46 research outputs found
Demonstration of Weak-Link Physics in the Dynamical Response of Transition-Edge Sensors
We theoretically predict and experimentally observe the onset of weak-link
physics in the dynamical response of transition edge sensors (TES). We develop
a theoretical framework based on a Fokker-Planck description that unifies the
TES electrical response, stemming from Josephson phenomena, with electrothermal
effects due to coupling to a thermal bath. Our measurements of a varying
dynamic resistance are in excellent agreement with our theory, thereby ruling
out predictions based on a two-fluid model and establishing weak-link phenomena
as the main mechanism underlying the operation of TES. Furthermore, our
description enables the calculation of power spectral densities, paving the way
for a more thorough investigation of the unexplained "excess noise" in long
diffusive junctions and TES reported in recent experiments
Complete model of a spherical gravitational wave detector with capacitive transducers. Calibration and sensitivity optimization
We report the results of a detailed numerical analysis of a real resonant
spherical gravitational wave antenna operating with six resonant two-mode
capacitive transducers read out by superconducting quantum interference devices
(SQUID) amplifiers. We derive a set of equations to describe the
electro-mechanical dynamics of the detector. The model takes into account the
effect of all the noise sources present in each transducer chain: the thermal
noise associated with the mechanical resonators, the thermal noise from the
superconducting impedance matching transformer, the back-action noise and the
additive current noise of the SQUID amplifier. Asymmetries in the detector
signal-to-noise ratio and bandwidth, coming from considering the transducers
not as point-like objects but as sensor with physically defined geometry and
dimension, are also investigated. We calculate the sensitivity for an
ultracryogenic, 30 ton, 2 meter in diameter, spherical detector with optimal
and non-optimal impedance matching of the electrical read-out scheme to the
mechanical modes. The results of the analysis is useful not only to optimize
existing smaller mass spherical detector like MiniGrail, in Leiden, but also as
a technological guideline for future massive detectors. Furthermore we
calculate the antenna patterns when the sphere operates with one, three and six
resonators. The sky coverage for two detectors based in The Netherlands and
Brasil and operating in coincidence is also estimated. Finally, we describe and
numerically verify a calibration and filtering procedure useful for diagnostic
and detection purposes in analogy with existing resonant bar detectors.Comment: 23 pages, 20 figures, codes of the simulations are available on
request by contacting the autho
Development of frequency domain multiplexing for the X-ray Integral Field Unit (X-IFU) on the Athena
We are developing the frequency domain multiplexing (FDM) read-out of
transition-edge sensor (TES) microcalorimeters for the X-ray Integral Field
Unit (X-IFU) instrument on board of the future European X-Ray observatory
Athena. The X-IFU instrument consists of an array of 3840 TESs with a
high quantum efficiency (90 \%) and spectral resolution =2.5 eV
7 keV (2800). FDM is currently the baseline readout system
for the X-IFU instrument. Using high quality factor LC filters and room
temperature electronics developed at SRON and low-noise two stage SQUID
amplifiers provided by VTT, we have recently demonstrated good performance with
the FDM readout of Mo/Au TES calorimeters with Au/Bi absorbers. An integrated
noise equivalent power resolution of about 2.0 eV at 1.7 MHz has been
demonstrated with a pixel from a new TES array from NASA/Goddard (GSFC-A2). We
have achieved X-ray energy resolutions 2.5 eV at AC bias frequency at 1.7
MHz in the single pixel read-out. We have also demonstrated for the first time
an X-ray energy resolution around 3.0 eV in a 6 pixel FDM read-out with TES
array (GSFC-A1). In this paper we report on the single pixel performance of
these microcalorimeters under MHz AC bias, and further results of the
performance of these pixels under FDM.Comment: 8 pages, 4 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2014: Ultraviolet to
Gamma Ray