36 research outputs found
Principles of wide bandwidth acoustic detectors and the single-mass DUAL detector
We apply the standard theory of the elastic body to obtain a set of equations
describing the behavior of an acoustic Gravitational Wave detector, fully
taking into account the 3-dimensional properties of the mass, the readout and
the signal. We show that the advantages given by a Dual detector made by two
nested oscillators can also be obtained by monitoring two different acoustic
modes of the same oscillator, thus easing the detector realization. We apply
these concepts and by means of an optimization process we derive the main
figures of such a single-mass Dual detector designed specifically for the
frequency interval 2-5kHz. Finally we calculate the SQL sensitivity of this
detector.Comment: 29 pages, 10 figure
Experimental bounds on collapse models from gravitational wave detectors
Wave function collapse models postulate a fundamental breakdown of the quantum superposition principle at the macroscale. Therefore, experimental tests of collapse models are also fundamental tests of quantum mechanics. Here, we compute the upper bounds on the collapse parameters, which can be inferred by the gravitational wave detectors LIGO, LISA Pathfinder, and AURIGA. We consider the most widely used collapse model, the continuous spontaneous localization (CSL) model. We show that these experiments exclude a huge portion of the CSL parameter space, the strongest bound being set by the recently launched space mission LISA Pathfinder. We also rule out a proposal for quantum-gravity-induced decoherence
Dc superconducting quantum interference device amplifier for gravitational wave detectors with a true noise temperature of 16 μK
We report on the noise characterization of a two-stage dc superconducting quantum interference device (SQUID) amplifier developed for resonant gravitational wave detectors. The back action noise is estimated by coupling the SQUID to an electrical resonator at 1.6 kHz with Q=1.1×106. From measurements of back action and additive SQUID noise, performed in the temperature range 1.5–4.2 K, an upper limit is set on the noise temperature Tn of the device at the resonator frequency. The best value obtained at 1.5 K is Tn⩽16 μK and corresponds to 200 resonator quanta. The thermal component of the noise temperature is found in reasonable agreement with the predicted value
Development of highly sensitive nanoscale transition edge sensors for gigahertz astronomy and dark matter search
Terahertz and sub-terahertz band detection has a key role both in fundamental
interactions physics and technological applications, such as medical imaging,
industrial quality control and homeland security. In particular, transition
edge sensors (TESs) and kinetic inductance detectors (KIDs) are the most
employed bolometers and calorimeters in the THz and sub-THz band for
astrophysics and astroparticles research. Here, we present the electronic,
thermal and spectral characterization of an aluminum/copper bilayer sensing
structure that, thanks to its thermal properties and a simple miniaturized
design, could be considered a perfect candidate to realize an extremely
sensitive class of nanoscale TES (nano-TES) for the giga-therahertz band.
Indeed, thanks to the reduced dimensionality of the active region and the
efficient Andreev mirror (AM) heat confinement, our devices are predicted to
reach state-of-the-art TES performance. In particular, as a bolometer the
nano-TES is expected to have a noise equivalent power (NEP) of
W/ and a relaxation time of ns
for the sub-THz band, typical of cosmic microwave background studies. When
operated as single-photon sensor, the devices are expected to show a remarkable
frequency resolution of 100 GHz, pointing towards the necessary energy
sensitivity requested in laboratory axion search experiments. Finally,
different multiplexing schemes are proposed and sized for imaging applications.Comment: 12 page, 7 figure
High kinetic inductance NbTiN films for quantum limited travelling wave parametric amplifiers
A wide-bandwidth and low-noise amplification chain in the microwave regime is
crucial for the efficient read-out of quantum systems based on superconducting
detectors, such as Microwave Kinetic Inductance Detectors (MKIDs), Transition
Edge Sensors (TESs), Magnetic Microcalorimeters (MMCs), and RF cavities, as
well as qubits. Kinetic Inductance Travelling Wave Parametric Amplifiers
(KI-TWPAs) operated in a three-wave mixing fashion have demonstrated
exceptional dynamic range and low-noise performance, approaching the quantum
limit. These amplifiers can be fabricated using a single layer of a high
kinetic inductance film as weakly dispersive artificial transmission lines,
with the ability to control the phase-matched bandwidth through dispersion
engineering. In this study, we present the optimisation of the rf
sputter-deposition process of NbTiN films using a Nb80%T20 target, with the
goal of achieving precise control over film characteristics, resulting in high
kinetic inductance while maintaining a high transition temperature. The
parameter landscape related to the different sputtering conditions, such as
pressure, power, and nitrogen flow, has been explored and the film thickness
has been used as a fine-tuning parameter to adjust the properties of the final
NbTiN films used for the fabrication of KI-TWPAs. As a final result, we have
obtained a NbTiN film with a kinetic inductance of 8.5 pH/sq which we have
exploited to fabricate KI-TWPA prototype devices, showing promising
amplification performance
IGEC2: A 17-month search for gravitational wave bursts in 2005-2007
We present here the results of a 515 days long run of the IGEC2 observatory,
consisting of the four resonant mass detectors ALLEGRO, AURIGA, EXPLORER and
NAUTILUS. The reported results are related to the fourfold observation time
from Nov. 6 2005 until Apr. 14 2007, when Allegro ceased its operation. This
period overlapped with the first long term observations performed by the LIGO
interferometric detectors. The IGEC observations aim at the identification of
gravitational wave candidates with high confidence, keeping the false alarm
rate at the level of 1 per century, and high duty cycle, namely 57% with all
four sites and 94% with at least three sites in simultaneous observation. The
network data analysis is based on time coincidence searches over at least three
detectors: the four 3-fold searches and the 4-fold one are combined in a
logical OR. We exchanged data with the usual blind procedure, by applying a
unique confidential time offset to the events in each set of data. The
accidental background was investigated by performing sets of 10^8 coincidence
analyses per each detector configuration on off-source data, obtained by
shifting the time series of each detector. The thresholds of the five searches
were tuned so as to control the overall false alarm rate to 1/century. When the
confidential time shifts was disclosed, no gravitational wave candidate was
found in the on-source data. As an additional output of this search, we make
available to other observatories the list of triple coincidence found below
search thresholds, corresponding to a false alarm rate of 1/month.Comment: 10 pages, 8 figures Accepted for publication on Phys. Rev.