Study of six mechanical impedance matchers on a spherical gravitational wave detector

Frajuca, Carlos; Magalhães, Nadja S.; Bortoli, F. S.; Horiguti, A M

doi:10.1088/1742-6596/122/1/012029

Cited by 24 publications

(11 citation statements)

References 12 publications

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“…This is the case of Mario SCHENBERG, a GW detector built in Brazil and now disassembled due to a laboratory move, whose antenna consists of a solid, CuAl sphere with 65 cm in diameter. When operational, its surface was monitored by six microwave parametric transducers (Frajuca et al 2008) in a half dodecahedron distribution circumscribed to the sphere. Spherical resonant-mass GW detectors like this have been studied by the authors for quite some time now, particularly SCHENBERG (Bortoli et al 2016(Bortoli et al , 2019(Bortoli et al , 2020Costa et al 2004;Magalhaes et al 1995).…”

Section: Introductionmentioning

confidence: 99%

The challenge of calibrating a laser‐interferometric gravitational wave detector

et al. 2021

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In 2015, the first direct detection of gravitational waves was reported. Data analysis indicated that the waves had originated from the violent collision of two black holes, which scattered them through space-time as Einstein predicted. That detection was made possible by many advances in measurement technology, mainly vibration isolation of the detector optics, since, at 10 Hz, the motion of the laser-interferometric detector mirrors is at least one billion times smaller than the seismic motion of the ground. As well, it is difficult to lock the laser in the detection configuration in a large band of the spectrum; this was made possible by using many feedback and feed-forward control loops. However, in order to meet the many demanding requirements, more than a hundred of such active systems are included in a detector to allow locked acquisition and locked stability to, eventually, reach the desired sensitivity. In this work, challenges faced to reach some of these requirements will be described and we analyze how this scenario impacts the calibration of such detectors. In order to help reduce false alarm rates and provide data for veto systems, in this work we propose a specific kind of resonant-mass detector to operate in coincidence with laser-interferometric ones.

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Section: Introductionmentioning

confidence: 99%

The challenge of calibrating a laser‐interferometric gravitational wave detector

et al. 2021

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“…The first attempts to detect GWs started in the early 60s (Richard 1984) with resonant-mass detectors that were continuously improved during the following decades (Aguiar et al 2002;Andrade et al 2004;Bortoli et al 2010Bortoli et al , 2016Bortoli et al , 2019Frajuca et al 2000Frajuca et al , 2002Frajuca et al , 2004Frajuca et al , 2005Frajuca et al , 2006Frajuca et al , 2008Frajuca et al , 2012Magalhaes et al 1995Magalhaes et al , 1997aMagalhaes et al , 1997bMagalhaes et al , 2012Magalhaes et al , 2016Oliveira et al 2018;Ribeiro et al 2004). These investigations include works of the Graviton group.…”

Section: Introductionmentioning

confidence: 99%

The influence of rotation deceleration on the shape of a pulsar may reflect on the star's braking index

2021

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Pulsars are stars whose electromagnetic radiation is observed to pulsate in well-defined time intervals while they rotate as long as the electromagnetic signal is not emitted in the direction of the rotation axis. The frequencies of the pulses decay with time as quantified by the braking index (n). In the canonical model, n = 3 for all pulsars, but observational data yield n < 3. In this work, this model is modified to allow time change in the moment of inertia. According to that model, as the neutron star loses energy by the emission of electromagnetic radiation, its rotation decelerates under constant moment of inertia. Here, we propose that, as the rotation decelerates, the shape of the star changes due to an increasingly weaker centrifugal force that reduces its moment of inertia, a change that, under normal circumstances, would accelerate the star's rotation. In the case of pulsars, as the rotation decreases in view of electromagnetic energy loss, the rotation would decelerate less than in the canonical model, yielding a braking index less than three. This is a good result from our model, especially regarding stars with indices close to three. For lower indices, our model requires refinements as a complete explanation of braking index values probably demands that a series of phenomena be incorporated into the process.

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“…The detector operates with six electromechanical resonant transducers [7][8][9][10][11] connected to the antenna's surface and distributed on it according to a half dodecahedron configuration [12][13][14]. Signals from the sensors are expected to yield the amplitude, polarization, and source direction of a passing gravitational wave.…”

Section: Introductionmentioning

confidence: 99%

On the Dilution Refrigerator Thermal Connection for the SCHENBERG Gravitational Wave Detector

et al. 2020

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The resonant-mass gravitational wave detector SCHENBERG was designed by the Brazilian group Graviton to be sensitive to a central frequency nearing 3200 Hz and a bandwidth of 200 Hz. It has a spherical antenna weighing 1150 kg that is connected to the outer environment by a suspension system designed to attenuate local noise due to seism as well as other sources. Should a gravitational wave pass by the detector, the antenna is expected to vibrate. This motion will be monitored by six parametric transducers whose output signals will be digitally analyzed. In order to improve the sensitivity of the detector, it must be cooled down to the lowest possible temperature, and for this purpose a dilution refrigerator is planned to be implemented in the detector. It is known that such device produces vibration when operational, consequently introducing noise in the system. Using the finite elements method, this work investigates thermal connections between the dilution refrigerator and the sphere suspension that allow the detector to operate within its projected sensitivity. The finite elements method showed an attenuation of 240dB in the best-valued thermal connection.

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Study of six mechanical impedance matchers on a spherical gravitational wave detector

Cited by 24 publications

References 12 publications

The challenge of calibrating a laser‐interferometric gravitational wave detector

The challenge of calibrating a laser‐interferometric gravitational wave detector

The influence of rotation deceleration on the shape of a pulsar may reflect on the star's braking index

On the Dilution Refrigerator Thermal Connection for the SCHENBERG Gravitational Wave Detector

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