The development and integration of new detector payloads has been an important part of the Advanced Virgo (AdV) project, the major upgrade of the Virgo interferometric detector of Gravitational ...Waves, aiming to increase the detector sensitivity by one order of magnitude. During the integration phase of the new AdV payloads with monolithic suspension of mirrors we experienced systematic suspension failures later identified as caused by dust contamination of the vacuum system. In order to not postpone the detector commissioning, making possible to join the LIGO O2 observation run, the Collaboration decided to proceed with the integration of the payloads relying on steel wire suspensions for all the mirrors. In this proceeding the status of the currently integrated payloads is reported, including their angular control characterization and the Q-factor measurements for test mass steel wire suspensions. The payload upgrade for the re-integration of monolithic suspensions after the O2 run is reported in the last section.
SUMMARY
Einstein Telescope (ET) is a proposed underground infrastructure in Europe to host future generations of gravitational-wave (GW) detectors. One of its design goals is to extend the ...observation band of terrestrial GW detectors from currently about 20 Hz down to 3 Hz. The coupling of a detector to its environment becomes stronger at lower frequencies, which makes it important to carefully analyse environmental disturbances at ET candidate sites. Seismic disturbances pose the greatest challenge since there are several important mechanisms for seismic vibrations to produce noise in ET, for example, through gravitational coupling, stray light, or through harmful constraints on the design of ET’s control system. In this paper, we present an analysis of the time-variant properties of the seismic field at the Sardinia candidate site of ET connected to anthropogenic as well as natural phenomena. We find that temporal variations of source distributions and of the noise spectra generally follow predictable trends in the form of diurnal, weekly, or seasonal cycles. Specific seismic sources were identified such as road bridges, which produce observable disturbances underground. This information can be used to adapt a detector’s seismic isolation and control system.
To improve the sensitivity of the future generation of gravitational wave interferometers in the frequency range around 1 Hz it is necessary to decrease the seismic and Newtonian noise affecting the ...detector performance. This goal is achieved by installing the experimental apparatus in an appropriate underground site, where the Rayleigh surface wave of the microseismic motion should be attenuated. Here we report the results of an experimental campaign devoted to a long term characterization of one of the potential sites for the construction of a third generation of gravitational wave detector: the former mine of Sos Enattos (Sardinia, Italy). We analyzed the seismic stability within the low-frequency sensitivity band of a third generation gravitational observatory and the correlation between the microseismic band and the weather conditions, in particular focusing on the Tyrrhenian sea status.
The Advanced Virgo monolithic fused silica suspension Aisa, D.; Aisa, S.; Campeggi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
The detection of gravitational waves is one of the most challenging prospects faced by experimental physicists. Suspension thermal noise is an important noise source at operating frequencies between ...approximately 10 and 30Hz, and represents a limit to the sensitivity of the ground based interferometric gravitational wave detectors. Its effects can be reduced by minimizing the losses and by optimizing the geometry of the suspension fiber as well as its attachment system. In this proceeding we will describe the mirrors double stage monolithic suspension system to be used in the Advanced Virgo (AdV) detector. We also present the results of the thermal noise study, performed with the help of a finite elements model, taking into account the precise geometry of the fibers attachment systems on the suspension elements. We shall demonstrate the suitability of this suspension for installation in AdV.
•Suspension system design for the test masses of the gravitational wave detectors.•Finite element model studies.•Suspension thermal noise studies.
In this paper, we report a study of the seismic noise measured in the underground Baksan neutrino observatory in the framework of the site qualification for third generation Gravitational Wave ...detectors like the Einstein Telescope (Einstein gravitational wave telescope conceptual design study, ET-0106C-10.
http://et-gw.eu/etdsdocument
, 2011) and Cosmic Explorer (
https://cosmicexplorer.org/
). The main spectral feature below 1
Hz
is the oceanic microseism, while for greater frequencies the measured horizontal and vertical accelerations approach the Peterson low noise model. Using two synchronized seismometers, we also studied the coherence in the microseismic band (0.1–0.5Hz) between three underground stations located at 0.3 km, 1.4 km and 3.7 km from the tunnel entrance. Finally, on the base of our measurements, we evaluate the Newtonian noise contribution from the seismic noise background of body waves.
In this work we report the ongoing characterization of the Sos Enattos former mine (Sardinia, Italy), one of the two candidate sites for the Einstein Telescope (ET), the European third-generation ...underground interferometric detector of Gravitational Waves. The Sos Enattos site lies on a crystalline basement, made of rocks with good geomechanical properties, characterized by negligible groundwater. In addition, the site has a very low seismic background noise due to the absence of active tectonics involving Sardinia. Finally, the area has a low population density, resulting in a reduced anthropic noise even at the ground level. This location was already studied in 2012-2014 as a promising site for an underground detector. More recently, in March 2019, we deployed a new network of surface and underground seismometers at the site, that is currently monitoring the local seismic noise. Most of the energy carried by the seismic waves is due to the microseisms below 1 Hz, showing a significant correlation with the waves of the west Mediterranean sea. Above 1 Hz the seismic noise in the underground levels of the mine approaches the Peterson's low noise model. Exploiting mine blasting works into the former mine, we were also able to perform active seismic measurements to evaluate the seismic waves propagation across the area. In conclusion we also give a first assessment about the acoustic and magnetic noise in this underground site.
The Japanese gravitational wave observatory KAGRA will be operated at cryogenic temperatures to reduce thermal noise. Four main mirrors and their suspension systems, called cryogenic payloads, will ...be cooled in the cryostat. Vibrations of the cryostat and the cryocooler can contaminate the output of the detector. One of the noise paths is the heat link made from the pure soft metal between the cryogenic payload and cryocoolers to cool the payload. In order to evaluate this noise amplitude, we measured the vibration of the radiation shield at cryogenic temperatures at the cryostat production site in Yokohama, Japan. For this measurement, we developed cryogenic accelerometers. Based on the result of this measurement, we calculated the noise in the KAGRA interferometer. Our results show that with the current design, the seismic noise goal formulated for KAGRA cannot be achieved. Finally, we present a possible design optimization that is meant to reach the nominal sensitivity of the detector.
The design of third-generation gravitational-wave detectors requires dedicated sensors to perform very accurate measurements of the residual motion of mechanical components cooled down at cryogenic ...temperatures and accommodated close to the test masses. For this reason, we developed a vertical accelerometer prototype derived by the classical scheme widely used in Virgo seismic suspension control. Thermal contractions are the main concern when cooling down such a device and the calibration check at low temperature, in the absence of commercial sensors working in parallel, plays a crucial role. The accelerometer was conceived to be used at low frequencies (0.3-3 Hz) in a quite specific environment, where the noise produced by cryocoolers has to be suppressed. However, it can be easily operated over a wider frequency band, up to ∼100 Hz. The achieved sensitivity is ∼10−8 m s−2 below 3 Hz. During 2013, the device was successfully installed in the KAGRA cryostat, where it was tested at low temperatures down to 8 K and provided the measurement of vertical vibrational modes of the inner thermal shield.
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