Experimental validation for low frequency isolation of six degree of freedom systems using inertial sensors

peer reviewe

Experimental validation for low frequency isolation of six degrees of freedom systems using optical inertial sensors

peer reviewe

High resolution compact vertical inertial sensor for atomic quantum gravimeter hybridization

peer reviewedInertial sensors are devices capable of measuring the absolute motion of the support they are fixed onto. The advance of very high-end scientific instruments such as gravitational wave detectors, always pursuing ever greater sensitivities and performance, puts a large demand on ultra-high-resolution inertial sensors, capable of measuring very low-frequency and small-amplitude motions. Our group has a long experience in the design of low-frequency inertial sensors intended to be used in active isolation systems. The latest horizontal and vertical interferometric inertial sensors that have been designed have performance that competes with industry standards. They were shown to reach a resolution of 2×10−13 m/Hz−−−√ at 1 Hz and are capable of measuring ground motion from 0.1 to 100 Hz. However, they are large and heavy, measuring approximately 20 × 20 × 30 cm3 each, which makes their integration into practical systems tedious. In addition, experimental characterization of these sensors revealed three main limitations to their resolution. They are: (i) thermal noise, (ii) electronic readout noise and (iii) broadband white noise caused by mechanical and optical nonlinearities. The present paper presents a revised version of the vertical sensor, where the size of the device has been made to fit a 10 × 10 × 10 cm3 while simultaneously addressing the aforementioned sources of noise. The mechanics of the compact sensor is made of a leaf-spring supported pendulum, connected to the frame using a flexure hinge. A moving mirror is connected to the mass and guided using a so-called "4-bar" mechanism, providing the moving mirror with linear translation motion (iii). The joints of the mechanics are made of fused silica, allowing to reach a low natural frequency of ≈1 Hz with a compact design, in addition to significantly reducing structural thermal noise (i) due to the low dissipation rate of fused-silica. On the other hand, the readout system used in this sensor is a homemade design of a Michelson interferometer. The optical scheme features numerous polarizing elements that allow the propagation of two laser beams in phase quadrature, and custom hardware is developed for minimizing electronic noise (ii). Lastly, the vertical sensor is operating in closed-loop, using a homemade actuator design, so as to reduce non-linear effects related to either the mechanics or the optical readout (iii). The sensor frequency response is characterized using a test bench that has been specifically developed for testing low-frequency sensor response. The noise floor is extracted using a Huddle Test

E-TEST Active Platform assembly procedure

Assembly procedure for the construction and installation of the Active Platform for the E-TEST project. The assembly procedure was then presented to the full E-TEST collaboration and approved

Compact isolation of a large mirror at low frequency

info:eu-repo/semantics/publishe

Einstein Telescope Euregio-Meuse-Rhin Site and Technology

info:eu-repo/semantics/publishe

E-TEST prototype design report

E-TEST (Einstein Telescope Euregio-Meuse-Rhin Site and Technology) is a project recently funded by the European program Ineterreg Euregio Meuse-Rhine. This program is dedicated to innovative cross boarder activities between Belgium, The Netherlands and Germany. With a total budget of15MC and a consortium of 11 partners from the three countries, the objective of the project is twofold. Firstly, to develop an eco-friendly and non-invasive imaging of the geological conditions as well as the development of an observatory of the underground in the EMR region. Secondly, to develop technologies necessary for 3rd generation gravitational wave detectors. In particular, it is proposed to develop a prototype of large suspended cryogenic silicon mirror, isolated from seismic vibrations at low frequency. The total budget of the project is equally spread over the two activities. The first activity is not discussed at all in this report. The E-TEST prototype will have some key unique features: a silicon mirror of 100 kg, a radiative cooling strategy (non contact), a low-frequency hybrid isolation stage, cryogenic sensors and electronics, a laser and optics at 2 microns, a low thermal noise coating

E-TEST: a compact low-frequency isolator for a large cryogenic mirror

peer reviewedAbstract To achieve the expected level of sensitivity of third-generation gravitational-wave observatories, more accurate and sensitive instruments than those of the second generation must be used to reduce all sources of noise. Amongst them, one of the most relevant is seismic noise, which will require the development of a better isolation system, especially at low frequencies (below 10 Hz), the operation of large cryogenic silicon mirrors, and the improvement of optical wavelength readouts. In this framework, this article presents the activities of the E-TEST (Einstein Telescope Euregio Meuse-Rhine Site & Technology) to develop and test new key technologies for the next generation of GW observatories. A compact isolator system for a large silicon mirror at a low frequency is proposed. The design of the isolator allows the overall height of the isolation system to be significantly compact and also suppresses seismic noise at low frequencies. To minimize the effect of thermal noise, the isolation system is provided with a 100-kg silicon mirror which is suspended in a vacuum chamber at cryogenic temperature (25-40 K). To achieve this temperature without inducing vibrations to the mirror, a radiation-based cooling strategy is employed. In addition, cryogenic sensors and electronics are being developed as part of the E-TEST to detect vibrational motion in the penultimate cryogenic stage. Since the used silicon material is not transparent below the wavelengths typically used for GW detectors, new optical components and lasers must be developed in the range above 1500 nm to reduce absorption and scattering losses. Therefore, solid-state and fiber lasers with a wavelength of 2090 nm, matching high-efficiency photodiodes, and low-noise crystalline coatings are being developed. Accordingly, the key technologies provided by E-TEST serve crucially to reduce the limitations of the current generation of GW observatories and to determine the technical design for the next generation