448 research outputs found
MiniGRAIL progress report 2004
The MiniGRAIL detector was improved. The sphere was replaced by a slightly larger one, having a diameter of 68 cm (instead of 65 cm), reducing the resonant frequency by about 200 Hz to around 2.9 kHz. The last four masses of the attenuation system were machined to increase their resonant frequency and improve the attenuation around the resonant frequency of the sphere. In the new sphere, six holes were machined on the TIGA positions for easy mounting of the transducers. During the last cryogenic run, two capacitive transducers and a calibrator were mounted on the sphere. The first transducer was coupled to a double-stage SQUID amplifier having a commercial quantum design SQUID as a first stage and a DROS as a second stage. The second transducer was read by a single-stage quantum design SQUID. During the cryogenic run, the sphere was cooled down to 4 K. The two-stage SQUID had a flux noise of about 1.6 ÎŒ0 Hzâ1/2. The detector was calibrated and the sensitivity curve of MiniGRAIL was determined
Sensitivity of the spherical gravitational wave detector MiniGRAIL operating at 5 K
We present the performances and the strain sensitivity of the first spherical
gravitational wave detector equipped with a capacitive transducer and read out
by a low noise two-stage SQUID amplifier and operated at a temperature of 5 K.
We characterized the detector performance in terms of thermal and electrical
noise in the system output sygnal. We measured a peak strain sensitivity of
at 2942.9 Hz. A strain sensitivity of better than
has been obtained over a bandwidth of 30 Hz. We expect
an improvement of more than one order of magnitude when the detector will
operate at 50 mK. Our results represent the first step towards the development
of an ultracryogenic omnidirectional detector sensitive to gravitational
radiation in the 3kHz range.Comment: 8 pages, 5 figures, submitted to Physical Review
Aperture synthesis for gravitational-wave data analysis: Deterministic Sources
Gravitational wave detectors now under construction are sensitive to the
phase of the incident gravitational waves. Correspondingly, the signals from
the different detectors can be combined, in the analysis, to simulate a single
detector of greater amplitude and directional sensitivity: in short, aperture
synthesis. Here we consider the problem of aperture synthesis in the special
case of a search for a source whose waveform is known in detail: \textit{e.g.,}
compact binary inspiral. We derive the likelihood function for joint output of
several detectors as a function of the parameters that describe the signal and
find the optimal matched filter for the detection of the known signal. Our
results allow for the presence of noise that is correlated between the several
detectors. While their derivation is specialized to the case of Gaussian noise
we show that the results obtained are, in fact, appropriate in a well-defined,
information-theoretic sense even when the noise is non-Gaussian in character.
The analysis described here stands in distinction to ``coincidence
analyses'', wherein the data from each of several detectors is studied in
isolation to produce a list of candidate events, which are then compared to
search for coincidences that might indicate common origin in a gravitational
wave signal. We compare these two analyses --- optimal filtering and
coincidence --- in a series of numerical examples, showing that the optimal
filtering analysis always yields a greater detection efficiency for given false
alarm rate, even when the detector noise is strongly non-Gaussian.Comment: 39 pages, 4 figures, submitted to Phys. Rev.
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