Towards a Soundcheck accelerometer: sensor testing at the E-TEST cold platform

The Lunar Gravitational-wave Antenna payload is composed of an array of seismic stations in a permanently shadowed crater. Cryogenic superconductive inertial sensors (CSIS) are deployed in the seismic stations and are aimed to detect the differential between the elastic response of the Moon and the suspended inertial sensor proof-mass motion induced by gravitational waves. First, The status of the sensors, as well as an overview of the additional auxiliary technologies embedded in the payload of the lunar gravitational-wave detection mission are reviewed. Then, the discussion is focused on the inertial sensors. It is composed of a frame and an inertial mass in niobium, assembled in a Watt’s linkage configuration. They work in closed loop, using an interferometric read-out and superconducting actuation. They are required to operate at 4K for superconductive purposes and to be sensitive to 1 fm/sqrt(Hz) from 1 Hz onwards. Such sensitive sensors need a specific test bench to assess their performance on Earth. A first version was developed in the framework of the E-TEST prototype. E-TEST is a prototype suspension of a 45 cm diameter silicon mirror cooled down radiatively to 25 K in a suspended cryostat and is aimed at validating R&D to meet ET’s requirements in the relevant environment. Among the novelties to be tested is the new architecture of the seismic isolation system. CSIS is integrated into ETEST, creating a mutually beneficial arrangement. On the one hand, E-TEST provides an adequate quiet cryogenic environment in which the sensitivity and the sensor can be assessed with a Huddle test, and, on the other hand, the sensors provide data on E-TEST new isolation architecture, by allowing the collaboration to determine the isolation reached at the test mass level. This talk focuses on describing the current status of the development of the CSIS, in its first version with the adaption made for E-TEST, and the future enhancements scheduled to fulfill LGWA goals

The ultimate performance of the Rasnik 3-point alignment system

The Rasnik system is a 3-point optical displacement monitor with sub-nanometer precision. The CCD-Rasnik alignment system was developed in 1993 for the monitoring of the alignment of the muon chambers of the ATLAS Muon Spectrometer at CERN. Since then, the development has continued as new CMOS imaging pixel chips became available. The system's processes and parameters that limit the precision have been studied in detail. We conclude that only the quantum fluctuations to which the light level content of sensor pixels are subject to, is limiting the spatial resolution. The results of two Rasnik systems are compared to results from simulations, which are in good agreement: the best reached precision of \SI{7}{pm/\sqrt{Hz}} is reported. Finally, some applications of high-precision Rasnik systems are set out

The alignment of the C3 Accelerator Structures with the Rasnik alignment system

The Rasnik 3-point alignment system, now widely applied in particle physics experiments and in the instrumentation of gravitational wave experiments, can be used as N-point alignment system by daisy chain N individual 3-point systems. The conceptual implementation of Rasnik chains in C3 is presented. The proper operation of a laser diode and a CMOS image sensor in liquid nitrogen has been verified. Next plans for testing a small but complete system, immersed in liquid nitrogen, are presented

Lunar Gravitational-Wave Antenna

Monitoring of vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. At laboratory scale, these experiments became known as resonant-bar detectors first developed by Joseph Weber in the 1960s. Due to the dimensions of these bars, the targeted signal frequencies were in the kHz range. Weber also pointed out that monitoring of vibrations of Earth or Moon could reveal gravitational waves in the mHz band. His Lunar Surface Gravimeter experiment deployed on the Moon by the Apollo 17 crew had a technical failure rendering the data useless. In this article, we revisit the idea and propose a Lunar Gravitational-Wave Antenna (LGWA). We find that LGWA could become an important partner observatory for joint observations with the space-borne, laser-interferometric detector LISA, and at the same time contribute an independent science case due to LGWA's unique features. Technical challenges need to be overcome for the deployment of the experiment, and development of inertial vibration sensor technology lays out a future path for this exciting detector concept.Comment: 29 pages, 17 figure

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects