New design of electrostatic mirror actuators for application in high-precision interferometry

We describe a new geometry for electrostatic actuators to be used in sensitive laser interferometers, suited for prototype and table top experiments related to gravitational wave detection with mirrors of 100 g or less. The arrangement consists of two plates at the sides of the mirror (test mass), and therefore does not reduce its clear aperture as a conventional electrostatic drive (ESD) would do. Using the sample case of the AEI-10 m prototype interferometer, we investigate the actuation range and the influence of the relative misalignment of the ESD plates with respect to the test mass. We find that in the case of the AEI-10 m prototype interferometer, this new kind of ESD could provide a range of 0.28 μm when operated at a voltage of 1 kV. In addition, the geometry presented is shown to provide a reduction factor of about 100 in the magnitude of the actuator motion coupling to the test mass displacement. We show that therefore in the specific case of the AEI-10 m interferometer, it is possible to mount the ESD actuators directly on the optical table without spoiling the seismic isolation performance of the triple stage suspension of the main test masses

Response of Bose gases in time-dependent optical superlattices

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose-Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally accessible signature for the quasi Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.Comment: 20 pages, 9 figures; added references and corrected typo

Review of the Laguerre-Gauss mode technology research program at Birmingham

Gravitational wave detectors from the advanced generation onwards are expected to be limited in sensitivity by thermal noise of the optics, making the reduction of this noise a key factor in the success of such detectors. A proposed method for reducing the impact of this noise is to use higher-order Laguerre-Gauss (LG) modes for the readout beam, as opposed to the currently used fundamental mode. We present here a synopsis of the research program undertaken by the University of Birmingham into the suitability of LG mode technology for future gravitational wave detectors. This will cover our previous and current work on this topic, from initial simulations and table-top LG mode experiments up to implementation in a prototype scale suspended cavity and high-power laser bench

Photon pressure induced test mass deformation in gravitational-wave detectors

A widely used assumption within the gravitational-wave community has so far been that a test mass acts like a rigid body for frequencies in the detection band, i.e. for frequencies far below the first internal resonance. In this article we demonstrate that localized forces, applied for example by a photon pressure actuator, can result in a non-negligible elastic deformation of the test masses. For a photon pressure actuator setup used in the gravitational wave detector GEO600 we measured that this effect modifies the standard response function by 10% at 1 kHz and about 100% at 2.5 kHz

Triple Michelson Interferometer for a Third-Generation Gravitational Wave Detector

The upcoming European design study `Einstein gravitational-wave Telescope' represents the first step towards a substantial, international effort for the design of a third-generation interferometric gravitational wave detector. It is generally believed that third-generation instruments might not be installed into existing infrastructures but will provoke a new search for optimal detector sites. Consequently, the detector design could be subject to fewer constraints than the on-going design of the second generation instruments. In particular, it will be prudent to investigate alternatives to the traditional L-shaped Michelson interferometer. In this article, we review an old proposal to use three Michelson interferometers in a triangular configuration. We use this example of a triple Michelson interferometer to clarify the terminology and will put this idea into the context of more recent research on interferometer technologies. Furthermore the benefits of a triangular detector will be used to motivate this design as a good starting point for a more detailed research effort towards a third-generation gravitational wave detector.Comment: Minor corrections to the main text and two additional appendices. 14 pages, 6 figure

Optimal time-domain combination of the two calibrated output quadratures of GEO 600

GEO 600 is an interferometric gravitational wave detector with a 600 m arm-length and which uses a dual-recycled optical configuration to give enhanced sensitivity over certain frequencies in the detection band. Due to the dual-recycling, GEO 600 has two main output signals, both of which potentially contain gravitational wave signals. These two outputs are calibrated to strain using a time-domain method. In order to simplify the analysis of the GEO 600 data set, it is desirable to combine these two calibrated outputs to form a single strain signal that has optimal signal-to-noise ratio across the detection band. This paper describes a time-domain method for doing this combination. The method presented is similar to one developed for optimally combining the outputs of two colocated gravitational wave detectors. In the scheme presented in this paper, some simplifications are made to allow its implementation using time-domain methods

DC-readout of a signal-recycled gravitational wave detector

All first-generation large-scale gravitational wave detectors are operated at the dark fringe and use a heterodyne readout employing radio frequency (RF) modulation-demodulation techniques. However, the experience in the currently running interferometers reveals several problems connected with a heterodyne readout, of which phase noise of the RF modulation is the most serious one. A homodyne detection scheme (DC-readout), using the highly stabilized and filtered carrier light as local oscillator for the readout, is considered to be a favourable alternative. Recently a DC-readout scheme was implemented on the GEO 600 detector. We describe the results of first measurements and give a comparison of the performance achieved with homodyne and heterodyne readout. The implications of the combined use of DC-readout and signal-recycling are considered.Comment: 11 page

La dynamique fait son cinéma : De l'apport de l'imagerie et des mesures de champs cinématiques pour l'analyse du comportement dynamique des matériaux

National audienceDepuis de nombreuses décennies, l'imagerie rapide a permis d'observer des phénomènes se produisant sur des échelles de temps très petites (de l'ordre de la milliseconde voire de la microseconde). Avec l'avènement plus récent des caméras numériques, de nouvelles applications sont possibles (p.ex. la tomographie rapide). L'utilisation quantitative d'images est également possible, notamment grâce aux techniques de corrélation et de stéréocorrélation d'images. Différentes applications seront présentées afin d'illustrer les apports pour l'analyse du comportement mécanique des matériaux sous sollicitations dynamiques

Projection-based measurement and identification

A recently developed Projection-based Digital Image Correlation (P-DVC) method is here extended to 4D (space and time) displacement field measurement and mechanical identification based on a single radiograph per loading step instead of volumes as in standard DVC methods. Two levels of data reductions are exploited, namely, reduction of the data acquisition (and time) by a factor of 1000 and reduction of the solution space by exploiting model reduction techniques. The analysis of a complete tensile elastoplastic test composed of 127 loading steps performed in 6 minutes is presented. The 4D displacement field as well as the elastoplastic constitutive law are identified. Keywords: Image-based identification, Model reduction, Fast 4D identification, In-situ tomography measurements. INTRODUCTION Identification and validation of increasingly complex mechanical models is a major concern in experimental solid mechanics. The recent developments of computed tomography coupled with in-situ tests provide extremely rich and non-destructive analyses [1]. In the latter cases, the sample was imaged inside a tomograph, either with interrupted mechanical load or with a continuously evolving loading and on-the-fly acquisitions (as ultra-fast X-ray synchrotron tomography, namely, 20 Hz full scan acquisition for the study of crack propagation [2]). Visualization of fast transformations, crack openings, or unsteady behavior become accessible. Combined with full-field measurements, in-situ tests offer a quantitative basis for identifying a broad range of mechanical behavior.Comment: SEM 2019, Jun 2019, Reno, United State