We present a compact, fibre-coupled interferometer with high sensitivity and a large working range. We propose to use this interferometer as a readout mechanism for future inertial sensors, removing ...a major limiting noise source, and in precision positioning systems. The interferometer's peak sensitivity is 2×10−14 m Hz−1 at 70 Hz and 7×10−11 m Hz−1 at 10 mHz. If deployed on a GS-13 geophone, the resulting inertial sensing output will be limited by the suspension thermal noise of the reference mass from 10 mHz to 2 Hz.
Abstract
We present a modified commercial L-4C geophone with interferometric readout that demonstrates a resolution 60 times lower than the included coil-magnet readout at low frequencies. The ...intended application for the modified sensor is in vibration isolation platforms that require improved performance at frequencies lower than 1 Hz. To illustrate it’s application a controls- and noise-model of an Advanced LIGO ‘HAM-ISI’ vibration isolation system was developed, and shows that our sensor can reduce the residual motion of the platforms by a factor of 70 at 0.1 Hz.
We have developed, produced and characterized integrated sensors, actuators and the related read-out and drive electronics that will be used for the control of the Advanced LIGO suspensions. The ...overall system consists of the BOSEMs (a displacement sensor with an integrated electromagnetic actuator), the satellite boxes (the BOSEM readout and interface electronics) and six different types of coil-driver units. In this paper, we present the design of this read-out and control system, we discuss the related performance relevant for the Advanced LIGO suspensions, and we report on the experimental activity finalized at the production of the instruments for the Advanced LIGO detectors.
We describe the design of the suspension systems for the major optics for Advanced LIGO, the upgrade to LIGO-the Laser Interferometric Gravitational-Wave Observatory. The design is based on that used ...in GEO600-the German/UK interferometric gravitational wave detector, with further development to meet the more stringent noise requirements for Advanced LIGO. The test mass suspensions consist of a four-stage or quadruple pendulum for enhanced seismic isolation. To minimize suspension thermal noise, the final stage consists of a silica mirror, 40 kg in mass, suspended from another silica mass by four silica fibres welded to silica ears attached to the sides of the masses using hydroxide-catalysis bonding. The design is chosen to achieve a displacement noise level for each of the seismic and thermal noise contributions of 10−19 m/√Hz at 10 Hz, for each test mass. We discuss features of the design which has been developed as a result of experience with prototypes and associated investigations.
eLISA is a space mission designed to measure gravitational radiation over a frequency range of 0.1-100 mHz (European Space Agency LISA Assessment Study Report 2011). It uses laser interferometry to ...measure changes of order in the separation of inertial test masses housed in spacecraft separated by 1 million km. LISA Pathfinder (LPF) is a technology demonstrator mission that will test the key eLISA technologies of inertial test masses monitored by laser interferometry in a drag-free spacecraft. The optical bench that provides the interferometry for LPF must meet a number of stringent requirements: the optical path must be stable at the few level; it must direct the optical beams onto the inertial masses with an accuracy of better than ±25 μm, and it must be robust enough not only to survive launch vibrations but to achieve full performance after launch. In this paper we describe the construction and testing of the flight optical bench for LISA Pathfinder that meets all the design requirements.
In 2015, the first observation of gravitational waves marked a breakthrough in
astrophysics and in technological research and development. The discovery of a
gravitational-wave signal from the ...collision of two black holes, a billion light-years
away, received considerable interest from the media and public. We describe the
development of a purpose-built exhibit explaining this new area of research to a general
audience. The core element of the exhibit is a working Michelson interferometer: a
scaled-down version of the key technology used in gravitational-wave detectors. The
Michelson interferometer is integrated into a hands-on exhibit, which allows for user
interaction and simulated gravitational-wave observations. An interactive display provides
a self-guided explanation of gravitational-wave related topics through video, animation,
images, and text. We detail the hardware and software used to create the exhibit, and
discuss two installation variants: An independent learning experience in a museum setting
(the Thinktank Birmingham Science Museum) and a science-festival with the presence of
expert guides (the 2017 Royal Society Summer Science Exhibition). We assess audience
reception in these two settings, describe the improvements we have made given this
information, and discuss future public-engagement projects resulting from this work. The
exhibit is found to be effective in communicating the new and unfamiliar field of
gravitational-wave research to general audiences. An accompanying website provides parts
lists and information for others to build their own version of this exhibit.
In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the ...test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20 μHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05) fm s^{-2}/sqrtHz above 2 mHz and (6±1)×10 fm s^{-2}/sqrtHz at 20 μHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.
Microfluidic chips with integrated fluid and optical connectors have been generated via a simple PDMS master-mould technique. In situ coating using a Zinc oxide polyvinylalcohol based sol–gel method ...results in ultrathin nanocomposite layers on the fluid channels, which makes them strongly hydrophilic and minimizes auto contamination of the chips by injected fluorescent biomarkers.
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