The array infrastructure comprises the mechanical structure of the array, the arrangement of the leads, and features added to improve the integrated thermal properties of the array in the focal-plane assembly
Fluctuation superconductivity limited noise in a transition-edge sensor
In order to investigate the origin of the until now unaccounted excess noise
and to minimize the uncontrollable phenomena at the transition in X-ray
microcalorimeters we have developed superconducting transition-edge sensors
into an edgeless geometry, the so-called Corbino disk (CorTES), with
superconducting contacts in the centre and at the outer perimeter. The measured
rms current noise and its spectral density can be modeled as resistance noise
resulting from fluctuations near the equilibrium superconductor-normal metal
boundaryComment: 9 pages, 4 figures.; Corrections to text and equations; replaced the
affected figures. Added reference [12
Ultrasensitive TES Bolometers for Space Based FIR Astronomy
We present results from the development of a background limited transition edge sensor (TES) bolometer for the wavelength band 30–60 μm. The bolometer consists of a Ti/Au superconducting thermometer and a Ta radiation absorber deposited on a 200μm×300μm200μm×300μm membrane of SixNySixNy suspended on long, narrow legs. This device is voltage biased and the current through the device is measured by a SQUID amplifier. The thermometer has transition temperature Tc = 108 mKTc = 108 mK and the device is operated from a 70 mK base plate. FIR radiation is coupled into a multimodc horn with entrance aperture of 450 μm, length 4.5 mm and exit aperture of 45 μm, which feeds a metal integrating cavity containing the detector. The radiation band is defined by a pair of lowpass and highpass mesh filters in front of the horn. Here we present measurements of optical noise equivalent power (NEP), optical efficiency, dynamic range and time constant. The results show that measured TES detectors are close to meeting the requirement of the “Band 3” of SAFARI FTS imaging instrument [1] on the SPICA mission [2]
FALCO simulations of high-contrast polarimetry with the Nancy Grace Roman Space Telescope Coronagraph Instrument
The Coronagraph Instrument of the Nancy Grace Roman Space Telescope (Roman
Coronagraph) will be capable of both total intensity and polarization
measurements of circumstellar disks. The polarimetric performance is impacted
by polarization effects introduced by all mirrors before the Wollaston prisms.
In this paper, we aim to characterize these effects for the Roman Coronagraph
in bands 1 and 4 using the FALCO and PROPER packages. We simulate the effect of
polarization aberrations that impact the polarimetric contrast and the
instrumental polarization effects to study the polarimetric accuracy. We
include spacecraft rolls, but leave out systematic camera noise. We find that
polarimetric differential imaging (PDI) improves the contrast by a factor of
six. The PDI contrast of is limited by polarized
speckles from instrumental polarization effects and polarization aberrations.
By injecting polarized companions with at various contrast levels and
demodulating their polarimetric signal, we recover their source Stokes vector
within 2%.Comment: 16 pages, 16 figures, SPIE Optics + Photonics - Techniques and
Instrumentation for Detection of Exoplanets X
Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter
At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Delta E(sub FWHM) = 3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterized the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter
EURECA: European-Japanese microcalorimeter array
The EURECA project aims to demonstrate technological readiness of a micro-calorimeter array for application in future X-ray astronomy missions, like Constellation-X, EDGE, and XEUS. The prototype instrument consists of a 5 × 5 pixel array of TES-based micro-calorimeters read out by two SQUID-amplifier channels using frequency-domain-multiplexing (FDM) with digital base-band feedback. The detector array is cooled by a cryogen-free cryostat consisting of a pulse tube cooler and a two stage ADR. Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray energy resolution of 1.5 eV at 250 eV for read-out of one TES-pixel only. Next step is deployment of FDM to read-out the full array. Full performance demonstration is expected end 2008.This work was financially supported by the Dutch Organization for Scientific Research
(NWO).Peer Reviewe
Principles of the Field Theory of High Temperature Superconductivity in Underdoped Copper-Oxides
Here I extend my last work about the origin of the pseudo-gaps in underdoped
cuprates (arXiv: cond-mat. 1011.3206), to include the mechanism of
superconductivity. This is done by adapting the formalism of the double
correlations in systems with nested Fermi surfaces to the semi one dimensional
system of strings of holes. It is proposed that magnetic interaction is crucial
for the establishment of the pseudogap and the high temperature
superconductivity. It is shown that superconductivity disturbs the completeness
of the strings of holes, and creates fluctuations in their shapes. This, in
turn, reduces the magnetic interaction and the pseudogap order.Comment: This paper has been withdrawn by the author. 27 page
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