The planning and the construction of 3G detectors represent technological challenge for the next two decades, aimed to great scientific expectations. The talk will be focussed on main experimental aspects of Einstein Telescope, the leading 3G project in Europe.
The funding of the Australian Research Council Centre of Excellence in Gravitational Wave Discovery (OzGrav) has significantly expanded the volume of experimental work that is being conducted in gravitational wave astronomy. Part of this work has focused on the development of the Australian High Frequency Detector (OzGrav HF). This detector aims to access the "matter region" of the...
An adaptive optics system (named thermal compensation system - TCS) is currently in operation in Advanced Virgo to monitor and compensate wavefront distortions with an accuracy of the order of nanometers ensuring a duty cycle of the interferometer higher than 75%. During preparatory phase for O3, the TCS actuators have been commissioned and tuned. New research and development activities are...
The LISA mission, which has been accepted by ESA as the ESA-L3 Gravitational Wave Mission,
aims at measuring gravitational waves in the sub-Hz band using inter-spacecraft interferometry.
LISA consists in a constellation of three satellites in triangle formation with 2.5 Gm-long arms
following along an Earth-like heliocentric orbit. The ambitious sensitivity of pm/Hz$^{1/2}$ presents
many...
Mátra Gravitational and Geophysical Laboratory was established in Hungary in 2015 with the aim to measure and analyze the advantages of the subterranean installation of third generation of gravitational-wave detectors. The laboratory is located 88 m below the ground. Seismic, infrasonic and electromagnetic noise have been monitored. The seismic data have been collected for almost two years....
Increasing sensitivity of GW detectors in the low-frequency band is important for studying the intermediate mass black holes and accumulating signal from the lighter binary systems. Existing gravitational-wave detectors are limited at low frequencies by seismic noise and mode cross-coupling. Seismic isolation at low frequencies is challenging due to a tilt injection, reduced seismometer...
The direct detection of the first Gravitational Waves signals by using a ground based laser interferometric network, put in evidence the importance of having a filtering system of seismic noise and local disturbances integrated into the experimental apparatus. The third generation detectors will have more stringent requirements, in terms of sensitivity, and the new instrument should be...
With the next generation of gravitational wave detectors being planned to operate at cryogenic temperatures we are facing many new challenges. ET Pathfinder will be a test facility for establishing new techniques required in future cryogenic detectors. In this talk we would like to introduce ET Pathfinder and some of the techniques we are planning to implement, with a focus on test-mass...
The talk will shortly review the key instrumental aspects of LISA, including the legacy of LISA Pathfinder, and its current status of development. The talk will also briefly touch on other efforts toward space-borne GW detectors
Quantum noise limits the performance of gravitational-wave (GW) detectors, optomechanical experiments, and even recently proposed dark matter searches. This talk discusses the effort of the Birmingham group towards studies of the quantum noise in these experiments. In particular, we will show how to employ the couple cavity resonance for high GW frequency detectors, heterodyne squeezing...
Cavity optomechanics can be used to improve the sensitivity of gravitational-wave detectors via optomechanical filtering and ponderomotive squeezing. Here we present a concept for double resonant enhancement of optomechanical interaction in a multi-cavity optomechanical system that exhibits resonance splitting tuned to be equal to the mechanical resonant frequency. In a detuned cavity in the...
The decades of advancement in technologies pertaining to interferometric measurements have made it possible for us to make the first-ever direct observation of gravitational waves(GWs). These GWs emitted from violent events in the distant universe bring us crucial information about the nature of matter and gravity. In order for us to be able to detect GWs from even farther or weaker sources,...
Squeezed light has been employed at GEO 600 for almost 10 years, recently reaching the highest level ever measured on a large scale interferometer. This improvement was achieved after work towards the reduction of optical losses in the squeezed light injection path.
The in-air injection path was rebuilt by cleaning and substituting some optics. Faraday isolators were carefully tuned in order...
The development of thin-film coatings with lower mechanical losses is of critical importance for the performance of future generations of interferometric gravitational-wave detectors. Significant experimental effort has led to improvements during these years and currently the most advanced technology is the one of amorphous coatings. Yet, there is still a lack of fundamental understanding of...
Thermal noise associated with the mechanical loss of highly reflective mirror coatings is a critical limiting factor to the sensitivity of interferometric gravitational-wave detectors. Several alternative coating materials have been shown to have low mechanical loss, but however, due to their high optical absorption, cannot be implemented in upgrades to these detectors.
New multimaterial...
We study the dissipation φ of a silicon µ-cantilever coated with 300nm of Tantala. From the thermal noise spectra, a fit of 10 resonances for flexion modes, and 6 resonances for torsion modes can be performed, giving access to φ from 2 kHz to 600 kHz. Dissipation presents a weak maximum around 50 K in temperature, and is a slowly increasing function of frequency (power law $f^α$ with α~0.06)....
Fluorides like MgF2 and AlF3 have the lowest refractive index among the known coating materials; using them in a high-reflection (HR) Bragg mirror instead of SiO2, one could reduce the total HR coating thickness and hence its coating thermal noise.
A succession of annealing treatments at different temperatures (but with the same duration) were performed on a silica disk coated with MgF2. The...
A fundamental and intrinsic property of any device or natural system is its relaxation time \tau_{\rm relax}, which is the time it takes to return to equilibrium after the sudden change of a control parameter. Reducing \tau_{\rm relax} is frequently necessary, and is often obtained by a complex feedback process. To overcome the limitations of such an approach, alternative methods based on...
Thermal noise manifests itself as a tiny variance around the mean value of an observable $x$ of a physical system. Usually too small to be noticed, it becomes important in an increasing number of applications, such as quantum systems operated close to their ground state, MEMS and NEMS, frequency standards, or the next generation of gravitational wave detectors$^1$. Its understanding is thus...
We discuss a one-dimensional model of a vibrating rigid rod, in and out of equilibrium. We study stationary states when the system is subject to temperature gradients, which is the nonequilibrium scenario, as compared to constant temperature for the equilibrium situations. While some thermomechanical properties remain substantially unchanged comparing in and out of equilibrium situations, the...
We build a continuous fluctuating description of elastic, conductive and dissipative solids
subject to heat fluxes, which takes fully into account linear thermoelastic couplings.
Under the assumption of local equilibrium, we derive an extension of the fluctuation-dissipation theorem
and obtain the strain fluctuations in the nonequilibrium steady state.
We outline next steps towards the...
Squeezed light now has a firm place as a key technology for reducing the quantum noise in gravitational-wave detectors. Quantum noise of coherent and squeezed states is characterized by gaussian measurement uncertainties in their amplitude and phase quadratures. While in a coherent state both quadratures have the same (minimal) uncertainty, in squeezed states the uncertainty in one quadrature...
Vacuum fluctuations entering the dark port of an interferometric Gravitational Wave (GW) detector are responsible for Quantum Noise (QN).
The high-frequency component of QN is Shot Noise (SHN), while the low-frequency one is Radiation Pressure Noise (RPN).
The sensitivity of the present detectors is only affected by the first, being the RPN covered by techinical noises. SHN reduction,...
In 2015, after many years of R&D efforts of the LIGO-Virgo collaboration for the upgrade to the second generation of ground based gravitational wave detectors, for the first time it has been possible a direct observation of a gravitational wave event (GW). In the following years, many other GW events have been detected by both LIGO and Virgo. Nevertheless, in the very near future the present...
KAGRA is an only gravitational wave telescope using cryogenic mirror system. Although cryogenic sapphire mirror and suspension is the most direct way to reduce thermal noises, a technical issue is to cope with both cooling and vibration isolation. We worked on this issue for 20 years and realized in KAGRA now. For example, special technologies in KAGRA cooling system are followings;
*...
KAGRA is a 2G interferometric gravitational wave detector constructed in Japan. Its unique features are using underground site and cryogenic sapphire mirrors. In this talk, I will talk on current status and difficulities of cryogenic mirror suspension and our plan to overcome these issues.
In order to increase strain sensitivity in the 10-200 Hz region of current gravitational wave detectors it is necessary to further reduce the thermal noise of the detector. Proposals have been put forward for the next generation (3G) detectors which will operate at cryogenic temperatures. Silicon is a promising material due to its low mechanical loss, high thermal conductivity and zero thermal...
The observation of gravitational waves is highly influenced by the detectors sensitivity, that is limited for the low frequencies (10 -100 Hz) by the thermal noise. For this reason, the monolithic suspensions are one of the most important upgrades of the interferometric detectors including Advanced Ligo (aLigo) and Advanced Virgo (AdV). Currently the silica fibers are built to minimize the...
The third generation gravitational wave detectors like Einstein Telescope and LIGO Voyager, will adopt cryogenics mirrors and suspension systems as KAGRA interferometer, to reduce thermal noise and improve the sensitivity. The suspension systems or part of them will operate at low or cryogenic temperatures. The problems and challenges of operating the suspension systems and the interferometers...
